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Long K.,North China Electrical Power University | Long K.,RMIT University | Du X.,RMIT University | Du X.,MCC Central Research Institute of Building and Construction Co. | And 3 more authors.
Composite Structures | Year: 2016

Recent studies have shown that the stiffness of composites in one or more directions could increase dramatically when the Poisson's ratios of constituent phases approach the thermodynamic limits. In this paper, we establish a computational framework for the topology design of the microstructure of a composite material whose constituent phases have distinct Poisson's ratios. In this framework, the composite is assumed to be composed of periodic microstructures and the effective mechanical properties are determined through the numerical homogenization method. Topology optimization for maximizing the effective Young's modulus is performed to find the optimal distribution of material phases, subject to constraints on the volume fractions of the constituent phases. Four 3D numerical examples are presented to demonstrate the capability and effectiveness of the proposed approach. Various microstructures of optimized composites have been obtained for different objective functions and for different parameters. © 2016 Elsevier Ltd

Zhou C.,Beijing Jiaotong University | Zeng X.,Beijing Jiaotong University | Zhao F.,MCC Central Research Institute of Building and Construction Co. | Zhou H.,MCC Central Research Institute of Building and Construction Co.
Journal of Earthquake Engineering and Engineering Vibration | Year: 2016

To analyze the seismic behavior of high-rise RC chimney, this paper selected one 240 high RC chimney as the research object. On the basis of distributed plastic fiber beam-column element, a detailed three-dimensional structural nonlinear analytical model is developed using the finite element software OpenSees. In order to consider the uncertainties in ground-motion realizations, according to the principle of spectral compatibility, 21 natural ground motion records are selected as the basis of incremental dynamic analysis. The peak ground acceleration and curvature ductility ratio have been selected as the intensity measure and structural seismic demand parameters, respectively. Based on lognormal assumptions, nonlinear incremental dynamic analysis is then performed for the case study RC chimney and statistically analyzed to build the probabilistic model of the seismic demand. According to concrete and longitudinal reinforcement strain levels, four damage limit states, named as the light, moderate, extensive and complete damage, were defined in terms of the analysis results of 95 sections. Then the fragility curves are developed for the RC chimney at various damage states and its vulnerability assessment and analysis are conducted. The study indicates that for frequent earthquake, basic earthquake and rare earthquake, the probabilities of exceeding the light damage state are around 0% , 20% and 75% , respectively; while the probabilities of exceedance corresponding to moderate, extensive and complete damage states are approximately zero. The results of the fragility analysis developed in this paper for the RC chimney would be helpful for seismic design, seismic risk assessment and seismic retrofit of RC chimney structures.

Liao J.,Beijing University of Technology | Liao J.,MCC Central Research Institute of Building and Construction Co. | Zhang Y.,Beijing University of Technology | Wu J.,Beijing University of Technology
World Information on Earthquake Engineering | Year: 2010

The short-member model considering the semi-rigidity of welded hollow spherical joints is presented. Equivalent short-member is used to simulate the welded hollow spherical joint. It simulates the mass and the initial stiffness of the joint through the conversions of mass, cross-sectional area and moment of inertia. The bending rigidity changing with the axial force in the plastic phase is simulated through self-defined PMM plastic hinge. In the SAP2000 finite element software, the calculation model is introduced and proved to be feasible in elastic-plastic analysis though calculation examples. Short-member model is appropriate to static and dynamic elastic-plastic analysis of reticulated shell considering the semi-rigidity of welded hollow spherical joints. The actual behavior and work performance of the reticulated shell with semi-rigid connections in plastic phase can be analyzed accurately through it.

Zhou C.,Beijing Jiaotong University | Zhou C.,Tongji University | Zhao F.,MCC Central Research Institute of Building and Construction Co. | Gao R.,Beijing Jiaotong University
Beijing Jiaotong Daxue Xuebao/Journal of Beijing Jiaotong University | Year: 2011

One rapid assessment method to the frame structures after the earthquake is provided. Based on the analysis of earthquake damages of frame structures, this method gives quantitative and qualitative judgments to the damage extent of the common components in the earthquake. By using the fuzzy mathematics method, the security level of the components can be evaluated and the judgment matrix of membership grade can be established. Then the weights of components and structures are evaluated by using the AHP. Finally, Through analyzing the judgment matrix of level membership grade and the weights of components and structures comprehensively, the safety evaluation of the whole structure can be acquired. This method is feasible and systematic. The identification result of this method is accurate. In accordance with this method, a computer program can be easily compiled to make the identification work procedurally, thus to reduce the workload and identification time. Besides, by using this method, the judgment reference can be provided to make the policies of salvation and put the rescue measures into practice.

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