In the last two decades,the damage detection for civil engineering structures has been widely treated as a modal analysis problem and most of the currently available vibration-based system identification approaches ar...In the last two decades,the damage detection for civil engineering structures has been widely treated as a modal analysis problem and most of the currently available vibration-based system identification approaches are based on modal parameters,namely the natural frequencies,mode shapes and damping ratios,and/or their derivations,which are suitable for linear systems. Nonlinearity is generic in engineering structures. For example,the initiation and development of cracks in civil engineering structures as typical structural damages are nonlinear process. One of the major challenges in damage detection,early warning and damage prognosis is to obtain reasonably accurate identification of nonlinear performance such as hysteresis which is the direct indicator of damage initiation and development under dynamic excitations. In this study,a general data-based identification approach for hysteretic performance in form of nonlinear restoring force using structural dynamic responses and complete and incomplete excitation measurement time series was proposed and validated with a 4-story frame structure equipped with smart devices of magneto-rheological (MR) damper to simulate nonlinear performance. Firstly,as an optimization method,the least-squares technique was employed to identify the system matrices of an equivalent linear system of the nonlinear structure model basing on the excitation force and the corresponding vibration measurements with impact test when complete and incomplete excitations; and secondly,the nonlinear restoring force of the structure was identified and compared with the test measurements finally. Results show that the proposed data-based approach is capable of identifying the nonlinear behavior of engineering structures and can be employed to evaluate the damage initiation and development of different structure under dynamic loads.展开更多
An approach is presented to investigate the nonlinear vibration of stiffened plates.A stiffened plate is divided into one plate and some stiffeners,with the plate considered to be geometrically nonlinear,and the stiff...An approach is presented to investigate the nonlinear vibration of stiffened plates.A stiffened plate is divided into one plate and some stiffeners,with the plate considered to be geometrically nonlinear,and the stiffeners taken as Euler beams.Lagrange equation and modal superposition method are used to derive the dynamic equilibrium equations of the stiffened plate according to energy of the system.Besides,the effect caused by boundary movement is transformed into equivalent excitations.The first approximation solution of the non-resonance is obtained by means of the method of multiple scales.The primary parametric resonance and primary resonance of the stiffened plate are studied by using the same method.The accuracy of the method is validated by comparing the results with those of finite element analysis via ANSYS.Numerical examples for different stiffened plates are presented to discuss the steady response of the non-resonance and the amplitude-frequency relationship of the primary parametric resonance and primary resonance.In addition,the analysis on how the damping coefficients and the transverse excitations influence amplitude-frequency curves is also carried out.Some nonlinear vibration characteristics of stiffened plates are obtained,which are useful for engineering design.展开更多
Y99-61712 99150621998年 SPIE 会议录,卷3277:半导体中的超速现象=1998 proceedings of SPIE.Vol.3277:Ultrafast phenom-ena in semiconductors[会,英]/SPIE-the InternationalSociety for Optical Engineering.—Bellingham,WA,1998....Y99-61712 99150621998年 SPIE 会议录,卷3277:半导体中的超速现象=1998 proceedings of SPIE.Vol.3277:Ultrafast phenom-ena in semiconductors[会,英]/SPIE-the InternationalSociety for Optical Engineering.—Bellingham,WA,1998.—316P.(EG)本会议录报道了在1998年1月28日至29日在美国圣何塞市召开的半导体中超速现象专题研讨会上发表的34篇论文。主要涉及半导体和超晶格中的相干效应;体与低维量子结构中超速光处理,超块激光与器件,半导体、超晶格和微空腔中非线性动态响应等内容。展开更多
基金The authors gratefully acknowledge the support provided through the National Natural Science Foundation of China (NSFC) under grant No. 50608031the Hunan Provincial Natural Science Foundation of China under grant No.08JJ1009the Key Project of Chinese Ministry of Education (No. 108102)
文摘In the last two decades,the damage detection for civil engineering structures has been widely treated as a modal analysis problem and most of the currently available vibration-based system identification approaches are based on modal parameters,namely the natural frequencies,mode shapes and damping ratios,and/or their derivations,which are suitable for linear systems. Nonlinearity is generic in engineering structures. For example,the initiation and development of cracks in civil engineering structures as typical structural damages are nonlinear process. One of the major challenges in damage detection,early warning and damage prognosis is to obtain reasonably accurate identification of nonlinear performance such as hysteresis which is the direct indicator of damage initiation and development under dynamic excitations. In this study,a general data-based identification approach for hysteretic performance in form of nonlinear restoring force using structural dynamic responses and complete and incomplete excitation measurement time series was proposed and validated with a 4-story frame structure equipped with smart devices of magneto-rheological (MR) damper to simulate nonlinear performance. Firstly,as an optimization method,the least-squares technique was employed to identify the system matrices of an equivalent linear system of the nonlinear structure model basing on the excitation force and the corresponding vibration measurements with impact test when complete and incomplete excitations; and secondly,the nonlinear restoring force of the structure was identified and compared with the test measurements finally. Results show that the proposed data-based approach is capable of identifying the nonlinear behavior of engineering structures and can be employed to evaluate the damage initiation and development of different structure under dynamic loads.
基金supported by the China Postdoctoral Science Foundation(Grant No.2013M540656)the Fundamental Research Funds for the Central Universities,South China University of Technology(Grant No.2013ZB0023)the National Natural Science Foundation of China(Grant No.11132002)
文摘An approach is presented to investigate the nonlinear vibration of stiffened plates.A stiffened plate is divided into one plate and some stiffeners,with the plate considered to be geometrically nonlinear,and the stiffeners taken as Euler beams.Lagrange equation and modal superposition method are used to derive the dynamic equilibrium equations of the stiffened plate according to energy of the system.Besides,the effect caused by boundary movement is transformed into equivalent excitations.The first approximation solution of the non-resonance is obtained by means of the method of multiple scales.The primary parametric resonance and primary resonance of the stiffened plate are studied by using the same method.The accuracy of the method is validated by comparing the results with those of finite element analysis via ANSYS.Numerical examples for different stiffened plates are presented to discuss the steady response of the non-resonance and the amplitude-frequency relationship of the primary parametric resonance and primary resonance.In addition,the analysis on how the damping coefficients and the transverse excitations influence amplitude-frequency curves is also carried out.Some nonlinear vibration characteristics of stiffened plates are obtained,which are useful for engineering design.
文摘Y99-61712 99150621998年 SPIE 会议录,卷3277:半导体中的超速现象=1998 proceedings of SPIE.Vol.3277:Ultrafast phenom-ena in semiconductors[会,英]/SPIE-the InternationalSociety for Optical Engineering.—Bellingham,WA,1998.—316P.(EG)本会议录报道了在1998年1月28日至29日在美国圣何塞市召开的半导体中超速现象专题研讨会上发表的34篇论文。主要涉及半导体和超晶格中的相干效应;体与低维量子结构中超速光处理,超块激光与器件,半导体、超晶格和微空腔中非线性动态响应等内容。
