Seismic Performance of Special Truss Moment Frames With X-Bracing Type: Influence of Building Height

Abstract

This study investigated the implementation of Special Truss Moment Frames (STMF) X-braced type in accordance with the recommendations of the National Earthquake Hazards Reduction Program (NEHRP), 1997:2000 and Indonesian National Standards (SNI) 1726 where it is stated that the STMF may only be used up to a maximum building height of 48 m (160 feet) for Seismic Design Category of D. The analyses compared the seismic response of apartment buildings using STMF system with different height: 44 m (11 stories), 48 m (12 stories), and 52 m (13 stories). The nonlinear behaviors were investigated through a series of nonlinear time history and pushover analyses, including the inelastic response of the structural components, top-roof displacement, drift ratio, and ductility. The structural modeling and the selection of steel sections were performed in SAP 2000 based on SNI 1726 code, considering that the structure was built on medium soil in Aceh region. Seismic performance was examined through a series of pushover and nonlinear time history analysis (NLTHA) using three scaled accelerogram: Elcentro 1940, Northridge 1994 and Kobe 1995 records. The results of the study show that in case of STMF structure with the height of 52 m (higher than the maximum height of STMF structure stated in the codes), the seismic performance of the structure was excellent and met the requirements. Axial plasticization occurred only in X-braces, not followed by the formation of plastic hinges at the ends of the ductile segments. Meanwhile, the other structural components remained elastic. This indicates that the structure can still be used after the earthquake, by replacing only the X-braced components. The drift ratio met the requirements and the roof displacements behavior was asymptotic, indicating that there is no residual horizontal displacement of the building after the seismic loads occurred.