ce479 joists parti 12
TRANSCRIPT
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CE479: An Introduction to the Design
of Steel Joists and Joist Girders
Part I
Based on slides from:
Perry S. Green, Ph.D.,
Technical Director, SJI
Fall 2012J. Liu
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Steel Joists and Joist Girders
Introduction
Specifications
Manufacturing
More on Steel Joists and Joist Girders
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Top Chord
Bottom Chord
Web Members
Seat
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Joist Basics
Colu
mn
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 1928and produced its first Catalog andSpecifications in 1932.
The 2005 Catalog is the 42ndEdition, theprevious being published in 2002.
The K-Series, LH- and DLH-Series and Joist
Girder Specifications are ANSI accredited andare part of the 2006 International BuildingCode Section 2206.
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2005 SJI Unified Specifications
Unified specifications for the K-Series, LH-and DLH-Series and Joist Girders similar to
AISC and AISI allowing an ASDorLRFDapproach to joist design have been
developed.
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Rod (Round Bar) Web Members
Crimped Angle Web Members
Double Angle Web Members
Joist Web Types (not all inclusive)
Joist Manufacturing
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Crimped
Angle
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CrimpedAngle
DoubleAngle
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Joist Manufacturing
Shortspans
K-Series
KCS Joists
Joist
Subs
Longspans
LH-Series
DLH-Series
Joist Girders
G-Series
BG-Series
VG-Series
Joist Specification Types
Rod Web
Crimped Web
Double Web Members
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Joist Manufacturing
Usually Warren Web Configuration
K-Series, KCS Joists
Typically, all designations 8 in. to 24 in. deep(may vary by manufacturer)
2 in. to 5 in. deep seats OK for K-Series Finish Welding
Bundle of 3 joists in Pit
Multiple joist manufacturing
Rod (Round Bar) Web Members
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Joist Manufacturing
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Joist Manufacturing
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Joist Manufacturing
Usually Modified Warren Web ConfigurationCrimped Angle Web Members
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
Heavy LH-Series, DLH-Series, Joist Girders,
and Special Profile Joists including Barrel or
Arched, Bowstrings, Gables, etc.
Single Joist Manufacturing
Double Angle Web Members
Usually Modified Warren Web Configuration
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Meant to minimize rust, not prevent rust
Should not be considered a Finish Coat
Provisional Coating: Dip applied and air dried
Joist Painting
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Available Steel Joist Choices
Joists Directly Supporting Roof or Floor
Loads:
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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KCS Joists
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 stressreversal, 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 deepsections intended for use in very shortspans (less than 8 feet) where Open WebSteel Joists are impractical.
Typical 2 in. deep Joist Substitutes
Hot-Rolled Cold-Formed
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LH-, DLH-Series Joists
Designations: 18LH02 to 72DLH19 Depths: 18 to 72 in.
Standard Seat Depth (Height): 5 in. up to #17chords, 7.5 in. for #18 and #19 chords/section
numbers Span Range: 21 to 96 ft.; 61 to 144 ft.
ASDLoad Range: 174 to 1068 plf; 208 to 706 plf
LRFDLoad 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
Applicable to all joist manufacturers
Some joist manufacturers will be able to goup 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 kiploading
A Joist Girder can be made to fit within anyof the gaps in the weight table
The weight table is provided as a designaid for the structural engineer to helpprovide an approximate value for the JoistGirder self weight
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Joist Girders
Depths: 16 to 120 in. Standard Seat Depth (Height): 7.5 in.
Spans: 20 to 120 ft.
ASDPanel Point Loads: 4 to 100 kips
LRFDPanel 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 9Kis the unfactored load at each panel point 13.5Kis the factored load at each panel point
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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 - 60In terms of Moment
and Shear
Substitutes 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