Applied Mechanics and Materials Vols. 256-259

Abstract: To investigate the seismic response of long-span rigid frame bridges with high-pier, the shaking table test of a 1/10 scaled rigid frame bridge model is introduced in this paper. Details about test equipment, model design, test arrangement, input ground motion waves and test principle are provided. The response of bridge model under the seismic excitation included the uniform excitation and the multi-support excitation is observed. The influence of the soil-structure interaction on the bridge is considered through the real-time dynamic hybrid testing method. The impact effect for different ground motion input during the test is discussed. The influence of multi-support excitation, soil-structure interaction and impact effect on structural seismic responses are studied based on the test results. The isolation effectiveness and the damping effect are discussed as well.

Abstract: There are few researches on seismic response of reinforced concrete rib arch bridges at present; therefore, it is necessary to analyze seismic performance of this kind of bridges. Based on the engineering background of a three-span reinforced concrete rib arch bridge, a full bridge finite element model is built to analyze the structural dynamic characteristic and seismic response of the bridge. The internal forces and displacements of each key section is compared and discussed when the bridge is excited by horizontal unidirectional ground motion or the combination of vertical and horizontal ground motion. The structural seismic response calculated with different analysis methods is compared. The research results of this study can be used as a reference for the seismic design of similar bridges.

Abstract: Hong Kong-Zhuhai-Macao Bridge (HZM Bridge) is located in the LingDing Sea area outside the Pearl River estuary, where the hydrological and meteorological are very complex. Because the effective operating time was short and environmental protection requirements were high, the bridge construction is very difficult. For this feature, the method of non-navigable pier construction was used factory prefabrication and on-site installation. Unlike the traditional way of the bridge pier construction, this method can greatly shorten the time to operations at sea, by which all piers will be prefabricated in the factory and these will be only installed at the on-site. The construction of water stop between precast cap and steel pipe pile is the key aspects, and also one of the main focuses. This article introduces the water-stop system selection, design and test etc. three aspects.

Abstract: Based on the monitoring data of Jiujiang Bridge Health Monitoring System, the relation of the temperature and girder stress for the concrete cable-stayed bridge is analyzed. Firstly, taking the acquired stress and the corresponding temperature data for one month as analyzing samples, the daily mean of stress and temperature is calculated with all 72 sets of everyday data, and the relative value of stress and temperature is obtained by the comparison of the reference day. Result shows a strong linear correlation between stress and temperature. The trend equation between temperature and stress is then fitted by the least square method. Finally, the effect of temperature for girder stress have eliminated with the trend equation and the safety threshold of condition evaluation for the girder is set by probability statistics theory.

Abstract: A structural probabilistic resistance model was developed taking mechanical behavior of corroded reinforcing bars obtained from rapid corrosion specimens and real bridges and bonding performance between concrete and steels into accounts in this paper. Probabilistic model was used to capture randomness and variabilities of materials, geometrical size, corrosive process and corrosion ingredients. A time-dependent reliability model was used to predict probability of structural flexural failure incorporating existing dead load and live load model. It is found form results that probability of flexural failure for corrosive condition of highway bridges is about 18% higher than that predicted for no deterioration condition over next 100 years. It is from results indicated that an improvement in concrete durability specification such as increasing concrete cover and concrete strength can ameliorate the time dependent safety performance of highway bridges.

Abstract: In order to learn more about the composite steel-concrete bridge which the Djoué bridge of Congo (Brazzaville) National Road One Phase- II Project has selected, promote the design technologies of bridges and better understand and improve the relevant standards, The overall optimization design analysis of Djoué Bridge aiming at saving steel and improving bearing capacity is necessary. The Doctor Bridge was used in optimization of bridge type, concrete thickness and height of steel beam and they have been selected. It can provide technical references for the construction of the Djoué Bridge, the follow-up study of the composite steel-concrete bridge and the specification improvement.

Abstract: The paper deduced visual safety evaluation models in each layer under the action of internal forces for the pole bracing system of bridge structure ,based on failure envelope theory. It calculated and analyzed the actual Xugou especially big bridge project with these evaluation methods. Analyzed visibility graph of bridge structure, tried to find out directly concrete distribution and the safety degree of structure on visible group points in intra-regional each point to corresponding coordinateof octahedral failure envelope. It can finally realize quantitative and visual safety assessment for bridge structure, and can provide necessary reference to scientific management and planning optimal maintenance scheme of bridge engineering.

Abstract: In this paper, the crack diseases of 106 simply supported-to-continuous split-type box girder bridges from G55 Taichang and G55 Changjin highways were statistically analyzed by the number of bridges, the frequency of each meter cracks appeared and the degree of cracks developed. According to the norm that Standard for Technical Condition Evaluation of Highway Bridges and which was recommended by the department of transportation, the crack diseases were evaluated by the two indexes, which were maximum crack width and crack length divided corresponding section size . The conclusion provides a technical basis for the effective prevention and treatment of cracks in the design, construction, repair and maintenance in the future. The proposed crack disease statistics method and evaluation method are provided with practical application value for management and maintenance departments to effectively evaluate the crack development and make decisions to repair.

Abstract: The main aim of this paper is to describe the results obtained applying a new methodology developed in order to assess the presence of overloaded areas in steel bridges. The methodology is based on the principle that if the load applied (also just once) in a particular area is higher than the yield strength, it changes the residual stress in this area, inducing a different value of stress if compared with the other areas not overloaded. Using X-Ray diffraction it is possible to detect the value of residual stress on the surface of metals, also in small areas, in a non-destructive way. Therefore this technology is used to detect the presence of overloaded areas on steel bridges. As the areas sampled from X-Ray diffraction are very small (1-2 millimeters of diameter) compared with the dimensions of a bridge, it is necessary to know exactly the position of the areas subjected to the maximum load during the life of the bridge. For this reason FEM analysis are previously conducted in order to evaluate maximum load regions. The construction drawings necessary to perform the FEM analysis are not always available, especially for old bridges, therefore reality-based 3D models are created this problem. Such method is also useful by itself, as beside providing suitable drawings for the FEM analysis, it allows to quickly identify possible large deformations of the bridge structure.

Abstract: Though the prestress degree that is selected under control of the specified stress limit is a key design parameter in design of the prestressed concrete bridges, study on long-term deformation of the long span prestressed concrete beam bridges is not popular both here and abroad. This paper reveals the time-dependent regularity of long-term stress and deformation effect to the critical sections of the long span prestressed bridges from various prestress degrees, thereby the necessity of stress and deformation control consideration during design of the long span prestressed bridge structures is verified, and the prestressing expression based on stress and deflection control for relative study and design reference is given.