Study On The Bearing Capacity Of Large Opening Ratio CFST Column

In recent years,concrete filled steel tube(CFST)is widely used in bridge tower in some cable-stayed bridges with medium and small span because CFST not only has great bearing capacity but also can solve the problem of bridge tower construction template.Although CFST has the above advantages,as a new kind of structure,its force law,characteristics and bearing capacity calculation require a further systematical study.The use of concrete-filled steel tubular pylon will cause the concrete-filled steel pipe tower carrying capacity decline due to cable duct through the bridge tower,especially for the large void rate.Because it is difficult to consider the influence of cable action on the force law of the specimen,this paper only considers that the stress law of the concrete-filled steel tubular tower under axial compression and the influence of hole on the axial compression bearing capacity of CFST column.Through detailed simulation analysis and scale model test,the law of axial load bearing capacity of CFST under the condition of large volume damage rate is studied.Through the study,a clear understanding of the basic concept of finite element analysis of CFST with hole is established.In order to solve the above problems,the paper analyzes the volume perforation rate,the cable duct inclination and the concrete strength in detail at first,and obtains the force and failure law of the concrete-filled steel tubular column.It is found that the specimen with large empty rate has a certain deviation if we still adopt the formula,so a test program is developed furthermore.In this paper,the finite element model of CFST columns is established by means of simulation analysis and experimental research.The large-scale CFST columns are designed and fabricated.The test phenomena and failure modes of CFST columns with hole are expounded.The ultimate bearing capacity of the specimen,the overall deformation and local buckling of the CFST column,the longitudinal and transverse strain of the steel pipe wall and the load-displacement curve of the whole specimen are analyzed.On the basis of the experiment,the force mechanism of the large-sized CFST columns with hole is studied,and the influence of the initial defects on the ultimate bearing capacity of the specimen is considered.The comparison between experimental results and the theoretical results shows that the load displacement curve and the test curve are in good agreement with each other.The research results provide a scientific and reasonable reference for the application of CFST in cable-stayed bridge.