| The design in elastic state of structure in the earthquake is not economical and reasonable. Good design can ensure structural components have enough ductility and can dissipate a part of earthquake energy by the way of plastic deformation. Confining the core concrete by using reinforcement steel to improve the deformation performance of concrete is an important means to improve the ductility of concrete components. Configuring confining reinforcement reasonably to effectively express ductility performance of concrete structure is a major task of aseismic optimum design. On the basis of the summarization of previous research achievements of confined concrete, this paper make some improvement on the optimum design program of reinforced concrete called SARCF, and explore the overall frame seismic performance impact of changes on strain condition of the component by using the damage analysis function of SARCF. The main research work is as follows:(1) According to the relevant document literature of confined concrete collected, fix original concrete model of SARCF program so as to reflect the improve effect of confining reinforcement number, interval, strength and configuration forms to the material constitutive relation.(2) Complete moment-curvature skeleton curve of component. Propose piecewise calculation method of moment-curvature skeleton curve of confined concrete component according to the theoretical of strain compatibility and the principle of force balance. Referencing the beam and column test date of confined concrete, calculate the skeleton curve of component by using SARCF program, and analyze the variation law of confining reinforcement in skeleton curve by comparing with the existing test curve.(3) Revising hysteretic model of SARCF program, and introduce a stirrup constraint effect coefficient to consider the effect of constraints. According to the hysteresis curve of existing test, make quantitative research on the strength drop value of hysteresis curve in the cycle load and find out the corresponding relation with the stirrup ratio change so as to provide the decline coefficient of hysteretic model bearing capacity.(4) Calculate damage index of a frame by using amended SARCF program, and choose representative components to make a different change on their stirrup ratio. Compared the frame pitch point and component damage index before and after the change of stirrup. Analyze the improve effect of confining reinforcement to the seismic behavior of frame construction.After research work, we have the following findings:(1) The number, interval, strength and configuration type of restraint reinforcement has direct impact on concrete constitutive model. Using the material model revised SARCF program can effectively simulate moment-curvature skeleton curve of confining concrete beam and column.(2) The form of moment-curvature skeleton curve is dominated by axial compression ratio and stirrup ratio. And axial compression ratio determined the nature of the curvature ductility coefficient.(3) Adjust strength drop value on the basis of hysteresis curves of existing test measured value, and get the drop value of bearing force which reflects the refinement confining effect. Using new ratio SARCF hysteretic model can simulate hysteretic curve of confining beam and column well.(4) The simulation of frame structure damage index by using SARCF program indicate that the improving effect by using confining reinforcement is related to the component ductility index. Improving the stirrup ratio of bottom column can obviously improve the damage situation of frame construction in earthquake. |
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