Monitoring of longitudinal cracks in an empirically designed reinforced concrete bridge deck

摘要

Full-depth longitudinal cracks have been developed in many empirically designed bridge decks. Such cracks run along the entire length of the bridge over the top flange edges. Star City Bridge is among those bridges that developed longitudinal deck cracking. The bridge was instrumented with 750 sensors during its second phase of construction in November 2003 and the longitudinal cracks were visible on the deck surface in 2005. Therefore, additional twelve sensors were installed across the cracks in June 2007 to continuously monitor their opening and closure as well as the differential settlement across the cracks. The collected data indicate that some cracks have continued to open. In particular the crack along the first interior girder at the edge bay developed a permanent opening of 0.25 mm and a permanent settlement of 0.08 mm. The opening of the longitudinal cracks was correlated to the lateral bending of the steel girders, which adversely affect their flexural capacity as well as the axial stresses in the transverse steel rebar and diaphragm members. Additionally, the presence of the longitudinal cracks induce shear stress in the transverse steel rebar due to the passage of traffic loading that would affect their fatigue life.