Applied Mechanics and Materials Vols. 71-78

Abstract: In the past 50 years, many long-span continuous stone arch bridges have been built in China. Analysis of mechanical performances and load capacities of long-span continuous stone arch bridges has important significances for the safety assessment of the similar bridges. 3D elastoplastic finite element method is employed to analyze ultimate bearing capacity of a three-span arch bridge with sandstone masonry in this paper. The characteristics of structural geometric and material nonlinearities and cracking and crushing of the masonry are taken into account. Compared with single-span arch bridge, both the coaction of spandrel structure and main arch and the influence of loading arrangements on ultimate bearing capacity is analyzed. The failure characteristics of the structure under the ultimate load are also introduced. The analysis results and conclusions can be referenced for the safety assessment of similar bridges.

Abstract: The present work experimentally investigated the operating characteristics of a miniature loop heat pipe (LHP) under different power cycle. The miniature LHP with flat evaporator of 8mm thick is made of copper. The evaporator with sintered copper power wick is in series structure with compensation chamber. Water is working fluid. It is found that the LHP can start up at heat load of 15W with temperature oscillation and the maximum heat load is 160W with R_l=0.068°C/W. The LHP operates unstably under low heat load. The oscillating frequency of temperature rises with heat load increased. The operating performance of the LHP is affected by the power cycle.

Abstract: Based on the tests of six reinforced concrete slabs strengthened with fibre reinforced plastic (FRP) sheets and one reference slab without the sheet, the influences of factors such as type of FRP sheets (CFRP and GFRP), amount of FRP sheets and strengthening scheme upon the crack resistant performance were presented and discussed in this paper. In the end, a calculation method was put forward, which can be used to calculate cracking moment and crack width in reinforced concrete slabs strengthened with FRP sheets.

Abstract: This paper presents one new configuration called little-character-toggle-brace. This paper analyses the effect of different toggle-brace position in the story and different angle of the toggle-brace to the magnification factor and provides the damping radio of the structure. Based on vibration control test of the structure with energy dissipation devices, the dynamic behavior and dynamic response of the structure with little-character brace, diagonal brace or little-character- toggle-brace have been investigated. The different control effects of the structure with the different energy dissipation braces have been studied. The result demonstrates that the little-character-toggle- brace is the best energy dissipation brace.

Abstract: With the rapid development of high-speed railway in soft foundation, foundation treatment technology has become mature, the most outstanding is CFG pile composite foundation technique. CFG pile composite foundation is made of cement fly ash gravel pile(CFG pile), pile of soil and sandstone , between sand and gravel several problems such as the medium material composition together constitute layer. It has high bearing of capacity, convenient, low costing, strong adaptability and quality control easier.So it is widely applied and promoted. Under static and dynamic loads, the relations of the high-speed railway CFG pile composite foundation is very complex. In order to further understand the intensity of pile-net structure subgrade stability and deformation, pile , requirements of the high-speed railway roadbed ,it needs to do pile-net structure parameter sensitivity analysis. According to high-speed railway CFG pile composite foundation , the numerical analysis can well solve the coupling effect of piles and soil. So, this paper adopts FLAC3D finite difference software is simulated and analyzed.

Abstract: A 10000kN lead rubber bearing is taken as an example to study the energy dissipation mode of isolated bridge and optimal lead rate of the bearing. Bilinear spring model considering the effect of real lead rate on the stiffness is used to simulate the bearing. Optimization of the lead rate in different site soil conditions and different axial compression ratio of pier is carried on by using nonlinear dynamic time history analysis. It is shown that the axial compression ratio of pier has great influence on the energy dissipation mode of isolated bridge and the optimal lead rate of the bearing. Site soil conditions have little effect on the energy dissipation mode of the isolation bridge and the optimal lead rate when the axial compression ratio of pier is fixed.

Abstract: In this paper, applicability study on high damping rubber bearing for highway bridges in soft soil conditions is carried out by using nonlinear time history analysis. 5-span continuous girder bridges with same superstructure but different substructure stiffness are taken as case bridges. Artificial ground motions with long characteristic period were fitted for the analysis. Seismic response comparison of case bridges with high damping rubber bearing and laminated rubber bearing show that: high damping rubber bearing does not prolong the natural period of the bridge, so compared with laminated rubber bearing, it acts more like a damper than isolator during strong earthquake. And the substructure stiffness of the bridge has great influence on the damping effect of high damping rubber bearing. When the substructure of the bridge is too flexible, the high damping rubber bearing has little damping effect. But, when the substructure of the bridge is rigid, the high damping rubber bearing still have great damping effect even in soft soil.

Abstract: Long period ground motion has great influence on long period structures such as large oil tank, high-rise building and long span bridge. In this paper, a long span cable-stayed bridge is taken as an example to study the seismic response of long period structure under long period ground motions and conventional ground motions by using nonlinear dynamic time history method. It is shown that although the peak acceleration of the long period ground motions are no more than half of conventional ground motions, the displacement and force response of the bridge at key points under long period ground motions are much greater than that of conventional ground motions. Constraint cables and fluid viscous dampers are used to reduce in the influence of long period ground motion of the bridge, and the effects of the two countermeasures are also analyzed in this paper. The results show that constraint cables have unstable effect and even negative effect under long period ground motion. While fluid viscous dampers have stable effect under both long period ground motion and conventional ground motion with proper damping parameters.

Abstract: Accurate population prediction has fundamental importance in small town planning. In this paper, two empirical prediction models, integrated growth rate and regression analysis, have been developed with demographic data of 2000-2005 in Gaotang county, Shandong province. The two models were then applied to predict the population in 2008, and their results were compared with the actual population, respectively, to evaluate the modeling accuracy. The results showed that both methods were capable of providing accurate population prediction; however, the accuracy of the integrated growth rate was a little higher than that of regression analysis in terms of their differences from the actual population in 2008.