Air void and ring gap effect on CFST arch bridges dynamic performance

Abstract Many old concrete-filled steel tube (CFST) arch bridges constructed using common concrete, the fluidity before initial setting and dry shrinkage during use create ring gaps at the interfaces of concrete core column (CCC) and spiral welding tube (SWT), and air voids in CCC. Also, unfavorable conditions of nature increase the number of gaps and voids, create more serious defects, decrease arch rib stiffness, and even change the dynamic properties of the whole bridge structure. Therefore, a finite element analysis (FEA) verified by scale-model experiments on CFST arch bridge rib members with air void and ring gap composite defects was conducted to determine the tangential stiffness of the structure. Secondly, the natural vibration and frequency of the whole bridge were analyzed using tangential stiffness and the influences of various defects on the dynamic performance of bridge was investigated. Therefore, a novel trans-scale determine system was developed for the detection of the tangential stiffness of bridges with composite defects in CFST ribs, so as to evaluate the influences of these defects on the dynamic performance of bridges. This study can provide a strong foundation for the maintenance repair of CFST arch bridges.