Acceptability of the Equivalent Static Method for Designing Multi-Story Structures

Abstract

Equivalent static is a simplification method to design earthquake loads that must be calculated in the structural design. This method is practical and easy to apply, but only appropriate for low structures with high rigidity. The structures having low rigidity and irregularity in geometry must be analyzed using the time history method. This paper aims to investigate how high structures are still allowed to be designed using equivalent static earthquake loads. The investigation was carried out by comparing the equivalent static analysis results with time history analysis results representing the reality. The structure models were four 2D open resistant conc rete frames, with 7, 9, 10 and 15 stories. The analysis used the SAP2000 program resulting in structure responses, including story horizontal forces, base shear, story shear forces, and story displacement. The analysis revealed that a 9-story or higher structures were not acceptable if designed using an equivalent static method. Thus, they must be analyzed using the time history method. The potential damage of structures designed using equivalent static methods was estimated at the bottom areas. These results can be used as a consideration to determine an analysis method in earthquake-resistant structural design.