Applied Mechanics and Materials Vol. 470

Abstract: In order to avoid the black-hole effect, illumination of higher luminance should be installed at the entrance/exit segments of urban tunnels during the day because the luminance of outside urban tunnels is relatively high. But it basically remains the same higher (current status in China) during the night while the illuminating brightness of outside-tunnel urban roads is relatively lower, which is not conducive to driving safety and wastes lots of energy. Through the comparison research of domestic and foreign relevant standards of tunnel and road lighting, as well as measurement and analysis of the present status of entrance/exit segments lighting of 11 tunnels in Fujian, Guizhou, Chongqing, and the present status of some roads lighting in Beijing, Shanghai, Chengdu and Chongqing, it is found that there are significant differences between the luminance of tunnels entrance/exit segments and the luminance of outside-tunnel roads. Especially when drive from the bright inside to the outside, that is from the inside photopic vision environment to the outside scotopic vision and mesopic vision environment. Due to high speed and poor visual fitness, there exist potential safety hazards. At present, there is no visual fitness standard for lighting of entrance/exit segments of urban tunnels and outside-tunnel roads in china, the domestic and foreign relative researches are still not enough. Based on visual features, with response time as parameter, this article applies the visual efficiency method to study the lighting of entrance/exit segments of urban tunnels and outside-tunnel roads. In this thesis, the method of weakening illumination of entrance/exit segments of urban tunnels on the basis of existing standards and enhancing illumination of outside-tunnel roads has been provided. Thus the reduced value of entrance/exit segments of urban tunnels illumination and outside-tunnel roads illumination can be controlled from 3:1 to 5:1 to adapt to visual features. This thesis provides a new research approaches for achieving driving safety and lighting energy saving.

Abstract: Many frame structures were damaged for the column hinge mechanism in the Wenchuan earthquake because of the biaxial seismic action. Four reinforced concrete columns with corner focus longitudinal bars were tested to improve the seismic behavior of RC columns subjected to multiaxial loading. The hysteretic behavior, skeleton curves and feature points were discussed. The results indicate that the method can improve seismic behavior of RC columns

Abstract: In this study, the fire resistance performance of high-strength concrete columns was evaluated to see the influence of lateral confinement reinforcement with wire ropes for improving ductility, fire resistance reinforcement with fiber cocktail and load ratio. For this, loaded fire test was conducted under ISO834 standard fire condition. The axial ductility of the 60MPa high-strength concrete column reinforced with pre-stressed wire ropes was improved and its fire resistance performance was also improved by 23% compared with its counterpart without wire ropes. The appropriate load for the 60MPa concrete column reinforced with wire ropes was found to be 70% of design load. The fire resistance performance of the 100MPa high-strength concrete column reinforced with pre-stressed wire ropes and fiber-cocktail was improved as much as 4 times compared with that reinforced with tie bars only. The appropriate load for the 100MPa columns was found to be less than 70% of design load in order for the columns to secure required fire resistance performance.

Abstract: In order to control the construction of asphalt pavement more precisely, an analytical hierarchy process (AHP) was used to screen the major control index during the construction process.. The results show that compactness, air void and thickness of surface course are the control indexes affecting construction quality, and are the major factors that lead to early damages. The weights of the three indexes are 0.43788, 0.2614, and 0.1818, respectively. Obvious correlations are shown between compactness and air void as well as thickness of surface. Finally, the compactness is chosen as the control index of construction based on the principle of convenient measurement and used to calculate reliability.

Abstract: The contact between aggregates is an important feature of asphalt mixture skeleton. By comparing skeleton-dense and suspended-dense structure asphalt mixture test results, this paper studied the distribution characteristics of coarse aggregate contacts by using two-dimension digital image processing technique. The results indicate that skeleton-dense asphalt mixture has more homogeneous distribution of contact points, and a relatively stable skeleton structure than suspended-dense mixture. In two-dimension image, homogeneous distribution of contact points and little unrestrained coarse aggregates are two evident characteristics of asphalt mixture with good rutting resistance. The rutting resistance of asphalt mixture has no correlation with contact points, but is related to the spatial distribution of the contact points.

Abstract: Building design codes typically specify seismic forces based on a 5-percent damped elastic design spectrum. To consider the case of structures with damping ratios other than 5%, damping correction factors are used. While these factors are determined for elastic systems, several studies have shown that the effects of damping are different for systems with nonlinear behavior. A study concerning the influence of damping on the nonlinear seismic response of building structures is presented. To separate the influence of nonlinear behavior, spectra of the ratio between the seismic strength demands corresponding to nonlinear and linear behavior, respectively, were computed, for damping ratios ranging between 2% and 10% and various constant ductility values. A database of ground motion records from the three strongest earthquakes that affected Romania during the last four decades was used in the study. The records were grouped into two sets, according to their frequency bandwidth. The spectral values computed for each set were processed statistically and results were expressed with reference to the 5%damped spectra. It was found that, for the analyzed damping range, the influence of this parameter on the nonlinear response is weak to moderate, for both considered types of frequency content.

Abstract: Reinforced concrete two-way slabs are widely used in industrial, civil, public buildings. However, the calculation method of curvature of deflection wasn’t clearly put forward in Code for design of concrete structures in China. Considering the nonlinear characteristics of concrete and bidirectional bending the formula of curvature deflection for reinforced concrete two-way slabs was derived based on plate theory in this paper. The iterative method is adopted in order to solve stress and strain of reinforced and concrete in reinforced concrete two-way slabs. The whole calculation process was realized by MATLAB software programming. The correctness of method in this paper was confirmed by comparing the results and the test data of the literature.

Abstract: The stress path division of soil strata surrounding the excavation tunnel was obtained by numerical simulation, and based on this, the impact variation of different stress paths to the surrounding soil strength was gotten by laboratory triaxial test. The results show that tunnel excavation can result in four different stress path divisions of the soil strata, which have deferent failure to the tunnel stability. Deferent paths have respective failure forms, and the failure strengths are basically the same when the forms are identical (extrusion failure or compression failure) even if the paths are different, but to deferent forms, the failure strength are deferent, generally speaking, the strength of extrusion failure will be 10% ~25% lower than that of compression failure. These researches can provide strong basis for accurately study about the influence of engineering property of environmental soil strata.

Abstract: In the nature, most phreatic or confined aquifers are of layered distribution. Based on the actual distribution of aquifer and whether there exists transfluence contact between each aquifer, the layered distribution aquifer basically is simplified as multi-aquifer or double aquifer structure. In this paper, all of the aquifer structure models proposed by domestic and foreign scholars are summarized. Furthermore, the mathematical model of each aquifer structure is detailed illustrated.

Abstract: Underground engineering accidents occurred recently have highlighted the importance of groundwater control. At present, there is little analysis about the groundwater control for shallow pedestrian tunnel located in high permeable round gravel layer. In this paper, the groundwater control method for pedestrian tunnel in such strata is researched. The proposed groundwater control scheme is eventually adopted, and has been proved effective with the successful completion of Kerry – Huarun Pedestrian tunnel project.