| The frame shear wall structure is a type of dual structure,composed by frame and shear wall with various stress characteristics and deformation modes,which is widely used in high-rise buildings.The frame-shear wall structure remains elastic under the action of a frequent earthquake.The seismic response is assigned according to the elastic stiffness of the components including frame and shear wall.The shear wall bears most of the seismic response,and the frame part bears the seismic effect.However,the structure will undergo elasto-plastic property under rare earthquakes,in which a difference between the stiffness degradation of the frame and the shear wall will happen.The seismic response and internal force will be redistributed between the frame and the shear wall,in which the distribution regularity on the internal force response of the structure is different from that under the frequent earthquake.Based on the multi-line defence design method,it is stipulated in Chinese code that the shear force in the frame should be adjusted.However,the stipulation is proposed by the common engineering experience which is lack of theoretical basis.Therefore,this paper studies the regularity and reason of shear force distribution in the frame-shear wall structures under strong earthquakes by theoretical derivation and numerical analysis,while the rationality of the standard adjustment method is further validated.The main researching work is completed as follows:A "bending-shearing" simplified model to analyze the law of shear distribution is established.The parametric analysis shows that the stiffness eigenvalue of the frame shear wall structures is the key factor which affects the distribution of internal forces.This value considered the effect of the structural height,the stiffness of the frame,and the stiffness of the shear wall roundly.The structural internal force distribution is consistent in a same stiffness eigenvalue.The shear distribution ratio of the frame of the bottom floor is less than 0.2V0 under frequent earthquakes.However,the internal force redistribution of the structure is mainly concentrated in the low stories under rare earthquakes due to the yield of shear wall,which lead to the phenomenon that the shear force in the frame part far exceeds the normative shear adjustment limits 0.2V0 and 1.5Vfmax.The refined numerical simulation method of the frame-shear wall structure is introduced.The accuracy of the numerical simulation is verified with the existing component tests and structural tests.It can be concluded that fiber beam columns and shear wall elements can accurately simulate the yield,reinforcement,stiffness degradation and hysteretic behavior of frame columns.Besides,the period of the structural model which is based on the fiber model is consistent with the experimental study.The roof-displacement timehistory curve of the structure under the rare earthquake is well fitted with the test results.In this paper,the nonlinear analysis model of frame shear wall structure could accurately analyze the nonlinear response of structures under rare earthquakes.A numerical analysis model of frame shear wall structure based on fiber model is designed according to the Chinese code to study the shear force distribution under frequent earthquakes,design earthquakes and rare earthquakes,respectively to analyze the reasons and evaluate the seismic performance.It can be seen that the shear wall stiffness degrade and structural shear redistribution mainly occurs on the bottom floor of the structure under rare earthquakes.However,the frame beams of the upper floors yield,which restrain the increase of shear force in the frame column,and arise the shear force of the shear wall.Therefore,performing shear force on the upper floor will further delay the occurrence of plastic hinges on the frame beams,and amplify the shear force of the frame columns under rare earthquakes,which will make the frame columns more unfavorable.The influence of standard adjustment methods on the reinforcement of shear wall structures with different stiffness eigenvalues are quantitative studied.Further comparisons are made on the seismic performance and collapse resistance of the frame-shear wall structures in rare earthquakes with or without shear force adjustment.The research shows that shear force adjustment has little influence on column reinforcement,with a great influence on beam reinforcement in contrary.By considering the shear force adjustment,the roof-displacement of the structure and the inter-story drift angle under the rare earthquakes are slightly reduced,with the bearing capacity of the beam end improved,and the rotation capacity of the plastic hinge is reduced.Simultaneously,the frame columns bear an increased shear force under rare earthquakes,which make the upper columns yield easier.Adjusting shear force to increase the frame beam reinforcement is more unfavorable to the force of the frame column.It can be concluded that adjusting shear force has little effect on the collapse resistance of the structure.Base on the above analysis,it is not necessary to adjust the shear by ensuring strong column weak beam and plastic hinge rotation. |
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