Experimental Study On Seismic Performance Of High-strength Concrete Frame Structure Reinforced With High-strength Rebars

The study of this dissertation focuses on the seismic performance of high-strength concrete frame structure reinforced with high-strength rebars. Based on design experience, high-strength concrete frames reinforced with pre-stressed rebars can provide efficient and economical alternatives to traditional reinforced concrete construction. Apart from the economies achieved by effective use of materials, researches show the frames can provide strength exceeding that in conventional reinforced concrete frames and acceptable ductility. A sub-structure pseudo-dynamic test on8-storey1/2scale building model with a test used sub-structure of two freedom degrees and a compute used sub-structure of six freedom degrees has been firstly launched domestically, and its crack patterns, deformed features and failure models, etc. have been observed and analyzed. The FEM software OpenSees was applied to perform the nonlinear seismic response analysis of the structure. The main research achievements may be summed up in the following aspects:Firstly, effects of axial compression ratio and stirrup ratio on hysteretic characteristics of the high strength concrete columns reinforced with high strength reinforcement(HSC) and the seismic performance parameters for performance based seismic design of HSC columns were investigated. The failure mechanism, ductility, and hysteretic behavior of the columns were analyzed based on the experimental data. Based on the results of the cycle loading tests of the columns, the damage indexes of12HSC columns with the different story drifts were calculated using the modified Park-Ang model. According to the deformation with different performance levels and results of the corresponding tests, it was indicated that the crack width and stress level of longitudinal bar, residual drift and ultimate drift index can be adopted as the key parameters to appraise the seismic performance of functional, repairable and collapse avoidable capacities, respectively. Comparison between the calculated damage indices using the proposed model and test results shows good agreement, and the proposed method can be referenced for the performance based seismic assessment of HSC columns.Secondly, at present, pseudo dynamic testing method has the development potential and is popular in all seismic testing methods. Sub-structure pseudo-dynamic test is more flexible and less expensive than traditional pseudo-dynamic test. The methods of sub-structure pseudo-dynamic tests were introduced in the paper based on its principles and features. Seismic testing had been carried out for high-strength concrete frame structure reinforced with high-strength rebars to illustrate that the sub-structure pseudo-dynamic testing method can not only obtain the dynamic performance of the structure, but also characterize the structural displacement and force distributions under earthquake. The test results were in agreement with the monitored earthquake responses. The study revealed that rational selection of the testing sub-structure was the key for sub-structure pseudo-dynamic tests. Therefore, the sub-structure pseudo-dynamic testing method shows that it is an effective tool for investigating the seismic behavior of high-strength concrete structure.Thirdly, in the paper, based on the seismic behaviors of high-strength concrete (HSC) frame structure reinforced with high-strength rebars and pseudo-dynamic testing method, the pseudo-dynamic tests had been conducted on the two specimens of two-story, two-bay and one-span frame model with1/2scale by MTS computer-actuator system in order to research the seismic behaviors of high-strength concrete structure system under earthquake action. The specimen was subjected to10loading cases by using three kinds of acceleration records of ground motion with the adjusted amplitude, focusing on study of change of dynamic character during earthquakes, cracking pattern, hysteretic behaviour and seismic responses in elastic and elastic-plastic stages. After pseudo dynamic test, the frame was subjected to a pseudo-static loading. The test results showed that this kind of HSC frame structure can meet the requirement of the seismic performance. The results of the test may open a new road for application of HSC frame structure in seismic zone.Fourthly, this paper presents an experimental analysis on energy dissipation and seismic property of a high-strength concrete structure reinforced with pre-stressed rebars. Based on the results of the pseudo dynamic and pseudo-static loading tests, the analysis of the hysteretic response and energy dissipation capacity of the structure under seismic action, and discussion of the damage mechanism were experimentally performed. The experimental results showed that the ductility coefficient was greater than4.0and the equivalent damping ratio was higher than0.055. It also showed that this kind of frame structure had good deformation and dissipation capacity as well as great seismic performance. The proposed method can be applied in high-strength concrete structures in seismic zone.Fifthly, the finite element analysis on the the members and structures was performed and the results between the numerical simulation and experiments were compared in this paper. Based on the previous works, a nonlinear FEM analysis was performed by using OpenSees software. The dynamic responses of the frame structure were numerically analyzed. During the simulation, the nonlinear development of the compressive concrete was specially considered. The plastic hinge and P-â–³effect of the structure were also considered. The results of the simulation showed that the developed constitutive model was suitable to calculate the seismic responses of the frame structure by FEM. The test offers additional opportunities to validate performance simulation models. In terms of peak displacements and overall response, the numerical and measured frame response agreed fairly well. But for late loading events, divergences occur, which were likely due to degradation effects and damage accumulation that were not modeled in the analysis. The observed damages suggest the need for further research to improve the performance simulation tools.