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Su X.,Tongji University | Zeng J.,Tongji University | Wang L.,Shenzhen General Institute of Architectural Design and Research Co.
Jianzhu Jiegou Xuebao/Journal of Building Structures | Year: 2015

The variation of secondary moments in post-elastic range, including whether the secondary moment shall be considered in ultimate limit state calculations, has been a subject of much controversy for many years. Towards a better solution to this problem, the concept of secondary moment due to prestressing is extended into nonlinear stage. By using the method of stiffness variation, fifteen prestressed continuous beams with bonded tendons were numerically simulated in which the ratio of initial secondary moment (M2) to ultimate elastic loading moment(Me) was 0.15-0.36. Based on the extended secondary moment concept, a formula for moment redistribution at the ultimate limit state was put forward with relative depth of compression zone (ξ) and M2/Me as the influencing parameters. A test specimen (ξ=0.35) from literature was analyzed to compare the proposed formula and existing formulas for moment redistribution. A two-span prestressed continuous beam(ξ=0.18) with large degree of moment redistribution was designed and tested under monotonic loading whose support reactions were measured and used in checking the prediction by the proposed formula. It is shown that the proposed formula is conservative and gives predictions that are closer to the test results than the existing formulas. ©, 2015, Science Press. All right reserved.


Yu L.,Central South University | Ma W.,Central South University | He L.,Shenzhen General Institute of Architectural Design and Research Co. | Li L.,Central South University | And 2 more authors.
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2015

A mathematical physics model of a railway waiting room was established, which was confirmed by experimental data later. Numerical simulation was used to analyze indoor thermal comfort and air quality of the waiting room in the worst operating condition in winter. Three different heating systems i. e., stratified air conditioning system, radiation floor heating system combined with ejector nozzle air supply and radiation floor heating system with artificial pillar air supply were researched. The results show that relatively hot air goes upward in stratified air conditioning system, which results in heat accumulation, uncomforting and enormous loss of energy. Combined with stratified air conditioning system, radiation floor heating system contributes to more uniform temperature field and less temperature difference in perpendicular direction of occupied zone, which is beneficial to ameliorating the feeling of "warm feet and cool head". Moreover, it can reduce the heat loss of heat convection and decrease energy consumption of heating by 20 percent. ©, 2015, Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology). All right reserved.


Xiong Z.,Xian University of Architecture and Technology | Chen X.,Xian University of Architecture and Technology | Yu Z.,Shenzhen General Institute of Architectural Design and Research Co.
Xi'an Jianzhu Keji Daxue Xuebao/Journal of Xi'an University of Architecture and Technology | Year: 2015

The dynamic response of pure friction-sliding isolation system under seismic action is analyzed through the Matlab/Simulink, and the MDOF calculation model of sliding isolation structure is set up. The sliding displacement spectrum and sliding displacement with time history analysis of curve to the SDOF equivalent rigid model, the DDOF equivalent model and the MDOF equivalent model of the sliding isolation system are contrasted respectively. The results show that the dynamic response of the DDOF equivalent is close to the response of the MDOF equivalent model; the maximum amount of sliding isolation layer is only related with coefficient of the friction and seismic wave put in and nothing is related with the overall mass of the structure. When coefficient of friction of the isolation layer is less than 0.1, the SDOF equivalent rigid model is fitted with the DDOF equivalent model. Accordingly, the rationality and feasibility of using sliding displacement spectrum which is determined by the equivalent rigid model to simulate actual sliding structure is confirmed, and a foundation for the spread of sliding isolation system is established. ©, 2015, Science Press. All right reserved.


Cui Q.,Zhejiang University of Technology | Yang J.,Zhejiang University of Technology | Wang Q.,Shenzhen General Institute of Architectural Design and Research Co. | Xu Y.,Shenzhen General Institute of Architectural Design and Research Co. | Kang G.,Tianjin University
Jianzhu Jiegou Xuebao/Journal of Building Structures | Year: 2012

In order to study the seismic performance of Z-shaped reinforced concrete columns, cyclic loading tests were carried out on nine 1/2 reduced-scale specimens and monolithic loading tests on two specimens. The effect of axial compression ratio (n=0.30, 0.45), lateral loading direction (α=0°, 45°, 90°, 135°), web depth-thickness ratio (3:1, 4:1) and strength of the longitudinal bars (HRB400, HRB500) were studied. And the failure characteristics, mechanical behaviors of Z-shaped section columns such as the loading-displacement hysteretic loops and skeleton curves, load bearing capacity and displacement ductility were analyzed. The experimental results indicate that the major failure made of the tested column is flexural failure, and the destruction mainly occurs at the mid-span cross-section which parallels the force direction. The hysteretic loops of Z-shaped section columns are symmetric and plump. The specimens have good ductility, indicating excellent seismic behavior. A computer program aiming at obtaining the bearing capacity of Z-shaped columns under axial compression and biaxial bending was compiled. The analytical results are in good agreement with the test results.


Xu Y.,Shenzhen General Institute of Architectural Design and Research Co. | Wang Q.,Shenzhen General Institute of Architectural Design and Research Co. | Chen Y.,Tianjin University
Jianzhu Jiegou Xuebao/Journal of Building Structures | Year: 2012

According to the principle of biaxially eccentric loading for RC column and nonlinear analysis, ductility of 16539 square columns' section were calculated and analyzed, including many relevant factors including direction angle of action of bending moment, axial force ratio and scheme of lateral reinforcement etc. The dominating factors of ductility of square columns were obtained in terms of axial compression ratio and arrangement of hoop reinforcement. Ductility behavior of square columns were summarized. The following conclusions are drawn. With increased axial compression ratio, ductility of square column is down. When the volumetric ratio of reinforcement for the stirrups or hoops is same, columns' ductility with arrangement of lesser diameter stirrup and space between hoops is more than bigger diameter stirrup and space between hoops. On the other hand, only considering longitudinal bar of brace length at the same time, improving the volumetric ratio of reinforcement of the stirrups or hoops with different diameter stirrup and space between hoops will effectively improve columns' ductility. On the base of regression analysis for the ductility of square columns', the limiting value of axial compression ratio of square column is obtained in relation with characteristic value of providing stirrup or hoop.

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