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Copyright © 2016 Steel Joist Institute. All Rights Reserved.

Steel Joist Floor Systems Best Practices

A P R I L 2 0 , 2 0 1 6

Presented by: Michael A. West, P.E., F.ASCE

David Samuelson, P.E.

Learning Objectives •  Identify Codes and Standards providing requirements and guidance for

selecting joists and Joist Girders for steel joist supported floor systems.

•  Review of where standard joists, constant shear joists (KCS joists), “Special Joists” for supporting non-uniform and concentrated loads, or CJ-Series Composite Joists may be advantageous.

•  Discuss SJI publications that are available to assist the Structural Engineer to design steel joist floor systems for serviceability, for selecting appropriate UL fire resistance ratings, and for adapting joists for future building uses.

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Learning Objectives •  Demonstrate SJI’s future Floor Bay Analysis tool showing how this tool can

optimize the layout and select optimal depths for non-composite K-Series, LH-Series, and DLH–Series joists and Joist Girders as well as CJ-Series composite joists.

•  Learn how the recent incorporation of SJI’s Virtual Joist Girder tables within RAM Structural System, RISA, and SCIA Engineer facilitates the selection of Joist Girders within lateral load resisting frames.

•  Learn how SJI’s new Virtual Joist tables can yield a reasonable approximate joist effective moment of inertia and weight for joists with non-uniform loading, concentrated loads of varying magnitude, and / or externally applied local moments.

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Copyright © 2016 Steel Joist Institute. All Rights Reserved.

Successfully Using Steel Joists in Floor Construction

A TOOL KIT

Presented by Michael A. West, P.E., F.ASCE

Outline

Loads and Resistance Non-composite vs. Composite v. KCS-Series Joists Deck Lateral Load Resisting Frames w/ joists and JG

Serviceability Deflection Vibration

Fire Resistance Accommodating M-E-P Adaptability – modifying joists & Joist Girders

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Loads IBC Table 1607.1

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TABLE 1607.1 MINIMUM UNIFORMLY DISTRIBUTED LIVE , LO AND

MINIMUM CONCENTRATED LOADS LIVE LOADS

OCCUPANCY OR USE UNIFORM (psf) CONCENTRATED (pounds)

22. Office buildings

Corridors above first floor 80 2,000

Files and computer rooms Based on occupancy Based on occupancy

Lobbies and 1st flr. corridors 100 2,000

Offices 50 2,000

27. Schools

Classrooms 40 1,000

Corridors above first floor 80 1,000

First floor corridors 100 1,000

IBC 1607.4 Concentrated LL

Distributed over an area 2 ½ feet by 2 ½ feet:

2000/(2.5)2 = 320 psf 1000/(2.5)2 = 160 psf

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43RD Edition Catalog

Standard Specifications, 43rd Edition

K-Series LH-Series DLH-Series Joist Girders

Load and Weight Tables SJI Code of Standard Practice

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Composite Steel Joist Catalog

Standard Specifications for Composite Steel Joists, First Edition CJ-Series How to specify and more

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Composite Steel Joist Catalog

Standard Specifications Responsibility of the Specifying

Professional Design Guides Examples Code of Standard Practice for Composite

Steel Joists -Composite Joist Floor Design Parameters

Check List

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Designating CJ-Series Joists

30 is the joist depth 2188 is the “Total Factored Composite

Design Load” 1168 is the “Total Factored Composite

Live Load” 420 is the “Total Factored Composite

Dead Load”

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30CJ 2188/1168/420

Steel Decks in Floor Construction

Form decks vs. Composite decks Profiles (and thicknesses) (Gage numbers)

1” Form Deck (0.017”-0.04”) (26-20) 1-1/2” Form Deck (0.023”-0.04”) (24-20) 2” Form Deck (0.023”-0.04”) (24-20) 1-1/2” Composite Deck (0.03”-0.06”) (22-16) 1-1/2” Comp. Deck Inverted (0.03”-0.06”) (″) 2” Composite Deck (0.03”-0.06”) (22-16) 3” Composite Deck (0.03”-0.06”) (22-16) 12

Framing Layout – A Function of

Loads and required resistance Slab thickness &

deck profile & joist spacing &

joist depth & structure depth &

story height The combinations are nearly infinite! Stay tuned for SJI’s Floor Bay Analysis Tools

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AISC Design Guide No. 3

Serviceability Design Considerations for Steel Buildings

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IBC – 2015 & AISC Design Guide 3

IBC Table 1604.3

AISC Design Guide 3 Non-composite, “across the bay” Span/360, max. 1 inch for dead load Span/360, max. 1 inch for 50% live load

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Construction Live Snow/Wind Dead + Live*

Floor Members L / 360 - L / 240

* For steel structural members, the dead load shall be taken as zero.

SJI Technical Digest No. 5

Vibration of Steel Joist – Concrete Slab Floors

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Acceptance Criteria – Walking (3-9 Hz)

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Tolerance acceleration ratio

Peak acceleration ratio

Vibration – Walking Excitation

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Activity Recommended Live Load (psf)

Walking – Paper Office 11

Walking – Electronic Office 6 – 8

Walking – Residence 6

Walking – Assembly Area 0

Walking – Shopping Mall 0

Dancing 12.5

Lively Concert 31

Sports Event 31

Rhythmic Activities 4.2

Table 1.2 - TD 5 (DG 11) Recommended Live Loads for Vibration Analysis

(For use in determining natural frequency)

Damping, β

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Vibration – Walking Excitation

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Table 3.1 Recommended Tolerance Accelerating

Limits

Occupancy Tolerance Acceleration Limit (ao/g)x100%

Offices, Residences 0.5 – 0.55% Assembly Areas, Worship,

Schools 0.5 – 0.55%

Shopping Malls 1.5%

AISC Design Guide No. 11

Floor Vibrations – Due to Human Activity

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Fire-proofed vs. Unprotected

A required class of construction is a function of

Occupancy, and Height and area

Fire rated construction can be achieved in joist/Joist Girder construction, but it’s costly and makes M-E-P installation and maintenance more difficult

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Construction Classification

IBC, Chapter 6 and Table 601 Type II, B – Noncombustible materials Type II, B – Fire-Resistance Ratings

Primary structural frame – 0 (zero) Floor construction and associated secondary

members – 0 (zero)

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Height and Area Limits

IBC, Chapter 5 and Table 503 for Type II, B Maximum height – 55-feet Assembly (A-1 through A-5)

Stories – 2 (unlimited for A-5) Area – 8,500 to 9,500 sq.ft. (unlimited for A-5),

per story Business (B)

Stories – 3 Area – 23,000 sq.ft.

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Height and Area Limits, cont.

IBC, Chapter 5 and Table 503 for Type II, B Educational (E)

Stories – 2 Area – 14,500 sq.ft.

Factory (F-1 and F-2) Stories – 2 for F-1 and 3 for F-2 Area – 15,500 sq.ft. for F-1 and

23,000 sq.ft. for F-2

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Height and Area Limits, cont.

IBC, Chapter 5 and Table 503 for Type II, B Mercantile (M)

Stories – 2 Area – 12,500 sq.ft.

Residential (R-1 and R-2), not incl. R-3 and R-4

Stories – 4 for R-1 and R-2 Area – 16,000 sq.ft. for R-1 and R-2

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SJI Technical Digest No. 10

Design of Fire-Resistive Assemblies with Steel Joists Floors and Roofs

Membrane and Spray-Applied Fire Resistive Materials

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SJI Technical Digest No. 10

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Appendix Tables for Floors and Roofs w/ UL Design Numbers

Group D – Concrete and Steel Floor Units Group G – Concrete and Steel Joists

UL Design G501

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AISC Design Guide No. 19

Fire Resistance of Structural Steel Framing

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Accommodation of M-E-P Under the framing:

Simpler Probably increases story height Need to consider structure depth vs. story ht.

Through the framing: Requires greater attention to structure/M-E-P co-ordination, including turning the corner May limit duct sizes Joists as deep as possible X-bridging provisions (TD 2)

And a hybrid (of course) 31

SJI Technical Digest No. 12

Evaluation and Modification of Open Web Steel Joists and Joist Girders

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Modification of Joists and Joist Girders

Modify to increase load capacity Modify for new concentrated loads Modify to shorten at headered openings

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SJI Technical Digest No. 11

Design of Lateral Load Resisting Frames Using Steel Joists and Joist Girders

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In Conclusion - Consider

Loads and Resistance Serviceability

Deflection Vibration

Fire Resistance Accommodation of M-E-P Adaptability And using the SJI Floor Bay Analysis Tools

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Copyright © 2016 Steel Joist Institute. All Rights Reserved.

SJI Floor Design Tools

Presented by David Samuelson, P.E.

SJI Floor Design Tools

SJI Floor Bay Analysis Tool SJI Virtual Joist Tables SJI Virtual Joist Girder Tables

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SJI Floor Bay Analysis Tool

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Joist Spans

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Joist Girder Spans

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Noncomposite or Composite

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Standard K, LH, & DLH or Load / Load Joist

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Loads, Deck & Concrete Criteria

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Steel Deck Options

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2 – 18 Gage 3 – 22 Gage 3 – 20 Gage 3 – 18 Gage 9/16 Form – 28 Gage 9/16 Form – 26 Gage 9/16 Form – 24 Gage 9/16 Form – 22 Gage 1 Form – 26 Gage 1 Form – 24 Gage 1 Form – 22 Gage 1 Form – 20 Gage 1.5 Form – 22 Gage 1.5 Form – 20 Gage 1.5 Form – 18 Gage

Min. & Max. Joist / Joist Girder Depths, Deflection Criteria and Minimize X-Bridging

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Deck, Concrete & Joist Summary

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Bridging & Joist Girder Summary

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Estimated and Actual Joist / Joist Girder Weights

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User Defined Cost Data

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Final Design

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Design Run Comparisons

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Run Data copied to Run Comparison

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Composite Joist Comparison

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Joist Depth must be entered for Composite Joists

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Composite Joist Design

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Copy Composite Joist Design to Run Comparison Table

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Total Cost, $/sf for Noncomposite vs. Composite Joist Design

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Future Release of SJI Floor Bay Analysis Tool – May, 2016

https://steeljoist.org/product-category/design-tools/

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Classic Roof and Floor Framing Programs

“Standard” SJI joists only managed as simple-span infill joists supporting vertical gravity loads.

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SJI’s Virtual Joist and Virtual Joist Girder Load Tables

Standard programs such as RAM Structural System, RISAFLOOR, SCIA, etc. do an excellent job of selecting “Standard” SJI joists.

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Standard Joists Selected Based on Span and Uniform Loading

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RAM Structural System Partial Framing Plan

Classic Roof and Floor Framing Programs

“Standard” joist designations and definition do not address concentrated loads, end moments, negative moments or axial loads.

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Steel Joist \ Joist Girder Stiffness not Included in Structural Model

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Quote from STAAD-PRO Technical Reference Manual

What are Virtual Joist / Virtual Joist Girder Tables

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Virtual Joists and Virtual Joist Girders are a set of pseudo section properties based on commonly available joist chord pairs. The major axis moment of inertia (Ixx) is based directly on a pair of double angle joist chords and pre-adjusted for approximate deflection contribution from web strain. Allows joists and Joist Girders to be checked for flexure, shear, axial, and combined forces by treating them as doubly symmetric I –shaped beam sections. Can be inserted into stiffness based structural analysis programs such as RAM, RISAFLOOR, SCIA, etc.

What are Virtual Joist / Virtual Joist Girder Tables

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Virtual joist and Virtual Joist Girder tables allow joist member stiffness to be accounted for in the overall building model. Once the building model is completed, standard SJI joist and Joist Girder designations are called out on the plans.

SDSM&T Comparison Study of VJ and VJG Tables

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Joist Girder Frame Model

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24 @ 5'-0" = 120'-0"

23'-6"

FRAME MODEL @ GRID LINE B & E

P P P

WIN

D =

100

0 pl

f

1 2 3 4

5 6 7

WIN

D =

100

0 pl

fG3 G3G4P : DL = 2.4 kips LL = 4.0 kips TL = 6.4 kips WL = 7.0 kips

VJ / VJG Tables permit easy determination of required effective Ixx for joist /Joist Girders in the structural model.

Virtual Joist Girder

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Reporting Loads

Note: Please contact the Project Structural Engineer of Record if the final effective Joist Girder Moment of Inertia (Ixx) varies from the tabulated target value by more than 10%.

Virtual Joist / Virtual Joist Girders

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SCIA Screen Shot

Joist and Girder Designations displayed in VJG Format

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RAM Steel Partial Framing Plan

RISAFLOOR – Draw Virtual Joist Girders

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Virtual Joist Girder

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RISAFLOOR- Draw Virtual Joists

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Virtual Joists

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RISAFLOOR

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RISAFLOOR Weight Takeoff

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RISAFLOOR – VJ / VJG Moment of Inertia

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RISAFLOOR – VJ / VJG Moment of Inertia

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Min Izz effective = 134 in4

SCIA Virtual Joist Designation

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SCIA Special Joist Designation

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SCIA VJG Designation

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How should a Virtual Joist or Virtual Joist Girder be Specified on the Structural Drawings?

It is important to specify all joists and Joist Girders using conventional SJI designation nomenclature.

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185/100 Uniform Load (PLF)

50’ Span

ASD 28K7 Joist

Standard Joist Designation ASD 28 K 7

Allowable Strength Design

Joist Depth in inches

Joist Series

Chord Size

How should a Virtual Joist or Virtual Joist Girder be Specified on the Structural Drawings?

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Joist Space 11.9K 11.9K 11.9K 11.9K 11.9K 11.9K 11.9K

Joist Girder Span (C.L. of column to C.L. of column)

Standard Joist Girder Designation

ASD 44G 8N 11.9K Allowable Strength Design

Depth of Girder in inches

Number of Joist Spaces

Load in Kips at Each Panel Point

SCIA – Standard SJI Joist Designations Shown on Structure Labels in Structure

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Conclusions SJI’s Virtual Joists permit the determination of joist weight and effective Ixx for complex load cases. Recent incorporation of SJI’s Virtual Joist Girder Tables within RAM Structural System, RISAFLOOR, and SCIA Engineer allows one to readily determine Joist Girder weights and effective moments of inertia in a lateral load resisting frame. Utilizing SJI’s Virtual Joist / Virtual Joist Girder Tables, one can now determine the estimated weight and cost for complex loaded “Special” joists and non-symmetrically loaded Joist Girders.

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Conclusions

SJI’s Floor Bay Analysis Tool facilitates the calculation of estimated total floor costs for K, LH, DLH and CJ-Series composite joists. Current codes, specifications, design guides, and design tools make the design of joists and Joist Girders more efficient than ever before.

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Future SJI Webinars on VJ / VJG Tables

May 18, 2016 RAM Structural System June 1, 2016 SCIA Engineer June 15, 2016 RISAFLOOR

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https://steeljoist.org/product-category/webinars/

Copyright © 2016 Steel Joist Institute. All Rights Reserved.

THANK YOU

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