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Load Combinations for OCBF design per AISC 341-16 with ideCAD

How does define ideCAD load combinations, according to AISC 341-16?

  • Load combinations are automatically generated according to ASCE 7-16 by ideCAD Structural.


D = Dead load
Em = Combined applied design force on the horizontal and vertical seismic load effects
Emh= The effect of horizontal seismic forces, including overstrength
L = Live load
Lr = roof live load
S = snow load
W = Wind load
Eh = Horizontal seismic load effect
Ev = Vertical seismic load effect

The internal forces to be taken as basis in the design of OCBF are the internal forces calculated by considering the load combinations, including the earthquake effect defined according to the appropriate building codes. According to ASCE 7-16 Load Combination and Strength Design per ASCE 7-16 §2.3, there are two different approaches to determining load combinations:

  • Strength-based design

  • Allowable stress design

The required strength of the columns, beams, braces, and connections of the concentrically braced frames with moderate ductility level, as specified in the relevant building codes, are obtained by using the internal forces Ed determined by multiplying the earthquake effects by the overstrength factor Emh in the load combinations.


  • 1.2D + Ev + Eh + L + 0.2S

  • 0.9D - Ev + Eh

For ASD;

  • 1.0D + 0.7Ev + 0.7Eh

  • 1.0D + 0.525Ev + 0.525Eh + 0.75L + 0.75S

  • 0.6D - 0.7Ev + 0.7Eh

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