Preliminary Study On The Hysteretic Constitutive Model Of Stirrup Confined Concrete And Its Applicability

Dynamic nonlinear analysis of structural components is a main method in the research of seismic response of reinforced concrete structure. The accuracy of the analysis is decided by the ground motion which is entered as well as the rationality of analysis model and material model. Currently, nonlinear beam-column element based on fiber models has been proved that the accuracy is enough. However, in the matter of material model, due to the complexity of the concrete material and performance of the structure under various loading, the concrete hysteretic model in nonlinear analysis program is seriously simplified. Consequently, they can hardly reflect all of the hysteretic characteristics of concrete. However, the rationality of material model can easily affect the accuracy of nonlinear analysis. On the other hand, although researchers have proposed many hysteretic models, none of them can completely and rationally reflect all the hysteretic characteristics, like strength reduction, unloading-reloading stiffness deterioration, crack development and close, hysteretic energy dissipation, random unloading–reloading et al. As the result, to analyze existing confined concrete hysteretic models, and propose a more complete and reasonable model, can make good sence on enhancing the precision of dynamic nonlinear analysis.Many existing models about hysteretic stress-strain relationship of confined concrete have been collected in this paper.Nine typical kinds of models, such as Mander, Martinez, Sakai, Blakeley, Guo-Zhang, YuanJingen, ZuBolong, eng-Zhou are researched in this paper. Some parts of the models which have obvious mistakes are analysized, and then the features of each model have been explored and summarized. There are some key patameters in confined concrete hysteretic model, such as the shape of the load-displacement curve of specimens, the shape of skeleton line, strength, displacement ductility and energy-dissipation capacity.The influence of the key patameters on the reaction of the compression-bending specimens under low frequency cyclic loading is analyzed. On this basis, considering the advantages of the existing model and the accuracy and adequacy of the material model (it is easily to be added in nonlinear finite element analysis programs), a constitutive model which have more features, more reasonable loading-unloading rules and reflecting the various hysteretic characteristics of concrete material have been proposed. And the comparative result of this one with other models has demostrated this model is reasonable.This study shows that: the complexity and applicability of the existing hysteretic models has not been unified, the rationality of some models is well, but parameters is too many, and the expressions of them are too complex, though there are some models, the expression of them is relatively straightforward, but there are a lot of unreasonable factors. The change ofεcuhave an important effect on the level of force- displacement hysteresis curve, whether considering the energy dissipation of material have great influence the energy dissipation calculation results of components a lot. This model for considered various factors in a more comprehensive way, and makes modest simplification to the tension and other factors which have little affection, do take the complexity and applicability into consideration.