The Technical Study For Void Detection Of CFST Arch Bridge Based On Transient Impact

In recent years,a large number of concrete-filled steel tubular structures is applied to the construction of infrastructure in our country.Especially the arch bridge is built with concrete-filled steel tube are found everywhere in the country,with the span at a distance of three or four hundred metres.But the void of concrete-filled steel tube in-house and the disengaging at interface of steel tube-confined concrete has been occurred,because it is affected by the own specificity of concrete materials and the technical method of the pumping.It is unable to discover these flaws just by looking,and it directly affect the quality of the concrete filled steel tube,meanwhile it even threat to the use safety of structure in severe cases.The existing test methods have some shortcomings owing to the particularity of concrete filled steel tube.Therefore,it is of great importance for us to research the test method for void at interface of concrete-filled steel tube.Based on the principle of transient impact,this thesis discusses the test method for void at interface of concrete-filled steel tube through model test.And it makes exploratory and experimental research on the new directions properly.①.Project surveys,find out the mechanism and the harm of void at interface of steel tube-confined concrete,and it analyzes the existing test methods,then sums up their advantages,disadvantages.It describes the principle of transient impact,and intruding it into the vibration of cylindrical shell structure.②.It obtaines the modal shape of the first ten orders commendably through finite element analysis and a great deal of modal test in the laboratory.And an general method for the modal test of cylindrical shell structure with hammer excitation is presented.③.The study for modal test of void at interface of concrete-filled steel tube and concrete filled steel tubular arch structure was carried out.And it researchs the detecting analysis system based on the results of the model test.Meanwhite,an analytical method and a judgment criterion for detection of void at interface of steel tube-confined concrete is proposed based on the energy density spectrum of acceleration.④.By combining the principle of acoustic-vibration with the transient impact,This thesis discusses the detection method for void at interface of concrete filled steel tube based on the principle of acoustic-vibration.And a great deal of modal test was carried out,then the test results validates the rightness and feasibility of the theory.