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Construction sequence analysis of long-span cable-stayed bridges


In cantilever construction of long-span cable-stayed bridges the stressing sequence of stays is fundamental for establishing the final configuration of the bridge. The structural behaviour of these bridges is usually evaluated through a forward staged construction analysis, in which the values of the prestressing forces to be applied to stays are the main unknowns. A unified procedure for determining the initial cable forces and for analyzing the entire sequence is presented here, considering the geometric nonlinearity of stays through the Dischinger equivalent elastic modulus. The target is the simultaneous determination of the initial cable forces with the simulation of the construction stages in the forward analysis, taking into account the cable-sag effect, in order to achieve the required geometric configuration at the end of the sequence together with an advantageous state of stress for deck and pylon. Furthermore, a probabilistic approach is proposed for the evaluation of the effects that uncertainties of stay forces, occurring in the actual stressing sequences on site, have on the bridge behaviour. With this purpose probable errors during the real work operations on site are considered here in addition to the theoretical analysis of construction stages. Finally, the evaluation of the reliability of the proposed procedure is tested on a case-study of a long-span cable-stayed bridge, considering the influence of the deck typology on the stressing sequence.