Study on the Seismic Collapse Prevention

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Experimental study and numerical model calibration for earthquake-induced collapse of RC frames with emphasis on key columns, joints and overall structure Journal of Earthquake Engineering, 2015  
Development of seismic collapse capacity spectra and parametric study Advances in Structural Engineering, 2014
Force-displacement mixed control for collapse tests of multistory buildings using quasi-static loading systems Earthquake Engineering & Structural Dynamics, 2014
Comparison and selection of ground motion intensity measures for seismic design of super high-rise buildings Advances in Structural Engineering, 2013  
An improved ground motion intensity measure for super high-rise buildings Science China Technological Sciences, 2013  
Collapse simulation of reinforced concrete high-rise building induced by extreme earthquakes Earthquake Engineering & Structural Dynamics, 2013  
Study of collapse resistant capacity spectrum Journal of Building Structures, 2012 Download
Discussion on the Ground Motion Intensity Measures for Super High-rise Buildings China Civil Engineering Journal, 2012 Download
Single-degree-of-freedom hysteretic model for collapse analysis of building structures Engineering Mechanics, 2012 Download
Pseudo-static collapse experiments and numerical prediction competition of RC frame structure I: RC frame experiment Building Structure, 2012 Download
Pseudo-static collapse experiments and numerical prediction competition of RC frame structure II: key elements experiment Building Structure, 2012 Download
Pseudo-static collapse experiments and numerical prediction competition of RC frame structure III: simulation results analysis Building Structure, 2012 Download
Seismic damage simulation of urban buildings based on high performance GPU computing Journal of Natural Disasters, 2012 Download
Study on uniform collapse risk evaluation method for building structures under earthquakes Journal of Building Structures, 2012 Download
Prediction of seismic collapse vulnerability of RC frame based on pushover analysis method, Journal of Earthquake Engineering and Engineering Vibration, 2012 Download
A hysteretic model of conventional steel braces and an analysis of the collapse prevention effect of brace strengthening Applied Mechanics and Materials, 2012
Lessons from the collapse of typical RC frames in Xuankou School during the great Wenchuan Earthquake Advances in Structural Engineering, 2012  
Influence of three-dimensional ground motion input on IDA-based collapse fragility analysis Earthquake Resistant Engineering and Retrofitting, 2011 Download
Study on the seismic collapse resistance of RC frame structures with equal spans in zones with seismic intensity VII Journal of Earthquake Engineering and Engineering Vibration, 2011 Download
Collapse simulation of a super high-rise building subjected to extremely strong earthquakes Sci China Tech Sci, 2011 Download
Evaluation of collapse resistance of RC frame structures for Chinese schools in seismic design categories B and C Earthquake Engineering and Engineering Vibration, 2011  
Study on the effect of strengthening a typical RC frame in Wenchuan Earthquake with attached substructures Journal of Architecture and Civil Engineering, 2011 Download
Study on the collapse-resistant capacity of RC frames with different seismic fortification levels Engineering Mechanics, 2011 Download
Comparison of different strengthening methods for a typical RC classroom frame in 7-fortification level zone Journal of Earthquake Engineering and Engineering Vibration, 2011 Download
A pushover analysis algorithm based on multiple point constraints Engineering Mechanics, 2011 Download
Research strategy on the building seismic design method that is aimed to control the collapse possibility under strong and mega earthquakes Proc. 8th National Earthquake Engineering Conference, 2010 Download
Seismic damage investigation and analysis on RC frames in Yushu 4.14 Earthquake Journal of Civil, Architectural and Environmental Engineering, 2010 Download
Study on the influence of stirrups confinement to the collapse resistance of typical RC frame in Wenchuan Earthquake Journal of Civil, Architectural and Environmental Engineering, 2010 Download
Numerical models for the progressive collapse of high-rise buildings due to earthquake Engineering Mechanics, 2010 Download
Study on the effect of strengthening a typical RC frame in Wenchuan Earthquake with BRB brace Journal of Catastrophology, 2010 Download
Influence of axial compression ratio to the seismic collapse resistance of RC frame structures Earthquake Resistant Engineering and Retrofitting, 2010 Download
Study on the seismic collapse resistance of structural system Earthquake Resistant Engineering and Retrofitting, 2010 Download
Seismic collapse resistance of RC frame structures
----Case studies on the seismic damage of several RC frame structures under extreme ground motion in Wenchuan Earthquake,
Journal of Building Structures, 2009 Download
Influence of structural parameters to the seismic collapse resistance of RC frames in 7-degree seismic fortification zone Proc. 4th Int. Conf. on Protection of Structures Against Hazards, 2009 Download
Analysis on damage mechanism of a typical RC frame in Wenchuan Earthquake China Civil Engineering Journal, 2009 Download
Numerical simulation for the progressive collapse of concrete building due to earthquake Proc. the 14th World Conference on Earthquake Engineering, 2008 Download
Analysis on Building Seismic Damage in Wenchuan Earthquake Journal of Building Structures, 2008 Download

Comparison and selection of ground motion intensity measures for seismic design of super high-rise buildings,
Advances in Structural Engineering, 2013, 16(7): 1249-1262..

Abstract: Ground motion intensity measures (IMs) are an important basis of structural seismic design. Extensive research has been conducted on the selection of IMs for building structures with fundamental periods shorter than 6 s. However, minimal work has been performed for super high-rise buildings whose fundamental periods are much longer than 6 s. To fill the gap in this research area, this paper aims to develop a simplified analytical model for super high-rise buildings based on the flexural-shear coupled beam model. The variation in correlation and dispersion between different IMs is evaluated and the structural seismic response demand measures (DMs) are analyzed for different structural fundamental periods. Subsequently, rational IMs for the seismic design of super high-rise buildings are suggested. In addition, the influence of different flexural and shear stiffness ratios, a0, on the selection of an IM for super high-rise buildings is also discussed. Finally, a series of incremental dynamic analyses (IDA) of the Shanghai Tower, with a total height of approximately 632 m, is performed to verify the rationality of using different IMs for super high-rise buildings. The numerical results indicate that with a minimum dispersion, the peak ground velocity (PGV) has a better correlation to the story drift ratio than any other IMs. While considering structural nonlinearity, PGV still yields the minimum coefficient of variation in the collapse analysis of the actual super high-rise building. It is therefore recommended that PGV be used as an IM for the seismic design of super high-rise buildings.
Keywords: super high-rise building; collapse analysis; ground motion intensity measure; simplified model.

An improved ground motion intensity measure for super high-rise buildings,
Science China Technological Sciences, 2013, 56(6): 1525-1533.

Abstract: Ground motion intensity measure (IM) is an important part in performance-based seismic design. A reasonable and efficient IM can make the prediction of the structural seismic responses more accurate. Therefore, a more reasonable IM for super high-rise buildings is proposed in this paper. This IM takes into account the significant characteristic that higher-order vibration modes play important roles in the seismic response of super high-rise buildings, as well as the advantages of some existing IMs. The key parameter of the proposed IM is calibrated using a series of time-history analyses. The collapse simulations of two super high-rise buildings are used to discuss the suitability of the proposed IM and some other existing IMs. The results indicate that the proposed IM yields a smaller coefficient of variation for the critical collapse status than other existing IMs and performs well in reflecting the contribution of higher-order vibration modes to the structural response. Hence, the proposed IM is more applicable to seismic design for super high-rise buildings than other IMs.
keywords: ground motion intensity measure, super high-rise building, time-history analysis, collapse analysis

Collapse simulation of reinforced concrete high-rise building induced by extreme earthquakes,
Earthquake Engineering & Structural Dynamics, 2013, 42(5): 705-723.

Abstract: Collapse resistance of high-rise buildings has become a research focus because of the frequent occurrence of strong earthquakes and terrorist attacks in recent years. Research development has demonstrated that numerical simulation is becoming one of the most powerful tools for collapse analysis in addition to the conventional laboratory model tests and post-earthquake investigations. In this paper, a finite element method based numerical model encompassing fiber-beam element model, multilayer shell model, and elemental deactivation technique is proposed to predict the collapse process of high-rise buildings subjected to extreme earthquake. The potential collapse processes are simulated for a simple 10-story RC frame and two existing RC high-rise buildings of 18-story and 20-story frame¨Ccore tube systems. The influences of different failure criteria used are discussed in some detail. The analysis results indicate that the proposed numerical model is capable of simulating the collapse process of existing high-rise buildings by identifying potentially weak components of the structure that may induce collapse. The study outcome will be beneficial to aid further development of optimal design philosophy.
Keywords: collapse simulation; high-rise buildings; elemental deactivation; fiber-beam element model; multilayer shell model

Study of collapse resistant capacity spectrum,
Journal of Building Structures, 2012, 33(10): 1-7.

Abstract: This paper quantitatively evaluates the earthquake-induced-collapse resistance of the single-degree-of-freedom structural system through collapse fragility analysis based on incremental dynamic analysis, and proposes the concept of the collapse resistant capacity spectrum (referred to henceforth as the CRC spectrum). The collapse resistant capacity spectrum is composed of the median (CRC50%) spectrum and the dispersion (h) spectrum. The CRC spectrum is useful to estimate the collapse probability of building structures subjected to the earthquake of given intensity level; and also it is utilized to establish the collapse probability targeted seismic design by which the structure is designed to satisfy the prescribed collapse probability under collapse-prevention-level earthquakes/mega-earthquakes. It is proposed that, the elastic seismic forces demanded by the fortification-level earthquake and the collapse-prevention-level earthquake/mega-earthquake are reduced by the classical R-m-T relation and the CRC spectrum, respectively, so as to rationally realize the three level seismic design target as prescribed in the Chinese code for seismic design.
Keywords: Collapse Resistant Capacity Spectrum; Collapse Fragility Analysis; R-m-T Relation; Performance-Based Seismic Design; Strength Reduction Coefficient

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Discussion on the Ground Motion Intensity Measures for Super High-rise Buildings
China Civil Engineering Journal, 2012, 45(S1):292-296
.

Abstract: Ground motion intensity measure (IM) is an important basis for structural seismic design. A simplified analytical model for super high-rise buildings on the basis of the flexural-shear coupling beam model is developed in this work. The variation of correlation and dispersion between different IMs and the structural seismic response demand measures (DMs) are evaluated for different structural fundamental periods. A series of incremental dynamic analysis (IDA) of the Shanghai Tower, with a total height of about 632 m, is carried out to verify the rationality of different IMs for super high-rise buildings. The numerical results indicate that with a minimum dispersion, PGV has a better correlation to story drift ratio than any other IMs. It is therefore recommended that PGV can be used as an IM for seismic design of super high-rise buildings.
Keywords: super high-rise building; collapse analysis; ground motion intensity measure; simplified model

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Single-degree-of-freedom hysteretic model for collapse analysis of building structures,
Engineering Mechanics, 2012, 29(10): 5-12.

Abstract: A simplified single-degree-of-freedom (SDOF) hysteretic model for collapse analysis of building structures is proposed in this work. The simplified hysteretic model is capable of simulating strength deterioration under monotonic loading, pinching, strength and stiffness deterioration under cyclic loading as well as P- effect, so that it can be applied to collapse analysis. To validate the applicability and effectiveness of the proposed SDOF hysteretic model, an eight-storey RC frame structure is simplified as an equivalent SDOF system according to its fundamental mode of free vibration and IDA-based collapse fragility analysis is implemented to the prototype structure and simplified SDOF system, respectively. The results show that the collapse fragility curves of the prototype structure and simplified SDOF system agree quite well with each other.
Keywords: Collapse Fragility Analysis; Single-Degree-of-Freedom; Hysteretic Model; Strength Deterioration; P-D Effect

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Pseudo-static collapse experiments and numerical prediction competition of RC frame structure I: RC frame experiment,
Building Structure, 2012,42(11):19-22+26.

Abstract: In order to investigate the seismic damage mechanism of reinforced concrete(RC) frame structures during the Wenchuan Earthquake,a series of pseudo-static collapse experiments of RC frame structure were carried out by Tsinghua University,including one 3-story-4-span RC frame,two key beam-column joints and four key columns.Numerical prediction competition is also conducted together with the tests.The results of the experiments and numerical simulations are published on the internet,which can be freely downloaded by the researchers and engineers.The design,the experimental process and the test results of the 3-story-4-span RC frame are introduced.
Key words: Wenchuan Earthquake; frame; collapse; reinforced concrete; numerical simulation;

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Pseudo-static collapse experiments and numerical prediction competition of RC frame structure II: key elements experiment,
Building Structure, 2012,42(11):23-26.

Abstract: In order to investigate the seismic damage mechanism of reinforced concrete(RC) frame structures during the Wenchuan Earthquake,a series of pseudo-static collapse experiments of RC frame structure were carried out by Tsinghua University,including one 3-story-4-span RC frame,two key beam-column joints and four key columns.Numerical prediction competition is also conducted together with the tests.The results of the experiments and numerical simulations are published on the internet,which can be freely downloaded by researchers and engineers.The design,the experimental process and the test results of the 2 key beam-column joints and 4 key columns are introduced.
Key words: Wenchuan Earthquake; frame; collapse; reinforced concrete; numerical simulation;

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Pseudo-static collapse experiments and numerical prediction competition of RC frame structure III: simulation results analysis,
Building Structure, 2012, 42(11):27-30.

Abstract: In order to investigate the seismic damage mechanism of reinforced concrete(RC) frame structures during the Wenchuan Earthquake,a series of pseudo-static collapse experiments of RC frame structure were carried out by Tsinghua University,including one 3-story-4-span RC frame,two key beam-column joints and four key columns.Numerical prediction competition is also conducted together with the tests.The results of the experiments and numerical simulations are published on the internet,which can be freely downloaded by researchers and engineers.The results of numerical simulation competition for the RC columns,joints and frames are introduced,and corresponding conclusions and suggestions are proposed.
Key words: Wenchuan Earthquake; frame; collapse; reinforced concrete; numerical simulation;

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Seismic damage simulation of urban buildings based on high performance GPU computing,
Journal of Natural Disasters, 2012, 21(5): 16-22.

Abstract: To meet the continuously increased needs for seismic damage prediction,refined models have become an important development trend in urban regional seismic damage prediction.However,the application of refined models is limited by the high cost of computation if it is implemented on traditional CPU platform.In recent years,a technology with powerful parallel computing capability and lower cost,GPU technology,has been developed and applied rapidly.In this paper,a simulating method for urban regional seismic damage that can significantly reduce the computation time,was developed based on GPU-CPU cooperative computing technology.The proposed method was then applied to the seismic damage simulation of a medium-sized city to illustrate the unique advantages of GPU technology in large-scale regional seismic damage simulation.
Key words: urban region; seismic damage simulation; GPU; parallel computing;

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Study on uniform collapse risk evaluation method for building structures under earthquakes,
Journal of Building Structures, 2012, 33(6): 1-7.

Abstract: Seismic design should quantitatively evaluate and control the earthquake collapse risk that building structures are likely to encounter during the design service life,which needs taking both the structural collapse resistant capacity and the earthquake demand into consideration.Firstly,this paper introduced IDA-based collapse fragility analysis and seismic hazard analysis,which evaluated the structural collapse resisting capacity and the earthquake demand in terms of probability,respectively.Furthermore,the structural collapse probability was proposed for measuring the earthquake collapse risk and its calculation method was provided.Finally,the collapse probabilities of RC frame structure for three seven-fortification areas with different seismic hazards were calculated as an example.The result shows the inadequacy of evaluating earthquake collapse risk only based on seismic fortification.The uniform-risk-targeted seismic design was proposed for collapse safety.
Key words: building structure; earthquake demand; collapse fragility; seismic hazard; uniform-risk-targeted collapse safety;

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Prediction of seismic collapse vulnerability of RC frame based on pushover analysis method,
Journal of Earthquake Engineering and Engineering Vibration, 2012, 32(4): 1-6.

Abstract: The collapse-vulnerability analysis based on collapse probability is the most reasonable method to evaluate the collapse resistant capacity of structures. However, currently collapse probability analysis is mostly based on incremental dynamic analysis (IDA), which is difficult to be directly used for engineering design due to relatively large workload and complicated procedure. Therefore, it is necessary to develop a new method, which is convenient for engineering application. In this paper, 18 RC frames are analyzed respectively using pushover analysis and IDA. Then, the correlation between the results of pushover and those of IDA are studied. The results show that there are fairly good correlated relations between the collapse margin ratio (CMR), the collapse probability under maximal considered earthquake (MCE) and the displacement margin ratio from pushover analysis. Based on these relations, the design displacement margin ratio of pushover analysis to meet the requirement of the collapse probability under MCE is recommended. Nine additional RC frames are used to validate the proposed displacement margin ratio, which shows this method is easy to implement and can provide reference for engineering design of regular multilayer RC frame.
Keywords: Pushover Analysis; Seismic Collapse Vulnerability; IDA; Collapse Probability; Margin Ratio

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A hysteretic model of conventional steel braces and an analysis of the collapse prevention effect of brace strengthening,
Applied Mechanics and Materials, 2012, 174-177: 3-10.

Abstract. A hysteretic model of conventional steel braces consisting of 18 parameters is proposed. This model is able to simulate the hysteretic behavior of conventional steel braces accurately. The collapse-prevention strengthening effect with steel braces for a typical reinforced concrete (RC) frame that was close to the epicenter and collapsed during the Great Wenchuan Earthquake is discussed via push-over analysis and collapse fragility analysis based on incremental dynamic analysis. The result could be referred to for the seismic collapse prevention design of RC frames.
Keywords: brace; hysteretic model, Wenchuan Earthquake; collapse probability; strengthening.

Lessons from the collapse of typical RC frames in Xuankou School during the great Wenchuan Earthquake,
Advances in Structural Engineering, 2012, 15(1): 139-153.

Abstract: 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.
Keywords: collapse; seismic damage; Wenchuan Earthquake; RC frames; nonlinear finite element analysis

Influence of three-dimensional ground motion input on IDA-based collapse fragility analysis,
Earthquake Resistant Engineering and Retrofitting, 2011, 33(6): 1-7.

Abstract: Collapse safety is the most important objective of performance-based seismic design, and IDA (incremental dynamic
analysis)-based collapse fragility analysis is able to quantitatively evaluate structural collapse safety under earthquakes. In this paper, it is illustrated that IDA considering single horizontal component of ground motion will over-estimate structural collapse safety through examples of an 8-storey RC frame structure and a 20-storey RC frame-core wall structure. More collapse modes may be appear with three-dimensional ground motion input, so that more potential seismic vulnerability is clearly exposed. Therefore, IDA considering three-dimensional ground motion input should be adopted for collapse safety evaluation.
Keywords: incremental dynamic analysis; three-dimensional earthquake ground motion; collapse mode; collapse safety subjected to earthquake

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Study on the seismic collapse resistance of RC frame structures with equal spans in zones
with seismic intensity VII,

Journal of Earthquake Engineering and Engineering Vibration, 2011, 31(5): 13-20.

Abstract: The seismic design of Chinese building structures is mostly depended on the structural elemental loading capacity design under minor earthquake and the detailed design to ensure the deformation capacity£® However£¬it is lack of quantitative analysis of seismic collapse resistance under severe earthquake£® And the actual seismic damage shows that even for the same structural types£¬the global structural parameters will greatly influence the seismic collapse resistances£® Therefore£¬this paper designs 24 RC frame structures in zones with seismic intensity VII according to the Chinese Seismic Design Code£¬which have different spans£¬storey heights and storey number£® Incremental dynamic analysis is performed for the structures to assess their seismic collapse resistance£® The result shows that global structural parameters£¬especially the span and the storey number£¬have a great influence on the seismic collapse resistance£®
Key words: frame structure; collapse resistance; incremental dynamic analysis; elasto £­ plastic dynamic analysis;
collapse probability

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Collapse simulation of a super high-rise building subjected to extremely strong earthquakes
Sci China Tech Sci, 2011, 54(10): 2549-2560.

Abstract: In recent years, super high-rise buildings (>500 m) are developing very quickly and become an important frontier of civil engineering. The collapse resistance of super high-rise buildings subjected to extremely strong earthquake is a critical problem that must be intensively studied. This paper builds up a nonlinear finite element model of the tallest building in China, Shanghai Tower (632 m), and proposes the modeling method and failure criteria for different structural elements. The dynamic characters of this building are then analyzed, and the possible failure modes and collapse processes due to earthquakes are predicted, as well as the corresponding collapse mechanism. This work will be helpful in collapse prevention and the seismic design of super high-rise buildings.
Key words: super high-rise building, collapse simulation, extremely strong earthquake, finite element method

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Evaluation of collapse resistance of RC frame structures for Chinese schools in seismic design categories B and C
Earthquake Engineering and Engineering Vibration, 2011, 10(3): 369-377.

Abstract: According to the Code for Seismic Design of Buildings (GB50011-2001), ten typical reinforced concrete (RC) frame structures, used as school classroom buildings, are designed with different seismic fortifi cation intensities (SFIs) (SFI=6 to 8.5) and different seismic design categories (SDCs) (SDC=B and C). The collapse resistance of the frames with SDC=B and C in terms of collapse fragility curves are quantitatively evaluated and compared via incremental dynamic analysis (IDA). The results show that the collapse resistance of structures should be evaluated based on both the absolute seismic resistance and the corresponding design seismic intensity. For the frames with SFI from 6 to 7.5, because they have relatively low absolute seismic resistance, their collapse resistance is insuffi cient even when their corresponding SDCs are upgraded from B to C. Thus, further measures are needed to enhance these structures, and some suggestions are proposed.

Study on the effect of strengthening a typical RC frame in Wenchuan Earthquake with attached substructures,
Journal of Architecture and Civil Engineering, 2011, 28(2): 21-27.

Abstract: This paper is based on a typical RC frame that was closed to the epicenter and collapsed during the Wenchuan Earthquake. The seismic collapse resistance of the frame was strengthened by attached substructures, including conventional brace, BRB brace and viscous damper. Collapse fragility analysis based on incremental dynamic analysis is implemented for each strengthening scheme to compare their effects and to analyze the influence of critical parameters. The results show that the viscous damper performs better than the BRB brace, and the BRB brace performs better than conventional brace. With the same strengthening parameters, the A-shaped bracing scheme is better than the X-shaped scheme.
Keywords: Wenchuan Earthquake, RC frame structure; collapse probability; collapse prevention measure; strengthening.

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Study on the collapse-resistant capacity of RC frames with different seismic fortification levels
Engineering Mechanics, 2011, 28(3): 41-48.

Abstract: Collapse safety is the most important objective of performance-based seismic design. Buildings should have enough safety margin to avoid collapse during severe or mega earthquake. However, current Chinese seismic design code does not have explicit design specification or quantitative evaluation for collapse-resistant capacity. In this paper, the collapse-resistant capacities and safety margins against collapse of multi-story reinforced concrete (RC) frames with different seismic fortification levels are quantitatively evaluated, with collapse fragility analysis which is based on incremental dynamic analysis (IDA). The influences of axial compression ratio and the collapse mechanism on the collapse-resistant capacity are discussed, and suggestions are proposed to improve current design.
Keywords: frame structure; incremental dynamic analysis; seismic fortification intensity; collapse mechanism; safety margin against collapse

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Comparison of different strengthening methods for a typical RC classroom frame in 7-fortification level zone,
Journal of Earthquake Engineering and Engineering Vibration, 2011, 31(1): 124-129.

Abstract: In the Wenchuan Earthquake, many school buildings collapsed which caused huge casualties. So after the earthquake, Ministry of Housing and Urban-Rural Development, China Academic of Engineering, and China Earthquake Administrator proposed different strengthening methods to upgrade the seismic design of school buildings. However, the actual effects of these proposals have not been quantificationally evaluated. So in this work, fiber-beam element model with validated stirrups confined concrete constitutive law is used to buildup the nonlinear finite element model of a typical reinforced concrete (RC) classroom frame in 7-fortification level zone during the Wenchuan Earthquake. The effects of different strengthening methods on collapse-prevention are studied with collapse-fragility analysis that is based on incremental dynamic analysis (IDA). Further design suggestions are then proposed.
Key words: Wenchuan Earthquake; RC frame structure; collapse possibility; collapse-prevention; strengthening method

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A pushover analysis algorithm based on multiple point constraints,
Engineering Mechanics, 2011, 28(2): 18-23.

Abstract: This paper proposes a new numerical method for pushover analysis. By using multiple point constraints, the lateral force distribution is maintained and displacement-controlled pushover analysis is achieved. The method is derived from the principle of virtual work and the rigidity of multiple point constraint. It is applicable to both elastic and inelastic structures. The proposed pushover analysis method can be implemented with user-defined subroutine interfaces of finite element software MSC.MARC. The outstanding performance of the method is then demonstrated using monotonic and cyclic pushover analysis of reinforced concrete structures. The evolution of deterioration from onset to eventual member and structural failure can be tracked, suggesting that the proposed method is a powerful tool offering complete pictures and considerable insight into pushover performance and collapse mechanism of structures.
Keywords: pushover analysis, multiple point constraint, displacement control; principle of virtual work; collapse analysis

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Research strategy on the building seismic design method that is aimed to control the collapse possibility under strong and mega earthquakes,
Proc. 8th National Earthquake Engineering Conference, 2010.12, Chongqing, China: 291~297.

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Seismic damage investigation and analysis on RC frames in Yushu 4.14 Earthquake,
Journal of Civil, Architectural and Environmental Engineering, 2010, 32(sup.2): 6-8.

Abstract: Yushu 4.14 Earthquake made serious damage to buildings. Sent by Ministry of Housing and Urban-Rural Development of the P.R. China, authors made an investigation on the seismic damage of buildings in Yushu autonomous county, and special investigation was made on the damage condition and characteristic of RCframe buildings. Some suggestions are proposed in this paper.
Keywords: Yushu earthquake; frame structure; seismic damage investigation;

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Study on the influence of stirrups confinement to the collapse resistance of typical RC frame in Wenchuan Earthquake
Journal of Civil, Architectural and Environmental Engineering, 2010, 32(sup.2): 322-325.

Abstract: The lateral confinement of steel stirrups can improve the deformation capacity of kernel concrete, which will increase the global collapse resistance of the reinforced concrete (RC) frames. Existing stress-strain models of stirrups confined concrete are summarized and compared with test results to validate their accuracies. Then with validated stirrups confined concrete models and incremental dynamic analysis (IDA), the collapse resistance of a typical RC frame in Wenchuan Earthquake is quantificationally evaluated. The influence of stirrups confinement to the collapse resistance is discussed.
Key words: stirrups confined concrete, constitutive models, fiber beam model, collapse resistance, Incremental Dynamic Analysis

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Numerical models for the progressive collapse of high-rise buildings due to earthquake,
Engineering Mechanics, 2010, 27(11): 64-70.

Abstract: Progressive collapse means the collapse of whole building due to local weak stories or weak zones. Though collapse should theoretically be avoid for any buildings under any earthquake, it is important to study the collapse behavior of buildings to get a better understanding for the collapse mechanism and to find efficient method against it. The collapse process highly depends on the whole structural system, numerical simulation becomes a major method to study it. With the numerical program developed by the authors for the collapse simulation of complicated structures, the extreme nonlinear behavior of structural elements can be properly simulated. Two real buildings are analyzed to study the failure mechanism of the structures. The models proposed are helpful to study the collapse mechanism of high-rise seismic buildings.
Keywords: disaster prevention and mitigation; progressive collapse; earthquake; numerical model; nonlinear; reinforced concrete

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Study on the effect of strengthening a typical RC frame in Wenchuan Earthquake with BRB brace,
Journal of Catastrophology, 2010, 25(S0): 157-160.

Abstract: This paper is based on a typical RC frame that was closed to the epicenter and collapsed during the Wenchuan Earthquake. The seismic collapse resistance of the frame was strengthened by BRB brace. Collapse fragility analysis based on incremental dynamic analysis is implemented for each strengthening scheme to compare their effects and to analyze the influence of critical parameters. The results show that the BRB brace performs better than the conventional brace. With the same strengthening parameters, the A-shaped bracing scheme is better than the X-shaped scheme.
Keywords: Wenchuan Earthquake, RC frame structure; collapse probability; collapse prevention measure; strengthening.

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Influence of axial compression ratio to the seismic collapse resistance of RC frame structures
Earthquake Resistant Engineering and Retrofitting, 2010, 32(5): 26-35.

Abstract: The seismic collapse resistances of 24 reinforced concrete (RC) frame structures (in 7-degree seismic intensity zone, with different span, storey height and storey number) which are designed according to the Chinese Seismic Design Code are analysis with fiber-beam element model and incremental dynamic analysis (IDA) that is recommended by ATC-63 Report. The results show that the axial compression ratio of columns is the most important factor affecting seismic collapse resistance of these structures and there is a negative linear correlation between axial compression ratio of columns and collapse margin ratio of structures. The upper limit of current seismic design code is too big which mostly results in the lack of collapse resistance of frame structures. Then, the axial compression ratio of all structures is unified by adjusting their column size and the modified structures are analyzed again, which shows that by controlling the axial compression ratio, the seismic collapse resistance is obviously improved.
Keywords: frame structure; collapse performance; incremental dynamic analysis; collapse

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Study on the seismic collapse resistance of structural system,
Earthquake Resistant Engineering and Retrofitting, 2010, 32(1): 13-18.

Abstract: Structural system is very important for the collapse resistance of structures under extreme disasters. But currently there is still lack of quantitative evaluation method for structural system. This paper takes aseismic structures as examples, discusses the safety margins of structures, and points out that the structural safety margin is make up of safety margin that is beneath the structural element level and the safety margin of global structural system. Factors that may control the safety margin of global structural systems is then analyzed. In order to give a better evaluation for the safety of whole structure, Collapse Margin Ratio (CMR) is introduce, which is based on Incremental Dynamic Analysis (IDA) and is receiving more international focus recently. Frame examples are given to illustrate how to evaluate the structural collapse resistance under Mega-earthquake with CMR.

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Seismic collapse resistance of RC frame structures
----Case studies on the seismic damage of several RC frame structures under extreme ground motion in Wenchuan Earthquake,

Journal of Building Structures, 2009, 30(6): 67-76.

Abstract: The seismic damage of several groups of RC frames in the hardest-hit zone of Wenchuan Earthquake is introduced. In each group, some frames collapsed while others survived, despite that they have similar site conditions. The collapse resistances of two typical frames in earthquake are analyzed with nonlinear time-history analysis, pushover analysis and collapse margin ratio (CMR) analysis which is based on incremental dynamic analysis (IDA). The corresponding collapse resistance researches and calculation methods in foreign countries are introduced. The main influencing factors and the evaluation indices that control the structural collapse resistance, as well as the global redundancy and integrity, are discussed. Based on this study, the collapse resistance of frames can be effectively improved with the following methods: (1) Guarantee the global loading resistance capacity and lateral deformation capacity; (2) Increase the redundancy and integrity; (3) Achieve rational yield mechanism with proposed engineering method; (4) Buildup dual-system for frame structures with infill walls. Finally, the problems that may need further researches on structural collapse are proposed.
Keywords: Wenchuan Earthquake; RC frame; collapse; elastic-plastic analysis; collapse margin ratio; redundancy; integrity

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Influence of structural parameters to the seismic collapse resistance of RC frames in 7-degree seismic fortification zone,
Proc. 4th Int. Conf. on Protection of Structures Against Hazards, Oct. 2009, Beijing, China: 331-338.

Abstract: Currently in China structural seismic design mostly focuses on design and verification of member strength under minor earthquake. However, during actual earthquakes, structural systems play a more important role in seismic collapse resistance. Therefore, in order to find the influence of structural parameters to the seismic collapse resistance, this paper designs 24 reinforced concrete (RC) frames in 7-degree seismic fortification zone according to the Chinese Seismic Design Code, which have different spans, storey heights and storey numbers. Incremental dynamic analysis (IDA), recommended by ATC-63 Report, is implemented for the frames based on fiber-beam element model to evaluate their seismic collapse resistances. The result shows that structural parameters have a great influence to seismic collapse resistance. The seismic collapse resistance of frames designed according to the Chinese Seismic Design Code with different span has obvious difference. The result could be referred for the further study of seismic collapse resistance.
Keywords: frame structure, collapse performance, incremental dynamic analysis, nonlinear dynamic analysis, collapse probability

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Analysis on damage mechanism of a typical RC frame in Wenchuan Earthquake
China Civil Engineering Journal, 2009, 42(5): 13-20.

Abstract: Many RC frame structures were damaged seriously with plastic hinges occurred at column ends rather than beam ends in the Wenchuan earthquake, which is significantly different to the failure mode expected in the seismic design. Based on the investigation of a typical RC frame structure damaged in the earthquake area, time history analyses using sophisticated finite element method were conducted. Three models were considered, i.e. pure frame, frame with floor slab, and frame with both floor slab and infill wall. A ground motion recorded at Bajiao town in the earthquake was used for the analyses, and comparison between three models were carried out to investigate the effect of floor slab and infill wall on the structural base shear, distribution of plastic hinges, and failure mechanism. Major finding from the analysis results are as follows: 1) ¡°strong column weak beam¡± is not able to achieve for the RC frame designed by following current Chinese design code. 2) Infill walls significantly change the failure mechanism of the RC frame. 3) Soft story mechanism is prone to occur for the structure with non-uniform distributed infill walls. The findings suggest that the effects of floor slab and infill wall have to be considered in the seismic design, and increasing stiffness and strength of columns is needed to achieve ¡°strong column weak beam¡±.
Keywords: RC frame; seismic performance; floor slab; infill wall; finite element model; collapse mechanism

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Numerical simulation for the progressive collapse of concrete building due to earthquake
Proc. the 14th World Conference on Earthquake Engineering, October 12-17, 2008, Beijing, China, CDROM.

ABSTRACT : Collapse is a critical ultimate state for buildings under earthquake. Though collapse should theoretically be avoid for any buildings under any earthquake, it is still very important to study the collapse behavior of buildings so as to get a better understanding for the collapse mechanism and to find efficient method to against it. Progressive collapse, which means that collapse of whole building due to local weak stories or weak zones, is a most common failure mode in earthquake. And as its collapse process highly depends on the whole structural system, numerical simulation becomes a major method to study it. With the fiber-beam-element model and multi-layer-shell-element model, which is developed by Tsinghua University for reinforced concrete (RC) frames and RC shear-walls respectively, the extreme nonlinear behavior of RC structural elements can be properly simulated including the cycle behavior under coupled axial force-bending moment-shear force, the breakdown of structural elements at ultimate states, and the contact between structural elements during the collapse. Simple RC frames and RC frame-shear wall structures are firstly used to demonstrate and to benchmark the capacity of the numerical model, and real complicated buildings are analyzed to study the failure mechanism of the structures.
KEYWORDS: progressive collapse, earthquake, numerical model, nonlinear, reinforced concrete

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Analysis on Building Seismic Damage in Wenchuan Earthquake
Journal of Building Structures, 2008, 29(4): 1-9.

Abstract: On May, 12, 2008, an earthquake with a magnitude of 8.0 happened in Wenchuan, Sichuan Province. The earthquake resulted in a large number of collapses and damages of buildings, and brought huge loss to the people's lives and properties. This paper gathers the building seismic damage data in major disaster area from the investigation work of the civil and structural groups of Tsinghua University, Xinan Jiaotong University and Beijing Jiaotong University. The data are classified according to structural type, construction time, earthquake intensity and function of usage. The characters of building seismic damage in this earthquake is analyzed with typical building damage cases, and the lessons are concluded on structural type selection, structural design and construction management and so on.
Keywords: Wenchuan earthquake, Seismic damage analysis, seismic damage cases

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