Nonlinear Finite Element Model Seismic Analysis Of Shot-leg Shear Wall

Short-leg shear wall structure is a new type of structure system.For its rationality in architectural layout,structural property and construction cost,it is widely applied in residential buildings in china now.But it was seldom applied in earthquake hazardous zones,and lack of deep investigation and practical tests.For security reasons, 'Technical specification for concrete structure of tall building'(JGJ3-2002)applies more strict regulations for its seismic design.Study on the earthquake-resistant capability of shot-leg shear wall can provide essential foundations for its seismic design and perfect correlative regulations in the specification.Simulation analysis is a basic way of study the seismic analysis of nonlinear building structures.To study the seismic property of shot-leg shear wall using simulation method has not only academic sense but also wide application perspective.This paper centers on the aforementioned problems,and the main achievements are as follows:The basic load-beating property of shot-leg shear wall is studied,which provide a necessary foundation for the establishment of a new finite element model.(1)The shot-leg shear wall can be classified as ductile shear wall,bending failure is the main reason of it's destroy.And the reinforcement ratio can be adjusted to make its failure process tend to be bending failure,a better ductility failure process compared with shear failure.(2)The compact of shear-lag on the lateral stiffness of shot-leg shear wall get smaller with the increase of member slenderness ratio,and it can be neglected in tall buildings.(3)When the shot-leg shear wall is cracking or in the elastic-plastic stage,the neutral axis and principal axes of inertia will shift continuously due to the change of material stiffness of the sections.As a result,the flexural stiffness changes,member elongation and further oblique bending happen.(4)Shot-leg shear wall is a type of coupled wall with strong piers and weak beams,couple beam yield before the shear wall The inner force redistributed after the couple beam yield,thus provide further defense for the earthquake resistant system.(5)Some sectional factors which may influent its load-carrying and deformation capacity are discussed.Flexibility-based elastic-plastic fiber element model is established,which considers shear deformation and geometric nonlinearity.Thus it is suitable for small slenderness ratio members.Most of the finite element models are based on stiffness method now, but its deformation shape function is not accurate especially at the strong nonlinear stage,and the displacement function strongly deviate form the actual displacement of the element.Flexibility-based finite element method adopts the force as the basic variable,and uses shape function of the force.For supposed sectional force,the balance condition will always be strictly satisfied.One structure member can be simulated by one element,the number of element is reduced and calculative efficiency increased compared with stiffness method for nonlinear analysis.Fiber element model is a effective model in dealing with complicated physical phenomena such as protean axial force and two way bending moment coupling.The member elongation and oblique bending because of the neutral axis and principal axes of inertia shift are reflected in this model.Nonlinear analysis program is developed on the basis of flexibility-based fiber element model,which provide a potent way of study the material and geometric nonlinear properties of shot-leg shear wall.Incremental and Newton-Raphson solution procedures are combined in the solution of static problems,and Newmark-βmethod is used in dynamic problems.Module program is developed,in which each module is relatively independent,and data is communicated by interface.The user can achieve deferent purpose with deferent module.Each fiber of the element may have different material characteristics so as to deal with members composed of different materials. Besides the macro structure data,the detailed information such as stress and strain history of specified fiber can be obtained.Simulative analysis of some seismic test on various section shaped shot-leg shear wall member and symmetric double shear wall is done in the paper,some information which the test had not investigated is given too.The result reflects the main loadbeating property of the shear wall and show good agreement with the test.Thus the correctness of the theory and the validity of the program are tested.The program can institute parts of test and provide a way for the investigation of seismic property of shot-leg shear wall.Dynamic analysis on an eight story shot-leg shear wall structure is done at end of this paper.The results show that this kind of structure system possessed good earthquake resistance.The weak part of the structure is at the bottom,where the members should be strengthened when it is designed.