Advanced Materials Research Vols. 368-373

Abstract: Earthquake is a kind of natural disaster which is difficult to predict and the damage degree is very great, occurrence of the strong motion often leads to the tremendous life and property loss. Bridge is an important part of the lifeline engineering, it is very necessary to conduct the comprehensive and systemic investigation on the bridge aseismic. In this paper, a 670.56m span cable-stayed bridge was chosen as object of study, the FEM model of it was established, and the dynamic characteristic and nonlinear seismic responses under uniform and traveling-wave excitations were systematic studied. The results show that: 1) the mode of connection between the pier, tower and the beam is crucial to the dynamic response of bridge which should be simulated correctly. 2) Its former 10 rank frequency are located very close which shows that more mode shape should be taken into account when dealing with the dynamic analysis. 3) The traveling-wave excitation has appreciable impact on such kind of cable-stayed bridge, especially on the more flexible component, which should be paid much attention to while design.

Abstract: In this paper, a real high-piers bridge was taken as the example, the 3D nonlinear finite element model of this high-pier bridge is built based on OpenSees, then to do the analysis of seismic collision effects of the high-pier bridge under uniform excitation and multi-excitation considering the effect of traveling wave. And analyzing the reaction rule under different ground motions, and focusing on the differences of the effects of seismic pounding between uniform excitation and multi-excitation considering the effect of traveling wave. the seismic responses of high-pier bridge are closely related with its inherent dynamic characteristics and the spectral characteristics of ground motion and closer to the natural cycle of the bridge the main periods of ground motion is,greater the bridge collision response; traveling wave effect amplifies seismic pounding response, while the end of piers are adversely affected, exacerbating the damage. Although whether or not the traveling wave effect is harmful to the bearing, the traveling wave effect has obvious influences to bearing. Therefore, in the analysis of bridge seismic collision response it is necessary to consider traveling wave effect.

Abstract: Base the shortcomings of pre-simple-supported post-continuous girder bridge construction, a new beam-bridge convert structure system is proposed, that is a kind of structure form of prestressed concrete hollow multi-ribbed composite box girders, the calculation method of two phase and noting are put forward. the kind of Cast-in-place assembly structure is light self-weight, force structure reasonable, easy construction, overall good and overall cost low.

Abstract: In this paper, an analytical method of the beam with springs and dampers fixed at the ends was proposed based on equivalent single degree of freedom (SDOF) system and secondary Lagrange’s dynamic equations, in order to develop a new effective method to enhance the aseismic capability of underground structures. The dynamic response of elastically supported and damply supported beams subjected to both seismic loading and static axial loading was analyzed by the proposed analytical procedure. The theoretical results were validated by the numerical simulation. In order to further investigate the effects of springs and dampers fixed at the ends of the columns in nonlinear response situation, the 3D nonlinear seismic responses of the Dakai metro station structure with and without the isolators were analyzed by ABAQUS respectively. It is demonstrated that: (1) the proposed analytical procedure can predict the dynamic response of beams with elastic and damper supports subjected to both seismic loading and axial loading. (2) Setting isolators at the supports of the column could enhance the aseismic capability of the structure effectively. (3) The axial static loading induced by the gravity of the soil and structure provide the constraint on the column, and therefore could not be neglected in the structural dynamic analysis.

Abstract: Based on researches in material properties of reinforced concrete under high temperature, and combined with the whole process of fire, the fire-resistance test curve of building components suggested by ISO834 instead of the actual heating-up process. nonlinear transient temperature field simulates and analyses under fire of concrete frame columns based on Abaqus in this study. And temperature field distribution laws of column section are obtained. Conclusions of the paper are helpful to further understand of the mechanical properties of frame column under high temperature, and provide theoretical support for safety evaluation and reinforcement techniques of the structure after fire.

Abstract: In ground fracture region, Xi’an subway adopted segmented lining to adjust for the differential settlement. We applied three-dimensional finite difference method to simulate “plateau type” ground fractures. The conclusion is that segmented lining structure can restrain tunnel surrounding soil deformation near ground fractures effectively. Far away from the tunnel longitudinal axis, the surface settlement is consistent with free field. The change region of the soil pressure mainly distributes in 30m of ground fractures upward and 20m of ground fractures downward. The axial stress, major principal stress and minor principal stress on the inner side of lining with tunnel axis is more tensile than the outside one, and their tensile region are concentrating in the waist lining structure, their compression region are mainly distributing in vault and arch bottom. Based on the results, we suggest that the pulling reinforcing steel should be used in the waist lining structure.

Abstract: Abstract. The paper investigates the gradient of relative humidity over time at different depth from dried surface and the relationship between relative humidity and concrete shrinkage. It shows that a drop in relative humidity over time is remarkable, and that drying shrinkage is linearly related to humidity. By measuring the weight of the sample and calculation of the capillary pressure, the relationship between the saturation and the capillary pressure is presented. Based on the experiment and Kelvin’s law, a model of shrinkage for non-saturated concrete taking the surface energy into account is presented. A comparison of computed and observed drying shrinkage is made, finding that the two values are in agreement very well.

Abstract: Post-earthquake fire is disaster which causes great harm to human. In this paper, post-earthquake fire risk assessment of urban area was analyzed, and a fire spreading probability model of urban area based on cellular automata was developed. The fire spreading process has been reproduced successfully by our model. The reproduction of fire process not only improves people’s cognition, but also provides the guide for city planning

Abstract: The fire design of semi-underground building is much strict according to the fire design of underground structure. Take the actual project of a Semi-underground building for example, evacuation distance of basement1 in this building over the standards. To solve the problem, the performance-based design uses the computer simulation to analyze the building. Using the simulated data judge the safety of the building. Then the paper gives advice of setting up the "Quasi safety zone" to solve the problem of evacuation distance. The paper discusses the fire safety of Semi-underground building and expects some advice to design of actual project.

Abstract: According to the general solution for waterhammer deriving by the author, this paper proved that the solution can be written in the form of the d'Alembert's wave functions. Some equations including the so-called the chain equation is derived with the help of the new solution. The periodical influence of the initial conditions on the results is discussed.