| The concrete-filled double-skin steel box column is composed of inner and outer steel boxes and concrete between them.It has many advantages of light self-weight,high bearing capacity,good seismic performance and so on.There are good prospects for application in high piers and large-span bridges.However,the thin-walled steel box is susceptible to local buckling under axial compression,which will reduce the structural load-bearing capacity.For this reason,PBL ribs are set on the inner and outer of thin-walled steel boxes to form concrete-filled doubleskin thin-walled steel box columns stiffened with PBL to effectively relieve the local buckling of thin-walled steel boxes,enhance the steel box-concrete combination,and improve the structural load-bearing capacity.In order to study the axial compression performance of concrete-filled double-skin thin-walled steel box columns stiffened with PBL and the effect of whether to set PBL ribs and section hollow ratio,the axial compression test of concrete-filled double-skin thin-walled steel box columns was tested in this paper,based on which FEM numerical simulation and analysis the influencing factors were carried out,and finally the axial bearing capacity calculation method was proposed in combination with the theoretical analysis.The main research contents are as follows.(1)Seven thin-walled steel box concrete hollow pier axial compression tests were designed and completed,according to the test results,the damage modes,initial stiffness,ultimate load and strength index,ultimate displacement and ductility,and strain distribution on the surface of the outer steel box were compared and analyzed for each specimen.The results show that setting the PBL ribs can significantly improve the local buckling of the steel box,enhance the restraining effect of the steel box on the concrete,and effectively improve the axial compression bearing capacity and ductility of the concrete-filled double-skin thin-walled steel box columns.(2)FEM modeling of concrete-filled double-skin thin-walled steel box columns stiffened with PBL was carried out by ABAQUS finite element software,where material properties,steelconcrete contact relationship,etc.were reasonably selected,then the damage modes and ultimate bearing capacity obtained from simulation and test were compared to verify the accuracy of the numerical simulation method.Finally,two representative specimens were selected to carry out the whole process stress analysis to compare the different stress performances of inner and outer steel tubes,concrete and PBL longitudinal ribs in different loading stages.The results show that setting the PBL longitudinal ribs can not only alleviate the local buckling of the steel box,thus improving the participation of inner and outer steel tubes sections in the force,but also make the parts work together to enhance the confinement effects of the steel box on concrete.(3)By using finite element numerical method,the parametric analysis of the influencing factors of the axial compression performance of concrete-filled double-skin thin-walled steel box columns stiffened with PBL were carried out,and explore the influence of main parameters such as outer steel tube width-thickness ratio,section hollow ratio,opening spacing and opening hole diameter of PBL on the axial compressive mechanical behavior of concrete-filled doubleskin thin-walled steel box columns stiffened with PBL.The results show that the increase of outer steel tube width-thickness ratio and section hollow ratio will reduce the ultimate bearing capacity,and the increase of opening spacing and decrease of opening hole diameter can increase the axial compressive ultimate bearing capacity of specimens to some extent.(4)Combining with the steel box local buckling and the effect of setting PBL longitudinal ribs on the axial compressive bearing capacity of the combined column,the calculation formula of the concrete-filled double-skin thin-walled steel box columns stiffened with PBL axial compression short column bearing capacity were proposed,and verified the reliability of the axial compression bearing capacity calculation formula proposed in this paper by comparing the formula calculation value with the test value. |
