Research On Axial Compression GFRP-concrete-steel With T-shaped Flanges Reinforced Double-skin Tubular Columns Such As The Number Of Ribs

FRP-concrete-steel double skin tubular columns is an emerging form of hybrid column composed of external FRP pipes and internal steel pipes and filled with concrete between the double pipes,referred to as DSTC column.Studies on DSTC columns over the past decade have generally confirmed the good structural performance of this column form,but it is worth noting that in DSTC columns,although the outward buckling of the steel tube is constrained by the surrounding concrete and FRP outer tube,its Inward flexion is still possible,and this is still an open question.To solve this problem,the inner steel tube must be reinforced to prevent or delay its inward buckling and to minimize its negative impact on the axial compression performance.In this thesis,the DSTC column is improved,that is,T-shaped steel is reinforced on the inner steel tube to form Fibre-reinforced polymer-concrete-steel with T-shaped flanges reinforced double-skin tubular columns,referred to as T-DSTC column.The test mainly takes Fibre-reinforced polymer-concrete-steel with T-shaped flanges reinforced double-skin tubular columns as the research object,and conducts axial compression tests on 18 composite columns,including 8 groups of T-DSTC composite columns and 1 group of DSTC composite columns.The main research of this thesis is as follows:（1）The T-shaped rib can not only effectively delay the local buckling inside the steel pipe,but also have the effect of longitudinal reinforcement to improve the bearing capacity of the composite column.In addition,in the T-DSTC column,the T-shaped rib also acts as an additional connector,and the web constrains the concrete through the traction flange to improve the composite effect between the concrete and the steel tube and effectively reduce the axial deformation of the T-DSTC column and lateral deformation.Thereby,the bearing capacity and deformation of the T-DSTC column are better strengthened.（2）Ensure that the total cross-sectional area of the T-section steel is similar.Compared with the T-DSTC column with the thicker T-section steel but a small number,the use of the T-DSTC column with the thinner T-section steel but the larger number is more effective in improving the structural performance of the hybrid DSTC column.efficient.（3）When only the diameter thickness ratio is the test variable,the axial compression performance of T-DSTC column is usually improved by appropriately reducing the diameter thickness ratio of steel pipe.With the decrease of the hollow ratio of the T-DSTC column section,the ultimate bearing capacity of T-DSTC column is improved.However,due to the increase of the proportion of sandwich concrete section area of T-DSTC column,the transverse deformation of concrete is large,which will reduce the ductility of T-DSTC column.（4）When all other parameters remain unchanged,with the increase of the thickness of the GFRP pipe,increased peak bearing capacity and maximum axial strain of T-DSTC columns,while the hoop strain develops slowly,indicating that the GFRP pipe is in the Under the same peak load,the lateral deformation is smaller,and the restraint effect can be continuously exerted,thereby improving the overall stiffness of the T-DSTC column.（5）Combined with the theoretical analysis of the experimental data,a design model suitable for predicting the ultimate axial compressive bearing capacity of GFRP pipe-Tsection steel reinforced steel pipe-concrete composite hollow short columns is proposed.