This paper introduces a new design form for prestressed shear walls with horizontal bottom slits utilizing cast-in-place technology. Horizontal slits are placed symmetrically at the wall-foundation interface of prestressed shear walls while the concrete in the middle of the wall width remains connected with the foundation. Furthermore, unbonded prestressed tendons inside the wall are adopted to provide self-centering ability. Tests on prestressed self-centering shear walls with horizontal bottom slits under cyclic loading were conducted to investigate their seismic performance. Test results were analyzed from the tests, and a comparison was made among traditional shear wall and self-centering shear walls with horizontal bottom slits of different configurations. The experimental results indicate that the tested cast-in-place shear walls exhibit excellent self-centering ability with the lateral load capacity similar to traditional shear walls. The quantity and distribution range of the cracking in t...

Quantitative assessment of seismic damage by using damage models has been proved feasible and effective in controlling the earthquake-induced damage of structures. In this study, a modification is proposed for the original Park-Ang model by eliminating its non-normalization problem. The combination coefficient of the modified model is derived using the cyclic test results of flexure-dominant RC members from the database provided by the Pacific Earthquake Engineering Research Center and the author's own tests. An empirical formula is developed through multivariable nonlinear regression analysis to relate the combination coefficient with three design parameters. The comparison between the modified model and the original model indicates that the damage index of flexure-dominant RC members can be determined by the modified model with higher precision and smaller scatter. At last, the damage indexes at principle damage states are calculated by the modified model.

Concrete-filled steel tube (CFST) columns are increasingly used in composite construction. Under axial compression, the steel tube will sustain partial axial force and meanwhile provides the confinement to the infill concrete. The high axial strength capacity of CFST columns is largely related to the confinement provided by the steel tube. Extensive studies on CFST columns have been conducted. Nevertheless, how to quantify the efficiency of confinement effect in CFST columns using concrete with different strength grades is still missing. To address this issue, a series of compressive loading tests on CFST columns were conducted in present study. The variable parameters studied include concrete strength and diameter-to-thickness ratio of the steel tube. Six CFST stub columns in total were designed and tested under uniaxial compression. Axial strength, stress state in the steel tube, confined concrete strength and confining pressure acting on the infill concrete were carefully investigated. Test results show that the confinement factor (defined as the ratio of the nominal strength of empty steel tube to that of the unconfined concrete) is the most dominant factor influencing the confinement effect, and a larger confinement factor gives higher confinement effect. The low-strength concrete exhibits better performance of ductility and confinement compared with the high-strength concrete. The index of equivalent confining pressure was used to quantify the level of passive confinement provided by the steel tube in CFST columns. Based on the test results, a method to quickly quantify the confining pressure provided by the steel tube was proposed.