Research On Several Key Problems Of Aseismic Design For Tied-Arch Bridges

So far, the tied-arch bridges have been widely constructed all over the country for their unique advantages, which include longer span, heavier gravity, higher centers of gravity are usually higher They make the aseismic design more complex. This paper research into three issues including the method of choosing wave input for time-history analysis, design of seismic isolation using resilient-friction isolator, and the design according to the ductility concept based on passive split piers.(1)The method of choosing wave input for time-history analysis. The choice of the earthquake waves is a key step concerning the correctness of the time-history analysis. However, the choice is hard to do for lacking of quantitative indicators. This paper takes the choice of waves for the choice of spectrum. And the characteristic period T g is adopted to quantify the spectrum. Four methods are presented to calculate T g, which can be done associating with the provisions of the corresponding codes. This approach is not only credible, but also easy to executed. And it is a project-oriented practical approach.(2)Design of seismic isolation using resilient-friction isolator. Among all the contemporary techniques for seismic hazard mitigation, the sliding isolator is appreciated for its great efficiency. But it can't return to the original place by itself. However, this problem can be settled by adding external restore equipment, which makes the resilient-friction isolator system with the sliding isolator. However, determining the parameters of the system is a hard challenge because of their complex mechanisms. And the error parameters could diminish the isolation effect, even enlarge the seismic response. This paper investigates the mechanism of the influences on the isolation effect by the wave amplitude, wave spectrum, the stiffness of the substructure, the stiffness of the super structure, the friction coefficient, and the stiffness of the restore equipment. The approach to the optimization parameters is also presented. Further, the constitution is preliminary investigated.(3)The design according to the ductility concept based on passive split piers. The ductility principle is recognized as an effective method to mitigate the seismic hazard . The main means to improve the ductility is to increase hoop reinforcement. This paper proposes another approach——the passive split pier. Both the experimental study and the theoretical analysis indicated that the passive split pier have many advantages compared with common pier, such as the ultimate compression strain of the core concrete is greater; the plastic hinge can rotate larger angles; the hysteresis loop is shuttle-shaped and its area is larger; the degenerate ratio is lower; the framework curve has obvious yield point and longer platform. In one word, the passive split piers have better aseismic performance and is suitable for the frame tied-arch bridges.