Applied Mechanics and Materials Vols. 226-228

Abstract: Two general approaches for the analysis of eccentrically loaded connections are described in the current AISC Specifications. The first method is the conservative elastic analysis. The second method is the instantaneous center of rotation method which gives more realistic values but is extremely tedious to apply. The 1989 AISC-ASD manual contains design tables intended for vertical loading only. The 2010 AISC manual considers eccentric loading with six specific inclination angles (θ) varying from 0 and to 75 degrees. However, actual loading condition may very likely differ from what has been assumed in the AISC design manual. This study proposes a more generalized solution (75° θ 360°) to overcome the design limitations as inherently made in the design manual. For uncovered cases, AISC Specifications do not offer a guideline on how to handle them. In such situation, engineers have the tendency to use the unjustified elastic method.

Abstract: Parabolic trough solar thermal power generation technology is the most mature technology in the world, which is also the only commercial operation of the solar thermal power generation technology. In order to the structure characteristics of the collector was accurately simulated and the result was calculated to reflect the performance of collector, the whole model of collector established. The internal force and deformation of steel under the external load was analyzed by nonlinear finite element method. For the connection problems of rectangular frame and mirror of the collector, the strength and rigidity of collector mirror were calculated by the finite element software for ANSYS, Which Ensured that the installation process of the collector remained unaffected to Mirror lateral displacement. While checking the shear strength of the connection bolts to ensure the collector's safety working, and to provide a useful reference for large-scale production of the solar Collector.

Abstract: In this paper, element-free Galerkin method was used to solve problems about the evaluation of slope stability. Based on the basic principle of element-free Galerkin method, a matlab program was compiled. In the program, moving least squares method was used to construct the displacement function. And the integration scheme of four Gauss integration point background grid was used to integrate. What’s more, Lagrange multiplier method was used to apply the displacement boundary conditions. When evaluating the stability of slope, the main indices which influence slope stability were determined and the analytic hierarchy process was used to determine the weight of the indices. Then the data of slope was input into the element-free Galerkin method program. By changing the data of the main indices, we can get the change value of the nodal displacement. So we can get the final weight of the indices based on the discussing of the element-free Galerkin method and the analytic hierarchy process. Finally, fuzzy comprehensive evaluation model was built. What’s more, we chose a slope in Changji expressway to be evaluated. The data of the slope was input into the program of fuzzy comprehensive evaluation model, and the result is basically stable which coincides with actual situation.

Abstract: This paper presents an accurate analytical method to obtain the rocking impedance function of a surface-supported strip foundation. The Green’s functions of the elastic half-space under concentrated or uniform loads with infinite length are derived and an elaborate integration method is used to calculate the multi-value improper integral. The interface between the foundation and the supporting medium is divided into a number of strip units. The rocking impedance function is solved by adding the moments in every strip, based on the fact that the vertical displacement of each unit can be uniquely determined by the rotation amplitude of the rigid foundation. Excellent convergence has been observed. Comparing the numerical results to those obtained by the thin layer method, good agreements are achieved. Finally, the effect of the Poisson’s ratio on the rocking impedance function of the strip foundation is discussed in detail.

Abstract: Two-dimensional finite element model of Qianning basin was built on the basis of depth study on geological structure conditions and of rock mechanical properties in Qianning basin, tectonic stress field characteristics of Qianning fault belt and Qianning basin formation mechanism were inversed. The results show that: (1)A remarkable low stress region is come into being in the central part of Qianning basin, the low stress environment in the strike-slip fault zone has a very important control function for the basin formation. (2)in the rock bridge area of secondary fault belt sinistral right order, high stress concentration zone are formed, rock body subject to extrusion, which often forms pushing structure, the surface morphology appears landforms phenomenon such as surface uplift, drum kits etc.

Abstract: Mechanics behavior of unloading rock slope is essentially different from the natural rock slope . But, stability analysis of rocky slope during and after excavating still need these parameters and constitutional relation came from the natural rock slope, thus, the difference between the unloading rock mass and natural rock mass is neglected. The calculation result is quite different from the monitoring result. In order to analyze the stability of unloading rock slope properly, corresponding mechanics parameters including mechanics state, unloading degree and others should be determined and applied. In this paper, IEM - Sample Element Method and Interface Element Method expounded systematically and used to determine the corresponding mechanics parameters of a layered rock slope- Xishan slope of the Jiangyin Yangtze River Bridge. Then, IEM computer program based on Interface Element Method used to calculate the displacement of Xishan slope. Compare with displacement site-monitoring results, IEM is better than Finite Element Method.

Abstract: The simulation optimization of internal force envelope in plane bar structure subjected to complex moving loads, including arbitrary concentrated force, concentrated couple, linearly distributed force and etc, was mainly discussed. By means of Vsap2011, the plane bar structure analyzing software, the effects of internal force envelope’s control sections on the solving precision of internal force envelope were analyzed. The research had reached to some important conclusions that in order to the obtain higher solving precision of internal force envelope, the element passed by moving loads should be divided by steps; more than enough dividing points should be inserted between load acting points for the element arbitrarily distributed with live loads; the element without any loads should be divided by defined interval when its both ends are rigid-jointed, while it should not be divided when its single or both ends are hinged-jointed.

Abstract: Once the tunnel fires happened, it will cause a major accident. And the smoke control of the runnel is important to fire prevention. A numerical simulation of the fire smoke flow in the tunnel model is presented by using FDS. The influence of different longitudinal ventilation on fire smoke flow of tunnel is obtained. And providing theory basis for tunnel ventilation system design, smoke spread control and safety evacuation. The results shown that in order to avoid reverse-flow and extend the time of smoke at the top of tunnel, the longitudinal speed should be controlled in 3.4 m/s; because of the role of longitudinal ventilation, smoke flow resistance and longitudinal ventilation generated by the effect of smoke flow resistance make the gas temperature first rise and then down.

Abstract: Yuan yanghui tunnel as the engineering background of this study, the layout of USTB micro-seismic monitoring system is introduced. The positioning accuracy of the system has been adjusted according to artificial fixed blasting tests. Combining with the relationship between activity rate and time of micro-seismic events, different types of micro-seismic events have been distinguished, which explain the emergence of those events. The results show that the design and implementation of micro-seismic monitoring system can meet the global monitoring of rock mass deformation during the construction of the tunnel. Imported with location condition, combining micro-seismic monitoring with conventional monitoring technique can find the concentration zone of rock failure more exactly and orientate the position of potential instable face, which has considerable engineering guiding significance and economic benefit.

Abstract: Concrete experiences thermal and hygral deformations at early ages due to it intrinsic properties and the environmental effects. Micro-cracking results on the top surface of pavement if deformations are restrained. These micro-cracks propagate transversely and downwards over time under traffic loadings, especially during early ages. This situation can be severe if upward curling conditions exist in pavements. Estimation of the remaining fatigue life of pavements with such cracks is of significance for scheduling prompt maintenance. Conventional fatigue models established based on uncracked beam tests are no longer applicable for such cases. It is necessary to develop a fracture mechanics-based fatigue model for pavement with cracks. This study provides a new fatigue life prediction methodology for pavement with cracks. Both model prediction and experimental test results suggest that fatigue life is significantly reduced if concrete develops a partial depth crack at early ages. These results can explain the observed premature transverse cracking failure in jointed concrete pavement. Crack growth behavior can be characterized as three stages, in which the steady stage is the most important one when prompt maintenance is needed to avoid structural failure.