Research On Seismic Behaviors Of Rectangular Steel Tube Confined Reinforced Concrete Ultra-short Columns

In frame structures of modern reinforced concrete industrial workshop, growing power load and the emergence of the split level l ead to increasing section size and length limit of the column. Then ultra-short column whose shear span ratio is less than 1.5 in local region of structure appears. In comparision with ordinary frame column, ultra-short column has poor ductility and is prone to shear failure under seismic action. Seismic code rules that it should take special form to improve the seismic performance, and the form of steel tube confinement has been proved to improve that effectively. This thesis mainly studies the seismic performance of rectangular steel tube confined reinforced concrete ultra-short column with more practical application.Based on the ultra-short column appeared in the frame structure of themal power plants, this thesis designed model test of large scale to study the seismic performance of rectangular steel tube confined reinforced concrete ultra-short column with the combination of finite element simulation. In the meantime, the impacts of the confinement of steel tube in local region on the structual seismic response of the whole model are studied. The main contents are as follows:(1) Experimential research on rectangular steel tube confined reinforced concrete ultra-short column:One rectangular ordinary reinforced concrete ultra-short column and two rectangular steel tube co nfined reinforced concrete ultra-short column have been designed, and load-displacement curves and stress information of the specimens have been got through the quasi static test. Through detailed analysis of failure mode, shear capacity, ductility, energy consumption and stress state, the impacts of steel tube confinement on the seismic performance of ultra-short column are studied.(2) Numerical simulation of rectangular steel tube confined reinforced concrete ultra-short column: Finite element model was built to prove the rationality of the test according to the result of the test and to study the impacts of different parameters on the shear capacity of rectangular steel tube confined reinforced concrete ultra-short column. At the same time, the formula of shear capacity was put forward.(3) Analysis of impacts of rectangular steel tube confined reinforced concrete ultra-short column on seismic response of the structure: Finite element model was built for the whole structure to compare the result of models regarding steel tube confinement as a variate, thereby it has a research on influence degree of seismic response of the whole model and ultra-short column region with steel tube confinement of local region.Through the study of this thesis, method that ca n effevtively improve the seismic performance of reinforced concrete ultra-short column is put forward. What’s more, certain basis of the design of seismic resistance is afforded.