Slanting Type CFST Arch Bridges Rib-Hoisting And Construction Stability Analysis

The construction of long-span concrete filled steel tubular (CFST) arch bridge is a complicated process. This paper is based on the construction of Han River North Bridge, which is the longest CFST arch bridge without any transversal braces in China. Optimization method is used for the curve model control of arch rib, and stability of each construction stage has been analyzed.(1)Element Birth and Death Technology and First Order Optimization Method in ANSYS are used in this paper to simulate the erection process of hollow steel tubular arch rib and predict the cable force. This method is different from other methods simulating the construction process in that nodes which are not connected with any active elements are not constrained, and the real constants of cables which are not stretched are abated. First Order Optimization Method is used to predict the cable force and prearranged height of each segment during the erection. The object of optimization is that when the erection accomplished, the shape of hollow steel tubular arch rib should satisfy the requirement of design. This method is used for simulating the rib-hoisting process of Han River North Bridge and calculating the cable force and prearranged height of each segment. The result indicates that, this method is reasonable and feasible, also with high precision.(2)Lateral rigidity of arch bridge without any transversal brace is relatively week. Although each rib of Han River North Bridge is slanting type, the stability under construction is still a critical problem. This paper calculates the stability coefficient on each erection stage, analyses four failure modes during the erection of hollow steel tubular arch ribs, discusses the effect of stress cumulation as the erection proceeds, and indicates the advantageous influence of wind resistent cable on mechanical behavior and stability of arch ribs. In the analysis, the geometrical and material nonlinearity are taken into account. Results indicate that, in the rib-hoisting process, the stability coefficients decreased, and the failure mode is changed from cable snap to arch rib failure. Wind resistent cables ameliorate mechanical behavior and stability of arch ribs. Cumulation of stress influences greatly on cable force but has only a little effect on stress of arch rib during the erection.(3)The paper selects three different construction sequences after the closure of arch bibs, calculates the stability coefficient of each construction stage, and analyses the eigenvalue buckling modes and failure modes of three typical construction stage considering dual-nonlinearity. During the construction, the stability of structure keeps decreasing. Spring of side ribs, crown of side ribs and spring of vertical ribs are dangerous positions on the whole construction stage.