PTtank-Manual.docx Page 1 · PTtank-Manual.docx Page 5 PTtank Program – Analysis and Design of Post-Tensioned Tanks 1. INTRODUCTION PTtank is a Windows standalone program that analyses

PTtank-Manual.docx Page 1


COPYRIGHT NOTICE

© Copyright 2009 Steven S Gikas & Associates. All Rights Reserved

This software is copy-protected.

Australian copyright laws and international treaties protect the software and manual. The software contained on the distribution media, remains the property of Steven S Gikas & Associates at all times, however the distribution media and this manual become the property of the purchaser. Steven S Gikas & Associates license the software for use only by the purchaser of the package.

DISCLAIMER No representations or warranties with respect to the contents hereof are made, and any implied warranties or fitness for any particular purpose is specifically disclaimed.

Although care has been taken in developing and testing the program described herein, it is possible that errors and inadequacies may emerge as it used in new applications. It is the responsibility of the user to ensure that the input data is appropriate, and to check and exercise his/hers own judgment in applying the results.


Table of Contents 1. INTRODUCTION 005

1.1. Program Help and Manual 006 1.1.1. PTtank Manual 006 1.1.2. PTtank Help 006 1.2. Program Versatility 007 1.3. Wall Types 007 1.3.1. Horizontal Stressing Arrangement 008 1.3.2. Anchor Types-Horizontal Tendons 008 1.3.3. Vertical Reinforcement Options 008 1.4. Ring Footing 009 1.5. Tank Slab 009

2. THEORY 010 2.1. Mathematical Theory 010 2.1.1. Boundary Conditions 011 2.1.2. Solution of Differential Equations 012 2.2. The Tank Model 013 2.2.1. Limits to Number of Elements 013 2.2.2. Recommended Number of Elements 013

3. USER INTERFACE 014 3.1. Start Screen 014 3.2. Creating and Opening Files 016 3.2.1. Staring New File 016 3.2.2. Opening Existing File 016 3.2.3. Loading Existing File Process 017 3.3. Program Navigation 018 3.3.1. General 018 3.3.2. Topic Specific 019

4. RUNNING THE PROGRAM 020 4.1. Initial Input Sequence 020 4.2. Initial Input in Detail 021 4.2.1. Project 021 4.2.2. Sign Convention 022 4.2.3. Calculation Options 023 4.2.3.1. Reduction Factors 023 4.2.3.2. Cross Section Transformation 025 4.2.4. Material Properties 026 4.2.5. Tank Geometry 027 4.2.5.1. Tank Size 027 4.2.5.2. Construction Type 027 4.2.5.3. Tank Elements 027 4.2.5.4. Tank Wall Fixity 028 4.2.5.4.1. The Rubber Condition 028 4.2.6. Tank Wall Details 029 4.2.6.1. Hydrostatic Load 029 4.2.6.2. Tank Details 030 4.2.6.2.1. Stressing Arrangement 030 4.2.6.2.2. Anchor Type 030 4.2.6.2.3. Wall Plan 031 4.2.6.3. Wall Prestress and Reinforcement 033 4.2.6.3.1. Horizontal Prestress 034 4.2.6.3.2. Vertical Details 035 4.2.6.3.2.1. Prestress-Strand 033 4.2.6.3.2.2. Prestress-Stress Bar 036 4.2.6.3.2.3. Reinforcement Only 037 4.2.6.3.3. Wall Secondary Reinforcement 038 4.2.6.3.3.1. For Vertically Stressed Walls 038 4.2.6.3.3.2. For Vertically Unstressed Walls 039 4.2.6.3.4. Minimum Wall Thickness 040

RUNNING PROGRAM (continued)

4.2.7. Wall Horizontal Anchors 041 4.2.7.1. Buttress Geometry Details 041 4.2.7.2. Z-Type(Pocket) Geometry Details 042 4.2.8. Hoop Losses 043 4.2.8.1. Hoop Losses-User Input 044 4.2.8.2. Tendon (Hoop) Spacing 045 4.2.8.3. Hoop Losses – Results 046 4.2.8.3.1. The Hoop Force Profile 046 4.2.8.3.2. The Hoop Design Forces 047 4.2.9. Determining Number of Hoops 048 4.2.9.1. Using Hand Calculation 049 4.2.9.2. Analytically 050 4.2.9.2.1. Total Applied Hoop Tension 050 4.2.9.2.2. Balancing the Hoop Tension 051 4.2.10. Vertical Prestress Losses 054 4.2.10.1. Vertical Losses-User Input 055 4.2.10.1.1. Vertical Tendons Spacing 056 4.2.10.1.2. Vertical Tendon Losses-Results 056 4.2.11. Tank Wall – Full Details 057 4.2.11.1. Vertically Prestressed - Precast 058 4.2.11.2. Vertically Prestressed – Insitu 059 4.2.11.3. Vertically Reinforced – Precast 060 4.2.11.4. Vertically Reinforced – Insitu 061

5. TANK LOADING and ANALYSIS 062 5.1. Loading Cases 063 5.2. Load Case Input 063 5.2.1. Gravity Loading 064 5.2.1.1. Self Weight 064 5.2.1.2. Dead and Live Load Cases 065 5.2.2. Hydrostatic Load Cases 066 5.2.3. Temperature Loading 067 5.2.3.1. Temperature Theory 067 5.2.3.1.1. Code – PTtank Comparison 068 5.2.3.2. Temperature Load Cases 069 5.2.4. Moisture Variation Loading 070 5.2.4.1. Moisture Variation Theory 070 5.2.4.2. Moisture Variation Load Cases 071 5.2.5. Earth Loading (Embedded Tanks) 072 5.2.6. Earthquake Loading 073 5.2.6.1. Earthquake Loading on Water 074 5.2.6.1.1. Equivalent Earthquake Reassures 075 5.2.6.1.2. Combination of Equivalent Reassures 076 5.2.6.2. Earthquake Loading on Soil 077 5.2.6.2.1. Equivalent Pressures 078 5.2.7. Loading due to Horizontal Stressing 079 5.2.7.1. Tendon Stressing Data 080 5.2.7.1.1. Tendon (Hoop) Heights 080 5.2.7.1.2. Tendon (Hoops) Stressing Order 081 5.2.7.1.2.1. Default Stressing Order 082 5.2.7.2. Stressing The Tendons (Hoops) 083 5.2.7.2.1. The Stressing (Hoops) Results 084 5.2.7.2.2. Stressing Moment Summery 084 5.2.7.2.3. Probe 085 5.2.7.2.4. Viewing Individual Stages 085 5.2.7.2.5. View Mode 086 5.2.7.2.6. Animation 087


Table of Contents -------- continued

TANK LOADING and ANALYSIS (continued)

5.2.7.3. Maximums During Stressing 088 5.2.7.3.1. Maximum Positive 088 5.2.7.3.2. Maximum Negative 089 5.2.7.4. End of Stressing (Transfer) 090 5.2.7.5. Service (Long Term) 091 5.2.8. Loading Due to Vertical Stressing 092

6. ANALYSIS RESULTS (Combinations) 093 6.1. Analyse All 093 6.2. Load Combinations 094 6.2.1. Load Combinations Required 094 6.2.2. Individual Load Combinations 095 6.3. Combination of Analysis –Results 096 6.3.1. Combinations –No Reduction Factors 096 6.3.2. Combinations – With Reduction Factors 096 6.3.3. The Reduction Factors 097 6.4. Analysis Results (Combinations) 097 6.4.1. Analysis Results – Plots 098 6.4.2. Load Combinations – Applied Loads 099 6.4.3. Cross Section Transformation 100 6.4.4. Analysis Results – Summary 101

7. DESIGN OF TANK WALL 102 7.1. Cross Section Analysis 103 7.2. Cross Section Analysis – Summary 104 7.3. Cross Section Analysis - Display 105 7.3.1. Using The Summary 105 7.3.2. Using The Tree View – Reporting 106 7.3.3. Using the Tabulated Results 107 7.4. Combination – Print/Plot Utility 108

8. RING FOOTING 109 8.1. Ring Footing Size 109 8.2. Design Base Shear 110 8.3. Ring Footing Design 111 8.3.1. For Reinforced Only Footing 112 8.3.2. For Prestressed Footing 113 8.3.2.1. Preliminary Design 113 8.3.2.2. Completing (Hoop) Design 114 8.3.2.3. Buttress Hoop Losses 115 8.3.2.4. Buttress Hoop Losses – User Input 116

9. TANK SLAB 118 9.1. The Slab-On-Grade Design Module 118 9.2. Slab-On-Grade (SOG) Theory 119 9.3. Slab Design – Dialogue Window 120 9.4. Slab Design - User Input 121 9.4.1. Geometry, Subgrade & Prestress 121 9.4.2. Slab Material Properties 122 9.4.3. Slab Tendon Losses 123 9.4.4. Slab Loading 124 9.5. The Slab Design 125 9.5.1. Determining number of Strands 125 9.5.2. Completing Design 125 9.5.3. Slab Design Results 125 9.5.3.1. Slab Analysis Results 126 9.5.3.2. Tendon/Subgrade-Friction Plots 126 9.5.3.3. Slab Edge Movement 127 9.5.3.4. Slab Design Tendons 128

10. QUANTITIES 128

11. REPORTS 129 11.1. Generating Reports 129 11.2. Viewing and Printing Reports 130

12. DRAWING 132 12.1. Generating The Drawing 133 12.2. Viewing and Printing The Drawing 134

13. FUTURE DEVELOPMENT 135


PTtank Program – Analysis and Design of Post-Tensioned Tanks 1. INTRODUCTION PTtank is a Windows standalone program that analyses and designs circular, liquid retaining structures. The program analyses and designs, all the Tank Elements, which are:

• Walls, (Precast or Insitu) • Ring Footing Beam • Tank Slab

The applied loads used in the Analysis are:

• Gravity • Hydrostatic • Tendon Stressing

o Horizontal (Hoop) o Vertical (if stressed)

• Temperature • Moisture (Swelling and Shrinkage) • Earth, if Tank is embedded • Earthquake

o On Water o On Soil, if Tank is embedded

For the design process, all possible combinations are considered for

• Long Term o Tank Full o Tank Empty

• Short Term o Tank Full o Tank Empty

The total number of combinations generated, to cover all possible loads is Thirty-nine (39) The Standards used are: AS 3735 Concrete Structures for Retaining Liquids AS 3735 Sup1 Concrete Structures for Retaining Liquids – Commentary AS 1170.4 Structural Design Actions Part 4 – Earthquake Actions in Australia AS/NZS 1170.0 Structural Design Actions Part 0 – General Principles NZS 3106 Design of Concrete Structures for the Storage of Liquids NZS 1170.5 Structural Design Actions Part 5 – Earthquake Actions-New Zealand


1.1. Program Help and PTtank Manual 1.1.1. PTtank Manual

The PTtank Manual is incorporated into the PTtank program and can be accessed by selecting PTtank Help from the Menu Bar, as shown

in Figure H1

This brings up the Manual, as shown in Figure 2, for which user can • Print part or all of it • Cycle through it • Text search

1.1.2. PTtank Help The Manual has been indexed, and uses the Keyboard Function Key F1, to display the relevant Help (Manual) page. Therefore the associated help for the visible window is displayed by pressing F1, as shown in Figure H2

Figure H1: PTtank Help

Figure H2: PTtank Manual

Figure H3: (F1) Topic Help


1.2. PROGRAM VERSATILITY

1.3. WALL TYPES

The Program can analyze and design tanks that have:

• Precast Walls

• Insitu Walls Figure 1: Precast and Insitu Tank Walls The Boundary Conditions (Wall Fixity) Options, at top and bottom of Tank Wall are:

• Top of Wall o Free o Pinned o Fixed. Currently switched off

Figure 2: Wall Top Fixity Options

• Bottom of Wall o Free o Pinned o Rubber o Fixed. Currently switched off o Partially Fixed. Currently switched off

Figure 3: Wall Bottom Fixity Options


1.3.1. Stressing Arrangement – Horizontal Tendons The wall can be stressed using • Two Stressing Locations • Four Stressing Locations • Six Stressing Locations

Figure 4: Stressing Options 1.3.2. Anchor Types – Horizontal Tendons The wall can be stressed using: • Buttress (Pilaster) • Pocket (Z-Type)

Figure 5: Anchor Stressing Type - Buttress (Pilaster) and Pocket (Z-Type

1.3.3. Vertical Reinforcement Options The Tank Wall, in the vertical direction, can have as main reinforcement • Tendons • Stress Bar • Only Passive Reinforcement

Figure 6: Vertical Main Reinforcement Options – Strand, Stress Bar or Passive Reinforcement

Two Locations T1–T2 Phase = 180°

Four Locations T1–T2 Phase = 90°

Six Locations T1–T2 Phase = 60°


1.4. RING FOOTING The program selects the type of (Ring Beam) footing to analyze and design, depending on the bottom wall fixity. The options are: • With Key • Without Key

Figure 7: Ring Beam with and without Key

1.5. Tank Slab The program selects the type of slab ends to analyze and design depending on, the bottom wall fixity and Ring (Footing) type The options for the Slab Ends are: • With Key • Without Key

Figure 8: Slab with and without Key Ends


2. THEORY The analysis of the cylindrical shaped structure is carried out by calculating exactly the solution of the differential equation for the deflection, along the height of the tank The load applied is expressed in terms of a Fourier’s Series. The complete solution involves the substitution of boundary conditions (Top and Bottom of Tank)

Figure 9: Controlling Parameters

2.1. Mathematical Theory The basic differential equation for the deflection of a cylinder, under a circumferential load is given by:

Therefore:

And:

Where: T=Wall Thickness H=Tank Height R= Internal Radius P = Total load per E=Young’s Modulus Circumference unit

I = Moment of Inertia

Where:

Where:

Ø =Internal Diameter

β

x

H

T

R P= Load per unit of Circumference

β = Position of Load x = Position of Section under Consideration T = Wall Thickness R = Tank Internal Radius H= Tank Height

H

β

2α x

y

P

P

-------------- (1)

-------------- (2)

Figure 10: Simplified Model

-------------- (3)


The Loading is represented by a Fourier sine series Where Therefore: Hence the differential equation for the solution is: This equation is solved for deflection, and Moments (M) and Shears (S) are calculated by

2.1.1. Boundary Conditions The Boundary Conditions are: • Pinned

o Deflection is zero o Moment is zero

• Free o Moment is zero o Shear is zero

• Fixed o Deflection is zero o Slope is zero

-------------- (4)

As α approaches 0

-------------- (5)

-------------- (6)

-------------- (7)

-------------- (8)


2.1.2. Solution of Differential Equation The equation is solved, taking into account the appropriate boundary conditions. These are: CASE 1 - Both Ends Pinned The deflection and Moment are zero at both ends At x=0 and x=H, y=0 and CASE 2 - Both Ends Free The Moment and Shear are zero at both ends At x=0 and x=H, and

CASE 3 – One End Free the Other Pinned 1 Pinned End - Moment and Deflection are zero

At x (pinned) y=0 and

2 Fixed End – Moment and Shear are Zero At x (free) and CASE 4 – Both Ends Fixed The deflection and slope are zero at both ends At x=0 and x=H, y=0 and CASE 5 – One End Fixed the Other Pinned 3 Fixed End – Deflection and slope are zero

At x (fixed), y=0 and

4 Pinned End – Deflection and Moment are zero At x (pinned), y=0 and CASE 6 – One End Fixed the Other Free 5 Fixed End – Deflection and slope are zero

At x (fixed) y=0 and

6 Free End – Moment and Shear are zero At x (pinned) and


2.2. The Tank Model The Tank is divided vertically, into elements The number of nodes is equal to the Number of Elements + 1

Figure 11: Tank Elements and Nodes All applied loads and results are reported at each node 2.2.1. Limits to Number of Elements The minimum number of elements of course is 1, but this is not recommended. The maximum, number of elements limit, based on computer capabilities and memory, has not been determined by Author. Needless to say is well over 1000 As all results are tabulated, showing each node, there is a maximum number of rows that can fit on an A4 Page. It has been decided to contain an Individual Load Results on a single A4 Page. The number of rows (nodes) that can be accommodated on an A4 page is 57. Based on this limitation the maximum number of elements is set to 50 2.2.2. Recommended Number of Elements The recommended minimum number of elements is 20 If the number of Hoops required is greater than the number of elements, the number of elements should be increased to the number of Hoops+1. This is recommended to maximize accuracy The program will inform user of this recommendation when it applies

n=Number of Elements Nodes = n+1

Node 0

Node n

If Number of Hoops > 20 Then the Number of Elements = Hoops +1


3. USER INTERFACE 3.1. Start Screen Figure 12: Start Screen When the program is activated the Start Screen is displayed. The parts are: A. Menu Bar. This contains a set of menus for the program. Figure 13: The Menu Bar B. Standard Tool Bar Contains Command Buttons for General operations

Figure 14: The Tool Bar

A

B

C

D

E

F


C. Tree View Used to navigate through program and to select Report options. It contains four different view lists, Input, Loading, Results and Report D. Tree View Tabs Used to select the view list to be displayed in Tree View.

Figure 15: View Tabs Figure 16: Tree View E. Main Display Window This is where all dialogue and graphs are displayed F. Status Bar, for program status information Figure 17: Main Display Window with Status Bar at the bottom


3.2. Creating and opening files When you start PTtank, you can create a new file or open an existing one 3.2.1. Starting New File This can be done in one of two ways • Mouse clicking the New Button • From the File Menu, select New This Action

• Resets all data to the default values

• Deletes all Results User must make sure the current file is saved Figure 18: New File Methods before activating this commend

3.2.2. Opening an Existing File This can be done in one of two ways

• Mouse clicking the Menu Button

• From the File Menu, selecting Open This action opens the standard windows file Display dialogue window Saved PTtank files have the extension of .ptk Figure 19: Open File Methods The dialogue window will display all files with this extension. User selects required file which is then loaded into program

Figure 20: Open File Dialogue Window


3.2.3. Loading Existing File … Process When programs load the selected file a backup file is created The backup file has the format: Name.XXX Where: Name is the name of the original file

XXX is a back up number generated, starting at 001 the first time the file is loaded and increasing by one each time the file is loaded

The program notifies user on the name, which includes the full path Figure 21: Open File Dialogue Window

The program does not save the design and analysis results, but once the file is loaded, it automatically analyses everything to the status it was saved. Figure 22: Progress Status Indicator

The re-calculation takes a while, and the program displays the Progress Status indicator, telling user what is happening Figure 23: Analysis and Results When program, finishes • Loading File • Calculating all It then displays the Summary page. This is the status of the file when it was saved


3.3. Program Navigation 3.3.1. General Navigating through program is simple and can be done in two ways • Using the Menu

This is done by o Selecting the required Group Activity, which

opens the associated drop menu o Then the selecting required Activity on the drop

menu or sub menu Figure 24 (and 26), show: Wall Loading & Analysis>Tendon Loading>Hoop Loading

• Using the Tree View

This is done by o Selecting the Tree Tab required o Selecting the Group Activity on the tree View.

This then expends the Tree View to display all the Sub-activities

o Selecting required Activity Figure 25 (and 26), show: Loading > Hoops

Figure 25: Tree Tab

Figure 26: Tree View and Menu Methods

Figure 24: Tree Tab


3.3.2. Topic Specific Navigation For a specific topic, that has more than one activity, the navigation is done in two ways • Using the Tabs on top of the displayed dialogue window

From there you can use the Tab (or Tree View) to move between sub-activities. Figure 27 shows: The Tab method to display the Hydrostatic-Overflow Dialogue window (Figure 29)

• Using the Tree View and navigating to the specific topic/activity. From there you can use the Tree View (or Tab) to move between sub-activities. Figure 28 shows: The Tree View method displaying the Hydrostatic-Overflow Dialogue window (Figure 29)

Figure 27: Topic Specific Dialogue Window Tabs (Hydrostatic

Figure 28: Topic Specific Tree View Hydrostatic > Overflow

Figure 29: Topic Specific Dialogue Window (Hydrostatic Loading and Analysis)


4. RUNNING THE PROGRAM The program initially needs to be run sequentially. Reason being, since it is a Post Tensioned tank the Hoops and wall thickness need to be assessed before any of the analysis is performed 4.1. Initial Input Sequence The recommended sequence of Input is • Project • Design Options • Materials • Tank

o Size o Type. Precast or cast-in-place (insitu) o Top and Bottom Wall Fixity o Water Heights

• Wall (Horizontal and Vertical Details)

o Stressing Arrangement o Anchor Type. Buttress (Pilaster) or Pocket (Z-Type) o If Precast, the Panel Constraints

Maximum Panel Weight Maximum Panel Width Wet Joint Width

o PT and Reo Wall Details In Horizontal (Hoop) direction Vertical Direction

Post Tensioned. Strand or Stress Bar Passive Reinforced only

o Hoop Losses Analysis o Required number of Hoops Analysis o Vertical Tendon Losses Analysis if stressed o Vertical Wall Panel Detail

At the end of Wall input the o Wall thickness has been determined o Hoops have been determined o Vertical Details have been determined o Minimum reinforcement has been specified


4.2. Initial Input In Detail 4.2.1. Project User inputs the Project Details to be echoed an all the reports. These are • Project Name • Project Number • Designer • Date, generated automatically to the current system date The Project Dialogue Window also displays the

• Licensee of the program • Licensee Logo

Figure 30, shows Hyder as the Licensee The Licenser’s Logo is part of the database registered to use the program It has to be supplied to the Author of the program to be implemented The implementation of the Licenser’s Details and Logo are of course optional

Figure 30: Project Dialogue Window showing: Project Details Licensee Details and Logo (Hyder)


4.2.2. Sign Convention There is no input required for the Sign Convention. The sign convention used by the program is displayed Sign convention dictates how the input parameters are used by PTtank and how the results are displayed. The Parameters are: • Horizontal Pressure • Surcharge (on soil) Pressure • Horizontal Force • Vertical Force • Hoop (Circumferential Moment) • Vertical Moment • Wall Deflection Generally for: • Moments

Positive moments cause tension on outer face of tank Negative moments cause tension on inner face of tank

• Stress Positive stress indicates Tension Negative stress indicates compression

Figure 31: Sign Convection


4.2.3. Calculation/Design Options This is where user specifies the design option for PTtank to use for analysis and design The Options are: • Reduction Factors • Cross Section Transformation • Earthquake

4.2.3.1. Reduction Factor (RF) The theory used for determining the induced forces due to Temperature and Moisture Variation, allow for the use of a Reduction Factor (RF) to be applied. Reference is made to: Australian Standard Concrete structures for retaining liquids – Commentary (Supplement to AS 3735-1991 Section C2.2.1 for Temperature Section C2.2.2 for Moisture variation

Figure 32: Calculation/Design Options


The Reduction Factor (RF) is used by PTtank as: The Reduction Factor (RF) is defined as: The Tension Stiffening factor (TSF) depends on the reinforcement ratio (ρ) Values for Tension Stiffening Factor (TSF) are given as:

• 100% increase at ρ=0.005 Therefore TSF =2

• 30% increase at ρ=0.02 Therefore TSF =1.3 • Linear interpellation between

PTtank calculates the Reduction Factor (RF) and applies the reduction depending on the user specified options. If a value of 1.00 is specified, PTtank applies no reduction. These are: For Temperature: • As Calculated • 1.000 Means NO REDUCTIONS • A maximum value

Used when the calculated value is less For Moisture Variation • 1.00 Means NO REDUCTIONS • As Temperature RF

-------------- (9)

-------------- (10)

Where:

MD =Moment Induced in element due to temperature (N/mm2)

FD =Axial force induced in cylindrical wall due to temperature (N/mm)

σI = Fibre stress on inside face of wall resulting from a temperature gradient through the wall (MPa)

σo = Fibre stress on outside face of wall resulting from a temperature gradient through the wall (MPa) tw = thickness of wall (mm)

Figure 33: Reduction Factors (RF) Options

Figure 34: Reduction Factors (RF) for Temperature and Moisture Variation

-------------- (11)


4.2.3.2. Cross Section Transformation Option PTtank performs working stress analysis and reports the Inner Wall Stresses Outer Wall Stresses Residual Compression (P/A) This option tells PTtank whether to use transformed cross section (Modular Ratio) when calculating the stresses 4.2.3.3. Earthquake Option If the Box is checked, PTtank, based on the controlling parameters will calculate the equivalent static horizontal force for earthquake loading in circular tanks. All in accordance to NZS 3106 and associated Australian Standards

Figure 35: Transformed Section Options

Figure 36: Earthquake Options


4.2.4. Material Properties This is where user specifies the: • Material Properties for

o Concrete o Reinforcement o Rubber base (Used if tank base is designed on a rubber pad)

• Durability Data • Exposure Data PTtank uses this data to analyze and design the Tank structural elements During the individual phases of analysis and design, there are more specific for that phase, data that will be required. PTtank will display dialogue windows when data is required

Figure 37: Material Properties Dialogue


4.2.5. Tank Geometry This is where user specifies the • Tank Size • Wall Fixities • Construction Type • No. of vertical design elements

Due to printing constraint the Maximum is set to 50

4.2.5.1. Tank Size The Tank Size is defined by • Internal Diameter • Wall Height • Overflow Height • Water (Service) Height PTtank displays the capacity in • Mega Liters (ML) • Cubic Meters (m3) 4.2.5.2. Construction Type User defines the Tank Type • Precast Walls • Insitu This determines the type of Ring Beam Footing designed

4.2.5.3. Tank Elements The recommended minimum number of elements is 20

The maximum number is set to 50. This is only due to printing constraints. It is recommended that the number be set to one more than the Hoops required. PTtank will alert user when this applies

Figure 38: Tank Geometry Dialogue Window

Figure 39: Tank Size Input Parameters

Figure 40: Tank Construction Options

Figure 41: Tank Elements

If Number of Hoops > 20 Then the Number of Elements = Hoops +1


4.2.5.4. Tank Wall Fixity User defines the Top and Bottom Wall Fixities • Top Options

o Free o Pinned o Fixed (switched off)

• Bottom Options

o Free o Pinned o Fixed (switched off) o Rubber o Partial (switched off)

4.2.5.4.1. The Rubber Condition The Free, Pinned and Fixed conditions are easy to model and analyze. The Rubber Boundary Condition is a special case and requires much more analytical power. In all but the Rubber case the analysis is run only once, for the Rubber Condition the model is run three times Analysis Procedure for Rubber Condition Step 1 Tank is analysed with pinned base, determining Pinned Base Shear (S0) Pinned Rubber Pad Force (Pf0) Step 2 Tank is analysed with free sliding base, determining Free Deflection (Ds) Free Sliding Pad Force (Pfs) Step 3 Compatibility Deflection (Dc) and Compatibility Shear (Sc) are evaluated from: Step 4 Tank is finally analysed with a predefined deflection of Dc at the base.

As a check, the Compatibility Base Shear (Sc), calculated above, should be the same as the Ring Shear returned by the Compatibility analysis

The Compatibility results are now used in the combinations

Figure 42: Top Wall Fixity Options

Figure 43: Bottom Wall Fixity Options

-------------- (12)

-------------- (13)


4.2.6. Tank Wall Details This is where the all the details for the wall in both directions are defined The Dialogue Window contains nine (9) Sections (Tabs). These are: • Hydrostatic Loads • Tank • Buttress Details • Z-Type • Hoop Losses • PT Losses Vertical • Vertical 4.2.6.1. Tank Wall Details-Hydrostatic Load Input is entered sequentially; as such the Wall Dialogue Window initially opens on the first Tab. The Window displays the • Type of Tank selected (Precast or Insitu) • Hydrostatic Loading The only Input required by user here is the Liquid density. The default value is 9.81 kg/m3 User can overwrite this value

Figure 44: Wall Dialogue Window

Figure 45: Tank Wall Details – Hydrostatic Loads

Figure 46: Tank Wall Details – Liquid Density


4.2.6.2. Tank Wall Details-Tank The Window Displays • Hydrostatic Load. For Information only • Stressing Arrangement • Anchor Type • Tank Wall Plan. Precast or Insitu

If Precast then, also displayed are o Wet Joint Width o Wall Panel Limiting Values for o Panel Weight o Panel Width

• Stressing Arrangement • Anchor Type 4.2.6.2.1. Stressing Arrangement User here selects the Stressing Arrangement to be used for the Hoop Tendons. This is used to determine the hoop force losses and the effective hoop tendon force to be used in the analysis and design The options are, two, four or six Stressing Location.

4.2.6.2.2. Anchor Type User here selects the Anchor type The selection depends on the number of strands in the Hoop Tendon to be used. Generally Buttresses are used when the number of strands/Hoop required is greater than 6 The more cost effective option is the Pocket or Z-Type. The limitation for the Z-Type anchor is that it can only have 2, 4 or 6 strands/Hoop

Figure 47: Tank Wall Detail – Tank Details

Figure 48: Tank Wall Detail – Stressing Arrangement

Figure 49: Tank Wall Detail – Anchor Types


4.2.6.2.3. Tank Wall Detail - Plan Here the Tank Wall Plan is displayed, depending on • Construction Type

o Precast o Insitu

• Stressing Arrangement o Two Stressing Locations o Four Stressing Locations o Six Stressing Locations

• Anchor Type o Buttress o Pocket (Z-Type)

The total number of possible Wall Types is 12. These Are

• Insitu o Buttress-Two, For and Six Stressing Points = 3 off o Pocket (Z-Type-Two, For and Six Stressing Points = 3 off

No further input is required for the Insitu case

Figure 50: Tank Wall Detail – Insitu, Buttress Options

Figure 51: Tank Wall Detail – Insitu, Pocket (Z-Type) Options


• Precast o Buttress-Two, For and Six Stressing Points = 3 off o Pocket (Z-Type-Two, For and Six Stressing Points = 3 off

For the Precast Case, the wall panel constraints are required to be defined by user. These are • Maximum Panel Weight in Tonnes • Maximum Panel Width in metres • Wet Joint (Vertical Pour Strip) width in mm These three Wall Panel Constraints are used by PTtank to size up the panel units, making sure the panel unit meets these requirements

Figure 52: Tank Wall Detail – Precast, Buttress Options

Figure 53: Tank Wall Detail – Precast, Pocket (Z-Type) Options

Figure 54: Tank Wall Detail – Precast, Panel Limits


4.2.6.3. Tank Wall Details-PT, Reo & Wall Details This is where user the Tendons, Reo and Wall Thickness details Input Required • In Horizontal (Hoop Direction)

o Hoop Tendon Properties o Minimum Secondary Reinforcement

• Vertical o Type of Main Vertical Reinforcement o Strand o Stress Bar o Passive Reinforcement o Minimum Secondary Reinforcement

• Wall Cross Section o Thickness o If vertically stressed, the PT eccentricity

• Wall Joint Reinforcement

Figure 55: Tank Wall Detail – PT, Reinforcement and Wall Thickness, Input Window


4.2.6.3.1. Tank Wall Detail – Horizontal Prestress The Hoop Tendon: User selects the required Strand Size (Diameter) from the Drop-Down List as shown in Figure 56 PTtank return all the properties associated with this size. These are: • Strand Area (mm2) • Breaking Force (kN) • Jacking Force (kN) • Young’s Modulus (MPa) • Duct to Strand Eccentricity (e) (mm) • Mass of Strand (kg/lm) • Number of strands/Hoop

Default is 4, unless altered by user • Tendon Minimum Radius of curvature (m)

This is calculated as a function of tendon force Number of Strands/Hoop The user selects the number of strand/hoop to be used Based on the number of strands/hoop specified, PTtank returns • Duct Internal Diameter (mm) • Duct Outer Diameter (mm) Hoop Stress-Strain Properties Based on the Strand Size, PTtank returns the Strand Yield Stress (MPa) Figure 57 shows the default value returned by PTtank of 1485 MPa for 15.2Ø mm strand size This is used for the Cracked Section Analysis The user can override this value

Figure 56: Tank Wall Detail – Hoop Input

Figure 57: Tank Wall Detail – Hoop Stress-Strain Curve


Figure 59 Tank Wall Detail – PT Vertical Input

4.2.6.3.2. Tank Wall Detail - Vertical The Tank vertically can be reinforced (Main Reinforcement) in three ways. • Strand • Stress Bar

This is recommended when Wall Height is less than 6 m • Passive Reinforcement Depending on Selection, PTtank displays the appropriate Input Windows 4.2.6.3.2.1. Prestress - Strand User selects the required Strand Size (Diameter) from the Drop-Down List as shown in Figure 59 PTtank return all the properties associated with this size. These are: • Strand Area (mm2) • Breaking Force (kN) • Jacking Force (kN) • Young’s Modulus (MPa) • Mass of Strand (kg/lm) • Number of strands/Hoop

Default is 4, unless altered by user Number of Strands/Hoop The user selects the number of strand/Tendon to be used Based on the: • Number of strands/tendon specified • Strand size PTtank, using the following logic If Strand Size is 12.7Ø or 12.9Ø, returns • Slab (Mono System) Duct

o Duct Internal Diameter (mm) o Duct Outer Diameter (mm)

If Strand Size is 15.2Ø or 15.7Ø, returns • Multi System Duct to suit the number of strand

o Duct Internal Diameter (mm) o Duct Outer Diameter (mm)

The associated Wall Horizontal Cross Section, for the input of minimum secondary reinforcement, is displayed

Figure 58: Tank Wall Detail – Vertical Options

Figure 60: Tank Wall Detail – Wall Section-Mono

Figure 61: Tank Wall Detail – Wall Section-Multi


Figure 63: Tank Wall Detail – PT Vertical Input

Figure 62: Tank Wall Detail – S-Bar Vertical

4.2.6.3.2.2. Prestress – Stress Bar User selects the required Stress Bar (Diameter) from the Drop-Down List as shown in Figure 63 Stress Bar diameter range is from 15mm to 73mm PTtank returns the properties associated with this selection. These are:

• Stress Bar Area (mm2)

• Breaking Force (kN)

• Jacking Force (kN)

• Duct Internal and External Diameters (mm)

• Young’s Modulus (MPa)

• Mass (kg/lm)

The associated Wall Horizontal Cross Section, for the input of minimum secondary reinforcement, is displayed

Figure 64: Tank Wall Detail – Wall Section-Multi


Figure 67: Tank Wall Detail – Reo Vertical

4.2.6.3.2.3. Reinforcement -For Verticaly Unstressed Walls If user has selected a Non-Prestressed wall vertically, (Figure 67), then main reinforcement needs to be defined.

Main Vertical Reinforcement User selects:

• inner and outer Bar Size, in the vertical direction from the Pull-Down Lists, as shown on Figure 68 The Bar range is N10 to N40

• Inner and outer Bar Spacing PTtank calculates and:

• Suggests the maximum bar spacing and

• Displays the associated Steel Areas in (mm2/m)

Note: In the Design Phase, PTtank will display any extra reinforcement required

Figure 68: Tank Wall Detail – Main Reinforcement Input


4.2.6.3.3. Tank Wall Detail – Secondary (minimum) Reinforcement

4.2.6.3.3.1. For Verticaly Stressed Walls For Vertically Stressed walls, secondary reinforcement needs to be defined by user. PTtank, displays the appropriate Input Window There are three possible displays, but apart for the Graphics, which indicate the type of vertical PT All else is the same

User Selects the Outer and Inner Face Minimum Reinforcement from the Drop-Down Lists as shown in Figure 66. This reinforcement is: • Used over and above the PT (Strand or S-Bars) and • Applies to both directions The options are: • Mesh: SL62, Sl72, SL82, SL92, and SL102 • N-Bars: 12Ø and 16Ø If N-Bars are selected, the bar spacing must be entered. The default spacing is 200 mm PTtank, returns and displays the associated Reinforcement Area in mm2/m Note: In the Design Phase, for both directions, PTtank will display any extra reinforcement

required

Figure 65: Tank Wall Detail – Minimum Secondary Reinforcement

Figure 66: Tank Wall Detail – Minimum Secondary Reinforcement Input


4.2.6.3.3.2. For Vertically Unstressed (Reinforced) Walls Secondary (Hoop)l Reinforcement As tank is being designed with passive reinforcement in the vertical direction, Minimum hoop reinforcement needs to be defined. For vertically stressed walls this is normally Mesh, but now bars (hoops) have to be specified The Users selects the minimum hoop reinforcement, from the Pull-Down Lists as shown on Figure 66 The Bar range is N10 to N40 PTtank calculates and displays the associated Steel Areas in (mm2/m) Note: In the Design Phase, for both directions, PTtank will display any extra reinforcement

required

Figure 66: Wall Detail – Minimum Hoop Reinforcement Input


4.2.6.3.4. Tank Wall Detail – Minimum Wall Thickness PTtank, takes all the specified data and calculates a minimum Wall Thickness The wall thickness has to accommodate • Reinforcement • Horizontal Tendons (Hoops) • Vertical Tendons/Stress-Bar/Reinforcement • Minimum Face Reinforcement • Concrete covers The equation used to determine the minimum wall thickness (Tm) is PTtank displays the appropriate Wall Cross Section Dialogue Window depending on whether the wall is stressed vertically. PTtank evaluates and displays: • Minimum Dimension from outer wall face, to Hoop Duct ¢ (CoverD¢) • Minimum Wall Thickness, based on User value for CoverD¢ and hardware • Vertical Tendon Location from inner wall face (stressed vertically only) • Vertical Tendon to Wall ¢ eccentricity User can accept or overwrite the minimum recommended values If the User specified CoverD¢ is greater than the minimum calculated, PTtank warns user as seen in Figure 68.

Where: Co = Concrete Outer Cover dv =Vertical Bar diameter

If mesh then the Vertical bar diameter Hd = Horizontal Tendon Duct Diameter Vd = Vertical Tendon or Stress Bar, Duct Diameter

Figure 67: Wall Details – Stressed or Reinforced Vertically Figure 68: Warning displayed when User specified > minimum

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4.2.7. Tank Wall – Horizontal Anchor Details Depending on the anchor type specified by user, PTtank will display the appropriate dialogue input window. These are: • Buttress Geometry • Z-Type (Pocket) Geometry 4.2.7.1. Buttress Geometry Details If the Buttress Anchor Type was selected earlier, PTtank displays the input dialogue window for it PTtank evaluates and displays, • Geometrical values

o Internal Diameter o Diameter to CGS of Tendon o Outer Diameter o Buttress Face Angle

Pressing the Adopt Recommended Values Command Button places all the PTtank recommended values into the input fields. User can overwrite one or all of them Pressing the Accept Values & Analyse signals PTtank to complete the Buttress Analysis and display the results for Tendon Lengths and Angular Deviations. These values will be used by PTtank to determine the Tendon Force Profile

• Recommended Geometrical Values These values need to be confirmed by user And can be overwritten as required

o Buttress Length o Buttress Depth o Minimum Anchor Edge Distance o Jack Seating Clearance o Anchor Recess Depth o Wall to Anchor CL Distance

Figure 69: Tank Wall– Buttress Details


4.2.7.2. Z-Type (Pocket) Geometry Details

If the Z-Type Anchor was selected earlier, PTtank displays the input dialogue window for it

PTtank evaluates and displays, • Geometrical values

o Internal Diameter o Diameter to CGS of Tendon o Outer Diameter

Pressing the Accept Values & Analyse signals PTtank to complete the Z-Anchor Analysis and display the results for Tendon Lengths and Angular Deviations. These values will be used by PTtank to determine the Tendon Force Profile

Figure 70: Tank Wall– Z-Type Details

• Recommended Geometrical Values These values need to be confirmed by user And can be overwritten as required

o Pocket Height o Pocket Depth o Pocked Length


4.2.8. Tank Wall – Hoop Losses (Force Profile) Here is where PTtank evaluates the • Tendon Force Profile • Design Forces

o Maximum during stressing o Maximum at end of stressing o Minimum Effective (Long Term) Service

• Tendon Extension (After Anchoring) The Force Profile is evaluated taking into account all the Tendon Losses. These are: • Immediate Loss of Prestress due to:

o Elastic deformation of concrete o Friction along duct o Anchoring

• Time-Dependent Loss of Prestress due to: o Shrinkage of Concrete o Creep of Concrete o Tendon Relaxation

Figure 71: Tank Wall– Hoop Losses Dialogue Window


4.2.8.1. Loss of Prestress in Tendons - User Input PTtank performs the Loss Analysis using: • The loss values as defined in AS 3600-2009, Section 3.4, assuming

o For the Time-Dependent Losses Age of Concrete as (30 years x 365) 10950 days Age of concrete at time of loading as 90 days Basic Tendon Relaxation of 2.5

• Default Tendon values for o Coefficient of friction o Wobble Factor o Draw-in o Anchor Force Loss %

• Staring value for Tendon Spacing User needs to confirm these loss parameters and make sure the Tendon related values, are applicable to the Prestress System used. Special attention should be given to the Tendon Spacing (Width) Parameter used in the losses analysis. This is explained in next section.

Figure 72: Tank Wall– Hoop Loss Parameters


4.2.8.2. Loss of Prestress in Tendons – Tendon Spacing (Width) Parameter The tendon Spacing parameter (Width) is used by PTtank to evaluate the Hypothetical Thickness required in the evaluation of the losses It can be shown, that the Losses are inversely proportional to the Tendon Spacing (Width) parameter That is: What Tendon Spacing (Width) to USE The correct Tendon Spacing (Width) to be used in the loss calculations is determined iteratively. The aim is to have: Procedure 1. Run Get Force Profile with a Tendon Spacing (width) = Wall Thickness, for example 250mm

PTtank evaluates the Design Forces The Minimum Effective Force is then used to determine the number of Hoops Required

2. Run Get Required Hoops (Tendon) Examine the Hoop Spacing and note the constant Spacing value, for example 360mm

3. Run Get Force Profile with the revised Tendon Spacing (width) = Constant Hoop Spacing, in this example 360mm. PTtank re-evaluates the Design Forces

4. Repeat steps 2. 5. Repeat steps 1 to 3 until both values are the same.

This should only take a few iterations In our example the: Tendon Spacing (width) =371mm Hoop constant Spacing =371mm

The higher the tendon spacing (Width), the Lower the Losses

Figure 73: Tank Wall– Hypothetical Thickness

Tendon Spacing (Width) used in Losses = Actual Hoop Spacing


4.2.8.3. Loss of Prestress in Tendons - Results PTtank evaluates the Force Profile and Design Forces when user presses the Get Force Profile Command Button. 4.2.8.3.1. The Hoop Force Profile The Force Profile of course is slightly different for the Anchor Type used. The differences being:

• For Buttress o The Hoop Length is larger. This is due to the extra lengths required at the Buttress. o The Total Angular Deviation is greater. This is due to the reverse angular change at the

buttress o The Anchor Draw-in is larger (generally 6.0mm) o The Force Loss through the Anchor is less (normally 2.0%)

• For Z-Type o The Hoop Length is smaller (no buttress) o The Total Angular Deviation is less (no buttress reverse angular change) o The Anchor Draw-in is smaller (generally 3.5mm) o The Force Loss through the Anchor is higher.

This is made up of: The loss due to the complexity of stressing (normally 10%) . Plus the Force Loss through the Anchor (normally 2%)

The Force Profile displayed shows:

• The two out of phase Hoops profiles superimposed,

• The resulting combined Force Profiles for: o During Stressing o After Stressing o After Losses

Figure 74: Tank Wall– Hoop Force Profile


4.2.8.3.2. The Hoop Design Forces PTtank evaluates the Force Profile and Design Forces when user presses the Get Force Profile Command Button. These are the Forces PTtank will use to evaluate:

• Number of Hoops

• Analysis and design Prestress actions o During Stressing o End of Stressing o Service (Long Term)

PTtank allows user to modify these values

Figure 75: Tank Wall– Hoop Design Forces


4.2.9. Tank Wall – Number of Hoops Required PTtank evaluates the Number of Hoops required when the Get Required Hoops (Tendons) Command Button is pressed by user. The Number of Hoops required, depends on

• Tank Geometry

• Top and Bottom Wall Fixity

• Residual Prestress specified

• Maximum Cable (Hoop) Spacing specified

• Minimum Effective Tendon (Hoop) Force

Figure 75: Tank Wall– Hoops Determination


4.2.9.1. Number of Hoops – Hand Calculation A hand calculation can be used to quickly assess the number of hoops required This only applies if the Tank wall is free top and bottom, but it is a good guide The Equation for the Number of Hoops is:

Example For a Tank with: -Diameter = 40m Where: -Wall thickness = 250 mm R = 20 m -Water Height = 6m =0 kN/m2 -Water Density = 9.81 kg/m3 =6 x 9.81 =58.86 kN/m2 -Residual Prestress = 0.7 MPa =0.7x 1000 kN/m2

-Hoop Effective Force = 440 kN T = 0.25 m

Using PTtank we get the same result

Where =Number of Hoops =Hydrostatic Pressure Top =Hydrostatic Pressure Bottom

H = Water Height

T = Wall Thickness R =Tank Internal Radius

= Hoop Effective Force = Residual Prestress

Figure 76: Tank Wall– Hoops Determination, Hand Calculation Example

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4.2.9.2. Number of Hoops – Determination There is a relationship between Base Fixity and the Number of Hoops As we already know, there are three options for the Base Fixity • Free • Rubber

For Hoop determination, the Rubber condition is treated the same as Free This allows for the event of rubber failure.

• Pinned Process of determining the number of Hoops

• Determine Total Hoop Tension

• Balance the Hoop Tension with Hoop Tendons Tendon Force is of constant value, which results in the varying tendon spacing

4.2.9.2.1. Total Applied Hoop Tension PTtank evaluates

• The Hydrostatic Pressure into Hoop Tension

• The Residual Prestress specified, as Hoop Tension

• Sums the two to get the Total Hoop Stress required to be Balanced by the Hoop Tendons This is shown in Figure 78

Figure 77: Wall– Geometry, Pressures, Fixity Figure 78: Total Hoop Stress to be balanced


4.2.9.2.2. Balancing the Applied Hoop Tension PTtank starts the balancing process at the bottom of the wall. It uses the Balancing Tendon (Hoop) Force and cycles through to the top. The process PTtank applies is: 1. Evaluates the ‘area of load’ that the Tendon can carry, based on

Tendon Force (balancing) = Total Force (applied) = Force-Height Area

If Trapezoidal (can be other shapes) = (Top Force + Bottom Force) x 0.5 x d-Height

2. It then evaluates the centre of gravity of this area (location of resultant). 3. A Tendon (Hoop) is then placed at this location 4. Repeats Cycle 1 to 3, with the constraint that

d-Height must be less than the Maximum spacing specified by user As the balancing process moves up the wall the • Pressure decreases • Tendon Spacing increases up to the maximum specified

Figure 78: Force Balancing

Figure 79: Force Balancing Tabulated Results Figure 80: Hoops Required

Tendon Force=Force-Height Area


For a Pinned Wall Base there are two options, for the Hoop Determination analysis • Using the Actual Force Distribution • Using the Idealized Force Distribution Using the Actual Force Distribution The actual Applied Hoop Tension Profile is used in the balancing process to determine the number of Hoops This can be seen in Figure 82, which shows the full process graphically. The Number of Tendons (Hoops) is always less than the Idealized Option

Figure 81: Actual Option Selected

Figure 84: Pinned – Actual, Equilibrium Plot

Figure 82: Pinned Base

Figure 83: Hoops for Actual Option


Figure 85: Idealized Option Selected

Using the Idealized Force Distribution An Idealized Applied Hoop Tension Profile is used in the balancing process to determine the number of Hoops The force Profiled adopted is as shown in Figures 85 and 87 in detail. Starting at the top, PTtank determines the Maximum Hoop Tension, and then uses

this value, all the way down to the base of the wall This can be seen in Figure 87, which shows the full process graphically. The Number of Tendons (Hoops) is always more than the Actual Option, as expected. This can be seen in Figures 83 and 86 It is common practice in the industry to use the Idealized Force Profile.

Figure 87: Pinned – Actual, Equilibrium Plot Figure 86: Hoops for Idealized Option

It is common practice in the industry, to use the Idealized Force Profile


4.2.10. Tank Wall – PT Vertical This Input Dialogue Window only applies if the tank wall is vertically prestressed. For vertically reinforced walls this window will not be accessible. Here is where PTtank evaluates the • Tendon or Stress Bar, Force Profile • Design Forces • Tendon Extension (After Anchoring) The Force Profile is evaluated taking into account all the Tendon Losses. These are: • Immediate Loss of Prestress due to:



Figure 88: Vertical Prestress – Losses and Results


4.2.10.1. Loss of Prestress in Vertical Tendons - User Input PTtank performs the Loss Analysis using: • The loss values as defined in AS 3600-2009, Section 3.4, assuming



• Staring value for Tendon Spacing • Tendon Anchor types, for top and bottom of wall User needs to confirm these loss parameters and make sure the Tendon related values, are applicable to the Prestress System used.

Special attention should be given to the Width (Tendon Spacing) Parameter used. This is explained in next section.

Figure 89: Vertical Tendon Losses


4.2.10.1.1. The Width (Tendon Spacing) parameter The Width (Tendon Spacing) parameter is used by PTtank to: • Evaluate the Hypothetical Thickness required in

the calculation of the losses. • Evaluate the prestress steel for the design phase The value entered should result in an Effective (P/A) stress, of at least 1.0 MPa. This is reported in the last column in the tabulated results, shown in Figure 91.

During the Design Phase, PTtank will analyze and display • Any extra reinforcement required OR the residual (Extra) capacity User can then assess, and return to this input window and increase or decrease the Tendon Spacing as appropriate.

4.2.10.2. Loss of Prestress in Vertical Tendons - Results

PTtank evaluates the Force Profile and Design Forces when user presses the Get Force Profile Command Button. The Results are tabulated and displayed graphically, as shown in Figure 91.

Figure 90: Vertical Tendon Spacing

Figure 91: Vertical Prestress - Force Profile and Tabulated Results


4.2.11. Tank Wall –Full Details This is the final phase for Wall Input, but there is no input required by user User need to press the Determine Vertical Details Command Button, for PTtank to put all the data together and display the results. This allows user to confirm all and continue with analysis and design The Details are displayed in three windows • Tank Elevation • Wall Cross Section • Wall Plan There are 12 possible number of wall types displayed. • Precast

o Buttress Vertically Stressed

• Strand • Stress Bar

Verticality Reinforced o Pocket (Z-Type)

Vertically Stressed • Strand • Stress Bar

Verticality Reinforced • Insitu

o Buttress Vertically Stressed

• Strand • Stress Bar

Verticality Reinforced o Pocket (Z-Type)

Vertically Stressed • Strand • Stress Bar

Verticality Reinforced

Figure 92: Tank Wall – Vertical Detail


4.2.11.1. Wall Full Details Details-Vertically Stressed, Precast For Precast Walls, PTtank evaluates and reports the: • Tank Wall Plan, showing:

o Anchor Type o Vertical Main Reinforcement Type o Wall centre line Circumference o CGS of Tendon Circumference o Design Tendon Spacing o Design Strands/meter

Figure 93 shows the wall plan: o For Buttress Type o Vertically Stressed with Strand

• Panel Cross Section Details, showing:

o Maximum weight per panel used o Maximum Length used o Total number of Panels o Total number of Tendons o Stressing Panels

Number off Panel weight Panel Centre Line Width Number of Tendons per Panel Spacing of Tendons

o Typical Panels Number off Panel weight Panel Centre Line Width Number of Tendons per Panel Spacing of Tendons

o Vertical Wet Joints Number off Centre Line Width

Figure 94 shows the wall plan: o For Buttress Type

• Wall Elevation, showing:

o Wall, Fixities, Height and Thickness o Prestressed used o Tendon/Wall Eccentricity o Top and Bottom

Tendon Effective Force Prestress Eccentricity Moment

Figure 95 shows the wall Elevation The reported details are similar for the Precast Z-Type Wall

Figure 93: Precast Tank Wall

Figure 94: Precast Panels

Figure 95: Precast Wall Elevation


4.2.11.2. Wall Full Details Details-Vertically Stressed Insitu For the Insitu case, PTtank evaluates and reports the: • Tank Wall Plan, showing:

o Anchor Type o Vertical Main Reinforcement Type o Wall centre line Circumference o CGS of Tendon Circumference o Design Tendon Spacing o Design Strands/meter

Figure 96 shows the wall plan: o For Pocket (Z-Type) Anchor o Vertically Stressed with Strand

• Insitu Wall Plan, showing:

o Total Number of Vertical Tendons o Spacing of Vertical Tendons

Figure 97 shows the wall Insitu plan: o For Pocket (Z-Type) Anchor

• Wall Elevation, showing:

o Wall, Fixities, Height and Thickness o Prestressed used o Tendon/Wall Eccentricity o Top and Bottom

Tendon Effective Force Prestress Exentricity Moment

Figure 98 shows the wall Elevation The reported details are similar for the Precast Buttress Wall

Figure 96: Wall Plan

Figure 97: Precast Tank Wall

Figure 98: Insitu Wall Elevation


4.2.11.3. Wall Full Details Details-Vertically Reinforced, Precast For Tank Walls that are vertically reinforced only, (no prestress), PTtank evaluate and reports: • Tank Wall Plan, showing:

o Anchor Type o Vertical Main Reinforcement Type o Wall centre line Circumference

• Panel Cross Section Details, showing: o Maximum weight per panel used o Maximum Length used o Total number of Panels o Stressing Panels

Number off Panel weight Panel Centre Line Width

o Typical Panels Number off Panel weight Panel Centre Line Width

o Vertical Wet Joints Number off Centre Line Width

• Wall Elevation, showing: o Wall, Fixities, Height and Thickness o Inner and Outer Face Main Reinforcement

Figure 99 shows the Wall plan, Cross Section and Elevation for:

o For Pocket (Z-Type) Anchor

The reported details are similar for the Precast, Buttress Type Wall

Figure 99: Precast (Pocket) Z-Type - Vertically Reinforced only


4.2.11.4. Wall Full Details Details-Vertically Reinforced, Insitu

For Tank Walls that are vertically reinforced only, (no prestress), PTtank evaluate and reports: • Tank Wall Plan, showing:

o Anchor Type o Vertical Main Reinforcement Type o Wall centre line Circumference

• Insitu Wall Plan o Nothing extra displayed

• Wall Elevation, showing: o Wall

Fixities top and bottom Height Thickness

o Inner and Outer Face Main Reinforcement Figure 100 shows the Wall plan, Cross Section and Elevation for:

o For Buttress Type Anchor

The reported details are similar for the Insitu, Pocket (Z-Type) Wall

Figure 100: Insitu Buttress Type - Vertically Reinforced only


Figure 102: Displaying Loadings & Analysis

Command Button

Command Button Figure 103: Loadings & Analysis Display Parts

Figure 104: Analysis and Plot Command Buttons

Figure 105: Analysis Display Plots, Vertical Deflection, Moment, Shear and Axial Forces Horizontal, Moment and Hoop Tension Force

5. TANK LOADING and ANALYSIS This is where user: • Verifies the default loading values used by PTtank • Enters required loading values • Executes analysis for each Loading Case The individual loading cases can be displayed using the • Tree-View.

o Loading Tab o Required Load Case

• Menu Bar Figure 102 shows both display methods Generally for all Load Cases, the display is divided into three parts • Plotted Results • Tabulated Results • Geometry and data The analysis is performed when the associated is pressed Once analysis, for the Load Case is completed, the required plot can be viewed by pressing the associated

All Analysis Results are Tabulated and Plotted. These are: • Vertical Deflection, Moment Shear and Axial Forces • Horizontal Moment and Hoop Tension

Figure 101: Tree-View, Loading Tab

All Wall Input MUST be completed prior to activating Loading and Analysis


5.1. Loading Cases PTtank generates all required Load Cases. These are: • Gravity Loads

o Self Weight o Dead Load o Live Load

• Hydrostatic Loads o Overflow o Service

• Tendon Loading o Horizontal (Hoop)

During Stressing During Stressing Maximum During Stressing Minimum At Transfer Service

o Vertical • Temperature Loads for

o Tank Full, with Temperature drop through wall o Tank Full, with Temperature increase through wall o Tank Empty, with Temperature drop through wall o Tank Empty, with Temperature increase through wall

• Moisture Variation o Swelling o Shrinkage

• Earth (Embedded Tanks) • Earthquake

o On Water o On Soil (Embedded Tanks)

• User Defined (switched off) 5.2. Load Case Input Load Cases that require user input • Dead and Live Loads • Earth (Embedded Tanks) Load Cases that require no further user input: • Self Weight • Hydrostatic Loads Load Cases that require only confirmation of the default parameters used by PTtank: • Temperature • Moisture Variation • Tendon Loading • Earthquake Loading

o On Water o On Soil (if soil depth defined)


Do Self Weight Load Analysis

Figure 106: Wall Self Weight Load case

5.2.1. Gravity Loading Three Load Cases are part of the Gravity Loading. These are

• Self Weight

• Additional Dead Load

• Live Load The Window firstly, opens with the Self Weight showing. Using the Group Tab at the top navigates to the others

5.2.1.1. Self Weight No user input is required for the Self Weight Loading Case. PTtank evaluates the Self Weigh of the wall, based on already specified parameters. The analysis is performed when the Command Button is pressed There is only one plot applicable, the Vertical Axial Load, as shown in Figure 106


Do Dead Load Analysis

Do Live Load Analysis

Figure 108: Additional Dead Load Plot. Vertical Deflection, Moment, Shear and Axial Forces Horizontal, Moment and Hoop Tension Force

Figure 107: Dead and Live Load Input

5.2.1.2. Dead and Live Load Cases User input is required for these Load Cases Three Loads can be applied: • P1, applied vertically, at top of Wall

o User needs to input Load Magnitude • P2, applied vertically, at a distance away

from outer wall face. User needs to input: o Load Magnitude o Distance, of Load from Wall Centre Line o Distance of Load from Base

• P3, applied at an angle, at inner face of wall User needs to input: o Load Magnitude o Horizon Angle of Load o Distance of Load from Base

The Input for Dead and Live Loads are similar. • The Magnitudes are as colour coded • The Load Locations are the common The analysis is performed when, in the appropriate Tab, the associated Command Button is pressed For Dead Load and for Live Load, All Analysis Results are Tabulated and Plotted. These are: • Vertical Deflection, Moment Shear and Axial Forces • Horizontal Moment and Hoop Tension The plots can be selectively displayed:


Do Hydro (Overflow) Analysis

Do Hydro (Service) Analysis

Figure 109: Hydrostatic Loads-Predefined Data

Figure 108: Hydrostatic Overflow Loading Plots. Vertical Deflection, Moment, Shear and Axial Forces Horizontal, Moment and Hoop Tension Force

5.2.2. Hydrostatic Load Cases There is no user input required for these load cases. PTtank uses the previously specified data. There are two cases considered • Overflow, for which

The Overflow Water Height is used in the analysis

• Service, for which The Water Height is used in the analysis

The analysis is performed when, in the appropriate Tab, the associated Command Button is pressed For Overflow and for Service, All Analysis Results are Tabulated and Plotted. These are: • Vertical Deflection, Moment Shear and Axial Forces • Horizontal Moment and Hoop Tension The plots can be selectively displayed:

When a Plot is selected the associated tabulated Column is highlighted.


5.2.3. Temperature Loading

5.2.3.1. Temperature Theory The Method used by PTtank and as recommended by AS-3735, to evaluate the temperature effects are as described by: The Method in brief Temperature across the tank wall changes linearly from: • on the inside • on the outside The triangular increase in temperature is divided into two components • An average temperature change

• A differential temperature change

The effects of the two components are considered separately and summed to give total stresses

Average Temperature Change It is shown that an equivalent gas pressure will induce the same radial strains and deflections as the average temperature effect. Thus Differential Temperature Change It is shown that the total stresses induced by the differential temperature effect are obtained by • Applying End Moments MV to top and bottom of wall and analyzing • Combining induced stresses with stresses and

PTtank performs all the above in one step and tabulates/plots the results.

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M.J.N PRIESTLEY Ambient Thermal Stress in Circular Prestressed Concrete Tanks TITLE NO. 73-45 ACI JOURNAL

Hoop Tension due to Temperature = (Hoop Tension due to ) -

Total Temperature stresses = (Average + Differential) Stresses

Where = equivalent gas pressure R = tank radius

t= wall thickness = linear coefficient of thermal expansion E = concrete modulus of elasticity

Where: = Poisson’s All else as above

Where: = vertical stress = circumferential stress

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-------------- (20)


Command Button

5.2.3.1.1. AS3735 – PTtank comparison

THE AS 3735 METHOD

This Priestley approach is used by AS 3735 Supp1 – 2001, to evaluate the thermal stress This is presented in: • Appendix A • TABLE A1 to A3

User needs to obtain the tabulated thermal stress coefficients, based on: • Wall Fixity • Shape Factor • Wall Height location

Then evaluate the Average, Differential or Total thermal stress, using equation

Where = thermal wall stress C = thermal Stress coefficient (obtained from Tables A1 to A3 = mean value of modulus of elasticity of concrete at 28 days = change of temperature at point in tank = Average, Differential or Total

Then combine thermal stress with all associated Load Combinations. It is immediately obvious this is a long time consuming process

For a Typical Tank There are normally 16 Load Combinations that include the Temperature Loading If tank is divided into 20 nodes vertically There are 320 Design checks to be made

The PTtank Method • Verify Temperature Gradients • Press to analyze All done


Set AS-3735 Temperatures

Command Button

Command Button Figure 109: Temperature Loadings, Analysis and Plots

Figure 110: Temperature -30°C Plots. Vertical Deflection, Moment, Shear and Axial Forces Horizontal, Moment and Hoop Tension Force

5.2.3.2. Temperature Load Cases Confirmation of the default parameters is only required by user Four Load Cases are part of the Temperature Loading Group PTtank uses the default temperature gradients as defined in AS3735 These are:

• Tank Full, with a 20° C Temperature drop through wall • Tank Full, with a 30° C Temperature increase through wall • Tank Empty, with a 12° C Temperature drop through wall • Tank Empty, with a 20° C Temperature increase through wall User can overwrite the default temperature gradients. Defaults Temperature Gradients can be restored by pressing the Command Button For the Temperature Load Cases, the display is divided into four parts • Plotted Results • Tabulated Results • Geometry and Temperatures • Equivalent Loads The analysis is performed when the associated is pressed Once analysis, for the selected Temperature Load Case is completed, the required plot can be viewed by pressing the associated All Analysis Results are Tabulated and Plotted. These are: • Vertical Deflection, Moment Shear and Axial Forces • Horizontal Moment and Hoop Tension The plots can be selectively displayed:



5.2.4. Moisture Variation Loading 5.2.4.1. Moisture Variation Theory The Method used by PTtank is as recommended by AS-3735 The stresses caused by volumetric changes in concrete are characteristically similar to those caused by thermal effects. Shrinkage is directly analogous to an average temperature decrease, while swelling corresponds to an average temperature increase. The similarity of thermal and moisture effects means that the method of analysis developed for temperature stresses can be used for calculating moisture variation stresses The thermal equivalent is derived by dividing the shrinkage (or swelling) strain by the coefficient of thermal expansion of concrete Moisture Variation as Equivalent Pressure As shown, for thermal (average) effects, an equivalent gas pressure will induce the same radial strains and deflections as shrinkage (or swelling) effects Thus For Swelling: For Shrinkage:

-------------- (23)

Hoop Tension due to Moisture = (Hoop Tension due to ) -

Where: = equivalent swelling gas pressure = equivalent shrinkage gas pressure

R = tank radius T = wall thickness

= Mean Swelling Strain (creep adjusted) = Mean Shrinkage Strain (creep adjusted)

E = concrete modulus of elasticity

-------------- (21)

-------------- (22)


Set AS-3735 Defaults

Command Button

Command Button Figure 111: Moisture Loading, Analysis and Plots

Figure 112: Swelling Plots. Vertical Deflection, Moment, Shear and Axial Forces Horizontal, Moment and Hoop Tension Force

5.2.4.2. Moisture Variation Load Cases Confirmation of the default parameters is only required by user. Two Load Cases are part of the Moisture Variation Loading Group. PTtank evaluates mean shrinkage and swelling strains as specified by AS-3735. These are:

• Swelling • Shrinkage User can overwrite the default Strain values. Defaults Strain values can be restored by pressing the Command Button For the Moisture Variation Load Cases, the display is divided into four parts • Plotted Results • Tabulated Results • Geometry and Equivalent Pressures for

o Swelling o Shrinkage

The analysis is performed when the associated is pressed Once analysis, for the selected Load Case is completed, the required plot can be viewed by pressing the associated All Analysis Results are Tabulated and Plotted. These are: • Vertical Deflection, Moment Shear and Axial Forces • Horizontal Moment and Hoop Tension The plots can be selectively displayed:



Do Analysis

Command Button

Figure 115: Soil Plots. Vertical Deflection, Moment, Shear and Axial Forces Horizontal, Moment and Hoop Tension Force

Figure 113: Soil Loading Parameters

Figure 114: Soil Loading, Analysis and Plots

5.2.5. Earth Loading (Embedded Tanks) This Load Case is only applicable if tank is embedded. User needs to: • Confirm (overwrite) the soil

parameters: o Soil Density (g):

Default = 1800 kg/m3 o Angle of Internal Friction (φ)

Default = 30° o Active Pressure Coefficient (Ka)

PTtank evaluates Ka based on the internal angle Ka=0.333 (for φ= 30°)

• Enter Loading parameters: o Surcharge, acting on soil o Depth of Soil acting on Tank

The analysis is performed when the Command Button is pressed. Results are tabulated and Plots are viewed by pressing the associated The plots can be selectively displayed:



Figure 116: Earthquake Option Selected

5.2.6. Earthquake Loading There are two Earthquake Load Cases: • Earthquake Loading on Water • Earthquake Loading on Soil (for embedded tanks only) These Load Cases are only applicable if the √ Yes Check box is ticked in the Calculation Options, as shown in Figure 116 For both Earthquake Load Cases, PTtank calculates the equivalent static horizontal force loading. All in accordance to NZS 3106 Appendix A and AS 1170

For both, Water and Soil, the Design Parameters and resulting equivalent pressures are calculated, without user having to look up anything, except to verify (or select) the:

• Soil Class • Seismic Zone Factor • Design Life • Importance Level

All else is generated automatically The defaults used by PTtank are shown in Figure 116 Normally this process takes a long time. User needs to look up Graphs, Tables and then interpolate for the required values PTtank does this by using algorithms to represent all the Graphs and Tables used. No looking up or interpolating required User can overwrite any of the values.


Figure 117: Earthquake on Water Screen

5.2.6.1. Earthquake Loading on Water This analysis calculates the impact of the movement generated in the contained liquid due to movement of the structure (earthquake) The earthquake analysis includes the: • Inertial forces generated by the horizontal acceleration of the structure itself

The tank inertial forces are combined with fluid inertial forces. • Hydrodynamic forces generated by the horizontal acceleration of the contained liquid

The hydrodynamic pressure of the contained liquid is considered to consist of two components: o The ‘Impulsive” (inertia) pressure, caused by the portion of the liquid accelerating with the

tank. o The ‘Convective’ pressure caused by the portion of liquid oscillating on the tank.

The three equivalent pleasures are generated by PTtank and combined using the user preference. For the Earthquake on Water Screen, the display is divided into six parts. • Individual and combined pressures • Plotted Results • Tabulated Results • Combination Option • Geometry • Design Parameters • Equivalent Analysis


Figure 118: Earthquake Design Parameters

Figure 119: Earthquake Equivalent Pressures

Figure 120: Earthquake Final Equivalent Pressures

5.2.6.1.1. Equivalent Pressures PTtank evaluates all the Earthquake Design Parameters, and displays them for user confirmation This is done by pressing the Get Suggested Values command button. Figure 118 Reference is also given to the associated parameter graph or table in the relevant Code. Once user has confirmed/changed the Design Parameters, pressing the Accept Values & Get Equivalent LOADS Command button, finalizes the process. PTtank evaluates and displays the Equivalent Pressures as shown in Figure 119. Reference is also given to the associated parameter graph or table in the relevant Code.

PTtank also displays the equivalent pleasures in the combination display, and depending on the combination method chosen displays the final pressures. Again user can overwrite these values


Command Button

Do Analysis

Figure 121: Combination Options

Figure 122: Earthquake on Water Plot: Vertical Deflection, Moment, Shear and Axial Forces Horizontal, Moment and Hoop Tension Force

5.2.6.1.2. Combination of Equivalent Pressures The evaluated individual pleasures (Convective plus impulsive) are combined to give the Total Pressure Resultant The combination method can be made using the: • Root Mean Square (Recommended) • Superimposed User selects preferred option. The Root Mean Square is the Code recommended. Figure 121 The Earthquake on Water analysis is performed when the Command Button is pressed. Results are tabulated and Plots are viewed by pressing the associated These are: • Vertical Deflection, Moment Shear and Axial Forces • Horizontal Moment and Hoop Tension The plots can be selectively displayed:



Figure 123: Earthquake on Soil Screen

5.2.6.2. Earthquake Loading on Soil This Load Case only applies to Embedded Tanks PTtank uses the method outline on NZS 3106-2009, Section A2.6. The method evaluate the horizontal earthquake pressures on a rigid wall, from a horizontal inertia forces on the soil For the Earthquake on Soil Screen, the display is divided into five parts. These are: • Plotted Analysis Results • Tabulated Analysis Results • Geometry and pressures • Equivalent Analysis • Design Parameters


Figure 124: Earthquake Soil Design Parameters

Figure 125: Earthquake Soil Design Parameters

Figure 127: Earthquake on Soil Plots: Vertical Deflection, Moment, Shear and Axial Forces Horizontal, Moment and Hoop Tension Force

Command Button

Do Analysis

Figure 126: Earthquake Soil Design Pressures

5.2.6.2.1. Equivalent Pressures PTtank evaluates all the Earthquake Design Parameters, and displays them for user confirmation, as shown in Figure 124 This is done by pressing the Get Suggested Values command button. Once user has confirmed/changed the Design Parameters, pressing the Accept Values & Get Equivalent LOADS Command button, finalizes the process. PTtank evaluates and displays the Equivalent Pressures as shown in Figure 125. Reference is also given to the associated parameter graph or table in the relevant Code. PTtank also displays the equivalent pleasures in the main display. Again user can overwrite these values The Earthquake on Soil analysis is performed when the Command Button is pressed. Results are tabulated and Plots are viewed by pressing the associated All Analysis Results are Tabulated and Plotted. These are: • Vertical Deflection, Moment Shear and Axial

Forces • Horizontal Moment and Hoop Tension The plots can be selectively displayed:



Figure 128: Hoop Stressing Screen

5.2.7. Loading Due to Horizontal Stressing Confirmation of the PTtank evaluated parameters is only required by user. Four Load Cases are part of the Horizontal Stressing Loading Group. These are

• During Stressing o Maximum Positive Moment o Maximum Negative Moment

• End of Stressing (Transfer)

• Service (Long Term) The Hoop Stressing opens up as shown in Figure 128. The display shows: • Tabs for all the individual Stressing Load Cases • Tabulation of Tendons in Order of Stressing

User here can alter for each tendon (Hoop) the: o Cable Height o Cable Stressing Order o Bottom Wall Fixity when this cable is stressed

• Tabulation of Tendons in Order of Location (height) • Tendon/Wall Plot • Tendon Design Forces • Wall Properties


Figure 130: Tendons (Hoop) Heights

Figure 129: Selected Height

5.2.7.1. Cable Stressing Data 5.2.7.1.1. Cable (Hoop) Height PTtank, during the Hoop Determination Phase, evaluated the number and exact location (height) of each tendon (Hoop) The user, for whatever reason, can modify the location (height) of each Tendon This is done by selecting the cable height to be change, and ‘double clicking’ with mouse, as shown in Figure 130. The selected cable height changes colour, waiting for user input, as shown in Figure 129 After change is made, pressing Enter on key board, or mouse clicking anywhere, will register the revised value


Figure 132: Fixity during Stressing Figure 131: Tendons (Hoop) Stressing Order

5.2.7.1.2. Tendons (Hoops) Stressing Order The Tendons Stressing Sequence generally controls the design of the wall vertically, and as such makes it very important. The aim of the Stressing Order is to minimize the resulting moments in the wall. There are many permutations and combination, but economics must be taken into account. Although one can stress the tendons say first at 25% then 50% then 75% then finally to 100%, while going up and down the tank, it is obvious this is not very economic.

When defining the stressing order of each tendon (Hoop), the wall Boundary Conditions for that stressing stage needs to be defined. For a rubber or free base, there is no need, as both are free. For a Pinned (keyed) base, the base is generally allowed to move (free) during the stressing of a number of Tendons, and then pinned for the remainder of the stressing process. This reduces the induced wall moment. The Wall Boundary conditions are defined by: • Mouse selecting the fixity to change • This displays a drop down window, with all Top-Bottom fixity options • Mouse selecting the required Fixity Combination This is shown in Figure 132. User can try several stressing combinations to establish the most efficient and economic one to adopt. PTtank displays the default sequence, and allows user to change as required


Sort Tendons Using Stressing Order

Figure 133: Sorted Stressing Order

Do ALL Remainder Stressing Analysis

5.2.7.1.2.1. Default Stressing Order It has been established over many design examples, that the most efficient and economic stressing sequence, is the ‘Odds-Up-Evens-Down’ This sequence consists of in two phases. Phase 1: • Stressing from tank wall bottom to top • Stressing all the odd tendons (1-3-5-etc) as shown in Figure 131 • Boundary Conditions during this phase

o For a Pin base wall, Free Top -Free Bottom The base of the wall, although pinned (keyed) eventually, is allowed to move for this phase

o For a Rubber or Free base wall, Free Top-Free Bottom Phase 2: • Continue Stressing from top to bottom • Stressing all the even tendons coming down(- - - - 6-4-2-etc) as shown in Figure 131 • Boundary Conditions for phase 2 are

o For Pin Base wall, Free Top-Pinned Bottom The base of the wall is pinned (keyed)

o For a Rubber or Free base wall, Free Top- Free Bottom On the completion of the stressing sequence definition, pressing the command button displays the Tendons (Hoops), in ordered of stressing as shown in Figure 133 There is no more input required by user, once the stressing sequence is defined. The Stressing Analysis: The stressing analysis is completed by pressing the Command Button User can choose to perform them individually, as shown in the following pages


Stress ALL Tendons

Figure 134: Hoop Stressing Analysis

5.2.7.2. Stressing The Tendons (Hoops) The Stressing Sequence Analysis, is performed by pressing the Command Button PTtank stresses each Tendon according to the Stressing Sequence defined, and the results are Tabulated and Plotted as shown in Figure 134. This display contains a lot of information and display utilities. These include • Plotted Results • Tabulated Results • Summary of Maximum Moments • Probe • Plot Selection • Plot Mode Selection • Stage Selection • Animation


Figure 136: Hoop Stressing Summary

Figure 135: Hoop Stressing Tabulated Results

5.2.7.2.1. The Stressing Results The results tabulated (table Rows), are for • Each Node • Each Tendon location • Each stage (cable stressing) That equates to [(Nodes+1 + No. of Cables) x (No. stressing stages)] of tabulated Lines For the example shown: Nodes=21, Tendons=14, Stages=14 Number of Tabulated Lines = 490 The results tabulated (table Columns) are • Stressing Data and Geometry

o Stage Number o Node or Cable Number o Cable being stressed

• Cable Number • Wall fixity • Stressing Force % • Cable Height

o Node Height • Results for both

o Instantaneous Moment, Deflection, Shear and Hoop Stress

o Cumulative Moment, Deflection, Shear and Hoop Stress

Figure 135 shows the tabulated results 5.2.7.2.2. Moment Summary PTtank displays the maximum Moments, and associated data: • During Stressing • End of the stressing This is shown in Figure 136


Figure 136: Hoop Stressing Probe

Figure 137: Stage Selection

Figure 138: Selected Stage Results and Moment Plot

5.2.7.2.3. Probe PTtank offers a Probe facility for user to examine the results at any wall height. Figure 137 This is done by entering the: • Stage Number (Tendon being stressed) • Wall Height

The requested results are displayed by PTtank when pressing the Get Results Commend Button, as shown in Figure 137 5.2.7.2.4. Viewing individual Stages User can select to view results for a specific stressing stage. This is done by selecting the required stage from the pull down list shown in Figure 137 PTtank will tabulate and plot the results for the selected stage Figure 138 shows the Tabulated Result and Moment Plot for the selected stage 4 When a Plot is selected the associated tabulated Column is highlighted.


Figure 139: View Mode Options

Figure 140: Cumulative and Instantaneous Moments

5.2.7.2.5. View Mode PTtank allows for two viewing modes. Figure 139 • Cumulative (Totals)

When this option is selected the plot will display the cumulative results

• Instantaneous When this option is selected the plot will display the instantaneous results. This is as though only that tendon is stressed (Single Ring Load)

Figure 140, shows the Stage 4 Moments, for Cumulative and Instantaneous plots


Figure 141: Animation Plots

5.2.7.2.6. Animation The animation feature helps user visualize the stressing sequence. This is done by selecting the: • View Mode Option

o Cumulative o Instantaneous

• Plot View Option o Moment Vertical o Deflection o Shear Vertical o Hoop

Then pressing the Animate Stages Command Button In response PTtank will animate the plot, from stage one to final stage. Figure 149 shows some of the individual plots used for the Animation. Example is for a 14 stage system

STAGE 1 STAGE 3 STAGE 5 STAGE 7 STAGE 9 STAGE 11 FINAL

Instantaneous

Cumulative


Get Max+ve During Stressing

Figure 142: Stressing-Predefined Data

Figure 143: During Stressing Max +Ve Plots. Vertical Deflection, Moment, Shear and Axial Forces Horizontal, Moment and Hoop Tension Force

Figure 143: Controlling Condition

5.2.7.3. Maximums During Stressing Once Stressing is completed the resulting design actions are evaluated. This Case evaluates the Maximum Positive and Maximum Negative Moments during stressing 5.2.7.3.1. Maximum Positive There is no user input required for this load case. PTtank uses the previously specified data and stressing results. The analysis is performed when, Command Button is pressed All Analysis Results are Tabulated and Plotted. These are: • Vertical Deflection, Moment Shear and Axial

Forces • Horizontal Moment and Hoop Tension The plots can be selectively displayed:

When a Plot is selected the associated tabulated Column is highlighted. PTtank also displays a Results Summary This displays the controlling condition, as shown in Figure 143


Get Max -ve During Stressing

Figure 144: Stressing-Predefined Data

Figure 145: During Stressing- Max -Ve Plots. Vertical Deflection, Moment, Shear and Axial Forces Horizontal, Moment and Hoop Tension Force

Figure 146: Controlling Condition

Command Button

5.2.7.3.2. Maximum Negative There is no user input required for this load case. PTtank uses the previously specified data and stressing results. The analysis is performed when, Command Button is pressed All Analysis Results are Tabulated and Plotted. These are: • Vertical Deflection, Moment Shear and Axial

Forces • Horizontal Moment and Hoop Tension Results are tabulated and Plots are viewed by

pressing the associated

When a Plot is selected the associated tabulated Column is highlighted. PTtank also displays a Results Summary This displays the controlling condition, as shown in Figure 146


Do Stressing Transfer Analysis

Figure 147: Transfer-Predefined Data

Figure 148: Transfer Plots. Vertical Deflection, Moment, Shear and Axial Forces Horizontal, Moment and Hoop Tension Force

Command Button

5.2.7.4. End of Stressing (Transfer) There is no user input required for this load case. PTtank uses the previously specified data and Transfer Tendon Force. The analysis is performed when, Command Button is pressed All Analysis Results are Tabulated and Plotted. These are: • Vertical Deflection, Moment Shear and Axial

Forces • Horizontal Moment and Hoop Tension Results are tabulated and Plots are viewed by pressing the associated



Do Stressing Long Term Analysis

Figure 149: Transfer-Predefined Data

Figure 150: Stressing Service Plots. Vertical Deflection, Moment, Shear and Axial Forces Horizontal, Moment and Hoop Tension Force

Command Button

5.2.7.5. Service (Long Term) There is no user input required for this load case. PTtank uses the previously specified data and Effective Tendon Force. The analysis is performed when, Command Button is pressed All Analysis Results are Tabulated and Plotted. These are: • Vertical Deflection, Moment Shear and Axial Forces • Horizontal Moment and Hoop Tension Results are tabulated and Plots are viewed by pressing the associated



Do Stressing Long Term Analysis

Figure 151: Vertical Stressing Loads

Command Button

5.2.8. Loading Due to Vertical Stressing (if any) This load case is applicable if Yank is stressed vertically There is no user input required. PTtank uses the previously specified data and Tendon Forces. The analysis is performed when, Command Button is pressed All Analysis Results are Tabulated and Plotted. Results are tabulated and Plots are viewed by pressing the associated Normally the vertical Tendons/Stress-Bars are placed centrally in respect to wall, and as such the only induced loads are Vertical Axial Loads, as shown in Figure 151.



Figure 151: Analyse All

Figure 152: Analyse All Missing Input

Figure 153: Analyse All Completed Input

6. ANALYSIS RESULTS (Combinations) The Analysis of all the individual Load Cases must be completed before entering the Design Phase 6.1. Analyse All The Analysis can of all the Load Cases can be done in two ways • Individually, as described on Section 5, of this manual. • Using the Analyse All in the drop down menu, in the Menu Bar, as shown in Figure 152

PTtank will analyze all, except where input is required by user. These are o Dead and Live Loads o Earth Loading. If for these two cases, the input has being completed, Analyse All will include them as well

PTtank displays the Load Cases that have been analysed. Figure 152, shows the analysis status, after Analyse All has been executed. As shown the Analysis for: • Earth Loading • Earthquake Loading has not being done, as the soil depth was not defined. Entering the soil depth (if applicable), and executing the Analyse All, includes the two missing load cases, as shown in Figure 153.


Where: D = the Dead Load P = the force in the tendons T = Temperature, or

= the load due to temperature variation Flp = the liquid pressure load Fep = the earth pressure load

Feq = the earthquake action Fsh = the loads resulting from shrinkage

Figure 154: Load Combinations

6.2. Load Combinations PTtank automatically generates all Load Combinations required for the design phase. This is all in accordance to AS 3735, Section 2.4. These Generic Combinations are: • Long-term effects (Group A)

o Tank Full: G + Flp + Fep + P + 0.5Fsw o Tank Empty: G + Fep + P + (Fsh or 0.5Fsw)

• Short-term effects (Group B) o Tank Full: G + Flp + Fep + P + 0.8Feq + 0.5Fsw o Tank Empty: G + Flp + Fep + P + 0.7Fsw + T o Tank Empty: G + Fep + P + T + (0.7Fsh or 0.35Fsw)

For both Groups A and B, if a worse effect is obtained by the omission of one or more of the transient loads , then such effects are taken into account. 6.2.1. Load Combination Required There are 40 Combinations (including a User Defined one) required to cover all possibilities. PTtank generates and displays them in tabular form, together with the associated Load Factors.

User can modify the load factors as required. Pressing the Command Button restores the default Load Factors.


Figure 155: Load Combinations and Factors

Figure 156: Factored Load Combinations – Combination 3

6.2.2. Individual Load Combinations PTtank automatically, generates each individual Load Combination, based on the default Load Factors The combinations are displayed sequentially using a Tab Bar, as shown in Figure 155

On top of each Load Case Tab, the associated factored Load Case is displayed. Figure 156 shows Factored Load Combination 3

If a load factor is changed by user, the generated individual Load Combinations need to be regenerated. The Individual Load Combinations are generated by pressing the Command Button.


Figure 159: Summation of Analysis Results (No RFs)

Figure 157: Without Reductions Button

Figure 158: With Reductions Button

Figure 160: Summation of Analysis Results (With RFs)

6.3. Combination of Analysis Results

PTtank has generated the templates for all the combinations. The analysis results need to be factored and combined accordingly. There are two combination options • Without using the Temperature and Moisture

Reduction Factors (RF). Compulsory This option needs to be activated first, as it evaluates the prerequisites for the ‘With’ option

• Using the Temperature and Moisture Reduction Factors (RF). Optional. User can choose to bypass this combination, which will result in a heavier design. PTtank will use the full Temperature and Moisture effects during the design phase. This option can only be activated once the No-Reduction action is completed.

6.3.1. Combination of Analysis Results – No Reduction Factors

PTtank generates the analysis results, without the Temperature and Moisture Reduction Factors. (Refer Section 4.2.3.1 of this Manual) when the Command Button is pressed As seen, in Figure 159, this is the only Command Button initially available to the user. This Action, using No Temperature and Moisture Reduction Factors, (Refer Section 4.2.3.1 of this Manual): • Populates all the individual Combinations (40 off) with:

o The analysed results: Moments, Shears, Deflections and Hoop Forces

o Resulting outer, inner and residual wall stresses • Reproduces the Limiting Concrete Stresses of AS 3735-2001 Table 3.6.

o Highlights the applicable Limiting Stresses for the displayed combination • Makes available plots of all the above, which can be selectively displayed Figure 158 shows the above for Load Case Combination 03.

6.3.2. Combination of Analysis Results – With Reduction Factors

PTtank generates the analysis results, using the Temperature and Moisture Reduction Factors. (Refer Section 4.2.3.1 of this Manual) when the Command Button is pressed As seen, in Figure 160, this Command Button is only enabled, after the No-Reduction action is completed.


Figure 161: Specified RFs

Figure 162: Analysis Results for Load Combination 04

6.3.3. The Temperature and Moisture Reduction Factor (RF)

The reduction factors used in the summations are, as defined by user in the Calculation Options. The user specified RFs are displayed in the summary screen, as shown in Figure 161 In the example shown in Figure 161, user has instructed PTtank: • If evaluated RFs are les then 0.35 to use 0.35

For example: Temperature Moment =100 Calculated RF = 0.15 User Specified RF(min) = 0.35 Reduced Temperature Moment = 100 x 0.35

= 35 (and not the calculated 15) • To use the same RFs for Moisture effects 6.4. Analysis Results (Combinations)

PTtank, for each combination tabulates and plots the analysis results. The parts of the display are: • Selected Plot • Plot Selection • Temperature and Moisture Reduction Factor used • Tabulated Analysis Results • Limiting Stress Table with:

o applicable condition highlighted


Figure 163: Selecting Plot Menu Buttons

Figure 164: Load Combination Plots

6.4.1. Analysis Results-Plots

For each combination, pressing the required plot Command Button will display the associated plot

The Plots as shown in Figure 163 are: • Combination Actions

o Vertical Deflection, Moment Shear and Axial Forces o Horizontal Moment and Hoop Tension

• Wall Stresses

Figure 164, Shows a Sample of the Plots for a Load Combination 11



Figure 165: Applied factored Loads for Load Combination 04

6.4.2. Load Combination (Applied Loads)

In a Load Combination Window, pressing the Button displays (hides) the factored summation of the Applied Loads Pressing the The applied loads exclude the Post Tensioning effects. Figure 165 shows the applied loads window for Load Combination 04


Figure 166: Calculation Options – Cross Section Criterion

Figure 167: The Specified Criterion

Figure 168: Stress Comparison

6.4.3. Analysis Results-Cross Section Transformation

PTtank allows user to select Criterion to be used when evaluating the concrete working stresses. Refer Section 4.2.3.2 on this Manual.

The options are: • Untransformed

o Stresses are evaluated using the Gross concrete cross section properties • Transformed

o Stresses are evaluated using the Transformed concrete cross section properties

The specified criterion is displayed in the Results Summary, as shown in Figure 167

Using the Transformed Criterion, results in slightly lower wall stresses. This can be seen in Figure 168, in which the two options are compared for the same analysis.

Untransformed Max Stress Transformed Max Stress 3.787 MPa 3.763 MPa


Figure 166: Analysis Controlling Results

Figure 167: Displaying Controlling Load Combination

6.4.4. Analysis Results Summary

PTtank performs all the combinations and displays a Summary of the: • Maximum Vertical and Horizontal Moments • Associated Location of Moment, Node number and controlling Combination User does not have to hunt through the 40 Load Cases, for the controlling conditions. They are summarized and displayed as shown in Figure 166

To quickly view a controlling case, user can mouse clicks at the load case field and the associates screen is displayed. Figure 167 shown the display of controlling combination 14


Figure 168: Design Summary and Tabulated Results

7. DESIGN OF TANK WALL The Design Phase follows the Summation Phase Once ether of the summation activities have been completed, pressing the Command Button, PTtank Designs the Tank Wall PTtank, performs a Cracked Section Design for • All Load Combinations • For each and every node And • Displays a Summery and controlling condition • Tabulates the Design Results on all Load Combinations All Load Combinations Tabulations have now being completed with: • Design Results • Analysis Results This is seen in Figure 168


Figure 169: Cross Section Analysis Display

7.1. Cross Section Analysis

PTtank performs a Cracked Section Analysis for each node for each load case, in both vertical and horizontal directions. This equates to a total of 1,680 checks (for a 20 node Tank. Each check can be vied as shown in Figure 169 The Cross Section Procedure is as per AS 3735-2001 Section 3.3.5 Partial Prestressing • Evaluate the section Working Flexural Capacity based on

o Limiting Stresses for the passive reinforcement o Allowable Tendon Stress Increase after decompression

• Tabulates the Capacity • Adds passive reinforcement if capacity is less then applied, and ensures that Capacity is equal

to Applied. • Tabulates the extra reinforcement required (if any) The Display of the Section Analysis, as shown in Figure 169, shows • Load Case, Location and Direction of Check • Geometry, Material and Applied Loads • Section Properties and Capacity (Ultimate and Working) • Added Reinforcement (if require)


Figure 170: Cross Section Analysis Summary

Figure 171: Condoling Combination and Results

7.2. Cross Section Analysis Summary

PTtank performs the Cracked Section Analysis and displays a Summary of the: • Extra (Vertical and Horizontal) Reinforcement added

o Associated Location of Check, Node number and controlling Combination • Minimum residual Capacity

o Associated Location of Check, Node number and controlling Combination This is useful in it tells user ‘how easy’ the Tank Wall is working

User does not have to hunt through the 40 Load Cases, for the controlling conditions. They are summarized and displayed as shown in Figure 170 To quickly view the controlling case, user can mouse clicks at the load case field, and the associates screen is displayed. Figure 171 shown the display of controlling combination 12, and the added reinforcement


Figure 172: Cross Section Display - Summary

7.3. Cross Section Analysis Display

User can View or Print any or all of the 1,600 (for a 20 node Tank) Section Checks There are three different methods 7.3.1. Using The Summary

To quickly view the Section Check for the Maximum Reinforcement Added, user can mouse clicks at the Field containing the added reinforcement field, and the associates Section Check is displayed

User can Print/Preview the displayed Cross Section Check Report by pressing the Preview Print Command Button


Figure 173: Cross Section Display - Tree View

7.3.2. Using The Tree View - Reporting

To quickly view the Section Check for the Maximum Reinforcement Added, user can use: • The Results Tree View • Selecting only the required item • Selecting Print/View Report from Drop Down

Menu This will bring up the associated Cross Section Report as shown in Figure 173


Figure 174: Cross Section Display -Tabulated Results Tree View

7.3.3. Using The Tabulated Results

Clicking the right mouse button over any cell in the: • Horizontal Capacity or Reo Added Table Columns • Vertical Capacity or Reo Added Table Columns Will display the Section Analysis Results for that cell As shown in Figure 174 User can Print/Preview the displayed Cross Section Check Report by pressing the Preview Print Command Button


Figure 175: Print/Plot Command Button

Figure 176: Report for Selected Combination

7.4. Load Combination Print/Plot Utility

PTtank allows user to Print/Plot any Load combination.

The visible Load Combination number is displayed within the in the Print/Plot Command Button. As shown in Figure 175 Pressing this command buttons generates the report for the associated Load Combination

The Report generated as shown in Figure 176 consists of the • Analysis Results • Analysis Plots • Design Results User has a choice to View or Print the Load Combination Report


Figure 178: Ring Footing – Without Recess Figure 179: Ring Footing – With Recess

8. RING FOOTING PTtank Analyses and designs the Ring Footing Beam Two types of Footings are catered for, as seen in Figure 178 and 179. • Without Recess (key) for tanks with Free or Rubber type base • With Recess (key) for a Pinned type base

The first step on the Analysis and Design process is to update the analysis data. This is done by pressing the Get Analysis Data Command Button 8.1. Ring Footing Size

The Ring Footing size is determined using • Applied Loads

o Gravity Loads applied at wall centre line o Vertical Earth Pressure (if any) o Vertical Water Pressure o Ring Shear (if any)

• Allowable Soil Pressure PTtank iterates thought and ensures that the: • Resultant Applied Force is within the footing middle third • Allowable pleasure is not exceeded • Moment Capacity at Wall Face location, is satisfied • Shear Capacity at ( Wall Face + 0.5Effective depth) location is satisfied


Figure 180: Base Shear Options

Figure 180: Base Shear distribution

Figure 181: Base Shear to be carried by Slab

8.2. Design Base Shear

This is only applicable for Pinned (keyed) Ring Footing Beams PTtank displays the Maximum Base Shears as determined from analysis. The user is given the choice to choose which to design for. The maximum values give as seen in Figure 180, are for: • Controlling combination, without temperature

and moisture (RF) reductions. This is Conservative.

• Controlling combination, with temperature and moisture (RF) reductions

• Hydrostatic Overflow loading only. PTtank displays the Hydrostatic Overflow, as the default Design Shear to be used. User can overwrite this. PTtank allows for the Design Shear to be distributed (shared), as shown in Figure 181, between the: • Hoop Footing Tendons • Slab Tendons The PTtank default, is for the Ring Hoop Tendons to carry the full amount The Base shear allocated to the Slab Tendons, will be designed for and carried by the tank slab. Displayed in Figure 181, is the Slab Input, showing an allocated base shear portion of 25.0 kN/m to be designed for and carried by slab


Figure 182: Design Status - Final Figure 183: Design Status - Preliminary

8.3. Ring Footing Design

Minimum input is required by user for the Footing Design. The user inputs are: • Maximum allowable bearing pressure • Base design shear to be carried by Hoop Tendons (keyed footings only) • For a Prestressed Ring Footing

o Minimum Residual Prestress in footing (optional) o The strand size

The analysis and design process is activated by pressing the Command Button. PTtank iterates through and displays the: • Minimum Footing Size

o User can overwrite dimensions • Final Design, if no Hoops are required • Preliminary Design if Hoops are required

This is an interactive procedure as PTtank has to: o Makes and assumption at the Hoop Effective Force o Evaluates the number of Hoops required, base on the assumption o Iterates through until assumed and actual values are the same

The design status is displayed as shown in Figure xxx.


Figure 184: No-Hoops Design

Figure 183: Analysis and Design Results

Figure 185: Reinforcement Cross Section

8.3.1. Ring Footing Design – Reinforcement Only

For a reinforced only footing, PTtank finalizes the design once the Command Button is activated. The analysis and design results are displayed, as shown on Figure 123 These are: • Footing Geometry • Maximum and minimum Bearing Stresses • Maximum Applied Moment at Wall Face • Moment Capacity • Maximum Applied Shear • Shear Capacity • Recommended Reinforcement

o Longitudinal Top and Bottom Bars o Transverse (Ligatures)

• Footing Cross Section showing the recommended reinforcement

• Design Status as Final User may change the footing geometry and repeat process


Figure 189: Preliminary Hoops Design

Figure 186: Analysis and Design Results

Figure 187: Reinforcement Details

Figure 188: Preliminary Hoop Details

8.3.2. Ring Footing Design - Prestressed For a Prestressed Footing the design is more complex. The first step of the process is to update the analysis data. This is done by pressing the Get Analysis Data Command Button. 8.3.2.1. Preliminary Design The Analysis and Design is commenced by pressing the Command Button PTtank evaluates and displays the • Analysis and Design Results

o Footing Geometry o Maximum and minimum Bearing Stresses o Maximum Applied Moment at Wall Face o Moment Capacity o Maximum Applied Shear o Shear Capacity

As shown in Figure 186 • Recommended Reinforcement

o Longitudinal Top and Bottom Bars o Transverse (Ligatures)

• Footing Cross Section showing the recommended reinforcement

As Shown in Figure 187 • Preliminary Hoop Details As Shown in Figure 188 • Design Status as Prelim


Figure 190: Footing Beam – Buttress Details

8.3.2.2. Completing Hoop Tendons Design Once the Preliminary Design has been completed, the next phase is activated by pressing the (now enabled) Command Button. PTtank takes User to the Buttress Geometry Input Window, as shown in Figure 190. Her Use can: • View Default Geometric Values

o Internal and External Footing Diameters o Diameter to CGS of Tendon o Buttress Angle

• Conform/Modify the assumed Prestress Data o Strand Properties and Stressing Forces

• Confirm/Modify Stressing Arrangement • Accept/Modify Recommended Buttress Geometry If User modifies any of the above data, PTtank will recommence the Analysis and Design process by going back to Preliminary Analysis and Design Pressing the Adopt Recommended Values Command Button places all the PTtank recommended values into the input fields. User can overwrite one or all of them Pressing the Accept Values & Analyse signals PTtank to complete the Buttress Analysis and display the results for Tendon Lengths and Angular Deviations. These values will be used by PTtank to determine the Tendon Force Profile


Figure 191: Footing Beam – Hoop Losses Dialogue Window

8.3.2.3. Buttress Hoop Losses Here is where PTtank evaluates the • Tendon Force Profile • Design Forces

o Maximum during stressing o Maximum at end of stressing o Minimum Effective (Long Term) Service

• Tendon Extension (After Anchoring) The Force Profile is evaluated taking into account all the Tendon Losses. These are: • Immediate Loss of Prestress due to:




Figure 192: Footing Beam – Hoop Design Forces

Figure 192: Footing Beam – Hoop Force Profile

8.3.2.4. Buttress Hoop Losses –User Input PTtank performs the Loss Analysis using: • The loss values as defined in AS 3600-2009, Section 3.4, assuming



User needs to confirm these loss parameters and make sure the Tendon related values, are applicable to the Prestress System used. PTtank evaluates the Force Profile and Design Forces, when user presses the Get Force Profile Command Button. The Design Forces as shown in Figure 193 will be used by PTtank to evaluate the number of Hoops required. The Force Profile can be vied by going to the Force Profile Tab, as shown in Figure 193


Figure 193: Repeating Cycle Notification

Figure 194: Final Hoops Design

Figure 193: Final Design Results

Figure 195: Final Hoops Tendons

PTtank completes the Preliminary Design cycle when the Command Button is pressed PTtank compares the Number of Strands Required to the Number assumed and: • If required, equals estimated (assumed) number, the Design is completed • If required is not equal to estimated (assumed) number, the user is notified. • PTtank cycles through processes until the two values are equal.

PTtank displays: • The completed Hoop Design • Updates the Design Status to Final. This

is shown in Figure 194 • The recommended Hoop Tendons, as

shown in Figure 195 In example the Estimated were 2/10s The Final are 2/9s


Figure 196: The PTsog Program

9. TANK SLAB 9.1. The Slab-On-Grade Design Module

The Slab-On-Grade (SOG) Design module used by PTtank is part of the commercially available PTsog software. The PTsog program is written by the same Author (Steven S Gikas) as PTtank. PTsog Designs Post-Tensioned and Reinforced: • Warehouse Slabs-On-Grade • Industrial Pavements • Container Pavements • Airport Pavements For further information contact Steven S Gikas & Associates


9.2. Slab-On-Grade (SOG) Theory

Three design criteria for prestressed SOG are normally considered Criterion 1 The effect of o Loads (post, wheel) o Subgrade reaction o Subgrade friction o Temperature o Shrinkage o Creep Are all considered and sufficient prestress is applied to keep the concrete tensile stresses to the allowable limit. The relationship for a safe performance is as follows Criterion 2 A minimum residual compression level, in the concrete is maintained after all losses. Criterion 3 Fatigue strength, or strength under repetitive loading is satisfied Strength under repetitive loading is measured in terms of Stress Ratio (SR). The Stress Ratio is a measure of net working tensile stress to the net cracking stress The allowable Stress Ratio ( ) is defined as The Stress Ratio calculated (Equation 26) must be equal or less than the allowable (Equation 27)

It should be noted that, the inverse of the SR is equal to the Safety Factor

-------------- (27)

-------------- (25)

-------------- (26)

Where: = Concrete Flexural Strength = effective prestress at the slab critical point

= temperature gradient stress = Subgrade friction at slab critical point = Load tensile stress at slab critical point

N = Life Load Repetitions

-------------- (24)


Figure 197: Slab Design Dialogue Window

9.3. Slab Design – Dialogue Window

The Slab Design Dialogue Window is displayed as shown in Figure 197. Dialogue Window is divided into several Parts. These are: • Input

o Geometry and Subgrade o Slab Material Properties (Tab 1) o Tendon Losses (Tab 2) o Loading (Tab 3) o Loading Analysis Results (Tab 4) o Edge Bars and Utilities (Tab 5)

• Design o Results o Plots o Tendon Selection

Normally the PTtank generated defaults are acceptable. To complete design all user has to do is

press the and Command buttons and

the design is completed.


Figure 198: Slab Ends – Without Recess

Figure 199: Slab Ends – With Recess

9.4. Slab Design – User Input User needs to confirm/amend the PTtank generated defaults. 9.4.1. Geometry, Subgrade and Prestress Level PTtank has carried from the Footing Design, the slab edge geometry. There are two types of Slab Ends. • Without Recess (key) for tanks with Free or Rubber type base. As shown in Figure 198 • With Recess (key) for a Pinned type base. As Shown in Figure 199

User needs to confirm the: • Geometry • Anchor centre line depth, from top of edge (Default is mid edge depth) • Slab thickness (default 130mm)

There is a practical minimum to the thickness of a prestressed slab on grade, which depends on the size of the prestressing hardware to be used. Given that generally the anchorages are cast into the edge thickening, 130 mm is normally considered to be the minimum achievable slab thickness

• Minimum Residual Prestress (Default 1.000 MPa) The level of residual prestress at mid-length of the slab, after all losses (including Subgrade friction) is normally proportioned to be not less than 1.0 MPa

• Subgrade Friction Coefficient (Default 0.40 ) The most practical method of base treatment is to use two layers of Polythene membrane on 25mm of sand. A coefficient of 0.4 is generally adopted for this case.

• Subgrade Modulus (Default 25.00 KPa/mm equivalent to a CBR of 3%) Generally the Subgrade Modulus or California Bearing Ratio (CBR), is obtained from the Geotechnical Engineer


Figure 200: Slab Design – Material Properties

Figure 201: Slab Design – Predefined Properties

9.4.2. Slab Material Properties PTtank displays default values for all material properties, as shown in Figure 200.

User needs to confirm/amend the: • Tendon Properties • Concrete Predefined Properties

These are defined in the Tank Material Properties. (Manual Section 4.2.4) • Concrete Flexural Strength

The Flexural Strength Criterion is defined in the Tank Material Properties. (Section 4.2.4) Here user can overwrite the value if a special concrete mix is used

• Flexural Strength Age Factor (Default 1.10) This is the Concrete Flexural Strength that PTtank uses to design the Slab. It should be the value at time of tank slab loading, which normally is taken as 90 days


Figure 202: Slab Design – Tendon Losses

9.4.3. Tendon Losses Here is where PTtank evaluates the Slab: • Tendon Force Profile • Tendon Extension (After Anchoring) The Force Profile is evaluated taking into account all the Tendon Losses, which are: • Immediate Loss of Prestress due to:



PTtank performs the Loss Analysis using: • The loss values as defined in AS 3600-2009, Section 3.4, assuming



User needs to confirm these loss parameters and make sure the Tendon related values, are applicable to the Prestress System used.


Figure 203: Tank Slab Loading

9.4.4. Tank Slab Loading Generally, User does not have to visit the Loading Tab, unless special extra loading needs to be applied. Applied Loads can be: • Post, Wheel or UDL

These are added in the form of Moments kNm/m Also required are the associated values for: o Stress Fatigue Ratios

This is evaluated from the Total (Life) Load Repetitions Default Values: Post 1 for No Repetitions Wheel 0.5 for Unlimited Repetitions UDL 0.75 for 580 Repetitions PTtank evaluates the Fatigue Factor based on the user selected Life Load Repetitions

o Material Safety Factors Reference: Cement and Concrete Association of Australia

Industrial Pavements • Temperature Gradient (Default 0.02 °C/mm for tension bottom)

Uniform temperature changes produce stresses, only because of frictional restraint. As a result of temperature gradient within the slab, the slab tends to warp, thereby resulting in longitudinal and transverse stresses. Common Values for industrial floors are: o For Internal Environments 0.02 °C/mm o For External Environments 0.04 °C/mm

• Tank Ring Tension to be carried by Tank Slab PTtank has carried the Ring Tension value from the Footing Design. User my amend this value


Figure 204: Slab Design – Strands required and Used

9.5. The Slab Design PTtank designs the slab, satisfying the three criteria described in Section 9.2 of this Manual. The design of the Tank slab is in two steps. These are: • Determining The Minimum Number of Strands required • Completing Design, using the determined strand or the user modified number of strands 9.5.1. Determining Number of Strands PTtank evaluates and displays the minimum required number of strands when user presses the Command Button, The required number of strand is displayed as shown in figure 204, and the user has the option to: • Accept and continue with finalizing design • Increase number and finalize design

9.5.2. Complete Design using Number of Strands PTtank completes the Slab Design, using the Strands to be Used value, when user presses the Command Button Note: The COMPLETE DESIGN Command button contains the number of strands used 9.5.3. Slab Design Results On completion of the Slab Design, PTtank displays and plots: • Analysis Results at each critical section, in Tabulated Form • Tendon/Subgrade Stress Profile Plot • Slab Edge Movements • Tendon Design Options


Figure 205: Slab Design – Analysis Results

Figure 206: Slab Design – Tendon/Subgrade Friction Stress Vs Slab Length

9.5.3.1. Slab Design – Analysis Results PTtank Tabulates the Controlling Location and condition as shown in Figure 205 Figure 205 shows: • The Controlling Criterion (Residual Prestress in this example) • Critical Location (At Slab mid-length for this example) This is expected as there is no Post, or Wheel loads

9.5.3.2. Slab Design – Tendon/Subgrade Friction Plot PTtank plots as shown in Figure 206, the: • Tendon and Subgrade Friction Stress as a function of Slab Length • Values at all critical points • Tendon Extension (After Anchoring)


Figure 207: Slab Design – Edge Movements

Figure 208: Slab Design – Tendon Figure 209: Slab Design – Tendon

9.5.3.3. Slab Design – Edge Movement PTtank evaluates and displays as shown in Figure 207, the Movement of the Slab Ends The Movements are: • Elastic • Temperature • Total The movements are particularly important, for pavement design, in the design of • Movement Joints • Dowels 9.5.3.4. Slab Design – Tendons PTtank displays the Tendon Design options, for user to select, as shown in Figures 208 and 209 The options are based on • Strand Properties defined by user • The number of strand used in the design

The Figures, for the same design, show: • Figure 208

o Options for 12.7 Ø mm Strand System o The user preferred as 3/12.7Ø/1.803m o The associated Duct Size as 19x14mm

• Figure 209 o Options for 12.7 Ø mm Strand System o The user preferred as 3/12.7Ø/1.803m o The associated Duct Size as 19x14mm


Figure 210: Tank Quantities

Figure 211: Tank Quantities - Defaults

10. QUANTITIES PTtank evaluates the Quantities, once the design has been completed The Quantities Window is displayed, as shown in Figure 210, using the: • Tree View (Results Tab) • Menu Bar

The Defaults used in evaluating the various quantities are displayed for user confirmation, as shown in Figure 211

Once Defaults are confirmed by user, pressing the Evaluate Command Button completes the task, and all Quantities are displayed, as shown in Figure 211.


Figure 214: Tree View

Figure 213: Report Tab

Figure 212: Group Options

Figure 215: Group Only Figure 216: Part of Group Figure 215: Full Report

11. REPORTS PTtank provides a range selection options to help user create professional printouts and reports 11.1. Generating Reports

The Report content selection is made using the Tree View, Report Tab, as shown in Figure 213 and 214. There are Three Grouped Report Options, as shown in Figure 212 • Input

Only the Input is included in the report • Analysis • Results User can choose to select • Individual Groups Only

o The entire Group (Figure 215) o Part of the Group (Figure 216)

• All three, for a Full Report (Figure 217)


Figure 216: Generating the Report

Figure 217: The Generated Report

11.2. Viewing and Printing Reports

The requested report is generated using the Menu Bar, as shown in Figure 216 Activating this Menu Command generates the report and displays it for user viewing and printing. The first page of the report is always the Title Page, as seen in Figure 217. The Print Preview Window contains: • Action Buttons for (top):

o Navigating through Report o Zooming o Printing

• Status Bar (bottom) showing: o Current page number o Total page numbers o Date and time


Figure 218: Print Preview – Menu Bar

Figure 219: Report Print Setup

The Report is printed by pressing, from the Menu Bar the Command Button

This action brings up the Print Setup Window, as shown in Figure 219, where user can make the required print selections


Figure 220: Generating Drawing

Figure 221: Drawing Data

12. DRAWING PTtank, on completion of Design generates an A3 size drawing in PDF format The drawing is generated using the Menu Bar, as shown in Figure 220 This action brings up the Drawing Data Window, as shown in Figure 221 This is where user enters the • Details to be appear in the drawing title:

o Project o Title o Drawing Number o Issue Number o Designer’s Name

• User Notes o Five Lines of notes that will be displayed in the drawing


Figure 222: The Displayed Drawing

12.1. Generating The Drawing

PTtank generates and displays the drawing when the Command Button is pressed (Figure 221) The generated drawing is Not To Scale (NTS) The Drawing, as shown in Figure 222, contains • General Notes • The User Notes • All the Tank details required for tender pricing and issue

The Print Preview Window contains: • Action Buttons for (top):

o Zooming o Printing

• Status Bar (bottom) showing: o Current / Total page numbers o Date and time


Figure 223: Print Preview – Print Command Button

Figure 224: Drawing Print Setup

12.2. Printing the Drawing

The Drawing is printed by pressing, from the Menu Bar the Command Button

This action brings up the Print Setup Window, as shown in Figure 219, where user can make the required print selections


13. FUTURE DEVELOPMENT The program will be developed to Analyse and Design: Fully Reinforced Tanks

To other Codes and Standards

Documents

PTtank-Manual.docx Page 1 · PTtank-Manual.docx Page 5 PTtank Program – Analysis and Design of Post-Tensioned Tanks 1. INTRODUCTION PTtank is a Windows standalone program that analyses