Column Design for Earthquake Loads According to ASCE 7

[Learner24]

In higher Seismic Design Categories, when using the equivalent lateral force (ELF) method, earthquake loads are applied as 100% of the seismic force in one direction (X or Y) and 30% in the orthogonal direction (ASCE 7 provisions).

However, when using dynamic analysis (modal response spectrum analysis or time history analysis), earthquake forces are considered 100% in both the X and Y directions simultaneously.

My Question:

• When designing a column using ELF, we obtain moments Mx and My based on the following load combinations:

• For My: 1.2D + EQx + 0.3 EQy + 1 (0.5) L

• For Mx: 1.2D + EQy +0.3 EQx +1 (0.5) L

• We then design the column as a biaxially loaded column with moments Mx, My, and axial load P, correct?

In the case of dynamic analysis, we apply 100% of the earthquake force in both X and Y directions, and design it as biaxialy loaded?

 

[HTURKAK]

Apparently you need to study section 12.4 SEISMIC LOAD EFFECTS AND COMBINATIONS and 2.3.6 Basic Combinations with Seismic Load Effects.
Each combination treated separate and envelope to get the maximum effects. ( E.g. 1.2D + EQx + 0.3 EQy + 1 (0.5) L would have Mx and My. )