Key Engineering Materials Vol. 574

Abstract: In this paper, several commonly-used Elliptical copulas and Archimedean copulas were introduced, and their application in the correlation analysis were also described in detal. For the two failure modes of two-dimensional series portal-framed bridge system, the performance function values with respect to the failure modes were considered as the analysis variables of the chosen copula functions, and the Baysian copula selection method was applied to select the proper copula functions. And then, the two-dimension mixed copula function was built. Thereinto, the uncertain parameters of copula function were determined with Monte Carlo Sampling (MCS) method, so the numerical modeling of the mixed copula fuction about the failure mode of two-dimensional series portal-framed bridge system was achieved. Finally the reliability of this system was analyzed with the built mixed copula function, and the structural system failure probability was obtained.

Abstract: Structural finite element model (FEM) updating in dynamics usually deemed the measured modal parameters as the goal. By modifying the theoretical FEM, the updated modal parameters obtained by the analytical FEM would finally tend to the testing results. But the own complexity of the civil structure leads the optimization problem of FEM updating to be super-size and high non-linear performance. Moreover, the uncertainty and nonuniformity of the structures, material and the environment effect cause the uncertainty of the updating parameters, even the optimization objective function of FEM updating. These features has brought greater difficulty to the model updating in civil engineering structure, especially for the application field. Therefore, in this paper several kinds of methods for FEM updating would be introduced with the comparison of their advantages, disadvantages and the range of application. At the end of this paper, the problems remained to be solved in FEM updating of civil structures are to be presented.

Abstract: An ANSYS-based spatial approach of analysis is proposed for the bridge-vehicle interaction to investigate the dynamic responses of a curved concrete box girder bridge and vehicles. The governing equations of a vehicle model with twelve-degrees-of-freedom (12DOF) are derived from the energy method using the Lagrange equation of motion. Both the bridge and the vehicle system are discretized adopting element type BEAM44, MASS21 and COMBIN14 in the ANSYS program. The interaction forces between the vehicle and bridge are deduced considering the road surface roughness and its velocity term based on the compatibility conditions of the contact points, and detailed formula are presented. The separate iterative algorithm is developed to solve the vehicle-bridge interaction problem. A three-axle cargo truck and a dual-cell box girder curved overpass bridge are chosen for both numerical and field test analysis. The dynamic properties and the dynamic responses of the bridge are both obtained from the numerical and experiment way, and the results agree well with each other by comparison. Its indicated that the procedures presented in this paper can be taken for the further vibration analysis study of curved concrete box girder bridges.

Abstract: The seismic design of Chinese Highway Bridge changed from single standard of fortification and one-step design performed nearly two decades to two-level fortification and two-stage design with the introduction of the new codes in 2008 and 2011. However, there are some shortcomings of the new codes such as the choice of response spectrum type, the determination of reinforced concrete constitutive relation, the discrimination of site-type and the bearing checking items, which leave a large room for improvement. Combined with the design codes of the developed countries like Japan and the United States, some useful suggestions are put forward in this paper for Chinese existing design codes. It is believed that Chinese seismic levels can be significantly increased so long as highway bridges are designed in accordance with the improved codes.

Abstract: With the development of long-span flexible bridges and the increase of highway transportation, both the dynamic responses of highway bridges under high-speed and heavy vehicles and the safety control of vehicles have deserved general concerns. First, this paper briefly discussed some researches on coupling vibration of vehicle and highway-bridges, then roundly summarized main research achievements accounting on the vehicle analytical model, bridge analytical model, surface roughness of road, numerical method of vehicle-bridge coupling vibration and some other aspects. Meanwhile, some research trends and challenge on vehicle and bridge dynamic interaction in engineering application were pointed out.

Abstract: This paper proposed a practical construction technology for the supporting system of covered excavation of deep foundation pit enclosure structure in urban subway. With the proposed method, the optimal management of the construction process was carried out in order to alleviate the construction difficulty, and a relative fast construction process was implemented. Finally, the proposed method was successfully applied to the construction of a practical metro station.

Abstract: The safety and load-bearing capacity of an in-service urban reinforced concrete slant leg rigid frame bridge over railway is assessed by field testing and finite element analysis. The bridge is located in Qitaihe city, the northeastern of China. The two heavy trucks and three different loading test configurations are used in experiment. The three load figuration is set up and performed based on the result of technical condition investigation and finite element numerical analysis. The vertical displacement and key section strain response are recorded during experiment. Loading-bearing capacity and safety performance of the bridge is analyzed and evaluated according to measured data combining with numerical analysis. The testing result shows that structural stiffness and strength of the bridge do not satisfy the requirements of the original design. Based on the assessment result, some proposals are proposed to the management office. A moderate maintenance and reinforcement treatment should be carried out for this bridge to improve the bearing capacity and ensure safety operation. Before that completed some traffic control measures should be taken to avoid aggravating diseases and damages of the bridge due to passing heavy vehicle.

Abstract: This paper presents an optimization model for investigating the influence on the ratio of side to main span in low-pylon cable-stayed bridge. Based on the structural analysis theory of cable-stayed bridge and combined with engineering practical, the optimization model considered that adjusting structural internal force by means of changing the side span length. Comparing and analyzing the optimization index in the result, the reasonable ratio of side to main span to this kind of bridge can be getting.

Abstract: The bridge inspection based on dynamical characteristics is the main technique for evaluating and diagnosing the performance of bridges, especially, for the situation that the bridge inspection based on static performance cannot be carried out. This study investigated the application of dynamical inspection to a bridge with accident during the construction. The dynamical performance of the damaged girders and piers were measured and compared with the healthy ones which have the same structural form in order to assess the performance of damaged bridge, and some treatment suggestions were proposed by account for the results obtained by visual inspection and crack observation.

Abstract: In this study, the modal identification methods based on time and frequency domain are summarized, and the working condition, identified accuracy and some fundamental idea of these approaches are discussed. By comparing the characteristic of different identification method, the identification technique based on ambient excitation is promising in bridges since it is difficult to measure the excitation information. Some challenge and key issues of modal identification of bridges are pointed out in the last part.