Jun Shang Kuang

Seismic Behavior and Ductility of Squat Reinforced Concrete Shear Walls with Nonseismic Detailing

This study investigates the seismic performance and available displacement ductility of squat reinforced concrete shear walls that were designed and detailed without explicitly considering seismic design requirements. In the study, large-scale shear walls with aspect ratios of 1.0 and 1.5, as practiced in low to moderate probability of seismic occurrence regions, are tested under reversed cyclic loading. Emphasis is placed on the inherent displacement ductility of the walls with nonseismic standard and improved reinforcement details. Experimental results show that the inherent displacement ductility factor of 2.5 to 3 is commonly achieved with the current nonseismic design practice and that of 4.5 to 5 with minor modifications in the reinforcement detailing techniques. These findings indicate that although an ordinary squat shear wall with nonseismic design and detailing may not possess sufficient ductility to respond adequately to an unexpected moderate earthquake, minor modifications to the detailing techniques can effectively lead to a reasonable improvement of ductile response behavior.

DYNAMIC BEHAVIOUR OF STIFFENED COUPLED SHEAR WALLS WITH FLEXIBLE BASES

Abstract The free vibration characteristics of stiffened coupled shear walls with flexible bases is investigated using a discrete–continuous approach, where the structure is considered as both a discrete system and a continuous system at different stages of the analysis. The stiffnesses of the flexible foundations are represented by rotational and translational springs at the base of each shear wall. The stiffened system is reinforced by an additional stiffening beam at some level of the structure. This induces additional axial forces, and thus reduces the bending moments in the walls and the lateral deflection, and increase the natural frequencies. The effects of foundation stiffness and the stiffening beam on the free vibration characteristics of the structure are studied. The optimal location of the stiffening beam for increasing as far as possible the first natural frequency of vibration is presented.

Dynamic coupling of asymmetric shear wall structures : an analytical solution

Abstract In this paper, a dynamic analysis is presented for coupled flexural-warping torsional vibration of asymmetric shear wall structures in tall buildings. Due to the asymmetry of the structure, the free vibration is a coupled one, where laterally flexural vibrations in two orthogonal directions are coupled by a warping torsional vibration. Based on the continuum approach and D’Alembert’s principle, the governing differential equation of free vibration and its corresponding eigenvalue problem for asymmetric shear wall structures are derived. Based on the theory of differential equations, an analytical method of solution is proposed to solve the eigenvalue problem and a general solution is derived for determining the natural frequencies and associated mode shapes of the structure. The proposed analysis is less approximate, and the numerical investigation pertaining to coupled vibration analysis of a generally asymmetric shear wall building shows that the results from the proposed analytical method and FEM analysis agree well. It is expected that the proposed analytical method of solution would enlarge the content of coupled vibration in the theory of dynamics of structures from theoretical research’s point of view.

Continuous transfer beams supporting in‐plane loaded shear walls in tall buildings

The failure mechanism and structural behavior of transfer beams supporting in-plane loaded shear walls have received added emphasis owing to their importance in connection with tall building construction. This paper presents an analysis of and investigation of the structural behavior of two-span transfer beam-shear wall systems in tall buildings. The interaction between the transfer girders and the shear wall has been investigated considering interior and exterior column interaction effects. The upper structural form has a significant effect on the failure mechanism of the transfer girders, which can act as full tension members or behave as ordinary flexural beams. Stress distributions in the shear wall interactive zone are presented. The relevant parameters that significantly influence the force transfer mechanism and structural behavior, such as the span/depth ratio of the transfer beam, the span of the shear wall and the stiffness of the support columns, are highlighted. The present paper provides a very useful reference for the design of continuous transfer girders supporting in-plane loaded shear walls in tall buildings.

Torsional behaviour of braced thin-walled open sections

Abstract A more rational and accurate analysis is presented for the torsion of braced thin-walled open section bars with transverse connections. The approach is based on Vlasovs thin-wall beam theory in conjunction with the continuous medium method. Shearing deformations in the middle surface of the thin wall are also taken into account. The analysis gives a generalized sectorial coordinate to estimate the realistic torsional stiffness of the thin-walled member, and provides a better physical interpretation of the relationship between the sectorial properties and the applied torque.

Interaction based analysis of continuous transfer girder system supporting in-plane loaded coupled shear walls

This paper presents a method of analysis for a structural system of coupled shear walls supported on continuous transfer girder framing into columns. It is proposed that the analysis of the system be discretised into two parts. The coupled shear wall is analysed first based on the continuum technique assuming an ideal fixed support. Charts are presented to modify the continuum forces for the interactive effect of the non-rigid support. The internal forces of the walls at the level of the transfer girder are defined as the interface forces of the girder and the coupled shear walls. These forces are then used in the anlaysis procedure for the supporting structure. Finite element simulation was used to capture and interprete the interaction mechanism of the system. Effects of different wall and support. system characteristics on the structural behaviour of the system are also discussed.

A plasticity model for punching shear of laterally restrained slabs with compressive membrane action

Abstract A plastic theoretical model is presented for the punching shear failure of laterally restrained concrete slabs, in which a parabolic Mohr failure criterion for concrete is adopted. The proposed method allows for the effect of compressive membrane action and a membrane-modified flexural theory of elasto-plasticity is used to calculate the compressive membrane forces. The predictions by the proposed analysis show good agreement with a wide range of experimental test results.

Masonry-infilled RC frames subjected to combined in-plane and out-of-plane loading

The structural responses of infilled frames subjected to combined in-plane and out-of-plane loadings are usually analyzed by separately applying in-plane and out-of-plane loads. The interaction effect of in-plane and out-of-plane loads on the structural behavior of the frames is ignored; thus errors in predicting the actual force-transfer mechanisms and modes of failure of the structures can be incurred. To solve the problem, this paper presents a discrete finite element modeling technique, which employs a damage-based cohesive crack representation of fracture behavior of masonry infills, followed by a study on the force-transfer mechanisms and failure modes of the anchored and unanchored infilled reinforced concrete (RC) frames subjected to interactive in-plane and out-of-plane loads. The analysis indicates that under out-of-plane loading the diagonal compressive thrust of masonry-infill walls, which is induced by in-plane lateral loading and acts on the walls, may reduce the in-plane load capacity of the RC frame by up to 50% and cause buckling of infill walls. On the other hand, the anchorage can effectively prevent the separation of infill walls from the bounding frame and provide stabilizing forces to the walls against buckling.

Some basic principles for linear coupled dynamic thermopiezoelectricity

According to the basic idea of classical yin-yang complementarity and modern dualcomplementarity, in a simple and unified way some basic principles for linear coupled dynamic thermopiezoelectricity can be established systematically. An important integral relation in terms of convolutions is given, which can be considered as the generalized principle of virtual work in mechanics. Based on this relation, it is possible not only to obtain the principle of virtual work and the reciprocal theorem in linear coupled dynamic thermopiezoelectricity, but also to derive systematically the complementary functionals for eleven-field, nine-field, six-field and three-field simplified Gurtin-type variational principles. Furthermore, with this approach, the intrinsic relationship among various principles can be explained clearly.

Horizontal hoops in non-seismically designed beam–column joints

Tests on full-scale reinforced concrete exterior beam–column joints with non-seismic design under reversed cyclic loading were carried out. The seismic behaviour of these non-seismically designed beam–column joints was investigated, where the effects of horizontal hoops in joint on the seismic performance and the shear strength of the joints were emphasised. It is shown that the horizontal transverse reinforcement provided in the beam–column joints with non-seismic design improves effectively the seismic behaviour and enhances the joint shear strength. It is found that to provide horizontal hoops in non-seismically designed exterior joints with a hoop ratio of greater than 0.4% may have less effect on the enhancement of the shear strength of the joints. This hoop ratio may hence be considered as one of the design criteria of the non-seismically designed exterior beam–column joints.