Applied Mechanics and Materials Vols. 90-93

Abstract: Multi stages such as side span closure, middle span closure, ten years after construction and so on are simulated with the finite element method in the main channel bridge on the left branch of Beijiang River. Many issues such as unreasonable incremental launching force in construction are found. The optimization made the vertical displacement of the main beam controlled, the secondary moment value on the top of the pier by the side bending of the anchorage and the secondary effect of pre-stressed tendons significantly reduced, and the force of anchorage more balanced. Construction sequence optimization can make the construction process more reasonable and provide a reference for the closing segment construction of the bridge.

Abstract: In order to solve the traffic jams and congestion of urban transportation in most cities, the steel trussed cable-stayed car overpass model is analyzed through the finite element modal analysis by ANSYS software based on the design concept of straight going fast assembling car overpass. After understanding the laws of free vibration characteristics of the structure, the variation of maximum deflections and stresses of the structure which is under the loads moved at different speeds are studied by moving load transient analysis of full method. The result further testifies that the structure is reliable and safe. Also, the range of the optimum speed is summarized to provide reference for the design of speed-limiting facilities of the car overpass.

Abstract: Large eddy simulation (LES) is utilized to simulate flow around a circular cylinder with/without an upper rivulet at Reynolds number 70000. Mean and fluctuating wind pressure coefficients on the artificial upper rivulet and the circular cylinder are obtained. The flow field and the vorticity magnitude in the wake flow zone of the cable model with rivulet at different positions were also investigated. It is found that a small vortex occur near the back of rivulet, when it locates in some particular positions, that might be the reason aerodynamic forces changing dramatically. These results lay foundation for the research on regulation about the influence of rivulet size and shape on cable aerodynamic in future.

Abstract: In order to effectively assess the concrete damage under sea water erosion environment, concrete prediction damage model was presented based on damage mechanical and the experimental test. The degeneration of tension strength of concrete was tested after dry-wet cycles. The fact is proposed that the degeneration of concrete is an interior damage evolving process. Freezing and thawing damage accumulation of concrete was analyzed based on the discrete grid with probability of stochastic method. Three-dimensional multi- parameters Weibull distribution model about concrete damage evolutions were presented. Parameters were estimated based on gradient method. The mathematical model was verified using measured data. Corresponding algorithm was designed to establish concrete durability prediction model under sea water chemical erosion conditions. The research can be referenced for prediction of frost damage of concrete.

Abstract: Hangers in through arch bridges are important components since they suspend the bridge deck from the arch ribs. Local damage at a hanger may lead to progressive damage of various components in the arch bridge or even progressive collapse of the bridge. In this paper, the conventional design of double-hangers in through arch bridges is reviewed. Then a new approach to design the double-hangers is put forward. The suitability and robustness of this approach is then verified by a numerical simulation of a real through arch bridge. The impact effects induced by local hanger fracture on other structural members are simulated by dynamic time-history analyses. The new approach to design the hangers for through arch bridges is shown to improve the structural robustness. With the application of the new way put forward here, when one or more hangers are damaged to fail, the through arch bridge will not be endangered and will still maintain the overall load-bearing capacity during an appropriate length of time to allow necessary emergency measures to be taken, which illustrates the leading principle of structural robustness well.

Abstract: The response surface method (RSM) developed in recent years is an effective way to solve the structural reliability problems with implicit performance function. In order to improve the computational efficiency and make RSM suitable well to large and complex engineering structures, the reliability analysis method based on uniform design method (UDM) and support vector machine (SVM) was proposed. UDM is adopted to select training data and SVM is used as response surface. Structural reliability index is calculated in combination with the traditional reliability analysis methods (such as, the first-order reliability method (FORM), the second-order reliability method (SORM) or Monte Carlo simulation method (MCSM)). Numerical examples show that sampled with the UDM can greatly reduce the number of samples required for training by SVM model, and a very good approximation of the limit state surface can be obtained to get the failure probability. The reliability analysis of the under serviceability limit-state of a typical self-anchored suspension bridge——Sanchaji Bridge was carried out with the improved response surface method.

Abstract: Aiming at eccentricity in the central position at the top of variable section pier during construction and based on the current stability theory, this paper studies the stability calculation of variable section slender pier with initial eccentricity in order to evaluate the availability of the pier. Firstly, theoretical equations to calculate the critical load of variable section compressed bar under ideal condition are derived in accordance with the functional principle. And the corresponding critical loads are worked out through using these formulae. Then, Finite Element Method (FEM) ANSYS is adopted to establish the spatial solid models of the bridge pier with or without initial eccentricity respectively. Critical load values of variable section slender pier under ideal condition are figured out, which are compared with the theoretical values in order to check the model’s reliability. On these bases, researches on stability of pier are performed and stability of the pier with initial eccentricity is calculated under the worst load condition at the stage of construction and completed state. Finally, all the calculated results are compared with Code’s specified values to judge the availability of this pier, which provides a firm protection for project constructions.

Abstract: In this paper, Jishan Bridge is taken for example to introduce a strengthening method focusing on strengthening the vault and arch foot control sections and making full use of the surplus cross section to thicken the main arch ring, i.e., the special-shaped section arch-strengthening method, and put forward the reasonable construction procedure. Subsequently, the strengthening effect is verified from three aspects: static load test, dynamic reliability-based post-strengthening life prediction and strengthening economic indicators. Finally, the finite element software ANSYS is used for further study on the strengthening Optimum design.

Abstract: To investigate the characteristic of coupled vibration of high speed train and bridge, the effect of the railway track irregularity, different train speeds were investigated based on analyzing the coupled vibration of the JR300 high speed train-bridge system The results show that the vertical acceleration of train will be influenced much when the railway track irregularity is considered. The study suggests that the dynamic response of the train and bridge decreases with an increase in the train speed, when the train speed is at a certain zone, and the dynamic response increase rapidly with the increased train speed when the train speed is out of this zone.

Abstract: Through the design practice of the green Leisure office center building, the paper discusses the technical measures of ecological architecture, and makes an in-depth analysis of the use of solar energy, natural ventilation and daylighting technology, water conservation measures, material recycle technology, sound insulation technology and other energy saving technologies. In addition, the paper summarizes the technical measures suitable to China's national conditions, which can be regarded as a reference for other design practice so as to promote the development of green building.