Effect Of Structural-pulse Coupled Parameters On The Seismic Response Regularity And Mathematical Models Of Ductility Column In Near-fault Regions

Previous earthquakes indicated that engineering structures in near-field（NF）regions would suffer more serious damage compared with buildings located in the far-field region.In this regard,bridges as an important part of the“Belt and Road”and“Urban and rural resilience”strategy often need to be constructed in the NF regions because of economic and geographical factors,which pose a threat to people’s life and plans of our nation.Many researchers,therefore,carried out a lot of studies on the characteristic of near-field earthquakes and its influence on structural response,which revealed that the damage to structures in the NF region is primarily caused by the high-amplitude and long-period velocity pulse in earthquakes.However,due to the complex mechanism of NF earthquakes and the limited number of recorded ground motions,the key parameters of pulse-like ground motions have not been fully studied.Meanwhile,the response laws of bridge structures under the action of pulse-like excitations were not clear enough.Hence,this research focuses on the coupled-effect of structure-pulse parameters and the seismic response of reinforced concrete piers and aims to quantify the influence of pulse-like ground motions on reinforced concrete piers by establishing a more efficient probabilistic seismic demand model（PSDM）.Meanwhile,the framework of a novel response spectrum analysis was also proposed in this paper.The main contents and conclusions of this paper are as follows1.The influence of key pulse parameters on structural response and its relative importanceDue to the limited number of recorded actual ground motions,the equivalent velocity pulse model was adopted in this study for generating artificial pulse-like ground motions.Then,the seismic response database of the reinforced concrete pier was established in Open Sees,which can be used for the investigation of key pulse parameters.A machine learning model was also introduced to evaluate the relative importance of pulse parameters.The results revealed that the peak pulse velocity（V_P）and pulse period（T_p）show a significant influence on the seismic response.In addition,with the increase of the structural fundamental period（T₁）,the relative importance coefficients of V_Pand T_Palso change correspondingly.It can be found that when T₁is relatively larger or smaller,the seismic response of piers would be more sensitive to T_Pthan V_P,while the V_Phas a more important influence on structural seismic response in other ranges of T₁.2.The coupling effect of structure and pulse parameters on structural response,and the establishment of PSDMThen,this study will focus on the effect of the ratio of structural and pulse period（T₁/T_P）on structural response,including the structural response from elastic to plastic stages.The Boltzmann model was proposed to obtain the relationship between peak structural response and T₁/T_p.The Gaussian-power function model was adopted to establish the PSDM considering pulse characteristics.The results show that with the increase of V_p,μ_Tgradually shifts from 1.0（when V_pis so small that the structures remain elasticity）to 0.5（V_pis quite large so that the columns experience cumulative structural damage）.Moreover,the proposed PSDM of the reinforced concrete pier has been validated to effectively evaluate the seismic demand of structure under pulse-like earthquakes.3.Proposed the method of response spectrum analysis considering the pulse characteristics based on Artificial Neural NetworkBased on the traditional nonlinear response spectrum,the influence of T_pon structural response was considered in the method by introducing the parameter T₁/T_p.The framework based on ANN model for the establishment of the novel response spectrum was also comprehensively presented in this study.Additionally,the effect of structural and pulse parameters on seismic demand spectra can be well captured by the defined spectra parameters including D_max,D_min,D_δ,μ_Tand sensitive interval,which make the spectra more practical for seismic response analysis.The proposed strategy is then applied to the analysis of reinforced concrete columns under the action of seismic loading where the influence of longitudinal reinforcement ratio and damping ratio is systematically investigated and compared.