Study On The Seismic Response Of LRB Base-isolated Buildings Under Near-fault Pulse-like Ground Motions

Base-isolated structure shows excellent performance in effectively reducing the damage resulted from the common ground motion (i.e., far-field ground motion or near-fault ground motion without prominent pulse); however, behaves poorly under near-fault ground motion with long period velocity or displacement pulse. At present, most of research related to the base-isolated structures is based upon the common ground motion; on the contrary, the investigation into the effect of near-fault pulse-like ground motion upon the base-isolated structures is limited. In order to realize the application standarization of base-isolated technology in civil engineering, it is necessary to comprehensive study the effect of near-fault pulse-like ground motions on the base-isolated structures, which can be regarded as the beneficial complement of the base isolation theory. Lead Rubber Bearings (LRB) is the most widely used base-isolated system; therefore, LRB base-isolated structure is selected as research object in this dissertation and corresponding study includes the following aspects:(1) systematically study the dynamic response of LRB base isolated structure under near-fault pulse-like ground motions. Non-iterative computational method for tine-history analysis of nonlinear structures is proposed based upon the well-known Masing criteria, after comparison with traditional Newton-Raphson iterative algorithm, it is indicated that the non-iterative computational method based on the Masing criteria can meet the accuracy demand in civil engineering; the more reasonable method to artificially generating near-fault pulse-like ground motions is given; paremetric study on the dynamic the dynamic response of LRB base isolated structure under near-fault pulse-like ground motions is carried out.(2) analyzing the possible pounding response of LRB base isolated structure under near-fault pulse-like ground motions. Based upon the evaluation of some commonly used impact analytical models, the modified Kelvin impact analytical model, which can reasonably account for physical nature of pounding phenomena and time facilitate the determination of relevant parameters, is for the first time put forward, theoretical derivation of expressions of relevant parameters and corresponding numerical verification are conducted, at the same time, the corrected expression for damping constant in the Hertzdamp impact analytical model is given; Comparison of pounding response of LRB base-isolated structures obtained by using various impact analytical models is made, which validate the modified Kelvin impact analytical model; After analyzing the pounding response of LRB base-isolated structures with adjacent structures using the modified Kelvin model, it can be observed that occurrence of pounding has adverse effect on the LRB base-isolated structure and significantly changes the vibration modes of superstructure; parametric research on some factors influencing the pounding response of LRB base-isolated structures is made.(3) conducting the research on the seismic response of asymmetric LRB base-isolated structrures under near-fault pulse-like ground motions. Analytical model and motion of equation of single-storey asymmetric LRB base-isolated structure, which can incorporate deformation of each LRB, is built; procedures to synthetically simulating bi-directional near-fault pulse-like ground motions is developed; comparative study on the seismic response of asymmetric LRB base-isolated structures under either near fault pulse-like ground motions or common ground motions is carried out; effect of isolation eccentricity, superstructure eccentricity, ratio of torsional-to-lateral frequency of superstructure and pulse period of near-fault pulse-like ground motions on the seismic response of asymmetric LRB base-isolated structures is analyzed.(4) investigating the possible pounding response of asymmetric LRB base-isolated structure subject to near-fault pulse-like ground motions. Analytical model and motion of equations of multi-stories asymmetric LRB base-isolated structure in the case of pounding with adjacent structrures is developed. Comparative study of pounding responses between symmetric and asymmetric LRB base-isolated structures is carried out, at the same time, comparison of torsional response of asymmetric LRB base-isolated structures in the case of both pounding and no pounding with adjacent structures, is made; discussion on the effect of isolation eccentricity, superstructure eccentricity, ratio of torsional-to-lateral frequency of indivisual story in the superstructure on the torsional response of superstructure in the case of pounding of asymmetric LRB base-isolated structures with adjacent structures.