Quan Sheng Yan

Parameter Sensitivity Analysis of Vertical Deflection for Long-Span Continuous Rigid-Frame Bridge

The excessive long-term deflections of a long span continuous girder bridge may induce vehicles to move unsafely and hazard to the bridge operation, thus to limit the development of this bridge type. In this paper the main parameters influencing the long-term deflections of a continuous rigid-frame bridge, such as pre-stressed losses, mass distribution of the box girder and Young’s modules of concrete etc., were investigated. With the establishment of the finite element model of a real bridge and the premise of describing mechanism of each parameter, detailed parameter sensitivity analysis of long-term deflections were carried out with numerical simulation method. The results of this study may help to understand the main mechanism about the long-term deflection of continuous rigid-frame bridge and provide some reference for the wide use of this type of bridges.

A Least Square Support Vector Machine Approach Based on Uniform Design Method for Structural Reliability Analysis

Since the performance functions of large complex structures can not be expressed explicitly in the process of reliability analysis, support vector machines (SVM) with good ability of generalization are used as the response surface function based on the small training samples. The uniform design method was adopted in selecting the training data. The least support vector machines (LS-SVM) were used to find the support vectors. The limit state function was expressed by the LS-SVM regression. Reliability analysis was then performed by the usual reliability method (e.g., the first-order reliability method, the second-order reliability method or Monte Carlo) on the response surface. The results of calculations of numerical examples and a typical cable-stayed bridge show that LS-SVM using the uniform design method can well approximate the real response of complex structures which has a good efficiency and accuracy and can be applied in complex structures.

Experimental Verification of Decentralized Approach for Modal Identification Based on Wireless Smart Sensor Network

This paper provides an experimental verification of decentralized approach for modal test and analysis of a 30 meters long railway overpass bridge. 11 Imote2 smart sensor nodes were implemented on the WSSN. In order to compare the identification precision of different topologies, acceleration responses were obtained under centralized and 3 different decentralized topologies. Local modal parameters were estimated by NExT/ERA within each local group; true modes were then distinguished from spurious modes by EMAC and finite-element analysis. In order to estimate global mode shape, a least square method was used for calculating the normalization factor. Then the global mode shapes were determined by normalization factors and local mode shapes. The result demonstrates that the more overlapping nodes in each group, the more accurate the global mode shape will be; the decentralized approach is workable for modal test of large-scale bridge.

Full-Scale Model Test for Anchorage Zone of Pylon of Cable-Stayed Bridge

In this paper, the construction technology for main pylon of cable-stayed bridge is researched through test of full-scale model of anchorage zone of pylon of Guangzhou Bridge. Stress distribution and deformation condition of model under prestressed tendons and cable force are analyzed. Numerical simulation on this anchorage zone model is carried out. By comparing FEM results to the test results, some important conclusions are drawn out and give some advices to the optimum design of the bridge pylon. Parts of the achievements have been applied to actual bridge work and obtained successful engineering experience.

Optimal Sensors Placement Based on Modal Strain Energy

For a space simply supported truss bridge model, a method named element modal strain energy (MSE) was firstly adopted in the field of the optimal sensors placement. By taking nodes MSE, nodes distance matrix reciprocal as weights, and combining with optimal matching in graph theory, how to apply the method for optimal sensors placement was stated. Through analyzing on the random vibration property of the bridge finite element model, the nodes position of larger acceleration response was compared with the optimal placement got from the above method, which could verified the effectiveness of optimal sensors placement.

Numerical Simulation of Railway Track Irregularities Based on Stochastic Expansion Method of Standard Orthogonal Bases

A new simulation method of stochastic process was accepted in the field of simulation for the track irregularities. This method adopted the Hartley orthogonal bases as the standard orthogonal bases. On the basis of the expansion method of stochastic process, and under the condition of ensuring accuracy, it could capture main probabilistic characters of a stochastic process with only a few independent random variables. Through the numerical simulation of the example, it testified the validity and effectiveness of the new method.

Geometric Nonlinear Effect on Large Span Cable-Stayed Bridge

It is introduced that three main factors cause geometric nonlinear effects of long span cable-stayed bridge: large displacement effect, cable sag effect, and the combination of bending moment and axial force effect. The iteration method of geometrical nonlinear problem is also introduced. The bridge deformation was calculated by establishing a plane truss finite element model of a long-span single tower cable-stayed bridge under consideration of nonlinearity and compared with that done with linear method. It is concluded that nonlinearity influenced differently to the bending moment of main girder, the displacement of tower root and the vertical displacement of girder.

Wireless Data Acquisition System for Vibrating Sensors

In order to overcome the disconnection and high cost and maintenance difficulties of the conventional data collection systems for structure monitoring of long span bridge, we developed a low-cost and effective data acquisition system composed of several wireless communication modules connected to vibrating wire type sensors. This system has the function to change conventional wire-based data collector into wireless one instantly. The prototype of wireless data acquisition system for vibrating sensors is described in this paper. Laboratory tests demonstrate that the wireless data acquisition system is of high accuracy and good stability. In addition, the application of this system to the strain monitoring of a large steel box arch shows the wireless data acquisition system with good performance improve the efficiency of data acquisition and reduces the cost of monitoring.

Study on Dynamic Behavior and Seismic Performance of Cable-Stayed Bridge with Different Auxiliary Pier Positions

Choosing the Panzhong Bridge of the Guangzhongjiang highway as the research object, the dynamic behavior and seismic performance of cable-stayed bridge with different auxiliary pier positions were studied. The results show that the position of the auxiliary pier has limited influence on dynamic behavior. Under the action of the earthquake, auxiliary pier restricts the deformation of side span effectively and reduces the bending moment at bottom of the pile caps.

Study on the Prestressed Arrangement in Cable-Pylon Anchorage Zone of Cable-Stayed Bridge

According to the study on the practical Chaolianxijiang bridge, the stress state of cable-pylon anchorage zone of cable-stayed bridge under two kinds of prestressed arrangements (that is, U-shaped arrangement and parallel arrangement) were calculated and compared. The results suggested that parallel prestressed arrangement could avoid the difficulty caused by other arrangements in the construction. Parallel prestressed arrangement with clear concept, simple structure, clear stress and small amount of work is suitable for the thick walled cable-pylon.