Finite Element Simulation Of Oblique And Curved Box-girder Bridge In Static Load Calculation

In company with the rapid development of highway and urban road in China, more and more elevated roads as well as grade separation projects have been built in recent years. Elevated structures and grade separation structures have the characteristics of curvy, inclined, skew, special shaped and so on due to the confine of terrain and ground objects, the continuity of holistic highway alignment and the transfigure of urban environment. Curved girder bridges are increasingly widely used for they can perfectly meet the requirment of designing and operation.Box section is adopted in most of the medium-span and long-span curved girder bridges. Box section has been widely used on long span bridges, curved girder bridges and skew girder bridge for its advantages as following: higher hollow ratios, less amount of material, lower structure weight, lager torsional rigidity and reasonable section stress distribution.Testing technology and analysis methods have made great progress and can provide reliable test data due to the improvement of automated technique and universal application of computer. Consequently, test is of greater importance in the scientific research, designing and construction of bridges. As an important mesure to solve new problems in the region of bridge engineering, test technoligy has been payed more and more attention by the bridge engineer.As for straight girder bridges with simple and clear mechanical characteristics, static tests can be carried out based on《Test Methods of Long-span Concrete Bridges》,《Design Specifications of Highway Bridges》and《Load Specifications of Urban Bridges》. We can choose testing sections and dipose sensors according to the specifications. Mechanical property of oblique and curved girder bridges are complex for it can be impacted by bridge span, section shape and ratio of reinforcement, as well as curvature radius, skew angle, central angle, beam width and ratio of bending and torsion stiffness. Static load test scheme of oblique and curved girder bridges is not given out in the specifications.Relying on the engineering practice of the long-term real time static load test of Xiaonan Interchange progress, related problems in the static load test of reinforced concrete oblique and curved girder bridges, such as loading scheme, static response and sensor placement. Civil engineering software of MIDAS/CIVIL is adopted to analyze the mechanical behavior and moving load effect of Xiaonan grade separation. Large universal finite element software of ANSYS is used to analyze the details. Chapter 3, Chapter 4 and Chapter 5 are the key parts of the paper.Chapter 1, in which the current situation of reinforced concrete continous oblique and curved girder bridges, the research status both at home and aboard, the significance, purpose and procedure of static load test and the purpose of research as well as the research content are introduced, is the exordium. Reinforced concrete continous oblique and curved girder bridges are widely used on the bridge engineering, especially on the urban interchange ramp bridges.While, for the health monitor of this kind of bridges include static load test and dynamic load test, no specification can be followed. Usually, in process of the static load testing of curved girder bridges, ignored the special mechanical behavior of curved bridges, engineers take the same loading scheme and sensor placement scheme as straight bridges with the same span. When the radius of curvature is not too small, the central angle is not too large, the beam width is not too large and the skew angle is not too large, the moment of a curved girder bridge is nearly as same as a straight bridge with the same span. That is to say, the discrepancy of normal stress between the two bridges is small. While, bending-twisting coupled effect impacts the shearing strain on the section a lot. Using the similar test scheme as straight bridge, real force condition can not be reflected. Hidden troubles are brought in the operation of the bridge. Consequently, it is of great engineering significance to analyze the force state in detail and to place the sensors based on the analysis.The mechanical properties, constructional characteristics and calculation methods of oblique and curved girder bridges are described in Chapter 2, which is the basis of this paper. Thanks to coupled action of bending with torsion, oblique curved bridges need girder sections with better flexural behavior and torsional behavior. Torsional behavior is of more importance. So that thin-walled box girder is adopted on a large amount of curved girder bridges. The existing analysis theories and methods are as follows: simple torsion theory, warping torsion theory, grillage theory, beam theory, orthotropic plate theory, beam-plate combination theory, folded plate theory, polygonal curved bridge theory, force transverse distribution theory, finite element method, finite strip method, energy method, sandwich plate method and so on.Chapter 3 is an important part of this paper. In company with the increasing application of computers, numerical method has gradually become an important mesure in thin-walled bar analyzing. Numerical method is mostly based on finite element method, finite strip method and finite bar element method. Different kinds of finite element software are adopted to analyze mechanical behaviour of box-girder. Among them, grillage analytical method has been used in the engineering practices. In this chapter, several influencing factors that influence the accuracy of grillage analytical method are discussed. The way to divide beam girder of Xiaonan interchange A ramp box girder based on the mentioned factors. Problems of section characteristics calculation and arrangement of virtual transverse beam are discussed. Space beam gird model is built by the civil engineering finite element software of MIDAS/CIVIL.Chapter 4 is one of the key parts of this paper as well. The design of loading scheme is vital in the static load test. Load effect brought by test loads should be close to that brought by design load. Based on the MIDAS beam girder model, interal force envelope and force brought by desigh load is worked out, then the control sections as well as the internal force influence line of these control sections are determined. Based on the space beam grid model and two-dimension dynamic loading theory, controlled by the load efficiency of the control sections, the location and type of the loading vehicles is ascertained.Chapter 5 is the core part of this paper. Even though the accuracy of beam grid method is higher than that of single beam method, the beam grid method is a simplified method. Warping effect is left out of account in the beam grid theory mentioned in this paper. That is to say, impact brought by restrained torsion and distortion is ignored. In order to simulate load effect in the static load test accurately, findthe most dangerous points on the section, placie sensors reasonably, reduce cost, raise the efficiency in the test, it is nessesary to build a solid element finite model of Xiaonan interchange A ramp left amplitude, and then simulate the bridge's force state as accurately as possible. SOLID65, a element type setted for reinforced concrete matierial, is adopted to simulate the box girder. Based on the space finite element model, the stress and strain status on the control sections under the load cases defined in chapter 4 is analyzed. The placement of sensors is according to the analysis results. The quantity of sensors is obviously reduced, so that the cost of the test is reduced as well. Chapter 6, as the conclusion of the whole paper, comes last. In this chapter, conclusion of the paper's work and prospect of the following work is carried out.