Advanced Materials Research Vols. 243-249

Abstract: Cable-stayed self-anchored suspension composed bridges have novel structures and aesthetic appearance with complex system and difficulty for design and construction. In order to acquire a better knowledge of the load-carrying capability of this type of bridges, based on a real bridge and the theory of abnormal similarity, a full-bridge scaled down(1:20) test model was built to simulate the whole process of construction. The test results were preferably fit the theoretical calculation value. It can be seen that the design of the bridge was reasonable, and the accuracy of the calculation of finite element model was verified at the same time. The test and the related results can be used as the reference for the test and design of the similar bridges.

Abstract: Using truck weigh device, the data of traffic stream was collected from a toll station in Shaanxi province for 24 hours. A standard fatigue truck was developed based on the regular traffic data. Then S-N curves and Palgrem-Miner summation method was introduced in assessing fatigue life of the reinforcement in negative region of one continuous concrete bridge. It was concluded that the welding detail of reinforcement in negative region had long service life under normal traffic state. The fatigue life of reinforcement would be weakened considering overloading vehicles.

Abstract: Based on the object of self-anchored suspension bridge constructed with long segment hoist method, the load-carrying characteristics and construction technique which is different from other self-anchored suspension bridge is analyzed, and the method of calculation and control on steel box girder configuration during the construction course of long segment hoisted are proposed. For different calculation methods of girder configuration lifting, the influences of the three manners of pre-cambering for steel girders on the configuration and internal force of finished bridge are analyzed. The results show that inverse erection— forward erection—unstressed state synthetic method can guarantee the minimum deviation of steel girder configuration of finished bridge with the design, and it is not necessary to adjust the suspension cable force, and there is no change in main cable configuration and internal force.

Abstract: Body rotating bridges are mostly rotation system in balance, whose gravity center are basically located in the rotation axis of turntable. In order to ensure bridges’ swivel construction successfully accomplished, the structural center of gravity should be made clear before the rotation. In the past, the structural center of gravity was usually ascertained in the method of mathematics, but the tedious calculation couldn’t get results with enough accuracy. In this paper, structural gravity center of cable-stayed bridge is calculated in the method of CAD and finite element, whose process and result are proved handy and accurate calculation. Taking Sui Fenhe cable-stayed bridge as an example, its theoretical eccentricity is 1.3cm.

Abstract: According to the mechanical characteristics of the continuous box girder bridge and the disaster situation, a combined strengthening method was used to strengthen Yingyugou Viaduct. The 3D numerical simulation method was used to analyze the effectiveness of external prestressing reinforcement technology, external sticking steel plate method, increasing section method and gluing CFRP method. Based on the analysis, the original design scheme was optimized to take advantage of each strengthening method, and improve the overall effectiveness of the combination strengthening method.

Abstract: A non-corrosion, high strength, light weight material – carbon fiber reinforced polymer (CFRP) is introduced to replace steel as cable system in long-span suspension bridge for improving loading efficiency, reducing maintenance cost, enlarging the span of suspension bridge. Because of the transverse weakness of CFRP, traditional cable saddle is not suitable. The contact forces between main cable and cable saddle slot under final state are investigated with a simplified analytical method. According to the mechanical characteristics of CFRP and the formulas deduced, the design suggestion of cable saddle for CFRP main cable of long-span suspension bridge are proposed.

Abstract: For hollow slab bridge, its concrete hinge joint is prone to be damaged under overload vehicles, as weakens the transverse integrity of bridge, leads to single slab bearing and threatens the safety of service. Aiming at the problem, a strengthening experiment of an actual concrete hollow slab bridge, which has experienced a destructive test with its transverse connections seriously damaged, was performed by applying external transverse prestressing to it. The strengthening design and construction technology of external prestressing were introduced. By means of truck static load test, the variation of deflections and strains of the bridge before and after strengthening under different tension force was obtained, and the influence of tension value to strengthening effect was emphatically analyzed. The test results proved the effectiveness of the strengthening method and some improvement suggestions were also presented.

Abstract: Optimum design for a cable-stayed bridge structure is very complicated because of large number of design variables. Use of ANSYS parametric design language in optimizing such structure consumes little computational time. The finished dead state analysis for single pylon double cable plane cable-stayed bridge with 120m long is performed. Mechanics equivalent are developed for the main pylon with concrete-filled steel tube. Prestress girder finite element model is established also. The theory of minimum bending strain energy is used in deriving the objective function as the quadratic form of the post-tensioning cable forces. In addition, the maximum deflection of the pylon and the maximum stresses of the main girder are both implemented in the optimization model. Optimized cable forces are found by optimization. Calculated results show that after the optimization, the cable force slightly changes, yet the internal force state under dead load remarkably improves, the bending stress of girder as well as the deflection of pylon significantly decreases. All these variations are satisfied for the limit value of engineering code. The results obtained revealed that the method presented indeed leads to optimal structural performance for the cable-stayed bridge in particular, and might be a useful reference for the design of other similar bridges.

Abstract: Damages in a structure alter its static and dynamic characteristics. These changes occur in some structural parameters such as the mass, the stiffness, the flexibility and the damping matrices of the structure and can be characterized by changes in the modal parameters, i.e., modal frequencies, modal damping values and mode shapes, and their derivatives, such as the modal curvature and modal stress energy. According to the properties of cable-stayed bridges, various damage indexes of static and dynamic are constructed to indicate damage of cable, tower and girder respectively. A comprehensive index accounting for their interaction and the whole bridge damage is presented which is robust to measurement noises and uncertainties in ambient conditions. The sensitivities of these damage indexes are illustrated by numerical studies. The effectiveness of the proposed damage detection method of cable-stayed bridges is demonstrated through an engineering project.

Abstract: In this study, aerodynamic forces on a bridge pylon are investigated by three-dimensional computational fluid dynamics using Large eddy simulation (LES) technology. The main objective is to identify the wind load parameters of the pylon and examine the accuracy of LES model applied to the bluff-body flows. The numerical results were compared with the available wind tunnel test results. Also, a comparison between using LES and Reynolds averaged Navier-Stokes equations with the RNG model have been made. It is found that the LES model competes the RNG model in accuracy for predictions of aerodynamic forces on the pylon.