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Development of dynamic slip model for a shear crack

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earthquake engineering and engineering vibration 2010年第1期9卷 1-7页

作者： Juin-Fu Chai Tsung-Jen Teng center for Research on earthquake engineering

The objective of this paper is to develop a dynamic slip model for a shear crack under constant stress drop. This crack problem is formulated by a traction boundary integral equation （BIE） in the frequency domain and then solved by the hyper-singular boundary element method as well as the regularization technique proposed in this paper. Based on the spectral integral form of the kernel function, the unbounded term can be isolated and extracted from the hyper-singular kernel function by using the method of subtracted and added back in wave number domain. Finally, based on the inverse transformation from the frequency domain to the time domain, the time histories of crack opening displacement under constant stress drop can be determined. Three rupture models （simultaneous rupture model, symmetric bilaterally-propagating model and unilaterally propagating model） with specified time histories of stress drop are considered in this paper. Even though these three models will cause the same final slip shapes because of the same constant stress drop, the associated slip time functions differ significantly from each other during the rupture process.

关键词： dynamic rupture model traction boundary element method (BIE) hyper-singular boundary element method (HBEM) regularization technique

Design equation for stability of a circular tunnel in anisotropic and heterogeneous clay

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Underground Space 2022年第1期7卷 76-93页

作者： Suraparb Keawsawasvong Boonchai Ukritchon Department of Civil engineering Thammasat Engineering SchoolThammasat UniversityPathumthani 12120Thailand Centre of excellence in Geotechnical and Geoenvironmental engineering Department of Civil EngineeringFaculty of EngineeringChulalongkorn UniversityBangkok 10330Thailand center of excellence on earthquake engineering and vibration Department of Civil EngineeringFaculty of EngineeringChulalongkorn UniversityBangkok 10330Thailand

The safety assessment of tunnel stability is critical to tunnel construction and requires accurate analysis to obtain a reliable *** anisotropy is an important aspect of clay behavior,but it is mostly neglected in practical stability *** this study,the effects of undrained strength anisotropy and strength nonhomogeneity on the stability of unlined circular tunnels in clays are *** static approach of lower-bound(LB)analysis using finite-element and second-order cone programming is employed to exam-ine the aforementioned *** anisotropic shear strength of clay is modeled by employing an elliptical yield function under plane strain conditions.A complete set of dimensionless parameters covering the cover depth ratios of tunnels,normalized overburden pressure ratios,normalized strength gradient ratios of clays,and anisotropic strength ratios,are systematically *** new LB solutions indicate that the stability load factor of the problem has a nonlinear relationship with the cover depth ratio and the anisotropic strength ratio,and there exists a linear relationship with the normalized overburden pressure and the normalized strength *** influ-ence on the predicted failure mechanism is parametrically evaluated.A statistically approximate stability equation of unlined circular tunnels in anisotropic and non-homogeneous clay is proposed for the first time,which contains four new stability factors,namely,con-stant undrained strength,linearly increasing strength gradient,undrained strength anisotropy,and soil unit weight,and it can serve as a fast and accurate tool for predicting the undrained stability of this problem in practice.

关键词： Circular tunnel Anisotropy Nonhomogeneity Lower bound Second-order cone programming

Numerical Simulation of the Seismic Response of a Horizontal Storage Tank Based on a SPH-FEM Coupling Method

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Computer Modeling in engineering & Sciences 2024年第5期139卷 1655-1678页

作者： Peilei Yan Endong Guo HouliWu Liangchao Zhang Key Laboratory of earthquake engineering and engineering vibration Institute of Engineering MechanicsChina Earthquake AdministrationHarbin150080China Key Laboratory of earthquake Disaster Mitigation Ministry of Emergency ManagementHarbin150080China

A coupled numerical calculation method combining smooth particle hydrodynamics(SPH)and the finite element method(FEM)was implemented to investigate the seismic response of horizontal storage *** of a horizontal storage tank featuring a free liquid surface under seismic action was constructed using the SPH–FEM coupling *** stored liquid was discretized using SPH particles,while the tank and supports were discretized using the *** interaction between the stored liquid and the tank was simulated by using the meshless particle contact ***,the numerical simulation results were compared and analyzed against seismic simulation shaking table test data to validate the ***,a series of numerical models,considering different liquid storage volumes and seismic effects,were constructed to obtain time history data of base shear and top center displacement,which revealed the seismic performance of horizontal storage *** simulation results and experimental data showed good agreement,with an error rate of less than 18.85%.And this conformity signifies the rationality of the SPH-FEM coupling *** base shear and top center displacement values obtained by the coupled SPH-FEM method were only 53.3% to 69.1% of those calculated by the equivalent mass method employed in the current *** the stored liquid volume increased,the seismic response of the horizontal storage tank exhibited a gradual upward trend,with the seismic response increasing from 73% to 388% for every 35% increase in stored liquid *** maximum von Mises stress of the tank and the supports remained below the steel yield strength during the *** coupled SPH-FEM method holds certain advantages in studying the seismic problems of tanks with complex structural forms,particularly due to the representation of the flow field distribution during earthquakes by involving reservoir fluid participation.

关键词： SPH-FEM coupling method horizontal storage tank seismic response sloshing

Experimental validation of a signal-based approach for structural earthquake damage detection using fractal dimension of time frequency feature

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earthquake engineering and engineering vibration 2014年第4期13卷 671-680页

作者： Tao Dongwang Mao Chenxi Zhang Dongyu Li Hui Key Laboratory of earthquake engineering and engineering vibration Institute of Engineering Mechanics China Earthquake Administration Key Lab of Structures Dynamic Behavior and Control (Harbin Institute of Technology) Ministry of Education center of Structural Monitoring and Control School of Civil Engineeing Harbin Institute of Technology

This article extends a signal-based approach formerly proposed by the authors, which utilizes the fractal dimension of time frequency feature （FDTFF） of displacements, for earthquake damage detection of moment resist frame （MRF）, and validates the approach with shaking table tests. The time frequency feature （TFF） of the relative displacement at measured story is defined as the real part of the coefficients of the analytical wavelet transform. The fractal dimension （FD） is to quantify the TFF within the fundamental frequency band using box counting method. It is verified that the FDTFFs at all stories of the linear MRF are identical with the help of static condensation method and modal superposition principle, while the FDTFFs at the stories with localized nonlinearities due to damage will be different from those at the stories without nonlinearities using the reverse-path methodology. By comparing the FDTFFs of displacements at measured stories in a structure, the damage-induced nonlinearity of the structure under strong ground motion can be detected and localized. Finally shaking table experiments on a 1：8 scale sixteen-story three-bay steel MRF with added frictional dampers, which generate local nonlinearities, are conducted to validate the approach.

关键词： earthquake damage detection time frequency feature fractal dimension signal-based shaking table test frictional damper

A tendon system to re-center steel moment frames with weak stories

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earthquake engineering and engineering vibration 2024年第4期23卷 1057-1072页

作者： Wang Tao Wang Fei Masayoshi Nakashima Institute of engineering Mechanics China Earthquake AdministrationBeijing 100190China Key Laboratory of earthquake engineering and engineering vibration Institute of Engineering MechanicsChina Earthquake AdministrationHarbin 150080China Disaster Prevention Research Institute Kyoto UniversityGokashoUjiKyoto 611-0011Japan

A wide open bottom story of a frame building is often expected by owners for use as a garage or ***,this leads to weak stories due to abrupt changes in lateral stiffness and often results in unexpected story collapse as observed in many previous *** retrofit frame buildings that have experienced weak story damage,a tendon system is proposed in this study,which consists of a set of swaying columns and *** swaying columns are used to uniformly redistribute the lateral deformation along the height,while the tendons provide extra lateral stiffness and renders the entire structural system a re-centering *** avoid unnecessary forces to swaying columns,pin-connections are used at the *** are placed over the entire story to gain large elastic *** analysis reveals that the swaying column,with a stiffness of about 0.9 times that of the weak story,and the tendons attached at the roof,with a stiffness of 0.04 times that of the weak story,can provide the optimal performance with a maximum residual story drift angle of less than 0.5%.Online hybrid tests were carried out,which demonstrated that uniformly distributed story drifts and acceptable residual deformation could be achieved by the proposed tendon system.

关键词： tendon system re-centering capability residual deformation rehabilitation collapse prevention

A multi-objective design method for seismic retrofitting of existing reinforced concrete frames using pin-supported rocking walls

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Frontiers of Structural and Civil engineering 2022年第9期16卷 1089-1103页

作者： Yue CHEN Rong XU Hao WU Tao SHENG Institute of engineering Mechanics China Earthquake AdministrationKey Laboratory of Earthquake Engineering and Engineering Vibration of China Earthquake AdministrationHarbin 150088China Research center of Industrialization Construction Technology of Zhejiang Province Ningbo University of TechnologyNingbo 315106China State Key Laboratory of Disaster Reduction in Civil engineering Tongji UniversityShanghai 200092China College of Civil and Environmental engineering Ningbo UniversityNingbo 315211China

Over the past several decades,a variety of technical ways have been developed in seismic retrofitting of existing reinforced concrete frames(RFs).Among them,pin-supported rocking walls(PWs)have received much attentions to researchers ***,it is still a challenge that how to determine the stiffness demand of PWs and assign the value of the drift concentration factor(DCF)for entire systems rationally and *** this paper,a design method has been exploited for seismic retrofitting of existing RFs using PWs(RF-PWs)via a multi-objective evolutionary ***,the method has been investigated and verified through a practical ***,a parametric analysis was executed to exhibit the strengths and working mechanism of the multi-objective design *** sum up,the findings of this investigation show that the method furnished in this paper is feasible,functional and can provide adequate information for determining the stiffness demand and the value of the DCFfor ***,it can be applied for the preliminary design of these kinds of structures.

关键词： pin-supported rocking wall reinforced concrete frame seismic retrofit stiffness demand drift concentration factor multi-objective design genetic algorithm Pareto optimal solution

Effect of near-fault earthquake on bridges:lessons learned from Chi-Chi earthquake

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earthquake engineering and engineering vibration 2002年第1期1卷 86-93页

作者： Chin-Hsiung Loh Wen-I Liao Juin-Fu Chai Department of Civil engineering Taiwan Universityand Center for Research on Earthquake EngineeringChinese Taipei Professor center for Research on earthquake engineering Chinese Taipei Associate Research Fellow

The objective of this paper is to describe the lessons learned and actions that have been taken related to the seismic design of bridge structures after the Chi-Chi,Taiwan *** variable near-fault ground motion data was collected from the rupture of Chelungpu fault during the Chi-Chi earthquake,allowing the seismic response of bridge structures subjected to these near-fault ground motions to be carefully *** study the near-fault ground motion effect on bridge seismic design codes,a two-level seismic design of bridge structures was developed and *** design code reflects the near-fault factors in the seismic design ***,a risk assessment methodology,based on bridge vulnerability,is also developed to assist in decisions for reducing seismic risk due to failure of bridges.

关键词： Chi-Chi earthquake near-fault bridge seismic design risk assessment

Large-scale seismic isolation through regulated liquefaction： a feasibility study

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earthquake engineering and engineering vibration 2016年第4期15卷 579-595页

作者： Seyed Amin Mousavi Morteza Bastami Seyed Mehdi Zahrai School of Civil engineering College of Engineering University of Tehran Tehran Iran International Institute of earthquake engineering and Seismology TehranIran center of excellence for engineering and Management of Civil Infrastructures School of Civil Engineering Faculty of EngineeringUniversity of Tehran Tehran Ivan

Using controlled liquefaction, a seismic isolation technique is introduced by which a large area with dozens of structures can be seismically isolated. The proposed Large Scale Seismic Isolation （LSSI） is in many ways similar to conventional base isolations. The required bearing is provided by a fully undrained pre-saturated liquefiable layer which has substantial vertical stiffness/capacity and minimal lateral stiffness. Moreover, required energy dissipation would be provided through material damping and Biot flow-induced damping within the liquefied layer. LSSI consists of a thick non- liquefiable crust layer and an underlying engineered pre-saturated liquefiable layer bounded by two impermeable thin clay layers. The liquefiable layer should be designed to trigger liquefaction as soon as possible within the early seconds of a design level seismic event. Adopting the energy-based GMP liquefaction theory, optimum gradation of the liquefiable layer is also investigated. It tumed out that LSSI would effectively reduce acceleration response spectrum within short to medium periods. Contribution of the proposed LSSI is more pronounced in the case of stronger ground motions such as near field events as well as ground motions with longer return periods.

关键词： liquefaction seismic isolation effective stress analysis ground response analysis passive control

Fracture analyses of different pre-holed concrete specimens under compression

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Acta Mechanica Sinica 2015年第6期31卷 855-870页

作者： Hadi Haeri Alireza Khaloo Mohammad Fatehi Marji Department of Civil engineering Sharif University of Technology Member of National Elites Foundation center of excellence in Structure and earthquake engineering Sharif University of Technology Mine Exploitation engineering Department Faculty of Mining and Metallurgy Yazd University

Crack propagation processes in specially prepared concrete discs and rectangular specimens containing a single cylindrical hole or multiple holes of varying diameters have been studied both experimentally and numerically. In this research, the cracks coalescence paths in Brazilian disc and rectangular specimens made from rock-like material containing multi-holes are investigated. These concrete specimens are specially prepared from an appropriate mixture of Portland Pozzolana Cement （PPC）, fine sands, and water. The pre-holed Brazilian discs and rectangular specimens are experimentally tested under compression. The breakage load in the ring type disc specimens containing an axial hole with varying diameters is measured and the distribution of the induced lateral stress is obtained. The mechanism of cracks propagation in the wall of the ring type specimens is also stud- ied. In the case of multi-hole Brazilian disc and rectangular specimens, the cracks propagation and cracks coalescence are also investigated. These experiments are numerically modeled by a modified higher order displacement discontinuity method. It has been shown that the corresponding experimental and numerical results are in good agreement with each other. The results presented in this research vali date the accuracy and applicability of these crack analyses procedures.

关键词： Concrete rings Pre-holed Brazilian disc ·Rectangular specimens Crack analyses Coalescence ·Induced lateral stress