MEASURED SUSTAINED DEFLECTION ANALYSIS OF LONG-SPAN PRESTRESSED CONCRETE BEAM BRIDGES

According to annual measured deflections and cracks of 2 three-span concrete box girder bridges constructed by free cantilevering method ten years ago, the characteristics of long-term deflections and crack propagation are analyzed. Firstly, the deflection growth of the bridges in the past ten years is summarized. It can be seen the growth of mid-span deflection is in the form of “fast- ease- speed up”. Then the characteristics of crack propagation are described. It is found the distribution of longitudinal cracks on the top and bottom plates is widespread and compact, and the diagonal cracking of web near the supporting points occurs relatively earlier. After that, major types of cracks are classified and quantified, and correlation analysis of measured deflection and cracks is carried out. It is found the deflection will continue to increase although some cracks remain relatively stable. Finally, the causes leading to the sustained deflection are discussed, and some suggestions on the calculation of long-term deflection are given.