Study On Seismic Performance Of Concrete-filled GFRP Tubes Column-Reinforced Concrete Beam Joints

Concrete-filled FRP tubes can meet the needs of modern engineering structures' development toward long-span, high rise, heavy load, high strength and light weight, providing an excellent alternative for concrete effectively subjected to corrosive environmets, in line with the industrial requirements of modern construction. Wide concen has been focused on since CFFT was initially recognized by the scholars at home and abroad,which has become one of the most popular item on new style composite structures.The results corresponding has been drawn a lot, and there are also examples of successful applications,however,studies on FRP Tubed reinforced concrete columns have been very limited(The FRP tubes are used to transversly confine concrete,not bearing the axial loads). In order to apply this structure to seismic requiremented bridges or buildings, The seismic performance of concrete-filled FRP tubes columns is urgently need to study. Based on applied concrete-filled FRP tubes columns to bridge pier and simulated the bridge pier-cap beam joint in bridge structure, concrete-filled GFRP tubes column-reinforced concrete beam joints of T type are designed,and the seismic performance of them under repeat low cycle load are researched.Completed the following work:1.Based on the test of concrete-filled GFRP tubes column-reinforced concrete beam joints of T type under repeat low cycle load,the working mechanism and failure shape of the joints under the both horizontal and vertical cycle load are researched,as well as the constraint effect of GFRP tube,the hysteretic curves,energy dissipation ability,ductility feature and the level limit capacity.2.1t can be found from the contrast with the RC joints that the GFRP tubes column-reinforced concrete beam joints have excellent ductility in the two loading mode,the constraint effect of GFRP tube and the increase of the seismic behavior are remarkable.3.The factors such as concrete strength and the axial load ratio that affected the failure mechanism,ductility and the level limit capacity of the joints in the two loading mode are analyzed.The ductility of common-strength concrete is better than that of high-strength concrete,but the common-strength concrete's level limit capacity is lower than that of high-strength concrete.In a certain range of axial load ratio,with the axial load ratio increased,the ductility decreased,but the decreased degree is less than RC joints. 4.The GFRP's circumferential strain and axial strain and the steel's strain in the joint area of concrete-filled GFRP tubes column in horizontal and vertical loading mode are researed.The mechanical behavior and failure mechanism of the core area of joints are analyzed.5.The ductility,deformation properties and level capacity of the two loading mode's specimens are compared.In the same axial load ratio,the specimens'horizontal seismic behavior is better than vertical seismic behavior.With the axial load ratio increased,the ductility of specimens decreased in a little degree. The decrease degree of horizontal specimens is less than vertical specimens.