The Whole Loading Process Parametric Analysis Of Lateral-torsional Coupling Of Soil-multistorey Bidirectional Regular Eccentric Structure

As modern cities continue to flourish,irregularly-shaped have emerged in large numbers.Studies of earthquake destruction have demonstrated that these structures exhibit vibrating characteristics of coupled translation and torsion under an earthquake ground motion.Currently,the available investigations primarily concentrate on the dynamic analysis of these typical multistorey eccentric structures.Due to the differences between the analysis assumptions and input seismic waves adopted by different researchers,a relatively universal conclusion is still lacking.Most of the parametic analysis of multistorey eccentric structures were limited to the elastic stage.There have yet to be studies that are concerned with the lateral-torsional coupling behaviours of multistorey eccentric structure in inelastic stage.At the same time,the lateral-torsional coupling behaviours is also significantly affected by the foundation soil.Therefore,it is necessary to carry out inelastic parametric study on the lateral-torsional coupling behaviours of the multistorey eccentric structure and the influences of foundation soil on lateral-torsional coupling behaviours.The results of this study can provide theoretical foundations for the seismic design of irregularly-shaped buildings and are of great significance to the perfection of relevant rules in structure specifications.Focusing on the multistorey eccentric structure and soil-multistorey bidirectional eccentric structure,the lateral-torsional coupling behaviours and the seismic responses from elastic to inelastic,and the influence of considering interaction on the lateral-torsional coupling behaviours were systematicly studied in this dissertation.In the end,the eccentric simplified model and its parametric analysis results were respectively validated by fine models established on ANSYS software.The main research and achievements are as follows:(1)Taking a typical multistorey bidirectional regular eccentric frame system as an illustrative example,a simplified bidirectional asymmetric multistorey dual lateral load-resisting model was constructed.And the inelastic simplified model was proposed based on the elastic simplified model.The development of simplified model laid the foundations for the successive parametric analyses in the following work.(2)For the convenience of conducting the whole process parametric analyses from elastic to inelastic,starting from the general regularity of natural frequency three-stage evolution of eccentric frames with different layers,the second stage,which has large frequency variation and is the most important one,was fit into a slant line via the least-squares method with a linear relation to the loading coefficient.Thus,three analytical stages were respectively defined for eccentric structure on the rigid foundation and soil-multistorey bidirectional eccentric structure,which provided conditions for the following parametric analysis.(3)The motion equation of multistorey bidirectional eccentric structure was derived.And the whole process parametric analysis of lateral-torsional coupling behaviours of the multistorey bidirectional eccentric structure were conducted for the first time from elastic to inelastic by taking advantages of the three defined analysis stages.The variation tendency of the lateral-torsional coupling behaviours under the major parameters,including the uncoupled torsion to lateral frequency ratio(?)and eccentricities with different values and stages was analyzed.The general laws of each parameter affecting the lateral-torsional coupling behaviours in three stages were concluded.The analysis results indicated that the first two vibration modes of the eccentric structures can be changed by the influence of eccentricities when ? is equal to 1.1~1.2;the first order vibration mode tends to the first order pure translation vibration mode in the loading direction of the equivalent symmetric system from the first to the third stage.(4)Based on investigating the lateral-torsional coupling behaviours,seismic response parametric analysis of the multistorey bidirectional eccentric structure on the rigid foundation was conducted in three stages.The variation tendency of displacement transfer functions and lateral-torsional coupling response degree with parameters were discussed.Thus,the generalized regularity of uncoupled torsion to lateral frequency ratio and eccentricities influencing seismic response in various stages was obtained.It was implied that the overall lateral-torsional coupling response of bidirectional eccentric structure is the strongest when ? is equal to 1.1~1.2,and it is very detrimental to torsional design.From the first to the third stage,the effects of eccentricities are weakened,and the translation displacement transfer function in the loading direction continuously increases which is decided by the variation features of the first order vibration mode during this process.(5)After acquiring the lateral-torsional coupling behaviours on rigid foundation,the motion equation of soil-multistorey bidirectional eccentric structure was deduced based on the Lagrange energy method.Parametric analyses of lateral-torsional coupling dynamic characteristics and seismic response in three stages were respectively carried out.The influence of different foundation soil conditions on the variation regularity of lateral-torsional coupling behaviours with parameters was studied.The results indicated that the lateral-torsional coupling behaviours of the bidirectional eccentric structure is not only closely related to the period ratio and bidirectional eccentricities,but it is also greatly affected by the foundation soil,especially when the foundation soil is relatively soft.Hence,it is convincing that the influence of foundation soil on the eccentric structure cannot be ignored.The foundation soil condition can cause obvious changes in variation tendency of normalized frequencies and displacement transfer functions of superstructure with parameters in different stages.Under some conditions,the evolution regularity is opposite to that under rigid foundation.(6)The dynamic characteristics and seismic responses of the proposed simplified model and SR foundation-simplified model were respectively validated by fine model of the eccentric structure and corresponding three-dimensional fine model of soil-eccentric structure established on ANSYS software.Based on analysis of lateral-torsional displacement ratios of fine models under different values of ?,the parametric analysis results of seismic response were validated.At the same time,by comparing the results of seismic response parametric analysis and the dynamic elastic-plastic time history analysis,the essential difference between the seismic response parametric analysis and dynamic elastic-plastic time history analysis was further demonstrated.The influences tendency and degree of uncoupled torsion to lateral frequency ratios and bidirectional eccentricities on the seismic responses,which was obtained via seismic response parametric analysis in different stages,can provide support for the dynamic time history analysis of the structures.