Applied Mechanics and Materials Vols. 638-640

Abstract: In order to optimize the structure of steel tube arched bridge, the parameterized model of steel tube arched bridge shall be established on the basis of APDL of ANSYS finite element. based on the huge computational power of ANSYS and the flexibility of APDL parameterization language, choose width of longitudinal beam, radius of arch ring and radius of suspender as design variables, regard maximum deflection and maximum stress as state variables, and take total volume as objective function. Realize structure optimization analysis of steel tubular arched bridge via parameterization computation.

Abstract: Existing bridge health monitoring systems neglect the benefit of support reaction index for the safeguard of bridge safety and generally do not include the monitoring of support reaction values. The basic setting method of vertical support reaction threshold was proposed in this paper. For concrete bridges, which have prominent discreteness, statistical analysis method should be employed to obtain the representative value of the modulus of elasticity. However, in practice, it is very difficult to obtain large amounts of data sample. The small sample analysis is necessary, with intent to reduce the uncertainty. For this purpose, t -distribution was introduced to carry out interval estimation for the mean value of modulus of elasticity. Confidence interval can be obtained and then be used as the representative value of modulus of elasticity. By adopting each endpoint of this interval respectively, two sets of vertical support reaction values under the most unfavorable load combination can be obtained and then multiplied by a reduction factor. For each bearing, there are two corresponding values, which can be used as boundary values and then interval threshold of vertical support reaction for concrete bridges early warning can be obtained. Finally, multiple level early warning based on the interval threshold can be actualized.

Abstract: Through the long-term deflection observation results and the measured data of effective pre-stress of Humen bridge before and after reinforcement, using three-phase bridge long-term deflection calculation method, compare the measured data and the calculation conditions in three kinds. Basing on the measure value of construction degradation, presenting the long-term deflection correction coefficient of long-term deflection to predict construction deflection. Analysis results show that the calculation model considering the construction degradation is more close to the practical situation. The long-term deflection calculation method based on the coefficient of correction can be used in the prediction calculation.

Abstract: The concrete shrinkage strain and creep coefficient calculation method in CEB - FIP MC90 model is briefly introduced. For application convenience in bridge design, a simplified formula for calculation of the concrete shrinkage strain and creep coefficient is derived. Considering the varying range of every influence factor, a correlation analysis for the factor is carried out. And the weights of those factors related to concrete shrinkage and creep coefficient are discussed. Considering the climate characteristics and the bridge structure features in the Pearl River Delta area, the variation ranges of concrete nominal shrinkage strain and nominal creep coefficient are calculated respectively.

Abstract: During the construction control in order to better control the elevation, the need for sensitivity analysis of the design parameters, the sensitivity analysis of design parameter adjustment principle, so as to adjust the measured deflection and deflection calculation error of judgment, and for the cross section should be the main design parameters of stress sensitivity. This method can identify accurately fast parameter error during the bridge construction, and ensure the smooth and long construction Liang Qiao. To provide reference for construction control of this kind of bridge deflection.

Abstract: To study the mechanism on the vortex resonance characteristics of the central-slotted box girders, the large-scale sectional model vibration measurement and pressure measurement are employed. This paper takes a long-span cable-stayed bridge over the Yangtze River as an example to conduct the wind tunnel tests of large-scale sectional model. The test results indicate that it is the inside maintenance rails located in the aerodynamic susceptible sites that cause the vortex-induced vibration (VIV) of bridge model. Accordingly, the inside maintenance rails are proposed to be moved towards the central axis by a certain distance. The static pressure test results show that when shifting the inside maintenance rails, the negative mean pressure at the soffit plate knuckle line will not change dramatically, the fluctuating pressures on the upwind and downwind inclined panels can be reduced, and the fluctuating energy will be dispersed without a consistent predominant frequency. Wind tunnel tests of modified section are conducted and the results show that the VIV of bridge model can be suppressed completely due to the shift of inside rails.

Abstract: Vehicle axle loads are modeled as moving loads and bridge is considered as a continuous beam. Based on the modal superposition theory, the model accelerations can be obtained from the accelerations of the bridge at several sections. Then based on the d’Alembertian theory, the inertia force of the bridge can be expressed approximately. Using the bending moment influence lines, the equations about flexural moment and moving force is obtained. Using the formulas, the moving force can be obtained at any time. Examples show that the method has high accuracy in identifying varying time moving force as well as constant moving force. This method has highly efficiency and appropriate to applying in engineering.

Abstract: A rigorous scheme must be formulated in advance before a viaduct is to be exploded, in this case, numerical simulation can provide effective guarantee to the formulation of the scheme. Focusing on the explosion engineering of a large-scale city viaduct, the process of its explosion and collapse were simulated by the LS-DYNA software. The vibration responses of soil surface caused by the explosion and collapse were analyzed, and also the numerical results were compared with the measurement data. The numerical results agreed well with the measurement data, which showed that the simulation method proposed in the paper could simulate the explosion process well and the results could be also an guidline for the similar projections in future.

Abstract: In the present paper, based on the three-dimensional finite element analysis for a three-span continuous PC box girder bridge with corrugated steel webs and the corresponding conventional box girder bridge with concrete webs, a comparative study on the shear lag effect under self-weight is carryied out together with the analyslis on the coefficient of the effective flange width. The results show that At the sections in the negative bending moment near the intermediate piers, the shear lag effect in the bridge with corrugated steel webs is more obvious than that in the bridge with concrete webs by 8%; and the corresponding effective flange width coefficient in the bridge with corrugated steel webs is even smaller than 0.9, so the shear lag effect at these sections should be considered in the design of this type of bridges. At the mid-span section of the middle span of a three-span continuous bridge either with corrugated steel webs or concrete webs, the shear lag effect can be omitted since the corresponding effective flange width coefficient there is close to 1.0.

Abstract: This paper focuses mainly on the case of a three-span prestressed concrete continuous girder bridge. A solid element model of the concrete upper rotation table and pier was established adopting the Midas/Civil Software, considering four unfavorable conditions including eccentric load effects. Then a strict inspection was given on the stresses and deformations of the model in each condition to check the safety of the structures during both processes of girder casting and bridge rotation. The results are positive and satisfactory.