Simplified deflection calculation method for PC box girder bridges with corrugated steel webs using asynchronous-pouring-construction technology

This paper introduces an asynchronous-pouring-construction (APC) technology for long-span prestressed concrete (PC) box girder bridges with corrugated steel webs (CSWs). The technology makes full use of the CSWs to support the hanging basket. The top slabs, bottom slabs and CSWs are divided into multiple independent working platforms to improve the construction efficiency. In present study, the authors conducted a theoretical analysis of the deflection in PC girder bridges with CSWs using APC technology. A simplified deflection calculation model was developed on the basis of the principle of section equivalence for different segment division. Consequently, a series of theoretical formulas was proposed considering additional shear deflection induced by bending moments. These formulas could be utilised to calculate the configuration and the total deflection of the bridge during APC process, facilitating the pre-camber application to eliminate the deflection and to ensure the closure of the bridge. Moreover, parallel finite element analyses (FEA) and field monitoring tests were conducted to validate the simplified calculation method. The comparison results showed that the calculated deflections using the simplified method agreed well with the FEA and test results. The proportion of shear deflection in the total deflection ranged from 17% to 39% from the forward movement of basket to the pouring slabs, the shear deflection could not be negligible. The segments' length had large effect on the deflection of the CSWs with 50 mm at the maximum cantilever state in this bridge case study, and the deflection induced by the pouring concrete of the slabs accounted for approximately 70% of the total deflection. The additional shear deformation due to bending moment at the end of area A (composite section with both concrete top and bottom slabs and CSWs) was basically the same as that in area B (composite section with bottom slab and CSWs). Therefore, the simplified method which takes into account the additional shear deformation of the segments in area A without considering area B was able to satisfy the engineering accuracy. In short, in comparison to traditional analytical methods and FEA, the proposed method could predict the deflection more efficient within accept accuracy.