Applied Mechanics and Materials Vols. 90-93

Abstract: In this article, an inclined leg bridge is taken as the research object. The three-dimensional finite element model is established, and soil spring is used to simulate soil-pile interaction. The dynamic characteristics of the two models are calculated. Two different ground motions are selected to analyze seismic response of the bridge. The dynamic characteristics and seismic response of bridge are compared in the conditions whether considering soil-pile interaction. The results show that the stress and displacement under qian’an ground motion action is bigger than that under Elcentro ground motion because the two ground motions have different frequency characteristics .After considering soil-pile interaction, the natural frequencies of inclined leg bridge decrease, and the longitudinal displacement of bridge increases obviously, at the same time the stress in the top and bottom of inclined leg increase obviously and the stress among main girder is not obviously increased. Soil-pile interaction maybe cause some adverse effect for inclined leg rigid frame bridge.

Abstract: Highway bridges played an important role in lifeline systems. Their seismic damage status made a direct influence on the implement plan of the earthquake relief work and the life and property security of the people. Therefore, accurate assessment and prediction for the seismic damage of highway bridges were of vital significance, based on which reasonable earthquake fortification could be implemented. This paper summarized and classified the existing seismic damage assessment methods for highway bridges, including certain index evaluation methods based on statistical results, vulnerability index evaluation methods based on probability theory and vulnerability index evaluation methods based on aggregation model. Then the capacity-spectrum method which could be used for calculating the fragility curve and the seismic assessment model of highway bridges used in HAZUS were specially explained. At last, the proposal for the development of seismic assessment systems related with highway bridges in China was put forward. Considering HAZUS’s good performance in seismic assessment, a similar assessment system should be built in China as soon as possible. The first step should be classifying highway bridges in China based on their current situation and obtaining their seismic assessment model parameters roughly, which tend to be safe. The second step should be carrying out sufficient experiments and numerical analysis and revising the model parameters obtained in the first step.

Abstract: The seismic response of curved girder bridge is more complex because of its irregular plane shape, therefore, the systematic study of an effective seismic mitigation method is required. In this article, the three-dimensional computational model of a double-pier curved continuous girder bridge is established and viscous dampers are added at the positions of sliding bearings. The full-bridge seismic response absorption effect is analyzed with the viscous dampers damping method under three ground motions of different frequency spectrum characteristic, and each ground motion contains three-direction. The results show that viscous dampers can reduce the difference of internal force between inner pier and outer pier in double-pier curved bridge, and it can also effectively reduce the bending and twisting coupling effect of curved bridge. But viscous dampers are sensitive to seismic spectrum to some degree, therefore seismic response absorption effect and sensitivity should be considered comprehensively when viscous dampers are selected.

Abstract: Under the earthquake, pounding between the beam and the bridge abutment causes great damages to skew girder bridge, and current study on pounding response is still less as the collision effect is complex. In order to study the displacement and collision force under Elcentro and Tianjin ground motion, a three-dimensional finite element computational model for seismic pounding of a 16m simply supported skew girder bridge was established and nonlinear time-history analysis was carried out with pounding element designed to simulate the pounding effect between beam and abutment. The results show that the displacement of side beam is more than that of middle beam in simply supported skew girder bridge. The maximum collision force of the side beam is more than that of middle beam, and the beam pounds the abutment several times. Appropriate expansion joint width should be set according to the displacement of the side beam when the expansion joint designed.

Abstract: The fatigue truck model is an important parameter in a fatigue evaluation, a 3-axle fatigue truck model was developed based on the weigh-in-motion traffic data and an analytical bridge model in the montane highway of Southwest China. The truck traffic data shows that the fatigue damage was dominated by the 6-axles trucks,a 3-axle fatigue truck model was developed based on the 6-axle truck statistic data,the damage accumulations caused by the Proposed fatigue truck righty meet the actual damage accumulations. Based on the cumulative probabilitie of the moment ranges, the peak stress range is suggested to be a stress level at 3 times of the effective stress range because of overload,however,the ratio of the effective stress in AASHTO was 2 times.The damage accumulations obtained from the simulation of the truck database were compared with BS5400,AASHTO and Proposed fatigue truck, Proposed fatigue truck and AASHTO fatigue truck with the actural daily flow of trucks are suggested in the montane speedway of Southwest China ,BS5400 is impropriety which relatively overestimate the damage.

Abstract: The natural frequencies and mode shapes of 2, 3 and 4 spans continuous beam with universal cross section are calculated, and these dynamic parameters of 2 spans continuous beam model are measured. From the analysis and the model test, the locations of the maximum curvatures of the mode shapes are determined, and comparing that with the maximum bending moment of the beam under the action of uniformly distributed load, the selection of the natural frequency of the beam is discussed with the General Code for Design of Highway Bridges and Culverts as the impact factors of the beam is calculated. It is shown from the results of the analysis and the test that, for the impact factor, when the effect of positive bending moment caused by impact force is calculated, the fundamental frequency must be used as shown in the General Code, and the 2^nd or 3^rd frequency must be used when the effect of negative bending moment caused by impact force is calculated. The selection of the frequency should be combined with the mode shape into account for the specific circumstances.

Abstract: Tunnel drainage influence range is a difficult hydrological problem. It relates directly to tunnel groundwater environment influence degree in construction and operation stages. Based on Shibanshan tunnel in Shijiazhuang-Taiyuan passenger line, this paper analyses influencing factor of tunnel drainage influence radius and flow transient process adopting heterogeneity and anisotropy equivalent flow models. This paper studies the tunnel drainage influence radius and construction progress , hydrology factors, geological factors and rainfall infiltration factors relations. Research results show that the influence factors are rock permeability, rainfall infiltration recharge and aquifer thickness on tunnel top, less influence factors are structure surface direction, anisotropy characteristic coefficient and primary support of the closed time. The conclusions will provide technical supports for evaluating the tunnel construction of groundwater environmental impact.

Abstract: The technologies of traffic information collection based on GPS equipped floating car have been become one of the main important means for real-time collecting traffic information in intelligent transportation system. So, the electronic map of route network is important to collect traffic information. As present, the link dividing methods can’t take into account the different conditions of traffic flow and the different attributes of the route. This paper presents a novel link dividing method: Firstly, the speed of the floating car history track is regarded as a stochastic and its frequency spectrum is obtained using Fourier transform; Secondly, the optimal sampling intervals of the link dividing are obtained using the frequency spectrum of speed and Shannon sampling theory; Finally, the novel link dividing model is founded based on the optimal sampling intervals and the attributes of the routes. This method not only considers the different conditions of traffic flow, but also distinguishes the different traffic flow of the different places of a link, which can improve application effect of the route traffic conditions and vehicle dynamic navigation.

Abstract: The ground structure, elastic and electronic properties of several phases of NbN are determined based on ab initio total-energy calculations within the framework of density functional theory. Among the five crystallographic structures that have been investigated, the hexagonal phases have been found to be more stable than the cubic ones. The calculated equilibrium structural parameters are in good agreement with the available experimental results. The elastic constants of five structures in NbN are calculated, which are in consistent with the obtained theoretical and experimental data. The corresponding Debye temperature and elastic ansitropies are also obtained. The Debye temperature of NbN in various structures consistent with available experimental and theoretical data, in which the Debye temperature of δ-NbN is highest. The anisotropies of ZB-NbN, NaCl-NbN, CsCl-NbN gradually increases. For hexagonal structure, the anisotropies of ε-NbN are stronger than that of δ-NbN. The electronic structures of NbN under pressure are investigated. It is found that NbN have metallization and the hybridizations of atoms in NbN under pressure become stronger.

Abstract: Fujian Province is one of Coal shortage for the southern provinces, under the premise to ensure safety of existing and the nowadays conditions of mining as much as possible recovery of coal resources under the old empty water. Uncle YongDing County, Fujian Province Coal mining under the old empty water, for example, to carry out joint working face with a high degree of water flowing fractured measured. Because the field complex geological conditions, the use of empirical formula and numerical simulation method to calculate the upper mining limit, and greater access to the actual situation. Only through in-situ measurement, to obtain specific geological mining conditions of the mine under the true information in order to obtain the actual situation of the mine found the correct data. To this end, this small coal mines in Fujian Province in the first the new technology that upward hole with a multi-stage water underground observation method was used to observe a high degree of fracture of Water, through in-situ construction and arrangement of holes and cracks under the conduction of water with a high degree of observational data analysis and results showed that after two coal face showed continuity with the overlying rock fracture characteristics, top boundary height 43.4m, 3.5m thickness calculated in accordance with mining, mining split ratio of 12.40.