CE479: An Introduction to the Design
of Steel Joists and Joist Girders
Part I
Fall 2012 – J. Liu
Based on slides from:
Perry S. Green, Ph.D.,
Technical Director, SJI
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Steel Joists and Joist Girders
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Introduction
Specifications
Manufacturing
More on Steel Joists and Joist Girders
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Top Chord
Seat
Web Members
Bottom Chord
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Joist Basics
Column
Joist Girder
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Joist Basics
Horizontal Bridging
Diagonal Bridging
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Steel Joist Institute
Background and Development
 The Steel Joist Institute was founded in 1928
and produced its first Catalog and
Specifications in 1932.
 The 2005 Catalog is the 42nd Edition, the
previous being published in 2002.
 The K-Series, LH- and DLH-Series and Joist
Girder Specifications are ANSI accredited and
are part of the 2006 International Building
Code Section 2206.
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2005 SJI Unified Specifications
 Unified specifications for the K-Series, LHand DLH-Series and Joist Girders similar to
AISC and AISI allowing an ASD or LRFD
approach to joist design have been
developed.
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Joist Manufacturing
Joist Web Types (not all inclusive)
Rod (Round Bar) Web Members
Crimped Angle Web Members
Double Angle Web Members
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Crimped
Angle
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Crimped
Angle
Double
Angle
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Joist Manufacturing
Joist Specification Types
Rod Web
Double Web Members
Crimped Web
Joist
Subs
Shortspans
Longspans
Joist Girders
K-Series
LH-Series
G-Series
DLH-Series
BG-Series
KCS Joists
VG-Series
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Joist Manufacturing
Rod (Round Bar) Web Members
Usually Warren Web Configuration
K-Series, KCS Joists
• Typically, all designations 8 in. to 24 in. deep
(may vary by manufacturer)
• 2 ½ in. to 5 in. deep seats OK for K-Series
• Finish Welding
 Bundle of 3 joists in “Pit”
 “Multiple” joist manufacturing
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Joist Manufacturing
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Joist Manufacturing
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Joist Manufacturing
Crimped Angle Web Members
Usually Modified Warren Web Configuration
K-Series, KCS Joists, “Light” LH-Series
• Typically, LH-Series from 18 in. to 32 in. or 36 in. deep
(may vary by manufacturer)
• Finish Welding
 Bundle of 3 joists in “Pit”
 “Multiple” joist manufacturing
(Similar process to Rod Web Manufacturing)
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Joist Manufacturing
Double Angle Web Members
Usually Modified Warren Web Configuration
“Heavy” LH-Series, DLH-Series, Joist Girders,
and Special Profile Joists including Barrel or
Arched, Bowstrings, Gables, etc.
“Single” Joist Manufacturing
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http://www.njb-united.com/ncj/jpdfs/j1617.pdf
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Joist Painting
•
Provisional Coating: Dip applied and air dried
•
Meant to minimize rust, not prevent rust
•
Should not be considered a “Finish” Coat
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Available Steel Joist Choices
 Joists Directly Supporting Roof or Floor
Loads:
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Open-Web Steel Joists, K-Series
 KCS Joists
 Joist Substitutes
Long-Span Steel Joists, LH-Series
Deep Long-Span Steel Joists, DLH-Series
 Primary Members
•
Joist Girders Supporting Other Joists
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K-Series Joists
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Designations: 8K1 to 30K12
Depths: 8 to 30 in.
Standard Seat Depth (Height): 2.5 in.
Span Range: 8 to 60 ft.
ASD Load Range: 127 to 550 plf
LRFD Load Range: 190 to 825 plf
Maximum Span/Depth Ratio: 24
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KCS Joists
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Designations: 10KCS1 to 30KCS5
Depths: 10 to 30 in.
Seat Depth (Height): 2.5 in.
Span Range: 10 to 60 ft.
Constant Moment Capacity
Constant Shear Capacity
Maximum Span/Depth: 24
Diagonals designed for stress
reversal, except end diagonal which
is designed for 100% tension only
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KCS Joists
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Joist Substitutes
 Joist substitutes are 2.5 inch deep
sections intended for use in very short
spans (less than 8 feet) where Open Web
Steel Joists are impractical.
Typical 2 ½ in. deep Joist Substitutes
Hot-Rolled
Cold-Formed
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LH-, DLH-Series Joists
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Designations: 18LH02 to 72DLH19
Depths: 18 to 72 in.
Standard Seat Depth (Height): 5 in. up to #17
chords, 7.5 in. for #18 and #19 chords/section
numbers
Span Range: 21 to 96 ft.; 61 to 144 ft.
ASD Load Range: 174 to 1068 plf; 208 to 706 plf
LRFD Load Range: 261 to 1602 plf; 312 to 1059 plf
Maximum Span/Depth Ratio: 24
Types: Parallel Chord, Single Pitch, Double Pitch;
Underslung or Bottom Chord Bearing
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http://www.canadianjoist.com/joistproducts.html
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http://www.njb-united.com/ncj/jpdfs/j1617.pdf
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Joist Girders
 Joist Girder Weight Tables
• Maximum chord angle size is 6 x 6 x ¾
Applicable to all joist manufacturers
• Some joist manufacturers will be able to go
up to a 8 x 8 chord angle, but that will be a
non-standard SJI product
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Joist Girders
 Joist Girder Weight Tables
• The weight table can not cover every
combination of span, panel spacing and kip
loading
• A Joist Girder can be made to fit within any
of the “gaps” in the weight table
• The weight table is provided as a design
aid for the structural engineer to help
provide an approximate value for the Joist
Girder self weight
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Joist Girders
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Depths: 16 to 120 in.
Standard Seat Depth (Height): 7.5 in.
Spans: 20 to 120 ft.
ASD Panel Point Loads: 4 to 100 kips
LRFD Panel Point Loads: 6 to 150 kips
Weights: 16 to 332 plf
Various Web Configurations: G, VG, BG
Designation: 48G8N9K; 48G8N13.5F
• 48G is the Depth in inches
• 8N is the Number of Joist Spaces
• 9K is the unfactored load at each panel point
• 13.5K is the factored load at each panel point
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Joist Girders
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Joist Girders
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SJI Load Tables
Joist Series
Depth
(in.)
Span
(ft.)
Capacity
(lbs/ft.)
K
8 - 30
8 - 60
Varies w/ Span
KCS
10 - 30
10 - 60
In terms of Moment
and Shear
2.5
4-8
Varies w/ Span
LH
18 - 48
21 - 80
Varies w/ Span
DLH
52 - 72
61 - 120
Varies w/ Span
SLH
80 - 120
80 - 190
Varies w/ Span
Substitutes
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