Copyright © 2016 Steel Joist Institute. All Rights Reserved.

Using SJI’s Virtual Joists and Joist Girders in SCIA Engineer

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Presented by: David Samuelson, P.E., Nucor New Products and Market Development

Ben Follett, P.E., SCIA

Learning Objectives •  Demonstrate and explain how to specify SJI’s Open Web Virtual

Joists and Virtual Joist Girders within SCIA Engineer.

•  Demonstrate and explain how to specify loads on Virtual Joists and Virtual Joist Girders within SCIA Engineer.

•  Demonstrate and explain how SJI’s “Standard” Joists and Joist Girders may be selected within SCIA Engineer.

•  Explain what SJI’s Open Web Steel Virtual Joists and Joist Girders are and how the tables were developed.

•  Receive general explanation and tips on how to operate SCIA Engineer in the most efficient manner.

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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 SCIA Engineer 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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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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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 SCIA Engineer.

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. They do yield reasonably close approximations of the final joist /Joist Girder chord area, effective moment of inertia, and weight for use in structural models. Once the building model is completed, standard SJI joist and Joist Girder designations are called out on the plans.

Verification of VJ / VJG Tables at South Dakota School of Mines & Technology

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Quote from STAAD-PRO Technical Reference Manual

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%.

Joist and Girder Designations displayed in VJ / VJG Format

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SCIA Engineer

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

SJI’s Virtual Joists permit the determination of joist weight and effective Ixx for complex load cases. Recent incorporation of SJI’s Virtual Joist and Joist Girder Tables within SCIA Engineer allows one to readily determine Joist / 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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Copyright © 2016 Steel Joist Institute. All Rights Reserved.

THANK YOU

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