【正文】 ly presents the energybased approach developed at UM as well as a modal displacementbased design procedure adopted by the research team at NCREE for calculation of design base shear for the frame. Results from inelastic response analyses of frames deigned by the two methods for a Taiwan earthquake are pared. The same frame was also designed for a . location and analyzed under ground motions scaled for . standards. The frames designed by the UM approach exhibited satisfactory dynamic responses for both Taiwan and . ground motions. INTRODUCTION Excellent seismic behavior of buckling restrained braces (BRBs) (Tsai [1]) encouraged an experimental program at the National Center for Research on Earthquake Engineering (NCREE), Taiwan, in conjunction with analysis and design studies by researchers in the . at the University of Michigan. In 1 . Candidate, University of Michigan, Ann Arbor, MI 2 Professor, University of Michigan, Ann Arbor, MI 3 Assistant Professor, University of Michigan, Ann Arbor, MI 4 Professor, National Taiwan University, Taiwan this program, the BRBs provide the primary seismic resistance mechanism to a 3story 3bay frame, tested under pseudodynamic loading at NCREE in October 2020. General layout of the prototype building is shown in Figure 1a, while a view of the test frame is shown in Figure 1b. For design purpose, two of such frames were assumed to resist the total seismic force for a 3story prototype building. The seismic frames are indicated by thick lines in Figure 1a. DESCRIPTION OF TEST FRAME The frame was designed to resist the seismic loading through two separate mechanisms. The primary resistance is provided by buckling restrained braces in the central bay of the frame (Figure 1b). This bay is designed to act as a purely braced frame with all beamtocolumn and bracetocolumn connections made as simple (pinned) connections. The braces are designed to resist 80% of the total seismic force for each seismic frame, while 20% of the load is resisted by the two external bays, designed as moment frames with moment connections at the joints of exterior beams and columns. All columns are made of concrete filled tubes. Different sections are chosen for interior and exterior columns, while keeping the same size along the building height. Wide flange sections are used for beams. Different beam sizes are used at different floors, while keeping the same size in all the bays at each floor. 423 ft 6ft 323 ft (a) (b) Figure 1: (a) Layout of the prototype building, (b) View of the test frame BUCKLING RESTRAINED BRACE PROPERTIES Buckling restrained braces are typically made by encasing a steel core member in a concrete filled steel tube (Figure 2a). The steel core is kept separated from the concrete filled tube by a layer of unbonding material applied on the surface of the steel core. The role of concrete encasing and steel tube is to prevent buckling of the steel core, so that a well formed loaddisplacement response of the brace is achieved under large displacement reversals. The unbonding material ensures that the force ing into the BRB is carried by the core only, without engaging the encasing material. Different configurations of BRBs were tested at NCREE under large reversed cyclic axial loading and an optimum configuration was selected for use in the test frame (Tsai [1]) (Figure 2a). A typical loaddisplacement response obtained from the selected BRB configuration is shown in Figure 2b. As can be seen, full hysteretic loops and excellent energy dissipation were achieved. However, it is to be noted that the yield load reached in pression was about 10% higher than that reached in tension. This needs to be accounted for while designing the frame. Seismic frame 313 ft BRBs 423 ft 623 ft 323 ft (a) (b) Figure 2: (a) Configuration of the BRB adopted, and (b) Typical loaddisplacement behavior of a BRB (From Tsai [1]) DESIGN CONSIDERATIONS A parative study is presented on the behavior of three prototype frames designed to meet mon performance criteria through different design procedures. The first frame was designed by the research team at NCREE. For this frame, calculation of base shear was done following a multimodal displacementbased seismic design (DSD) procedure and the guidelines stipulated in the 2020 Draft Taiwan Seismic Design Code. Design of that frame was done by elastic method. The second frame was designed by the team at University of Michigan. In this case, same base shear as calculated by the NCREE team was assumed. However, a plastic design procedure, recently developed by Goel, was adopted to design the frame (UM Frame 1). The third frame (UM Frame 2) was designed for a base shear calculated by following a simple energybased procedure developed at UM (Leelataviwat [2], Lee [3]). Frame design was done by the plastic design method as used for UM Frame 1. The basic design parameters were selected by the research team at NCREE following the 2020 Draft Taiwan Seismic Design code. Total seismic weight of each floor was divided equally between the two seismic frames. The seismic weights applied on each frame were as follows, 1st and 2nd Floor: 714 kips, and 3rd Floor: 564 kips In order to calculate the design base shear for the prototype building, two performance criteria were considered and the one that resulted in higher design base shear was chosen for the design of the test frame. In the first performance criterion (Life Safety), maximum roof drift was set at radian when the building is subjected to an earthquake that has a 10% probability of exceedance in 50 years (10/50). In the second performance criterion (Collapse Prevention), maximum roof drift was set at radian for a 2/50 seismic event. A real ground motion t