The principal procedure specified in most building codes to estimate earthquake forces is an Equivalent Lateral Force Procedure. Formulas for calculation of base shear, height-wise distribution of lateral forces specified in building codes are evaluated by approximate method in light of the first mode shape of regular buildings. However they do not properly recognize the effects of higher mode contributions and structural configurations.
The purpose of this study is to compare the Equivalent Lateral Force Procedure in building codes to the modal analysis and time history analysis. It will be shown how and why the Equivalent Lateral Force Procedure improper for irregular structures and tall buildings.
