Experimental Research On Seismic Behavior Of Concrete Partially-filled Round-ended Stainless Steel Tubular Piers

Concrete partially-filled round-ended stainless steel tubular pier is a new type of steel-concrete composite pier,which combined the advantages of both round-ended stainless steel tubular piers and concrete partially-filled steel piers.It inherits the advantages of good corrosion resistance,low maintenance costs and high transverse lateral stiffness of round-ended stainless steel tubular piers,as well as the advantages of fewer concrete usage and lower self-weight of concrete partially-filled steel piers,and is expected to have good seismic performance.In this paper,quasi-static experiments are conducted to study the seismic performance of this new type of composite piers,and further study is carried out by theoretical analyses and finite element simulation.The main contents of this paper are as follows:(1)Low-cycle cyclic tests were conducted on seven specimens with different concrete filling ratio,loading direction and existence of diaphragms.The test results showed that the hysteretic curves of all specimens were plump with no significant pinching.The ductility ratio were among 3.71 to 5.08.(2)The bearing capacity,energy dissipation capacity and ductility of specimens will decrease slightly with the concrete filling ratio.When bending about the strong axis,the specimen with 60%-filled concrete had similar failure modes as the fully-filled specimen,which occurred at the pier bottom,while the specimen with 30%-filled concrete had a failure mode associate with buckling of the hollow steel tube above the diaphragm,with a capacity decrease of 6.1%.Installing a diaphragm on top of the filled concrete could effectively increase the concrete restraining effects.When the concrete was 60%-filled,the bearing capacity of specimen with a diaphragm was 21.5% higher than specimen without a diaphragm;while the failure of both specimens occurred at the bottom,the specimen with a diaphragm had much less buckling of the steel tube there.When the concrete was 30%-filled,the bearing capacity of specimen with a diaphragm was 23.0% higher than specimen without a diaphragm,and the failure was due to buckling of the hollow steel tube above the diaphragm.(3)Nonlinear finite element hysteretic analyses of test specimens were carried out using ABAQUS,and parametric studies were conducted with verified models,including the nominal yield strength of stainless steel,thickness of the steel tube,concrete strength,concrete filling ratio,existence of diaphragms,form of diaphragm,axial load ratio and aspect ratio of the section.The results showed that the lateral bearing capacity of the piers were greatly influenced by the nominal yield strength and thickness of the steel tube,concrete filling ratio,axial load ratio,aspect ratio of the section and the existence of diaphragms,while the concrete strength and form of diaphragm have almost no effects.