A Comprehensive Research of the Air-void Defect of Concrete-filled Steel Tube

Welded spiral steel tubes are adapted for use in a majority of the large-diameter concrete-filled steel tube (CFST) arch bridges due to technical as well as economic reasons. However, the welding temperature and other factors during the process of manufacturing of steel tube, initially result in a reduced spiral-welded seam (SWS) strength. Moreover, with the pumping of concrete into a steel tube, numerous deformities of the likes of laitance coating and air-voids occurred inevitably, particularly with the lack of air-entraining agent in China almost 20 years ago. This work makes use of ultrasonic scanning field experience to investigate the capacity of bearing within a repaired and reconditioned CFST arch bridge rib having defects such as air-void and reduced SWS strength under negligible compression of eccentric axial by carrying out its finite element model analysis of group. The outcome reveals that CFST bearing capacity is only minimally affected by the SWS strength as compared to concrete air-void, which can be ignored. The effect of air-voids and the nonlinear behavior of the constituents on the CFST behavior have also been probed into. The impact of the air-void on the rib capacity of bearing was investigated by conducting parametric studies. To conclude, we proposed a new index defining the ultimate strength of the rib for the defect, and presented a rather simple blueprint to determine the influence of air-void on the final strength of the arch bridge rib of CFST.