| The self-centering energy dissipation(SCED)brace has good energy dissipation and self-centering capabilities,which can not only dissipate the seismic input energy but also effectively reduce the residual deformation of structures after earthquakes.Compared with the conventional braced steel frame,the self-centering braced steel frame structure has better seismic performance and self-centering capability.Current design method can not fully utilize the high performance of SCED brace and the self-centering braced steel frame structure can not achieve higher seismic performance objectives.In this thesis,a nonlinear restoring force model is developed to accurately discrible the hysteretic behaviors of SCED brace based on the working principle and mechanical behavior of an assembled SCED brace.Four-level seismic performace indexes and performance-based seismic design method are developed for self-centering braced steel frame structure where the beams are hinged to the columns.Typical 4-,8-and 15-story self-centering braced steel frame sturctures are designed.The effects of the near-and far-fault ground motions on seismic performace and self-centering capability of the low,mid-high and high-rise self-centering braced steel frame structures are investigated.The main contents are as follows:(1)The working principle and mechanical behavior of an assembled SCED brace under low cyclic reversed loading are investigated.Based on the classical Bouc-Wen model,a nonlinear restoring force model of the SCED brace is developed and the comparative analysis between the predicted results by the model and experimental results are conduted.The hysteretic curves predicted by the nonlinear restoring force model agree well with the experimental results.The difference of the predicted energy dissipation and experiemental results is only 6.5%.The maximum difference between the predicted residual deformations by the model and the calculated values by the theoretical formula is only 0.1mm.The results indicate that the proposed nonlinear restoring force model can accurately predict the energy dissipation and self-centering capabilities of the SCED brace under low cyclic reversed loading.(2)The proposed nonlinear restoring force model of SCED brace is developed in LS-DYNA.Four-level performance indexes and performance-based seismic design method are developed for self-centering braced steel frame structures where the beams are hinged to the columns.A typical 3-story self-centering braced steel frame structure is designed,and the seismic performance and self-centering capability of the structure under design basis earthquake,maximum-considered earthquake and mega earthquake are investigated.The results indicate the structure remains elastic under design basis earthquake.The maximun residual drift ratio under the maximum-considered earthquake is less than 0.5%,indiacting the favorable self-centering performance of the structure.The maximun interstory drift ratio under mega earthquake is less than the deformation capacity.The seismic responses of the self-centering braced steel frame structures meet the limit requirements of the performance indexes,which proves the effectiveness of the developed seismic design method.(3)The 4-,8-and 15-story self-centering braced steel frame structures are designed.The interstory drift ratio and residual drift ratio of the three structures under near-and far-fault ground motions are compared and analyzed.The effects of the near-and far-fault ground motions on the seismic performance and self-centering capability of the structures are investigated.The interstory drift ratio time history and the hysteretic behavior of SCED brace at the 8th floor of the 15-story structure under typical near-and far-fault ground motions are analyzed to study their effects on the structural damage and self-centering capability.The results indicate the interstory drift ratios and residual drift ratio of structures under near-fault ground motions are larger than that under far-fault ground motions.Two types of ground motions have little effects on the seismic performance of the structures under the frequently occurring earthquake and the maximum average interstory drift ratios are close.Under the maximum-considered earthquake and mega earthquake,the maximum average interstory drift ratios and the maximum residual drift ratios of structures under near-fault ground motions are significantly larger than that under far-fault ground motions.The near-fault ground motions cause more severe column damage and the residual deformations of the structure are also greater. |
