Steel design, or more specifically, structural steel design, is an area of knowledge of structural engineering used to design steel structures. The structures can range from schools to homes to bridges.
Contents
- Allowable Strength Design
- Load and Resistance Factor Design
- AISC Steel Construction Manual
- CISC Handbook of Steel Construction
- References
In structural engineering, a structure is a body or combination of pieces of rigid bodies in space to form a fitness system for supporting loads. Structures such as buildings, bridges, aircraft and ships are all examples under steel structure. The effects of loads on structures are determined through structural analysis. Steel structure is steel construction material, a profile, formed with a specific shape or cross section and certain standards of chemical composition and mechanical properties.
There are currently two common methods of steel design: The first method is the Allowable Strength Design (ASD) method. The second is the Load and Resistance Factor Design (LRFD) method. Both use a strength, or ultimate level design approach.
Allowable Strength Design
For ASD, the required strength, Ra, is determined from the following load combinations (according to the AISC SCM, 13 ed.) and:
D + F
D + H + F + L + T
D + H + F + (Lr or S or R)
D + H + F + 0.75(L + T) + 0.75(Lr or S or R)
D + H + F ± (W or 0.7E)
D + H + F + (0.75W or 0.7E) + 0.75L + 0.75(Lr or S or R)
0.6D + W + H 0.6D ± (W or 0.7E)
where:
Special Provisions exist for accounting flood loads and atmospheric loads i.e. Di and Wi
Note that Allowable Strength Design is NOT equivalent to Allowable Stress Design, as governed by AISC 9th Edition. Allowable Strength Design still uses a strength, or ultimate level, design approach.
Load and Resistance Factor Design
For LRFD, the required strength, Ru, is determined from the following factored load combinations:
1.4(D + F)
1.2(D + F + T) + 1.6(L + H) + 0.5(Lr or S or R)
1.2D + 1.6(Lr or S or R) + (L or 0.8W)
1.2D + 1.0W + L + 0.5(Lr or S or R)
1.2D ± 1.0E + L + 0.2S + 0.9D + 1.6W + 1.6H
0.9D + 1.6 H ± (1.6W or 1.0E)
where the letters for the loads are the same as for ASD.
For the wind consideration, the ASCE allows a "position correction factor" which turns the coefficient of wind action to 1,36:
1,2D + 1,36W + .... the same above or 0,9D - 1,36W
AISC Steel Construction Manual
The American Institute of Steel Construction (AISC), Inc. publishes the Steel Construction Manual (Steel construction manual, or SCM), which is currently in its 14th edition. Structural engineers use this manual in analyzing, and designing various steel structures. Some of the chapters of the book are as follows.
CISC Handbook of Steel Construction
Canadian Institute of Steel Construction publishes the "CISC Handbook of steel Construction". CISC is a national industry organization representing the structural steel, open-web steel joist and steel plate fabrication industries in Canada. It serves the same purpose as the AISC manual, but conforms with Canadian standards.