Test And Control Technology And Application Of Steel Tube Concrete Arch Bridge

In this paper,the concrete-filled steel tubular arch bridge is the main research object.Through the combination of theoretical analysis,model test and field test,the detection method and preventive measures of the occurrence of voiding in the CFST arch bridge are discussed.Further research was conducted on the real-time monitoring and prevention of the voiding phenomenon of concrete-filled steel tubes in actual projects,which verified the practicality of the theoretical system and achieved some useful conclusions.(1)In view of the phenomenon of voids in concrete-filled steel tubes,the effects of temperature gradients,concrete shrinkage,and expansion agents on the degassing of concrete filled steel tubes are analyzed.Based on OPENSEES software,the strength model of concrete-filled steel tubular column under eccentric compression was established,and the calculation and analysis of contact interface of concrete-filled steel tube were performed.(2)This study analyzed three possible ultrasonic first-wave propagation paths of ultrasonic testing method in the concrete-steel-concrete devoid area,and presented the theoretical calculation formula of acoustic time value under three different propagation paths.The actual propagation acoustic time value was obtained through experiments,and compared with the theoretical value calculated from the acoustic time-value formula,and finally the propagation path of the ultrasonic first wave in the two kinds of void area was obtained-the defect along the diffraction gap spread.This will provide conditions for the quantitative detection of the void area by ultrasound;the ultrasonic CT images of concrete-filled steel tubes were drawn by the inversion method,and the sound-time distribution chromatograms obtained by ultrasonic measurement were able to realize the quantitative detection of defects.(3)The studs(internal studs)on the inner wall of the steel tube of the concrete-filled steel tubular member can strengthen the combined effect of the steel tube and the core concrete.The results show that the force acting on the inner part of the concrete filled steel tube is composed of four stages:elastic section,elastic-plastic section,load falling section and load residual section.When the peg shears are broken,the load is maximized,the concrete does not crack and crush,and the stress generated in the steel pipe is also very small.The ultimate load of steel tube concrete specimens with internal studs is much larger than that of non-stuck specimens.The studs can greatly improve the joint performance of concrete-filled steel tube members after debonding.Based on the analysis of test results,a calculation formula for the shear bearing capacity of concrete studs in concrete-filled steel tubes is proposed,which can be used for engineering applications and further study.Through the use of heating method to carry out the model test,it shows that setting the stud can reduce the debonding value of concrete-filled steel tube.(4)Relying on the Shimen Reservoir Extra Large Bridge Project in Hanzhong City,Shanxi Province,the case of the steel pipe concrete arch bridge was established.The real-time dynamic testing technology and ultrasonic testing technology for the debonding of concrete-filled steel tubes based on displacement sensing can be monitored by adding the steel studs on the inner side,and the monitoring of the later dewatering of concrete-filled steel tubes can be carried out and verified.It can effectively improve the mechanical properties of the steel tube concrete arch bridge and avoid the bridge disease caused by the empty steel tube.The implementation of the technical scheme in shimen water kut bridge will provide reference for the design and construction of the concrete arch bridge in China,and improve the construction level of concrete-filled steel tubular arch bridge in China.