Optimal Structural Design Of "Stfc" Main Arch Rib During Construction Prior Period Based On Reliability

The work is associated with practicable engineering accident :"slumping accident of Zhuanghe Bingyu bridge during construction period ". Fault analysis of steel pipe lattice form arch rib's slump is done, and appropriate structural form is extracted. As a large span structure, it is necessary for steel tube lattice form arch rib to decrease the cost of engineering project and vertical displacement by optimum design. Among the existing optimum design models, majority only aim at the optimization which just in the definite conditions and the factor of structural reliability is ignored. Besides, to the arch rib of large span arch bridge, appropriate adjustment of arch axis can improve stress of arch rib. This paper lays the research emphases on the three aspects which were mentioned above.After analyzing original main arch rib, we generalize the reason of accident, do a redesign, and extract appropriate structural form. The result shows that the redesigned arch rib does not only reduce use-cost of steel, but its bearing capacity has great increase.During the course of determination for structure optimum model, the conception of structural system reliability based on functional requirement is indraught. The combination of structural system reliability and structure functional requirement makes he conception of structural system reliability more definite and practicable and the calculation gets easier. The reliability index for steel tube lattice form arch rib based on structure functional requirement can be determined, and it is introduced into the grid structure reliable optimum design as constraint. A model of optimum design based on reliability and structure functional requirement is established to make steel tube lattice form arch rib has the coordination both in economic and safety.During the adjustment and optimization of arch axis, sectional cubic spline is adopted to approximate the appropriate arch axis, and a adjusted and optimum model of the arch axis is established. The result shows that the arch axis formulated by the model can approximate the appropriate one well and improve stress of the arch rib.