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Zhou X.,Changan University | Zhou X.,Chongqing University | Li Z.,Changan University | Wang R.,Shanxi Electrical Power Exploration and Design Institute | Shi Y.,Changan University
Tumu Gongcheng Xuebao/China Civil Engineering Journal

Two full scale cold-formed steel joists and OSB (Oriented strand board) composite floors, which are single span and simply supported on both sides, were tested by monotone static loading to study the influence of screw spaces on the ultimate bearing capacity and the failure modes of composite floors were analyzed. The research shows that the composite floors have high bearing capacity and small deformation. The ultimate bearing capacity can be improved by reducing the space between screws. The main failure modes are bending-torsion buckling of floor joists, and the relatively buckling of compression flange, web and crimping. The wave length of bucking is the distance between adjacent screws. OSB is broke away from the profiled steel sheet round the support and distortion damage of floor joists present at the position concentrated loads acted. Considering the material, geometry and contract nonlinearity, the members are analyzed by ANSYS software and the nonlinear FE calculation results agree well with the test results. Furthermore, some parameters, such as the space of screws, oriented standard board thickness, steel thickness, space of the joists and the steel member strength are analyzed. The analysis results indicate that the load-carrying capacity of the composite floor can be increased by reducing the space of screw joists and the thickness of oriented standard board and steel joists or increasing the strength of steel members. Source

Chen G.,State Grid Corporation of China | Liu H.,Yanshan University | Liu H.,Shanxi Electrical Power Exploration and Design Institute | Qiu W.,State Grid Corporation of China | And 3 more authors.
Dianli Zidonghua Shebei/Electric Power Automation Equipment

When multiple faults occur in distribution network, both the supplies and teams can not meet the requirements of each fault repair task, aiming at which, a task allocation strategy based on fitness is proposed for the multi-fault repair. The fault task model, repair team model and material warehouse model are quantified, two external indexes, i.e. team fitness and supply fitness, are defined to respectively describe the matching degree between repair team and fault repair task and that between material warehouse and fault repair task, while two internal indexes, i.e. priority fitness and schedule fitness, are defined to respectively describe the priority of fault repair task and its repair schedule. The overall fitness index of each fault repair task is the integration of its external and internal indexes, which is compared among different fault tasks to obtain the optimal task allocation strategy. Simulation is carried out for IEEE 33-bus system and the simulative results verify the effectiveness and practicality of the proposed strategy. ©, 2014, Electric Power Automation Equipment Press. All right reserved. Source

Zong Y.,China University of Mining and Technology | Zong Y.,JiangSu JianZhu Institute | Han L.,China University of Mining and Technology | Qu T.,Shanxi Electrical Power Exploration and Design Institute | Yang S.,China University of Mining and Technology
International Journal of Mining Science and Technology

Based on uniaxial compression experimental results on fractured sandstone with grouting and anchorage, we studied the strength and deformation properties, the failure model, crack formation and evolution laws of fractured sandstone under different conditions of anchorage. The experimental results show that the strength and elastic modulus of fractured sandstone with different fracture angles are significantly lower than those of intact sandstone. Compared with the fractured samples without anchorage, the peak strength, residual strength, peak and ultimate axial strain of fractured sandstone under different anchorage increase by 64.5-320.0%, 62.8-493.0%, and 31.6-181.4%, respectively. The number of bolts and degree of pre-stress has certain effects on the peak strength and failure model of fractured sandstone. The peak strength of fractured sandstone under different anchorage increases to some extent, and the failure model of fractured sandstone also transforms from tensile failure to tensile-shear mixed failure with the number of bolts. The pre-stress can restrain the formation and evolution process of tensile cracks, delay the failure process of fractured sandstone under anchorage and impel the transformation of failure model from brittle failure to plastic failure. © 2014 Published by Elsevier B.V. Source

Liu D.-B.,North China Electrical Power University | Gu X.-P.,North China Electrical Power University | Zhao J.-Q.,Shanxi Electrical Power Exploration and Design Institute
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control

Fault restoration on regional power grids is a multi-objective, multi-contrained and complex optimization problem, and its efficiency of optimization is the key to its application on line. After studying the application of fault restoration technologies on regional power grids, an analytical model for on-line fault restoration is built and an improved Minimum Spanning Tree algorithm is presented. Based on modeling of the complex regional power grids, the algorithm can dynamically adjust searching space and growing direction of the minimum spanning tree according to the current properties of the subsystem and the present weight of the path in the analytical model to carry out the on-line quick search of the optimal restoration path. The validity of the algorithm has been verified by practical cases of fault restoration. Source

Yang S.-Q.,China University of Mining and Technology | Qu T.,Shanxi Electrical Power Exploration and Design Institute | Han L.-J.,China University of Mining and Technology | Zong Y.-J.,China University of Mining and Technology | Niu S.-J.,China University of Mining and Technology
Gongcheng Lixue/Engineering Mechanics

Based on the uniaxial compression experimental results of fissured sandstone under different anchorages by grouting, the failure modes of fissured sandstone were investigated, and the effects of bolt number and pre-stress on failure characteristics of fissured sandstone were discussed. In the failure process of fissured sandstone with two bolts, the initiation, propagation and evolution of three-dimensional cracks were analyzed. The results show that the final microscopic failure mode of fissured sandstone becomes more complexed with the increase of bolt number. For fissured sample with a fissure angle of 30°, the failure mode of the sample indicates a transition from tension failure to tension-shear mixed failure. However for fissured sample with a fissure angle of 45°, the failure mode of the sample indicates a transition from shear failure to tension-shear mixed failure. Pre-stress restrains the expansion and propagation of tension cracks in fissured samples, which leads to a smaller crack number than that under the condition of non-prestress. Finally, taking some fissured sandstones as typical examples, we analyzed the behavior of crack propagation during the whole deformation and failure process. It is evident that the failure of fissured sandstone is asymptotic. Source

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