Steel design

Steel design, or more specifically, structural steel design, is an area of structural engineering used to design steel structures. These structures include schools, houses, bridges, commercial centers, tall buildings, warehouses, aircraft, ships and stadiums. The design and use of steel frames are commonly employed in the design of steel structures. More advanced structures include steel plates and shells.
In structural engineering, a structure is a body or combination of pieces of rigid bodies in space that form a fitness system for supporting loads and resisting moments. The effects of loads and moments on structures are determined through structural analysis. A steel structure is composed of structural members that are made of steel, usually with standard cross-sectional profiles and standards of chemical composition and mechanical properties. The depth of steel beams used in the construction of bridges is usually governed by the maximum moment, and the cross section is then verified for shear strength near supports and lateral torsional buckling (by determining the distance between transverse members connecting adjacent beams). Steel column members must be verified as adequate to prevent buckling after axial and moment requirements are met.
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.
Load combination equations.
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 ± (0.6W or 0.7E)
D + H + F + (0.75W or 0.7E) + 0.75L + 0.75(Lr or S or R)
0.6D + 0.6W
0.6D ± 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
1.8(D+F)<cr/>
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 15th 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.