Research On Application Of Unstressed State Method In The Construction Control Of Long-Span Cfst Arch Bridge

Nowadays, unstressed state method is widely used in the construction control of cable-stayed bridges. However, it has not been developed in arch bridges. Based on a fly-bird-type CFST tied arch bridge with a span arrangement of (60+180+60) m (denoted by A Bridge) constructed by the cable-stayed suspension method, applications of unstressed state method in the bridge is discussed in this thesis. The main research covers the following aspects:(1) The basic principle of unstressed state method is introduced. Concerning the characteristics of A Bridge, the construction control procedures of unstressed state control method are determined.(2) Several line-shapes and their mutual relationships during the construction stages are discussed. And the arch rib erection stages of A Bridge are analyzed by established FEM model basing on tangent-initial-displacement method. Thus, the theoretical unstressed line-shape and erection line-shape of arch ribs are obtained.(3) The prefabrication and erection errors and geometrical nonlinearity effects, which have an influence on the unstressed line-shape of arch ribs, are analyzed. And then the influence rule of these factors on the line-shape of A Bridge arch ribs is discussed.(4) The influences of temperature variation and cable tower deviation on arch rib erection line-shape are analyzed. And then the measures to eliminate the influences by traditional control method and unstressed state method are explained, respectively. The relationship between the unstressed length and the increment of cable force is derived, by which the line-shape of arch ribs of A Bridge in large cantilever stage is adjusted.