Research On Vehicle-bridge Coupled Vibration Of Double-deck Highway Steel Truss Bridge

With the development of economy and society in China, the demand for transportation infrastructure construction is rapidly increasing. Meanwhile, the restrictions of construction of highway bridges are more complicated. Therefore, a large number of new structures and new technologies are emerging. Double-deck steel truss bridge, with characteristics of small floor area, fully taking benefit of bridge position, great transportation capacity and effectively relieving traffic pressure, will gradually become a trend of highway steel truss bridge in China.Double-deck steel bridge has the mechanical behaviors of strong spatiality and complexity of stress. Because of multiple-lane and random of traffic flow, dynamic responses of bars in upper deck and lower deck are very complex, and dynamic coupling becomes more obvious. After bridge’s long-term operation, deck roughness on the bridge surface becomes more serious, it will cause bigger dynamic response of bridge structure, and safety and service life of the bridge structure will face more severe challenges, which has become a key problem in design and operation stages. The research is partly supported by Research Fund for the Doctoral Program of Higher Education of China(Grant No.20090205110002):Vehicle-bridge Coupled Vibration of Double-deck Highway Steel Truss Bridge, and vehicle-bridge coupled vibration of highway double-deck steel truss bridge was studied, the main research contents, research methods and research results are as follows:(1) Generation, classical theory, development and status of the problem of vehicle-bridge coupled vibration were presented. on the basis of summarizing the predecessors’ research results, research method and technical route of this paper were determined according to the characteristics of the problem.(2) Regarding to the complexity of analyzing vehicle-bridge coupled vibration for highway bridges, combining principle of separation iteration method and theory of vehicle dynamics, a numerical analysis method of vehicle-bridge coupled vibration was presented based on ANSYS software. The vehicle and bridge models were built separately by using ANSYS, and the displacement coordination relation between the wheel and the bridge surface was fulfilled with the help of constrain equation at any time, meanwhile the balance of interaction between vehicle and bridge was automatically satisfied. When single vehicle or several vehicles driving through bridges, coupled dynamic time-history response of bridges was analyzed by APDL programming based on transient dynamics function of ANSYS, and the computed results were quantitatively compared with those in references. The results show that this method is reliable. Compared with references, the relative error of dynamic response of bridges is less 5% on smooth deck, while the changing trend of dynamic response of bridges is similar on roughness deck. Iterative computation is not needed in this method at any load step, so complicated program design is avoided and analysis efficiency is greatly improved.(3) Based on proposed numerical algorithm for solving vehicle-bridge coupled vibration, a vehicle-bridge coupled vibration analysis module VBCVA was developed by UIDL(User Interface Design Language) and APDL(ANSYS Parametric Design Language) programming language based on ANSYS software. After the bridge model(the superstructure of bridge can be simulated by shell element or beam element), lane information(lane center starting position, lane direction) and vehicle(traffic) information(vehicle type, lane number, vehicle weight, suspension stiffness and damping parameters) were entered in order, analysis of vehicle-bridge coupled vibration would be performed, and the dynamic time history responses, such as deformation of node and axial force, shear force and moment of elemnt, and their impact coefficient values could be gotten. Using the graphical user interface(GUI) mode to accept user input, the module VBCVA is simple to operate, and easy to grasp and application for engineerers.(4) Taking Dongjiang Bridge(the first double-deck highway bridge in CHINA)as an engineering background, 3D finite element model of Dongjiang Bridge was built by ANSYS, in which spacial beam element Beam188 was adopted in main truss simulation and shell element Shell63 was adoped for simulating bridge deck. The dynamic characteristics including natural frequency and vibration mode were analyzed in this dessertation. By comparing finite element results with dynamic loading test results on Dongjiang Bridge, accuracy and reliability of finite element model were verified. The finite element model can really reflect dynamical characteristics. The determination of elements, boundary condition and assumption were in good agreement with real bridge structure, which provided a finite model benchmark of double-deck steel truss bridge for carrying out vehicle-bridge coupled analysis..(5) A double-deck simply-supported steel truss bridge was designed based on Dongjiang Bridge, and the vehicle-bridge coupled vibration response of designed bridge was solved using VBCVA module. The influences of single deck and double deck loading mode, amount of vehicle, vehicle speed, vehicle weight, deck roughness, bridge damping and based frequency of vehicle on the deflection of controlled node and interal force of controlled bar were analyzed, the variation law of dynamic amplification factor was summarized.