ce479 joists parti 12

8/11/2019 CE479 Joists PartI 12

1/38

I - 1

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


2/38

II - 2

Steel Joists and Joist Girders

Introduction

Specifications

Manufacturing

More on Steel Joists and Joist Girders


3/38

I - 3

Top Chord

Bottom Chord

Web Members

Seat


4/38

I - 4

Joist Basics

Colu

mn

Joist Girder


5/38

I - 5

Joist Basics

Horizontal Bridging

Diagonal Bridging


6/38

I - 6


7/38

I - 7


8/38

I - 8

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.


9/38

I - 9

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.


10/38

I - 10

Rod (Round Bar) Web Members

Crimped Angle Web Members

Double Angle Web Members

Joist Web Types (not all inclusive)

Joist Manufacturing


11/38

I - 11

Crimped

Angle


12/38

I - 12

CrimpedAngle

DoubleAngle


13/38

I - 13

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


14/38

I - 14

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


15/38

I - 15

Joist Manufacturing


16/38

I - 16

Joist Manufacturing


17/38

I - 17

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)


18/38

I - 18

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


19/38


20/38

I - 20

Meant to minimize rust, not prevent rust

Should not be considered a Finish Coat

Provisional Coating: Dip applied and air dried

Joist Painting


21/38

I - 21

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


22/38


23/38

I - 23


24/38

I - 24

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


25/38

KCS Joists

I - 25


26/38

I - 26


27/38

I - 27

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


28/38

I - 28

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


29/38

I - 29


30/38

I - 30

http://www.canadianjoist.com/joistproducts.html


31/38

I - 31

http://www.njb-united.com/ncj/jpdfs/j1617.pdf


32/38

I - 32

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


33/38

I - 33

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


34/38

I - 34

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


35/38


36/38

I - 36


37/38

Joist Girders

I - 37


38/38

I 38

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

ce479 joists parti 12

Documents