Evaluating the Transition of System Efficiency between Special Moment Frames and Eccentrically Braced Frames across Building Height and Seismic Demand

The design efficiency of Special Moment Frames (SMF) and Eccentrically Braced Frames (EBF) was evaluated for various building heights and seismic demand levels in accordance with Indonesian seismic regulations for steel structures. A controlled parametric matrix was established with controlled variables, comprising three-, seven-, and eleven-story office building models. Analyses were conducted for Pontianak and Lampung, representing low and high seismic demand regions, respectively. The seismic force-resisting systems were alternated between SMF and EBF, while the architectural geometry and gravity framing were kept constant. The comparison used the governing maximum inter-story drift and the normalized mass of the seismic resisting steel frames. In all six matched cases, EBF produced lower design-level inter-story drift than SMF, with reductions ranging from 32.36% to 92.58%. However, EBF did not consistently require less steel. Under higher seismic demand, EBF was lighter at all three heights, with mass savings of 25.52%, 40.41%, and 33.03% for the 3-, 7-, and 11-story prototypes, respectively. The results indicate that the principal low-rise benefit of EBF is improved deformation control, whereas the frame-mass advantage is conditional on building height and seismic demand. Because the study is limited to six linear-elastic design cases, it does not establish a universal transition threshold or quantify nonlinear seismic performance.