Xinzheng Lu
Tsinghua University
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Featured researches published by Xinzheng Lu.
Advances in Structural Engineering | 2012
Xinzheng Lu; Lieping Ye; Yu-Hu Ma; Dai-Yuan Tang
The seismic damage of typical reinforced concrete (RC) frames in Xuankou School during the Great Wenchuan Earthquake in China is introduced. A simulation method for the seismic damage sustained was developed to enable analysis of the damage mechanisms. The simulation makes use of different nonlinear finite element (FE) models, including macro-scale fibre-beam-element models and a micro-macro-scale hybrid model. The results of the nonlinear FE simulations show that the design of RC frames do not properly allow for the influence of slabs and footing rotations, which results in incorrect predictions of the internal forces and hence, the seismic damage. The collapse resistances of different buildings are compared using incremental dynamic analysis (IDA). The IDA results show that the collapse resistance of the classroom buildings is much lower than that of the office buildings because the larger axial load ratio in classroom buildings limits their lateral deformation capacity. An optimum design is proposed which would improve the collapse resistances of classroom buildings at very low cost.
Advances in Structural Engineering | 2011
Zhiwei Miao; Lieping Ye; Hong Guan; Xinzheng Lu
Nonlinear static analysis (or pushover analysis) has been widely used in the last decade as a simplified and approximate method to evaluate the structural seismic performance and to estimate inelastic structural responses under severe ground motions. However most currently used pushover procedures with invariant lateral load patterns cannot fully reflect the effect of higher-order modes on structural dynamic responses. To overcome such a problem, a so-called Modal Pushover Analysis (MPA) was proposed based on the modal decoupling response spectrum method where the effect of higher modes was considered. To date, most research on MPA has been focused on frame structures. In engineering practice, however, most medium-to high-rise building structures are in the form of frame-shear-wall. Therefore it is necessary to extend the current research activity to implement the MPA to frame-shear-wall structures. In this study, two reinforced concrete frame-shear-wall structures of 10 and 18 stories are analyzed to evaluate the performance of the MPA method and the pushover procedures with invariant load patterns. The evaluation is based on the “exact” solutions of a nonlinear dynamic time-history analysis. The results show that the MPA method including higher-order modes is more accurate than the other pushover procedures. This is more evident when estimating structural responses for high-rise structures than the medium-rise counterparts.
Advances in Engineering Software | 2014
Xinzheng Lu; Bo Han; Muneo Hori; Chen Xiong; Zhen Xu
Refined models and nonlinear time-history analysis have been important developments in the field of urban regional seismic damage simulation. However, the application of refined models has been limited because of their high computational cost if they are implemented on traditional central processing unit (CPU) platforms. In recent years, graphics processing unit (GPU) technology has been developed and applied rapidly because of its powerful parallel computing capability and low cost. Hence, a coarse-grained parallel approach for seismic damage simulations of urban areas based on refined models and GPU/CPU cooperative computing is proposed. The buildings are modeled using a multi-story concentrated-mass shear (MCS) model, and their seismic responses are simulated using nonlinear time-history analysis. The benchmark cases demonstrate the performance-to-price ratio of the proposed approach can be 39 times as great as that of a traditional CPU approach. Finally, a seismic damage simulation of a medium-sized urban area is implemented to demonstrate the capacity and advantages of the proposed method.
Advances in Engineering Software | 2014
Zhen Xu; Xinzheng Lu; Hong Guan; C. Chen; Aizhu Ren
Smoke is a leading cause of death in fire. To minimize the potential harm from the smoke hazards in the course of a fire, a rational virtual reality (VR)-based fire training simulator taking full account of the various aspects of smoke hazards has been developed and is described herein. In this simulator, a visualization technique based on volume rendering and fire dynamics data has been especially designed to create a realistic and accurate smoke environment for the purposes of effective virtual training, which allows the trainees to experience a realistic and yet non-threatening fire scenario. In addition, an integrated assessment model of smoke hazards is also established in order to assess the safety of different paths for evacuation or rescue in virtual training, which allows the trainees to learn to identify the safest path. Two case studies of a subway station and a primary school demonstrated a high level of accuracy and smooth interactive performance of the proposed simulator, which is thus shown to be valuable for the training of both people who might become trapped in fire and firefighters engaged in learning the proper rescue procedures.
Natural Hazards | 2014
Zhen Xu; Xinzheng Lu; Hong Guan; Bo Han; Aizhu Ren
Effective seismic damage simulation is an important task in improving earthquake resistance and safety of dense urban areas. There exist two significant technical challenges for realizing such a simulation: accurate prediction and realistic display. A high-fidelity structural model is proposed herein to accurately predict the seismic damage that was inflicted on a large number of buildings in an urban area via time-history analysis, with which the local damage to different building stories is also explicitly obtained. The accuracy and efficiency of the proposed model are validated by a refined finite element analysis of a typical building. A physics engine-based algorithm is also proposed that realistically displays building collapse, thus overcoming the limitations of the high-fidelity structural model. Furthermore, a visualization system integrating the proposed model and collapse simulation is developed so as to completely display the seismic damage in detail. Finally, the simulated seismic damage of a real medium-sized Chinese city is evaluated to demonstrate the advantages of the proposed techniques, which can provide critically important reference information for urban disaster prevention and mitigation.
Aci Structural Journal | 2014
Yi Li; Xinzheng Lu; Hong Guan; Lieping Ye
Progressive collapses are resisted by the catenary mechanism in reinforced concrete (RC) frame structures undergoing large deformations. Research to date has mainly focused on the nonlinear dynamic progressive collapse resistance demand of this type of structures under the beam mechanism (that is, for small deformations), and that the catenary mechanism is lacking. As a first attempt, this study establishes a dynamic amplification factor for evaluating the resistance demands of RC frames under the catenary mechanism. To achieve this, an energy-based, theoretical framework is proposed for calculating the aforementioned demands. Based on this framework, the analytical solution for the collapse resistance demands of regular RC frames under the catenary mechanism is readily obtained. Numerical validation indicates that the proposed equations can accurately describe the progressive collapse demand of RC frames undergoing large deformations.
Journal of Performance of Constructed Facilities | 2013
Zhen Xu; Xinzheng Lu; Hong Guan; Xiao Lu; Aizhu Ren
AbstractProgressive collapses of arch bridges have repeatedly occurred in recent years, resulting in many casualties and significant property losses. Based on an actual recent and serious progressive collapse of a stone arch bridge, this paper simulated the complete progressive-collapse process using the general-purpose finite-element (FE) program, MSC.Marc. The simulation adopted a three-dimensional (3D) FE model and performed a nonlinear analysis using the contact algorithm in conjunction with the element-deactivation technique. The potential causes of the progressive collapse of the stone arch bridge were also evaluated. Furthermore, the importance of different components of the stone arch bridge was determined with the conception of generalized structural stiffness; thus, the most critical and vulnerable regions of the bridge were identified. The results of the simulated progressive-collapse process agreed well with the actual process, and the predicted critical regions were both correct and realistic...
Journal of Performance of Constructed Facilities | 2015
Peiqi Ren; Yi Li; Hong Guan; Xinzheng Lu
AbstractExisting research on progressive collapse of building structures mainly focuses on concrete and steel frame structures. To investigate the progressive collapse resistance of high-rise RC frame shear wall structures, two typical 15-story building models are designed with equivalent overall lateral resistance to seismic actions. However, the structural layouts in resisting the lateral forces are quite different for the two buildings. Building A is a weak wall-strong frame structure, whereas building B is a strong wall-weak frame system. Three-dimensional (3D) finite-element models of the two structures are established using fiber beam and multilayer shell elements. The progressive collapse resistances of the frames and the shear walls in both structures are evaluated under various column (shear wall) removal scenarios. Results demonstrate that there is a difference in progressive collapse prevention performance for different structural layouts. The progressive collapse resistance tends to be inadequ...
Advances in Structural Engineering | 2014
Yi Li; Xinzheng Lu; Hong Guan; Lieping Ye
Progressive collapse is a mechanical process that exhibits nonlinear and dynamic characteristics. The nonlinear dynamic effect on the progressive collapse resistance demand can be accurately evaluated by the nonlinear dynamic (ND) method. In engineering practice, however, the simplified and easy-to-use linear static (LS) method is often adopted. That is accomplished by using a dynamic amplification factor (DAF) to correct the LS resistance demand to approximate the true ND resistance demand. In this paper, the analytical expression of the DAF is established based on the energy conservation principle. The collapse-resisting substructure is firstly simplified as a single-degree-of-freedom (SDOF) equivalent. Then the energy conservation equation and the static balance equation of the SDOF equivalent are established to obtain the ND and LS demands. Finally, the DAF is obtained by dividing the ND demand by the LS demand. The DAF is validated through a series of the numerical examples including a SDOF system, a 3-storey planar frame and an 8-storey 3-D RC frame model structures.
Natural Hazards | 2016
Xinzheng Lu; T. Y. Yang; Zhen Xu
Earthquake-induced building collapses and casualties have been effectively controlled in the last two decades. However, earthquake-induced economic losses have continued to rise. Following the objective and procedure of next-generation performance-based seismic design, the economic loss prediction method proposed by FEMA-P58 is extended to regional earthquake loss prediction in this study. The engineering demand parameters for a large number of buildings within a region are efficiently obtained through nonlinear time history analysis using multi-story concentrated-mass shear models. The building data, including structural and nonstructural components, are obtained through field investigation, structural and architectural drawings, and default database published in the FEMA-P58 document. A case study of Tsinghua University campus in Beijing is performed to demonstrate the implementation and advantage using proposed FEMA-P58 method for regional earthquake loss prediction. The results show the advancement in loss simulation for a region, and in identifying the influence of the different ground motion characteristics (e.g., velocity pulse) on the regional loss.