Softening index‐based equivalent linear modeling approach for bolt‐connected precast concrete frame

Abstract Precast concrete structures with bolt‐connected joints have been widely constructed in the world, and their prospective application market is still considerable. Considering the clear load transferring path and damage mechanism, simplified analysis method is feasible for the bolt‐connected precast concrete frame. This paper proposes an equivalent linear modeling approach (ELMA) for this type of structure, which is convenient and high efficiency to help the preliminary design of structures and seismic assessment of existing buildings. In this method, a series of linear models are established to simulate the real structure in different seismic intensity levels. The softening indices summarized from the variation of modal frequencies are defined to represent the stiffness degradation of structures. In order to obtain specific softening indices, a shaking table test for a bolt‐connected precast concrete frame was implemented. Based on the test results, the recommended softening indices, applicable to bolt‐connected frames with similar design performance objectives, are 0.325, 0.713, and 0.816 for the minor, moderate, and major earthquake levels, respectively. Following the ELMA, the numerical model of the test frame was constructed and its equivalent seismic behaviors were analyzed. By comparison with the test results, the convenience and effectiveness of this method is validated, and the precision of simulation meets the requirement of engineering application. The ELMA is also applicable for precast frames with different joints or design requirements, if the softening indices are appropriately defined by shaking table test of the structure or cyclic loading test of its single‐connection model.