Experimental and Modeling Study on Long-Term Deformation of Three-Span Prestressed Concrete Continuous Box-Girder Bridge Model after Cracking

Abstract

To explore the long-term deformation performance of a large-span prestressed concrete continuous box-girder bridge after overload, a three-span prestressed concrete continuous box-girder bridge model with a length of 24.88 m was designed. The long-term deformation performance experiment was conducted for 558 days, and the prestress loss, deflection behavior, strain development, crack increase, and support reaction transformation of the bridge model were analyzed, which could indicate that the deformation of the bridge model developed rapidly in the first 3 months, reaching 60%–70% of the total deformation, and then tended to be stable. The midspan section appeared to reverse arch at the beginning, and with the extension of time, the negative bending moment at the two middle supports decreased owing to the redistribution of the bending moment, resulting in the disappearance of the camber phenomenon. Besides, considering the influence of cracking on the redistribution of the internal force of the structure, the moment modulation coefficient was modified by introducing a damage coefficient. Based on the bending performance test results of the bridge model, the bending moment amplitude modulation method and long-term deflection theory were used for analysis, and the long-term deflection calculation formula of the bridge model was established according to the conjugate beam method. The results showed that the theoretical calculation value of long-term deflection of each midspan section of the test girder was in good agreement with the test results, and the maximum error was less than 15%, which can provide a reference for the safety evaluation of the prestressed concrete continuous box-girder bridges.