Study On Compression Behaviours Of UHPC-Filled High-Strength Steel Tubular Composite Columns At Low Temperature

In order to study the compressive behavior of ultra-high performance concrete-filled high-strength steel tube composite columns at low temperature,the basic mechanical properties of high-strength steel tube at low temperature and the compressive properties of ultra-high performance concrete-filled high-strength steel tube short columns at low temperature were studied in this paper;At the same time,this paper analyzed the compression performance of ultra-high performance concrete-filled high-strength steel tubular composite columns at low temperature by numerical simulation.The purpose of the above research is to provide some theoretical support for the development of steel-concrete composite member materials.The main research contents and conclusions of this paper are as follows:(1)In order to study the basic mechanical properties of Q690 and Q960 high-strength steel at low temperature,39 low temperature tensile tests of Q690 and Q960 high-strength steel standard parts were carried out to study the effects of low temperature level and steel plate thickness on their strength and ductility indexes.At the same time,the constitutive models of Q690 and Q960 high-strength steel at low temperature were developed in this paper.Through the comparison with the existing test results,it is found that the model based on this paper can accurately predict the strength performance index of high-strength steel at low temperature.(2)In order to study the compression performance of ultra-high performance concretefilled high-strength steel tubular composite column at low temperature,the axial compression test of concrete-filled steel tube short column with Q690 or Q960 high-strength steel tube and ultra-high performance concrete at low temperature was carried out.The main research parameters were low-temperature level,width thickness ratio and high-strength steel strength;At the same time,based on the test,the theoretical model of the load displacement relationship of the concrete-filled steel tubular column at low temperature was developed,and its finite element model was established based on the large-scale general software ABAQUS.It is found that the concrete-filled steel tubular columns with highstrength materials and high-performance materials show good bearing capacity and ductility,and the theoretical model and finite element model proposed in this paper can accurately predict the load displacement relationship of ultra-high performance concrete-filled highstrength steel tubular composite columns.(3)Based on the existing axial compression,eccentric compression and pure bending tests of concrete-filled steel tubular columns,the finite element analysis of the compression performance of concrete-filled steel tubular columns was carried out.The simulation results could better simulate the failure mode and bearing capacity of the test,and verify the accuracy of the model.On this basis,the key parameters of ultra-high performance concretefilled high-strength steel tubular composite column at low temperature were analyzed to explore its working mechanism at low temperature.In addition,the calculation formula of bearing capacity in the code was modified at low temperature.Compared with the results of numerical simulation analysis,the theoretical formula in AISC 360-10 modified at low temperature can provide a more accurate and safe prediction of N-M curve of ultra-high performance concrete-filled high-strength steel tubular composite column at low temperature compared with EC4 and GB 50936-2014.