Abstract: Taking an actual tied-arch bridge project as the background, this thesis has a system static analysis by building up the finite element analysis model with Midas/civil, a large-scale FEM software, then establishes a mathematical optimization model for the back analysis to suspender tensile forces through two optimization schemes. Scheme one takes the reasonable bending moment distribution and minimum moment stain energy as the optimal control objective function to inverse analysis. Scheme two takes the bending moment distribution of dead load as the control objective of inversion optimization analysis, when the difference of the positive and negative absolute value is the minimum in the moment envelope under the load combination, which thinks about live load on the finished state. Through comparing the analysis results, the thesis demonstrates that the inversion optimization method could fulfill the requirement of factual project and be widely used for determining suspender tensile forces of tie-arch bridges.
Abstract: The real and measurable model is helpful for structure simulation. Photogrammetry technology provides a new method to model a structure by photos. This article explored the feasibility of photo-based 3D modeling for the arc bridge structures by ordinary digital camera. Firstly, the preparation processes before modeling were introduced, that included camera calibration, designation of shooting program, how to take photos and plan measurement. Secondly, photo orientation and modeling process were introduced, too. A measurement test was put forward to get some good points to enhance the accuracy. By comparing the measurement accuracy of modeling results from the four photos and eight photographs, some proposals were presented to improve the accuracy. The 3D model can be integrated with the loading conditions and material properties, to provide the detailed data for analyzing the structure.
Abstract: Characterized by light weight and high strength, cold-drawn galvanized cable wires are widely applied in all kinds of prestressed structures and cable structures. Investigation shows that cables are sensitive to corrosion. Severe corrosion of cables results in cable replacement which are costly, and even more, collapse of the whole bridge. In this paper, several tests were carried out to present the crack growth of wire in stress corrosion in different solutions. In particular, as Cl-, OH-, SO42- and NH4+ have major effect on stress corrosion in seawater and acid rain, these four kinds of ions are selected in tests. And all four kinds of corrosive solutions are tested with the concentration of 1.5 bsp and 3 bsp respectively. Effects on ultimate tensile strength and sensitivity of cable wires are different for each of chosen ions, and the increasing concentration for the same solution would drop ultimate tensile strength and the modulus of cable wires.
Abstract: This paper based on the structural characteristics of thin-wall steel truss of JiuJiang Yangtze River Bridge, designs a distorted model that thickness ratio is 1/10 and the length ratio is 1/40.Through the static test model, the cross-section stress of hangers chord, diagonal and the deflection of corresponding test point is tested, and the result is compared with numerical simulation result. It shows that the result of the test and numerical simulation satisfy the similar relations, thus verifying that the design of scale model is reasonable and correct.
Abstract: Finite element model updating is the important foundation of structural damage detection, condition assessment for engineering structure. A new method, for finite element model updating based on the quasi-static generalized influence line (QSGIL) residual objection, is presented to update the finite element model of beam-structure in order to improve the quality and precision of finite element analysis. Both of the theory and model experimental study show that the proposal method can efficiently update the finite element model in the previous study . In this paper, the updating techniques are further developed to update the finite element model of the existing T-Girder bridge, the QSGIL of the updating model agrees very well with the field QSGIL of the existing bridge, which illustrates that the proposal methodology is promising in the practical bridge structure and other structures.
Abstract: To get the certain response of vehicle during the driving process, it’s necessary to measure the road irregularities. Existing method of gauging the roughness is based on physical measurements and the instrument is installed under the vehicle, which is expensive and will affect the vehicle dynamic responses. This paper shows an easier method to estimate the road roughness by measuring and calculating the power spectral density (PSD) of unsprung mass accelerations. This approach is possible due to the relationship between these two via a transfer function. By comparing the power spectral densities of estimated road and the standard classes, we can classify the current road classes easily. Besides, this paper also shows that it’s feasible to estimate the road profile by calculating the PSD of unsprung mass accelerations directly.
Abstract: Under the coupling action of bending and torsion are there such complex mechanical characteristics in a small radius ramp curved bridge with single column in city. Based on Midas/Civil software, a small radius ramp curved bridge with single column is studied in this paper. Under the combined action of the first phase of dead weight, the temperature gradient, the system temperature, the second phase of dead weight and vehicle load, the mechanical properties of a ramp curved beam bridge have been studied in detail for different pre-eccentricity. Then, it is under different eccentric actions that different results with the changes of such variations as support reaction, displacement, shear force, bending moment, torque moment and torsion deformation are discussed. Our investigation shows that reasonable pre-eccentric setting could greatly reduce internal force in the bridge and improve the torque distribution so as to optimize the distribution of internal force in bridge.
Abstract: It’s very important that Bridge Structural Health Monitoring to bridge management and maintenance. In this paper,the authors study the Application of GIS and GPS in Bridge Structural Health Monitoring. Introduce the application field of GIS in bridge structural health monitoring and the method of GPS-RTK Technology to measure the bridge three dimension dynamic coordinate, proposed the System General Framework of GIS in Bridge Structural Health Monitoring,mainly study the problems that acquisition and collection of Monitoring information,the database management scheme of the system, the method that of GIS manage Spatial and attribute information which related to bridge structural health monitoring and to process and analysis the Monitoring data. Also analysis the feasibility of using GPS and GIS technology in a Bridge Structural Health Monitoring.
Abstract: The cable-stayed bridge which has been found longitudinal cracks in tower is taken as the background, combining with the original design information and the results of bridge inspection. The numerical simulation on temperature effect of cable tower has been done with MIDAS/Civil, and the results have the same trend with observed in bridge inspection, indicating that the cracks in tower probably are caused by temperature effect. Then, some suggestions are raised in the end of this paper about how to deal with these cracks. This work could be a valuable reference for similar large cable-stayed bridge. And the temperature stress should be paid more attention in design process to avoid appearance of temperature cracks which affect beauty and durability of structure.
Abstract: Recent advances in structural and construction technologies have enabled engineers to use the cable efficiently in relatively large structures such as long span cable-stayed bridges. It appeared that many factors and phenomena can generate cable vibration. The cables usually possess low damping and are therefore prone to many vibration problems, even causing large displacement. The active control method has been introduced to control the cable vibration in the cable-stayed bridges. The active control method is an effective method to suppress cable vibrations by adjusting the cable tension which is varied with time. This approach utilizes the axial motion of cables supported by an actuator installed at the anchorage to produce a time-varying force in the cable. To synthesize the feedback control signal, the cable vibration is measured by an optical tracking sensor attached at the mid-span cable. The studies are carried out to investigate the measurement error features of the control method as a design guideline.