Experimental Research And Analysis Of Flexural Rigidity And Strength Of Circular CFST Member Under Combined Compression And Bending

The concrete-filled steel tubular(CFST)column possesses high load-bering capacity,easy construction and good seismic performance,and has been widely applied in practice now.At present,there are many achievements in the study of concrete filled steel tubular structures at home and abroad.However,compared with the study on the mechanical properties of concrete filled steel tubular columns,most scholars focus on the analysis of mechanical properties of bias condition,and this kind of research focused on the complex bearing capacity of concrete filled steel tube under the force analysis on the stiffness change of complex stress condition.With the development of the economy,the span of the structure is increasing and the form of the building is becoming more and more complex,it is very important to study the stiffness and bearing capacity of the concrete filled steel tubular members under different parameters.This thesis intends to investigate the behaviour of the CFST columns under combined compression and bending experimentally.The main contents are as follows:1.Referring to domestic and foreign literatures on concrete filled steel tube,summarizes the research results of concrete filled steel tubular columns,and determines the test scheme of the mechanical properties of concrete filled circular steel tubular members under bending and compression2.A total of four specimens were tested,the axial compression ratio is used as the main research parameter,and the influence of different axial compression ratio(0,0.10,0.31,0.45)on the flexural rigidity and bearing capacity of concrete filled circular steel tube is investigated.Experimental results shows that proper axial compression ratio(0?0.31)can improve the flexural stiffness and flexural strength,but when the pressure is relatively large(0.45),The flexural rigidity and flexural bearing capacity of specimens are decreased.The difference is that the flexural rigidity decreases slightly,while the flexural capacity decreases obviously.3?According to the M-? curve in the test process,based on the analysis of related theory,the 5 foreign and 2 domestic standard specifications for the elastic flexural stiffness(initial stage stiffness)the calculated value was compared with the experimental values.Based on the test results,some reasonable suggestions are put forward for the calculation methods of different specifications.4.The design methods for CFST columns in code DBJ/T13-51-2010?CECS 28-2012 and GB 50936-2014 were used to compared with the experimental results.It was found that the method specified in GB50936-2014 can reasonablely calculate the N-M interaction curve of the CFST columns.In addition,the calculation method of N-M curve of concrete filled steel tube in CECS 28-2012 can also be applied to the actual design in the case of large safety margin.