Federal Electricity & Water Authority Water Directorate ... Tech... · condition of dead load, live load, ... For inaccessible roofs only 1 kN/m2 shall be ... vibrations of foundation

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Client: FEDERAL ELECTRICITY AND WATER AUTHORITY (FEWA) Project: STANDARD SPECIFICATIONS FOR WATER WORKS

Engineer WATER DIRECTORATE - ASSET MANAGEMENT DEPARTMENT

Title: Technical Terms / Chapter-4 / Engineering Specifications / Civil Engineering Works Specification

CS06-GENERAL REQUIRMENTS FOR CIVIL/STRUCTURAL WORKS

Office:

DUBAI Order: Document: MWA_PRO_07/WAM-04-CS06 Rev: OCT/2014 sheet: 1 of: 17

Federal Electricity & Water Authority

Water Directorate

Asset Management Department

STANDARD SPECIFICATIONS

FOR WATER WORKS

TECHNICAL TERMS

Chapter – 4

Engineering Specifications

[C-Civil Engineering Works Specifications]

CS06-General Requirements for Civil/Structural Works

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Office: DUBAI Order: Document: MWA_PRO_07/WAM-04-CS06 Rev: OCT/2014 sheet: 2 of: 17


TABLE OF CONTENT

1. GENERAL

2. DESIGN

2.1 Architectural Design

2.2 Structural Design

3. LOADINGS

3.1 Imposed Loads

3.2 Dynamic Loads

3.2.1 Static Deformation

3.2.2 Dynamic Analysis

3.2.3 Existing Force

3.2.4 Schematic Mechanical Model

3.2.5 Additional Requirements

3.3 Crane Loads

3.4 Thermal Effects

3.4.1 Thermal Loads

3.4.2 Thermo-Mechanical Forces and Stresses

3.5 Loads During Erection and Maintenance

3.6 Piping Loads

4. BEARING PRESSURES

5. DESIGN LEVELS

6. METEOROLOGICAL AND AMBIENT CONDITIONS

7. WATER TIGHTNESS

8. FOUNDATIONS

8.1 General

8.2 Calculations

8.3 Factors of Safety

8.4 Settlements

8.5 Foundation Bolts

8.5.1 Grouting Below Base Plates

8.6 Reinforcement in Concrete Upstand Over Floor

8.6.1 Particular Requirements

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9. STRUCTURAL STEEL DESIGN REQUIREMENTS

9.1 Type Of Construction And Bracing

9.2 Minimum Sizes Of Structural Members/Components

9.3 Definition of Loads In Various Conditions Of Application

9.3.1 Dead loads

9.3.1.1 Dead load Conditions

9.3.1.2 Weights of Building Materials

9.3.1.3 Equipment Weights

9.3.1.4 Additional Forces from Equipment/Piping

9.3.1.5 Electrical and Instrument Loads on Structures and Piperacks.

9.3.2 Imposed Loading

9.3.3 Contingency

9.4 Load Combinations

9.5 Load Factors For Limit State Design

9.6 Material Strength

9.7 Deflections

9.8 Miscellaneous Loading

9.9 Pre-Engineered Buildings

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1. GENERAL

Unless specifically mentioned hereafter, any work or supply of material shall be subjected to the compliance of internationally recognized Standards or Codes, such as BSI, ASTM, DIN or approved equivalent.

The Specifications of the CIRIA Guide to concrete construction in the Gulf/GCC region are also applicable.

2. DESIGN

All designs and details must be prepared to comply with the best Engineering practice, the appropriate Standards and Codes of Practice and the requirements of this Specification.

The Specification gives the minimum acceptable Standards for the design, workmanship and

materials with which the Contractor shall comply. The drawings supplied with the Tender documents are included only for guidance and indicate the

minimum requirements to be provided by the Contractor. The Contract price shall include the cost of any enlarged structures or modified layout required to

meet FEWA's design parameters.

In general the Contractor shall be responsible for but not limited to the following:

Preparation of detailed design calculations, construction and maintenance of the whole of the works in accordance with the relevant American/International/British Codes/Authorised local and national bodies taking into account the most unfavourable condition of dead load, live load, wind load, erection load etc. for foundation, sub-structures, superstructures for reservoirs, pump stations, service building, chlorination buildings, accommodation buildings, surge vessel foundations, auxiliary structures e.g. gate house, sun shades etc., external works e.g. boundary wall, fence, septic tanks, soak-way pits, trenches, roads, thrust blocks, chambers, cable/pipe RC trenches and other miscellaneous works...etc. (Minimum concrete grade, cover, reinforcement grade etc. shall be as per detailed specifications for materials submitted separately).

Preparation of detailed working drawings, reinforcement schedules, material lists, bill of quantities etc.

The works also include interface connections with the FEWA’s existing pipelines and tanks wherever mentioned.

2.1 Architectural Design

The design of the whole work shall be in accordance with the best standards of modern industrial practice.

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Finishing materials shall be selected so as to match each other and to present ample guarantees of durability. Samples shall be submitted for the FEWA’s approval, as well as selection of colours and textures. The structures as a whole with external works shall give a good aesthetic effect from every angle of look. The perspective drawings with 3D effect shall be prepared by the contractor as required by the Authority.

2.2 Structural Design 1. Calculation Methods Designs shall be carried out in accordance with accepted FEWA principles and shall meet

the requirements of the applicable Standards and Codes of Practice. Any static and dynamic calculation is to be submitted for the FEWA’s approval.

When the Contractor uses computerised calculation methods for special kinds of structure,

he shall provide a full explanation of such method, should the FEWA require it, together with adequate documentation and reference. Structural analysis shall be done with the latest software programmes with new technique and presentation.

2. Structural Design Principles

a) Foundations shall be so designed based on soil investigation report to minimize settlements, especially differential settlements, which shall be kept within limits preventing any danger to the construction and the equipment. When necessary, piles of suitable type shall be provided.

b) The requirements related to fire protections shall be taken into consideration. c) The requirements related to seismic force, wind force, erection loads, bouancy

effects and other unexpected forces shall be taken into consideration.

3. LOADINGS

The design loadings shall conform to the requirements of adopted standards and codes of practice, as well as special Site Conditions and Technical Specifications.

The loadings to be used in the design of structures and buildings shall generally be inaccordance with BS 6399 Part 1 'Code of Practice for Dead and Imposed Loads',Part 2 'Code of Practice for Wind Loads' or BSCP 3 Chap V (Part 2) Wind Loads Part 3 imposed roof loads, BS 2573 loads for crane Gantry Girders, BS 2655 'loads due to lifts' and loads due to machinery, vibration, construction, test loads etc.

Where known loads exceed those of BS 6399 the higher loading shall be adopted. The minimum

earthquake factor shall be taken as 0.15g as per UBC Standard (Uniform Building Code). The revised zone is 2A.

In the absence of information covering any special case, the design shall be based on loadings

indicated by previous experience or by the results of special tests as approved by FEWA/Engineer.

3.1 Imposed Loads The following live loads shall be taken into account:

The loads for platforms including staircases shall be 5.0 kN/m2, or a minimum single point load of 7.50 kN whichever is more unfavourable for the structure.

For inaccessible roofs only 1 kN/m2 shall be considered. In addition all roof members shall be checked for a single load of 2 kN.

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Other live loads shall be in accordance with BS. 6399 or equal.

Sand load shall be additive to live loads when area under consideration is used as a work area. A 0.75 kN/m2 load shall be used in design of flat roofs. The effect of sand accumulating behind barriers, walls and upstands shall be considered in the design of walls and roofs.

3.2 Dynamic Loads Each structure shall be designed to withstand the effects of vibration and impact to which it may be subjected. Each structure and foundation supporting a compressor, pump etc. having significant dynamic unbalance shall be designed to resist the peak loads specified by themanufacturer. Vibration amplitudes of the supporting structure or foundation shall be kept within acceptable limits of dynamic forces that occur during normal machine operation. The frequency ratio i.e. ratio of frequency of disturbing moment to the natural frequency of vibrations of foundation block shall be as per equivalent code. Centrifugal pump foundations for pumps less than 750 kW do not require a dynamic analysis.However, the foundation to pump assembly weight ratio shall not be less than 3 to 1. Foundations for step, centrifugal pumps etc. over 750 kW require a three dimensionaldynamic analysis.All natural frequencies below 2 times the operating frequency for reciprocating equipment and below 1.5 times the operating frequency for rotating equipment shall be calculated. It shall be demonstrated that the amplitudes at the natural frequencies between 0.35 and 1.5 times the operating frequency are within the allowable values even assuming that due to differences between the actual structure and the assumed model – resonance does occur. In this case a reasonable amount of damping should be estimated. The natural frequency of the supporting structure shall not coincide with any resonant frequency of the equipment.No load assumptions will be allowed for Dynamic Analysis. The loads to be considered are those given by the Manufacturer/Supplier.

3.2.1 Static Deformation The static deformation for rotating equipment foundation shall be calculated and shown to be within the limits stated by the Vendor of the equipment. The calculations shall include, but not be limited to, the following causes of deformation:

Shrinkage and creep of concrete;

Temperature effects caused by radiation and convection of heat or cold generated by machinery, piping and ducting;

Elastic deformation caused by changing vapour pressure in condensers;

Elastic deformation caused by soil settlement or elastic compression of piles.

3.2.2 Dynamic Analysis A three- dimensional vibration analysis for rotating equipment foundations shall be made where required and shall show that the dynamic amplitudes will not exceed the lower of the following values:

The maximum allowable values stated by the manufacturer of the equipment;

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The permissible amplitude of machine/equipment foundation shall not exceed 0.0125 mm.

3.2.3 Existing Force For the vibration analysis of structures and foundations or rotating equipment (subject tovibrations), the existing forces shall be taken as the maximum values that, according to theManufacturer/Supplier of the equipment, will occur during the lifetime of the equipment.

3.2.4 Schematic Mechanical Model The vibration calculation shall be based on mechanical model wherein the weights and elasticity of both structure and foundation and the weight of the equipment are presented in an appropriate way. The design of the structure supporting a vibrating machine shall be based on the following references:

Major - Vibration Analysis and Design of foundations

D.D. Barkan - Dynamics of Bases & Foundations.

3.2.5 Additional Requirements

The soil parameters shall be taken from the final geotechnical investigation report.

Soil bearing pressure shall not exceed 50% of the net allowable safe bearing capacity for static loads.

The maximum static plus dynamic soil bearing pressure shall be limited to 75% of the net allowable safe bearing capacity.

Machinery foundation shall be independent of adjacent foundations. Surrounding concrete slabs or paving shall be separated from machinery foundation by a 15 mm joint formed with compressible material and sealed with an approved elastic sealant.

Reinforcement shall be used at all faces. If the foundation is over 1m thick, shrinkage reinforcement should be provided spaced approximately 600mm, in three directions (cube reinforcing with minimum bar diameter of 16mm).

The underside of the foundation shall be at least one meter below finished level and above water table wherever possible.

Equipment weighing less than 500 kg may be supported on thickened paving subject to approval of FEWA/Engineer.

CP 2012 Part 1 - Foundations for Reciprocating machines, shall be used as design guidelines for machinery foundations.

Provision of suitable construction/expansion/control joints.

3.3 Crane Loads Crane loads provided by Manufacturer/Supplier shall be considered at their maximum values, including the lifting capacity as well as the maximum horizontal loads caused by braking or acceleration, producing worst conditions but not acting simultaneously with maximum wind forces.

The design of Gantry girders (Runaway beams) shall be in accordance with BS 2573 part 1. No load assumptions will be allowed.For the design of each structural element the most unfavourable position of the crane or other moving loads shall be considered. For moving loads an appropriate impact factor shall be applied according to the following guideline: Loads applied due to cranes and moving sources shall not be less than the following (Ref.

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ANSI/ASCE 7-95 CL 4.10.

Electric Operation Hand Operation

Vertical impact loads – increase maximum wheel loads by:

25% 10%

Horizontal forces on rails – taken as a percentage of the rated capacity of the crane and the weight of the hoist and trolley.

Transverse to each rail:

10%

5%

Horizontal forces on rails – taken as percentage of the maximum wheel loads of the crane.

Along the rails:

10%

5%

3.4 Thermal Effects 3.4.1 Thermal Loads When thermal expansion results in friction between equipment or pipes and supports, the friction forces shall be taken as the operating load on the support times the applicable friction coefficient given in the table below.

Surfaces Friction Coefficient

Steel to steel(not corroded) Stainless steel to PTFE

PTFE to PTFE Graphite to graphite

Steel to concrete Stainless steel to stainless steel

0.30 0.08 0.06 0.15 0.45 0.15

Note: The maximum sliding bearing pressures of the above material shall be taken into account.

In the design of pipe supporting beams, the horizontal slip forces exerted by expanding or contracting pipes on steel pipe racks shall be assumed to be 15% of the operating weight on the beam. These 'slip forces' shall not be distributed to the foundations. 3.4.2 Thermo-Mechanical Forces and Stresses Foundations and liquid retaining structures (including fireproofing) which are subject to thermo-mechanical effects shall also be designed for the thermal loads and for any temperature difference that may occur. Heat transfer calculations shall be used to determine the effects of:

a) Thermo-mechanical forces and stresses. b) Changing of any properties of materials used.

3.5 Loads During Erection and Maintenance All possible loading conditions during erection & maintenance shall be taken into ccount.The most unfavourable condition shall be taken into account for each member.

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The loads of scaffolding, including the wind loads, due to erection and maintenance shall be taken into account for the design of the structure. Heavy equipment lowered onto a supporting structure can introduce extreme point loads on structural members, exceeding any operating or test load. After placing of equipment, the exact positioning (lining out and levelling) can also introduce extreme point loads. The above should be interpreted on the basis of Contractor's practical experience and Manufacturer/Supplier information. Beams and floor slabs in multi-storey structures, e.g. fire decks, shall be designed to carry the full construction loads imposed by the props supporting the structure immediately above. A note shall be added on the relevant construction drawings to inform the field engineer of the adopted design philosophy.

3.6 Piping Loads

Structures

The following loads from piping shall be included in the design of all structures: a. Pipes larger than 300 mm diameter shall be considered as concentrated loads in their

actual locations under empty, normal operation and test conditions, whichever gives the most severe effect.

b. Piping less than 300 mm diameter shall be considered as a distributed load in the range 0.75 to 1.25 kN/m2 over the gross area of the supporting floor. The greatest value shall be assumed where extensive piping is anticipated. In area of structures where there is no piping, no allowance should be made.

c. The assumed loads given above are based on ANSI standard pipe and fitting. Where non-standard pipe and fittings are to be installed, the loads shall be adjusted to suit. d. Considerations shall be given to pipework where the configuration, operating loads and

operating temperatures may give rise to significant horizontal forces due to friction at supports.

Earthquake load where applicable and specifically required by FEWA/Engineer shall be applied in accordance with the provisions of Uniform Building Code (UBC).

4. BEARING PRESSURES

For the purpose of comparison with the allowable bearing pressures, the loads to be used in computing the maximum pressure under a foundation should be the dead loads and imposed loads on the plant, equipment or structure and including the weight of its foundation less the weight of the displaced soil. Foundations will be designed to withstand the maximum stresses from loads and forces, which are likely to occur simultaneously from combinations of the following load cases :

- Dead loads - Live loads - Wind loads - Dynamic loads - Impact loads

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- Erection can construction stresses load combinations as per BS 8110 Part 1 shall considered.

The maximum pressure under eccentric loading on foundations due to any cause other than wind pressure, should not exceed the specified allowable bearing pressure. Increase in safe bearing capacity under the acton of wind will be allowed as per the provisions of the relevant BS Codes. Maximum permissible soil bearing pressures shall be determined by site testing at the proposed founding levels.Unfactored load values will be used for stability calculations. Calculations shall be as per requirements of BS 8004 to ensure adequate stability against sliding and overtuning under the most adverse condition of load.

5. DESIGN LEVELS

Basic design levels relative to site grade level in process and utility areas should be as follows:

High point of finished grading Datum E.L. 100.00 m Basic grade level within plot limits H.P. Grade -0.15 m Concrete bases and plinths for columns, stacks, major vessels, grade level pumping units and similar equipment: minimum including 25 mm grout. H.P. Grade as per design Concrete bases and plinths for structural steelwork baseplates: minimum including 25 mm grout. H.P. Grade + 0.15 m Ladder footings on plant bases or plinths: including 25 mm grout. H.P. Grade + 0.15 m Stairway footings on plant bases or plinths: including 25 mm grout. H.P. Grade 1 stair riser

6. METEOROLOGICAL AND AMBIENT CONDITIONS

Climatic conditions are very severe. Dust storms are prevalent and the atmosphere issaliferous, humid and corrosive. Humidity is high, maximum relative humidity being 100% and periods of high humidity are long and continuous. Temperatures are high in summer. Following are climatic condition parameters which include Northern Emirates.

Max. peak ambient temperature : 55 deg. C Min ambient temperature : 0 deg. C Max. wind velocity : 160 km/hr Rainfall intensities: Roofs - 35 mm/hr Site - 25 mm/hr

7. WATER TIGHTNESS All water retaining structures shall be designed to the requirements of BS 8007.If the underground water table is high, or if the site tends to be flooded, all structures required to be free of water such

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as transformer compounds, cable trenches etc., have to be watertight using water proofing membrane composed of bituminous coatings with a minimum of two layers of fibre glass reinforcement or other system as may be approved by FEWA/Engineer. All construction joints below water level shall be made watertight by using 250 mm water bars as manufactured to an approved quality.

8. FOUNDATIONS

8.1 General Pressure for safe bearing foundation shall be as per the recommendations of the Geotechnical report.Detailed designs for all foundations are to be prepared by the Contractor and submitted to FEWA/Engineer for approval in accordance with the relevant clauses of the specification. In case of piled foundation the minimum number of piles under any foundation will be two piles.The Contractor in preparing his design shall give particular regard to the recommendation contained in British Standard for Foundations – BS 8004:1986 and CP 2012 Code of practice for foundations for machinery. Machinery foundations should be designed to spread the load of installed machinery on to the ground so that excessive settlement or tilting of the foundation block relative to the floor or other fixed installations will not occur; they should have sufficient rigidity to prevent fracture being under stresses set up by heavy concentrated loads, or by unbalanced rotating or reciprocating machinery; They should absorb or damp down vibrations in order to prevent damage or nuisance to adjacent installations or structures. The Contractor's foundation design will be subject to the approval of FEWA/Engineer.Any changes/modifications that may be required by FEWA/Engineer shall be incorporated by the Contractor.

8.2 Calculations The foundations shall be designed and constructed to safely prevent overturning, base failure, uplift and sliding.Due consideration shall be taken to the risk of detrimental deformation and settlement of the soil.Rotation (angle of inclination), horizontal and vertical movements of the foundations as a result of compression of the soil, must not exceed that which is acceptable with regard to the resulting forces in the structures and the safe operation of the electrical equipment. 8.3 Factors of Safety The minimum factors of safety against base failure, overturning, uplift and sliding are listed in the table below.

Failure Type Permissible load based on :

Factor of Safety for load Combinations

Base Failure Shear Strength 3.0

Overturning Ultimate overturning resistance 1.5

Uplift Ultimate uplift resistance 1.4

Sliding Accord. to DIN 1054 1.4

The influence of ground water shall be taken into account.The bulk density and the submerged density of the soil must be assumed to be greater than can be judged to correspond to the actual conditions in each individual case.Where the ground water table is high, shallow foundations are preferable from a constructional point of view.

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8.4 Settlements The risk of vibrations, erosion, change in the level of the ground-water table and other factors which can reduce the bearing capacity of the soil or give rise to settlement shall be taken into account when founded in soil. For foundations in cohesive soil types and loosely stratified friction soil, the risk of dangerous settlements shall always be taken into account. This applies in particular to foundations for structures which shall chiefly withstand prolonged unilateral loads and to foundations of statically indeterminate structures which are particularly sensitive to uneven settlements.

8.5 Foundation Bolts The performance of foundation bolts shall comply with the relevant approved standards and together with threads, nuts, plates and washers shall conform with the following :- The projecting part of external foundation bolts and the length within 100mm of the concrete surface shall be protected from corrosion by hot-dip galvanising/ rubber bush. Permissible tensile stress is obtained by dividing the yield and the ultimate stress by the factor of safety according to the table below. For each load combination the lower value calculated is chosen as the permissible stress.

Factory of safety for yield point 1.5 Factory of safety for ultimate stress 2.0

8.5.1 Grouting Below Base Plates Nominal thickness of grouting shall be 25 mm unless stated otherwise. Where thickness greater than 50 mm are to be produced, consideration shall be given to the integration of a fine aggregate filler. Prepacked bags of non-shrink self levelling cementitious grout material shall be used. The minimum compressive strength of grout shall be 75 N/mm2 and concrete adhesion shall be 6 N/mm2. Grout shall be mixed with requisite quantity of potable water and shall be placed by an approved method in strict accordance with Manufacturer/Supplier recommendations. 8.6 Reinforcement in Concrete Upstand Over Floor Upstands shall be reinforced where these project from a base by more than 25% of the plinth's minimum plan dimension, or where other than holding down bolts housed in tubes are used, or where plinths project from an unreinforced base.

In all cases the top levels of plinths are to be not less than 150 mm above the finished level of surrounding concrete floor.

8.6.1 Particular Requirements Reinforced concrete foundations placed below grade shall be protected from the harmful effects of sulphate and chlorine bearing soil by:

(a) Lining all trenches with polythene sheeting 1000gauge min thickness below blinding.

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(b) Painting with coal tar epoxy (300 microns) paint on bases and plinths which are in contact with earth or sand.

(c) Providing a 100 mm thick layer of blinding concrete over the sheeting at foundation formation level. (d) Self adhesive water proof membrane with built in protection board. (e) Torch applied Bitumn impregnated membrane. (f) Addition of crystaline w/p compound to concrete.

Low, grade-level, bases or plinths may be left unreinforced provided that the holding down bolts are sufficiently embedded in the foundation sub-structure. Bases as above, and normally reinforced bases, should be provided with a nominal reinforcing mesh across their top surfaces where necessary to resist thermal stresses. Concrete bases, plinths and piers shall extend not less than 50 mm beyond the edges of plant or equipment base rings, fixed base plates, or slide plates. The bottom of soil bearing foundations shall extend to good soil and be at least 500 mm below finished grade. Foundations for small equipment such as pumps and drums which do not weigh more than 500 kg may be supported on concrete paving or floors, provided the connecting piping is small and flexible to take care of differential settlement. Footings for stairs, ladders and light structural members may also be supported in this manner with the 500 kg limit, provided differential settlement will not cause any harmful effects to the structures or supporting piping.Where foundations or footings are supported on paving or floor slabs, these shall be locally reinforced as required and provision made for distribution of loading. This type of support shall be avoided over or near underground lines which will require excavation for inspection and maintenance.

9. STRUCTURAL STEEL DESIGN REQUIREMENTS 9.1 Type of Construction and Bracing

- All building and 'structures' or parts thereof shall be designed on the basis of elastic principle, utilising the 'fully rigid design' and/or 'simple design' philosophy. The principles of 'plastic design' shall not be permitted.

- All structural steelwork shall be designed to have adequate capacity to withstand all the loads or forces which are likely to occur simultaneously. - Where bracing is utilised, it shall be positioned so that the specified headroom and

other clearances are strictly maintained.

- All compound members comprising two sections (e.g. angles, channels or tees) placed back to back, welded or bolted, shall be spaced apart sufficiently to allow for subsequent material preparation, painting and future maintenance. Compound battened members shall also be arranged in such a manner that all surfaces are accessible.

- Areas which are subjected to wash down or spillage shall receive special attention as to the floor construction adopted, involving the use of solid steel plate or concrete flooring to replace open grid steel flooring.

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9.2 Minimum Sizes Of Structural Members/Components - The thickness of all structural members shall be a minimum of 7 mm except in the case of webs of structural sections which shall be a minimum thickness of 6 mm and sealed tubes which shall be not thinner than 4 mm. - The thickness of all plates and gussets shall not be less than 8 mm. - The thickness of all cap plates shall not be less than 10 mm. - In any structural steelwork connection a minimum of 2 (two) bolts shall be provided in

the direct shear plane. - Unless otherwise indicated on the structural drawings, all principal and minor

connections of members shall be made with 20 mm diameter bolts. In some circumstances the diameter of bolts is governed by the size of the connected part, and in this event the size may be reduced to suit, but shall never be smaller than 16 mm diameter.

- Stanchion bases generally shall be of 'pin type' philosophy but where the stanchion shaft is over 500mm deep and not tapered at the bottom, then 'rigid design' principles shall be adopted with the resulting forces and moments determined and shown on the appropriate foundation loading short.

- All shop connection shall be welded. - Minimum fillet weld size shall be 5mm. - Welds shall be continuous unless noted otherwise.

9.3 Definition of Loads in Various Conditions of Application Buildings and structures shall be designed for all anticipated loads and for combinations of loads to which they are likely to be subjected. This section covers the definition of the loads to be considered.

9.3.1 Dead loads 9.3.1.1 Dead load Conditions Dead loads shall be considered for the following three conditions.

A- Erection Condition Dead load for 'erection' condition shall be taken as the sum of the following:

1) Own weight of structure (excluding fireproofing). 2) Weight of pipes empty (excluding weight of insulation). 3) Weight of empty equipment (shipping weight of equipment). 4) Weight of cladding.

B - Operation Condition Dead load for 'operating' condition shall be taken as the sum of the following:

1) Owner weight of structure, fireproofing, platforms, ladders, etc. 2) Weight of pipes (including operating fluid and weight of insulation) 3) Operation weight of equipment. 4) Weight of cladding, electrical and instrument installations.

C -Test Condition Dead load for 'test' condition shall be taken as the sum of the following:

1) Own weight of structure, fireproofing, platforms, ladders etc. 2) Weight of pipes full of water.

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3) Weight of equipment under hydrostatic test. 4) Weight of cladding, electrical and instrument installations.

9.3.1.2 Weights of Building Materials Unit weights of building materials shall be in accordance with BS 6399, Part 1and BS 648.

9.3.1.3 Equipment Weights a. Weights of equipment in empty, operating and test conditions shall be taken from equipment Vendor's drawing, ensuring that weights are certified correct. b. Weight of equipment in empty condition (shipping weight) shall exclude the weight of all

removable vessel internals, trays, catalysts, etc. c. Operating weight of equipment shall be increased by 15% to allow for piping attached to

the equipment; piping and equipment insulation and fireproofing Vessel operating weight shall include weight of internal and weight of fluid content.

d. Test weights of equipment shall be increased 10% to allow for attached piping. e. Large vessels (test weight exceeding 200 kN), in close proximity to one another, shall not be considered under test condition simultaneously.

9.3.1.4 Additional Forces from Equipment / Piping These forces shall be considered as dead loads for the purpose of determining applicable Load Factors from BS 5950: to be used in design.

a. Friction Force

One equipment with one end free to slide, the friction force from expansion or contraction of the equipment shall be assumed at 25% of the operating weight carried by each stool or 4.5 kN per stool whichever is the greater. This force acts parallel to the main axis of the equipment, being equal in magnitude and opposite in direction at each support, and shall be applied at the top of the stool.

b. Pipe Thrust For all equipment with the largest nozzle over 6 inches nominal diameter a pipe thrust of 1.2 KN per inch of one largest diameter nozzle is to be allowed for, acting in any direction. Only 50% of the cumulative forces from various items of equipment shall be considered in the design of longitudinal and transverse frames.

9.3.1.5 Electrical and Instrument Loads on Structures and Pipe racks. Loading from electrical and instrument installation shall be allowed for, i.e. trays, troughs, control panels, cables, etc., including protection barriers to cables. Design weight of cables alone shall be taken initially as 1.5 KN/m2, but this figure should be checked against final electrical drawings. 9.3.2 Imposed Loading Imposed loads shall be determined in accordance with BS 6399: Part 1. Roofs, Floors, Platforms and Walkways.

a) Access platforms and walkways 5.0 KN/m2. b) Working/operating/maintenance floors 5.0 KN/m2. c) Special areas such as permanent storage, erection or maintenance etc. loading as specified by client or determined by calculation based upon usage. d) All roofs shall be designed for a minimum loading of 1.5 KN per sq.m in addition to the applied plant loads. At the same time all roofs shall be designed to withstand an additional load of 70 kg. placed in any position on and area 250 sq.mm without

distortion of the sheeting, overloading or abnormal deflection of any element.

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e) Roof areas liable to short term loading during the installation or maintenance of plant shall be designed to withstand such loading in addition to and at the same time as that described.

9.3.3 Contingency Load factors for contingency loads to be used in design to BS 5950: Part 1 shall be taken as those applicable to dead loads. The beams in floors, piperacks, platforms and walkways, etc., shall be designed for a concentrated load which shall be applied in such positions on the structural member under consideration so as to give the most severe conditions both for bending moment and for vertical shear.

This load shall be additional to the loads specified elsewhere in this specification.This load shall not be taken as cumulative to beams and stanchions. The following concentrated loads shall be applied:

a. Platform and walkways. b. Floor trimmers in buildings, equipment structures, and piperack ties. c. Beams in buildings and equipment structures (excluding floor trimmers) and all piperack

beams including longitudinal edge beams.

9.4 Load Combinations Load combinations shall be considered to determine the most unfavourable conditions forfoundations, structures, buildings and individual members.

9.5 Load Factors for Limit State Design

Ultimate Limit States Load factors to be applied to the loads when considering the strength requirements and stability of a structures shall be in accordance with Table 2 of BS 5950 Part 1.

Serviceability Limit States When determining deflection of a structure under serviceability loading, unfactored loads should be used (load factor = 1.0).

9.6 Material Strength Design strengths shall be reduced where steel members are subject to temperatures above 310ºC.

9.7 Deflections Horizontal elements of all structural frames shall be designed for the following vertical deflection criteria:

a. Operating condition 1/360 b. Test condition 1/200 c. Gantry girders 1/1000 or 1/600 d. Cantilevers 1/200 at free end e. Purlins 1/250 f. Beams carrying water tanks And vertical tall vessels, etc. 1/750 g. Beams supporting plant machinery and other similar equipment shall receive special consideration concerning allowable vertical deflection and shall be confirmed by the plant manufacturer.

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Maximum total horizontal deflection of portal frame construction due to all loads except thermal forces shall be as follows:

a. Equipment structures h/200 b. Buildings (clad steel framed) h/300 The maximum deflection of flooring shall not exceed 10mm.

9.8 Miscellaneous Loading Handrails for stairs, platforms or other uses shall be designed to withstand a horizontal uniform load of 0.75 KN/m applied at the top of rail. Davits shall be designed to withstand a lateral force of 20% of the lifted load.

9.9 Pre-Engineered Buildings Pre-engineered "package" type buildings may be provided as an alternative to buildings designed using hot rolled sections. In this case the builders shall conform to the intent of this specification, however alternative recognised national standards may be substituted for those referenced in the text above, provided these are approved by FEWA/Engineer.

Construction of such buildings may incorporate sections fabricated from steel plate in lieu of hot rolled sections provided these are demonstrated by calculations to be adequate. Design of structures for pre-engineered buildings shall be as per Metal Building Manufacturers Association (MBBA) recommendations and as approved by FEWA/Engineer.

Documents

Federal Electricity & Water Authority Water Directorate ... Tech... · condition of dead load, live load, ... For inaccessible roofs only 1 kN/m2 shall be ... vibrations of foundation