Comparison Of Shear Wall Special Boundary Element Requirements And Identification Of Nonelastic Behavior Of Frame-Tube Structure

Many earthquake reconnaissance reports imply that the loss of effectiveness forshear wall structures mainly occurs in such ways: the total loss of concrete in eachsurface of the bottom part; crushing of restrained concrete and the loss of stability oflongitudinal bars in the ends of shear wall; the deterioration of both failure paterns whenthe ratio of axial force of shear wall is not limited effectively and then the falling of theentire structure. The experimental research indicates that boundary elements at the endsof shear wall with reasonable ratio of axial force and transverse reinforcement are ableto optimize the behavior of concrete, hence enhance the ductility of shear wallstructures. The requirements of boundary elements of prevailing Chinese design codeare mainly based on engineering practice and cannot represent the state of the artexperimental and theoretical research findings.This paper introduced the provisions of boundary elements for the plastic hinge inthe bottom of shear wall in each national design code, mainly in American design code,and compared them with those of prevailing Chinese Code for Design of Concretestructures and Technical Specification for Concrete Structures of Tall Building. Thenthis paper utilized ETABS program to design a30-story shear tube structure in intensityregion7（0.10g）with repect to corresponding American design conditions, theearthquake force, loads combination, model method, story drift limitation and seismicmeasures etc. of this model were based on ACI318-2011and ASCE7-10. Thencompasrison for different boundary elements according to each national design codewas made. According to the model criteria of PERFORM3D program, the nonlinearmodel of this structure was built and comparison of modal analysis between ETABSand PERFORM3D program was accomplished. In the end, utilizing conditional meanspectrum at basic structural periodT₁andT₂as target spectrum, this paper chose14groups of ground motion records and scaled them at target period range. With the inputof these ground motion records and doubled ones, this paper completed the3Dnonlinear dynamic response analysis of this structure using PERFORM3D program,then the story drift, tube shear force, peak concrete compression strain distribution ofthe plastic hinge region of shear wall in axis X and peak strain distribution of the shearwall boundary fibers were displayed.Based on the research of this paper, conclusion can be made as follows: ①The requirements for storys and the horizontal length of special boundaryelements in current Chinese design code are less strict in comparison with those inforeign design codes, so are the requirements of transverse reinforcement in specialboundary elements.②With respect to other storys where special boundary elements are not needed,Chinese design code requires detailing boundary elements with less transversereinforcement while foreign design codes do not demand such detailing measures.③With the input of ground motion records that are selected based on thecomditional mean spectrum at structural periodT₂the mean value level of response ofthe structure is slightly less than that at basic structural periodT₁, however, a fewground motion records will lead to larger response. Structural periods other than basicperiodT₁are necessary when choosing ground motion records.④With the input of ground motion records of Maximum Consideration Earthquakelevel, the strain of boundary fibers of shear wall tube in the middle and upper storys ofstructure is large probably. When the strength of ground motion records are doubled, thestrain of boundary fibers of shear wall tube in the middle and upper storys of structure islarge universally, and in some storys it can ecceed the yield strain of longitudinalreinforcement.