Multi-Form Evolution Mechanism And Shape Control Parameter Of Precast Concrete Track Beam

Precast concrete(PC) track beam has an extremely important function in the track beam bridge of a monorail transportation system. Unlike other precast concrete components, special function of PC track beam requires not only the precision of finished appearance manufacturing scale is very high, and the shape change during the use period is very small. During manufacturing process, highly precise initial shape parameters and perfect surveillance mechanism are required, which is the only way to ensure the precision of PC track beam at last. During use period, A PC track beam must have the self-balancing ability to resist the disturbance of various unfavorable factors, and maintain the structure performance in the initial equilibrium state. Unfortunately, a valid method that calculates the shape parameter of a PC track beam does not exist, and the research about self-balancing ability does not exist too. It hinders the development of the monorail transportation system.Taken the Chongqing monorail as the object, this study merge numerical simulation, theoretical analysis, engineering test and laboratory test together to find the multi-form evolution mechanism and structure performance self-balancing ability. The curve parameter deducing model of PC track beam has been structured by digital image, wavelet, least square method, dichotomy, and fractal. With VB, Java and Matlab, straddle type monorail transportation simulation software is developed. This dissertation undertakes the following tasks:(1) A novel method to calculate the bottom center curve of a PC track beam is proposed against the traditional method. The reversal approach includes the following: First, according to the design conditions and construction process, the bottom center curve is assumed to be a plane in a spatial space domain similar to a football. Second, the surface of the top curve range is calculated based on the small grids using geometrical relations after the plane is vectorized by many small grids. The coordinate values of the points in these grids are utilized to establish a matrix. Another matrix is formed using the points in the top curve given by the monorail route. The two matrices are represented by two corresponding images. Third, the optimized top curve is obtained by successively subjecting the two images to image processing, wavelet disposing, and least square method. Finally, a criterion to assess the assumed top curve with the actual top curve is established based on fractal theory.(2) To ensure the installation precision and function of a PC track beam, the parameters used to control the precision of shape size are deduced according to the PC bottom curve. In deriving the parameters of multi-form control, the instantaneous structural deformation at different times and the ability to maintain balance of a PC track beam should be considered.(3) According to the growth route of concrete material properties at the early stage(0 to 28 days), the mechanism of multi-form evolution and the instantaneous structural deformations of a PC track beam are studied. First, several key construction stages are divided along the growth route of concrete materials as obtained from engineering experiments. This division also devises a scheme for the multi-form evolution of the research. Second, to coordinate the differences between different forms of PC track beams, the instantaneous structural deformations of the PC track beams are studied in finite element models. Finally, the results calculated by the finite element models are inspired by engineering experiments.(4) Throughout the entire life period of a PC track beam, its ability to maintain its function at the initial balance level is a very important objective. First, the ability of the PB track beam to resist acid corrosion is analyzed through tests based on the atmospheric environment and rainfall in Chongqing. The test result shows that PC track concrete materials can prevent acid corrosion on the surface of a PC track beam. Second, during the entire life period of a PC track beam, the dynamic load of the monorail vehicles will slowly alter the shape size of the beam, an effect that is verified in finite element models. Third, concrete creep also changes the shape size and function of a PC track beam, and the effect caused by concrete creep is analyzed through theoretical formulation. Finally, the comprehensive ability to maintain the function of a PC track beam is evaluated by indexes obtained previously.(5) For practical use, a design system is developed to calculate the construction parameters of the PC track beam and the error controls. This system can calculate the various construction parameters of the PC track beam, anchor box of support, and output of design documents. All the parameters are efficiently integrated. This software is easy to operate because it features a user-friendly interface and efficient manual operation.