Advanced Materials Research Vols. 639-640

Abstract: The study deals with the problem of turbulence effect on the instability of a long span suspended bridge. Wind tunnel test of three representative section models have been carried out in four type of passive grid turbulence flow to clarify the effect of turbulence intensity and turbulence scales. It was found that the turbulence has little effect on the derivatives of those streamlined deck sections, while it exhibits significant stabilizing effect on the bluff rectangular section prism. The loss of spanwise correlation may not be the main reasons induce the change of flutter stability in turbulence.

Abstract: The mechanism of train derailment was demonstrated to be the loss of lateral vibration stability of train-bridge (track) system. Based on the theory of energy increment analysis for system movement stability, the energy increment criterion for derailment evaluation and the method of analyzing critical speed of train derailment Vcr were presented. The critical speed of empty freight train on Laoluanhe bridge, Huanghe bridge and Youshui bridge were calculated as 65.2 km/h，64.8 km/h and 66.5 km/h respectively, which were close to actual derailment speed. It is manifested that the method of analyzing critical speed of train derailment is reasonable. According to the calculated results of the critical speed on bridges with different lateral rigidity, it is testified that the critical speed of train derailment rises with the bridge lateral rigidity strengthened. The measure to prevent derailment on bridge is to ensure enough bridge lateral rigidity to meet the running safety of train.

Abstract: A finite element model is proposed for numerical analysis of mechanical properties of precast segmental concrete test beam with external tendons. The 3D finite element model of test beam is established by SOLID65 element in ANSYS software, while the dry joint between segments is simulated by contact element, and the attachment between concrete beam and external prestressed tendons is achieved by node coupling method. Numerical simulation analysis reveals structural behavior, stress variations and crack opening cases of joints of the test beam by considering the concrete material and geometric nonlinearity. Influencing factors of the bending mechanical properties of the test beam are researched with different tendon types, secondary effect of external tendons and external tendon slip at deviation. Results of the numerical analysis reveal that the segmental joints are in the compressive state below the 300kN.Crack opening is the key factor of the mechanical properties of the test beam above the 300kN.The results can be used for structural design of precast segmental bridge.

Abstract: In this paper, the stiffness and load matrix of Jiujiang Changjiang River Bridge are established by truss section finite element method. The basic assumptions and calculating process is proposed, and the functions of bridge frames are also investigated. Finally, the lateral displacement is calculated under the action of wind load (or both wind and train load).

Abstract: A structure model of three-span continuous rigid frame bridge was constructed based on the finite element method. Firstly, the static performances were obtained. Secondly, the modal analysis was performed to get the natural frequencies and periods. The dynamic characteristics of the bridge structure were summarized, and some improvement guidelines are suggested to overcome the shortcoming for the bridge structure. Then, seismic response analysis was carried out based on the EL-Centro wave. The input excitations adopted the combination of vertical wave plus longitudinal wave, or vertical wave plus lateral wave, or the combination of three directions. Based on the three excitation cases, some useful results were obtained, which include internal forces, displacements, accelerations time-history curves of the critical sections for the bridge structure. And some comments about the time-history curves are given. At last, some helpful conclusions are drawn based on the calculation and analysis above. The calculation methods and results in this paper can provide some referenced information for the engineering design.

Abstract: The construction of highways has changed the state of the atmospheric flow field around this area. Adopting the model of SST k-ω，this paper carries out a numerical simulation of the atmospheric flow field around the highway. The affected area of highways with different parameters on surrounding atmospheric flow field and the altered state of flow filed are studied.

Abstract: One of the critical loads in engineering design is wind load, especially for high-rise structure or multi-story structure. In order to forecast the distribution of wind effects on structure, how to accurately predict the building surface wind pressure distribution is very important. Using the wind tunnel model test and numerical simulation calculation methods, the surface wind load on the mega-frame structure were comparatively analyzed and researched in this paper. The results show that combined the realized к-ε model with the standard wall function will not only satisfy the mega-frame structure surface wind pressure value requirement, but also provide complete wind filed around, which could provide meaningful information for further research on wind load.

Abstract: This paper presents numerical and experimental investigations of wind-induced interference effects on the pressure distributions on an adjacent building. The relative locations of the interfered building model and the interfering model are sited in staggered arrangement. The wind tunnel tests were carried out in a low-speed boundary layer wind tunnel. The numerical predictions for pressure distribution on the principal building are performed by solving the Reynolds-averaged Navier–Stokes (RANS) equations using the renormalization group (RNG) k–e turbulence model and then compared with the measurements. The RANS equations are solved by the pressure correction procedure of the SIMPLEC method. The simulated pressure, base force and base moment coefficients in different wind directions are generally in good agreement with the corresponding wind tunnel data. It is also found that the wind pressures, base forces and moments on the testing building are affected to some extent by the interference from adjacent buildings. The numerical simulation applying the SIMPLEC method using the QUICK upwind scheme and the RNG k–e turbulence model seems to be a useful tool for the predictions of wind pressures, and especially the wind forces acting on a building with an adjacent building.

Abstract: The hydraulic loading device commonly used for creep test necessitates continuous recharge of the hydraulic pressure with time and is accompanied by slight variation of the permanent load at each recharge. Therefore, accurate test results cannot be obtained for long-term creep tests requiring time-dependent behavioral analysis during more than 6 months. This study conducts creep test as part of the analysis of the long-term characteristics of fiber-reinforced lean concrete sub-base of pavement. The creep test is executed using the new load-amplifier device not a conventional loading device. Since the results of the preliminary verification test on the new creep test device show that constant permanent load is applied without significant variation, it can be expected that more accurate measurement of the creep will be possible in a long-term compared to the conventional hydraulic device. In addition, the creep test results of sub-base specimens reveal the occurrence of large instantaneous elastic strain, differently from the strain curve observed in ordinary concrete, as well as the occurrence of small creep strain leading to low creep coefficient.

Abstract: Calculate and analyze the frequency of the simple box girder based on the unfinished Ba gong River Bridge. The frequency values which were obtained by dynamic test method and theoretical analysis method were compared in this paper. The results showed that the measured values of dynamic test method are close to the results of theoretical analysis, the error is within permissible range, so dynamic test method is suitable for measuring the frequency of simply-supported box girder.