| The faults and the near-fault zone are the areas where the earthquake damage is most concentrated.The relevant national and international seismic codes have proposed that avoidance is the main shock-absorbing measure for the structure of the near-fault zone.However,due to topography,landforms,construction costs,and overall routing,it is inevitable that bridge structures will cross active faults.In recent years,many near-fault bridges damaged severely and even collapsed in previous earthquakes,lateral falling beams is the most significant damage characteristics of the cross-fault bridges,but systematic studies on the effect of shear keys on the seismic performance of cross-fault bridges are still very weak.In this paper,a cross-fault simply supported girder bridge was taken as the research object,and artificial cross-fault ground motion was used as the excitation,based on the platform of OpenSEES,a three-dimensional finite element numerical model of the cross-fault simply supported girder bridge was established.The influence of the strength V,the initial clearance s and the ductility of shear keys on the seismic responses of the cross-fault simply supported girder bridge were systematically studied.The main research work of this paper is as follows:(1)A cross-fault simply supported girder bridge was taken as the research object,based on the OpenSEES software,a nonlinear three-dimensional refined finite element model was established.At the same time,the bridge model was established with SAP2000.The rationality of the model was verified by comparing the period and vibration mode of the two models.(2)The relevant velocity pulse model and the equivalent pulse parameters of ground motion were systematically teased out.Based on the above work,the pulse parameters under design earthquake and seldom occurred earthquake were determined,and the horizontal ground motions with high frequency components that match the field were selected.Cross-fault design earthquakes and seldom occurred earthquakes were synthesized with low-frequency pulses and high-frequency waves.(3)The influence of the strength V of shear keys on the displacement of the bearings,pier top and beam-end,and the response of the pier bottom under design and seldom occurred earthquakes were systematically studied.The calculation results show that,relative to non-adjacent fault piers,in order to limit the relative displacement of the piers and beams effectively,higher strength of the shear keys is needed on the adjacent fault piers;under seldom occurred earthquakes,the structural responses are greater than the design earthquakes,higher-strength of shear keys is required.Under the two kinds of earthquakes,the response of the piers bottom increase with the strength of the shear keys increased and finally tend to stabilize.(4)The influence of the initial clearance s of shear keys on the displacement of the bearings,pier top and beam-end,and the response of the pier bottom under design and seldom occurred earthquakes were systematically studied.The results show that,compared with the non-adjacent fault piers,the adjacent fault piers need to set larger initial clearances,it can prevent premature failure of the shear keys and the shear keys can play a batter limit effects.Compared to design earthquakes,adjacent faults piers need to have larger initial clearance under rare earthquakes to achieve better limit effect.Under the two kinds of earthquakes,the response of pier bottom increase and then tend to stabilize with the augment of the initial clearance.(5)The influence of deformation ductility capacity of shear keys on the displacement of the bearings,pier head and beam-end,and the response of the pier bottom under design and seldom occurred earthquakes were systematically studied.The results show that,under two kinds of earthquakes,with the increase of shear keys ductility,the displacement of bearings decrease,and the response of the pier bottom increased,but they all have a small overall change. |
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