Study On Dynamic And Static Behavior Of Shaped Concrete Filled Steel Tubular Short Columns

Compared to ordinary concrete-filled steel tubular columns,special-shaped concrete-filled steel tubular columns(T-shaped,L-shaped,cross-shaped)have advantages like high bearing capacity,excellent seismic performance,good resistance to fire and easy construction,also they can avoid the appearance of building edges and corners to improve the effective use of room space,thus they have good prospects.At present,the researches on the mechanical properties of special-shaped concrete-filled steel tubular columns are mainly focused on the study of the axial and biasing mechanical properties under quasi-static load,and the seismic performance.Researches on mechanical properties of the special-shaped concrete-filled steel tubular columns which are under strong dynamic loads such as impact load are rarely reported.In this paper,with PVDF piezoelectric films’ excellent piezoelectric properties,a kind of implantable PVDF piezoelectric stress sensor is designed for direct monitoring of the internal time-varying stress of special-shaped concrete-filled steel tubular short columns under impact load.The calculation formula of special-shaped concrete-filled steel tubular short columns’ bearing capacity under the impact load is put forward which is based on the study of special-shaped concrete-filled steel tubular short columns’ mechanical properties under static load.The main contents of this paper are as follow:1.To take experimental study on T、L-shaped concrete-filled steel tubular short columns under impact load.To monitor the time-varying stress of the core concrete by using PVDF stress sensors which are embedded in the specimen and propose a type of method to monitor the local stress of special-shaped concrete-filled steel tubular column based on the PVDF piezoelectric stress sensor.At the same time,to understand the elastic-plastic stress development of the core concrete base on experimental data,and the relationship between the time-varying stress of the core concrete and the strength of the short column、the degeneration of the stiffness is studied,and the characteristics and laws of the core concrete’s stress evolution are revealed.The finite element software ABAQUS is used to simulate the dynamic performance of concrete-filled steel tubular columns under impact load.The numerical simulation results are compared with the experimental results to verify the correctness of the finite element model.2.To take experimental study on axial compression of special-shaped concrete-filled steel tubular short columns.Observe the influences of wall thickness on mechanical properties of special-shaped concrete-filled steel tubular short columns,and understand the failure modes of special-shaped concrete-filled steel tubular short columns with different wall thickness,load-deformation curve and ultimate bearing capacity are measured by testing specimens.And the ABAQUS model is built to calculate and compare the calculated results with the experimental results to verify the correctness of the model.Based on the specification and previous study,the formula for calculating the bearing capacity of special-shaped concrete-filled steel tubular short columns under static load is proposed.3.Based on the verified model,use ABAQUS to do parameter analysis on the specimen under impact load.The numerical simulation results are compared with the experimental results to analyze the variation law of the peak value of impact load on specimens under different parameter-conditions.Based on the calculation formula of bearing capacity under static load,the calculation of the bearing capacity under impact load of the special-shaped concrete-filled steel tubular short column is proposed.