Seismic risk assessment considering cumulative damage due to aftershocks          下载免费PDF全文

Fatemeh Jalayer  Hossein Ebrahimian 《地震工程与结构动力学》2017,46(3):369-389

Calculating the limit state (LS) exceedance probability for a structure considering the main seismic event and the triggered aftershocks (AS) is complicated both by the time‐dependent rate of aftershock occurrence and also by the cumulative damage caused by the sequence of events. Taking advantage of a methodology developed previously by the authors for post‐mainshock (MS) risk assessment, the LS probability due to a sequence of mainshock and the triggered aftershocks is calculated for a given aftershock forecasting time window. The proposed formulation takes into account both the time‐dependent rate of aftershock occurrence and also the damage accumulation due to the triggered aftershocks. It is demonstrated that an existing reinforced concrete moment‐resisting frame with infills subjected to the main event and the triggered sequence exceeds the near‐collapse LS. On the other hand, the structure does not reach the onset of near‐collapse LS when the effect of triggered aftershocks is not considered. It is shown, based on simplifying assumptions, that the derived formulation yields asymptotically to the same Poisson‐type functional form used when the cumulative damage is not being considered. This leads to a range of approximate solutions by substituting the fragilities calculated for intact, MS‐damaged, and MS‐plus‐one‐AS‐damaged structures in the asymptotic simplified formulation. The latter two approximate solutions provide good agreement with the derived formulation. Even when the fragility of intact structure is employed, the approximate solution (considering only the time‐dependent rate of aftershock occurrence) leads to higher risk estimates compared with those obtained based on only the mainshock. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Wall building stiffness and strength effect on content sliding in Wellington seismic conditions          下载免费PDF全文

Trevor Z. Yeow  Gregory A. MacRae  Rajesh P. Dhakal 《地震工程与结构动力学》2017,46(6):1023-1042

A numerical study of unobstructed content sliding within several low‐to‐midrise reinforced concrete cantilever wall buildings designed to Wellington conditions in New Zealand is performed to validate the belief that increasing a building's strength and/or stiffness would result in more severe sliding response. It was shown that contents within stronger buildings experienced larger sliding response. If the building was designed to be strong, the sliding response of contents with a friction coefficient of 0.1 was smaller in stiffer buildings compared with those in flexible buildings. However, the trends start reversing with an increase in friction coefficient or a decrease in building strength. Overall, content sliding is not necessarily more severe in stiffer buildings, and in many cases, the opposite is true. This study's findings were compared against an existing parametric equation for estimating the maximum sliding displacement. This equation, which was originally derived for contents located within elastic frame buildings, was found to be more efficient than considering total floor accelerations alone but was underconservative by a mean of 17% for yielding multistorey buildings. A design procedure considering content sliding using the parametric equation and an example are provided. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

论北极环境变化对中国国家非传统安全的影响          下载免费PDF全文

潘敏  周燚栋 《极地研究》2010,22(4):415-422

随着全球环境问题的升温,北极环境变化也越来越受到了国际社会的关注,中国作为一个近北极国家,深受北极环境变化的影响。本文从环境安全、经济安全、资源安全等非传统安全因素方面来探讨北极环境变化对中国可能产生的影响。就环境安全来说,北极环境变化对中国生态环境将产生直接的威胁,未来气温可能升高所导致北极海冰融化,对中国的社会和经济有着巨大危害;就经济安全而言,北极环境变化所带来的北极航道的全面开通,可能是中国未来发展的一个机遇,但是中国要想在北极航运资源的开发上分得一杯羹将面临着多重障碍;就资源安全来说,北极地区资源丰富,这对能源缺乏的中国而言,意义重大。但鉴于目前中国对北极问题的参与来看,即使北极地区的资源能得到良好的开发,其开发利用主要掌握在环北极国家手里,那么对能源供给越来越依赖国外的中国来说,必定会受制于人,无法从根本上保障中国能源供给的战略安全。  相似文献   

浅谈耗散结构和非平衡态热力学   总被引：2，自引：0，他引：2  

李鹏九 《现代地质》1994,8(1):88-93

具体说明了几个耗散结构的实例,综合对比了耗散结构与平衡结构的异同,并概括介绍了耗散结构的概念以及其生成条件。由闭系平衡态的摘产生和熵生率入手,借助局域平衡假设,从开系的平衡态进入线性非平衡态,讨论了不可逆过程唯象定律Ｏｎｓａｇｅｒ倒易关系、熵生率最小原理及该原理作为稳定性判据的不足．最后,提到了一般演化判据和非线性非平衡态热力学中讨论系统稳定性的办法。  相似文献   

无弹簧式振动锤周期运动稳定性的研究     

喻重山  孙孝庆 《现代地质》1995,9(3):363-371

摘要：本文讨论了无弹簧式振动锤锤体在每个运动周期内冲击一次的简单周期运动。通过建立运动方程,分析小扰动量对运动方程的影响,建立了锤体做简单周期运动时的稳定条件,并分析对比了无量纲冲击时间△Ｔ＝０和△Ｔ时的情况。理论分析的结果与实际实验的情况基本相符。  相似文献   

Seismic response of rotating machines–structure–RFBI systems     

Wen‐Chyi Su  Alan G. Hernried  Solomon C. S. Yim 《地震工程与结构动力学》2000,29(2):213-240

The seismic response of a critical rotating machine either rigidly attached to a floor or independently isolated housed within an initially aseismically designed or uncontrolled structure are investigated. A particular isolation system, the Resilient‐Friction Base Isolator (RFBI), is employed. Finite element formulations of a rotor‐disk‐bearing model on a rigid base are developed. The equations of motion for the combined rotating machine–structure–RFBI systems are presented. Parametric studies are performed to investigate the effects of variations in system physical properties including friction coefficient, mass ratio, shaft flexibility, bearing rigidity, bearing damping and speed of rotation on the response of rotating machines for the combined rotating machine–structure–isolator systems. Comparative studies in the peak response of the rotating machine supported on various isolation systems and the corresponding fixed base system are carried out. The study indicates that the Resilient‐Friction Base Isolator can significantly reduce the seismic response of rotating components to potentially damaging ground excitations. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

Effective location of active control devices for building vibrations caused by periodic excitation acting on intermediate storey     

Liping Xing  Eizaburo Tachibana  Yutaka Inoue 《地震工程与结构动力学》2000,29(2):177-193

In order to investigate ways of reducing vibrations of building structures subjected to excitation acting on intermediate storey, active vibration controls are conducted with active control devices installed on different floors of the structure, and the effective location of control devices is also investigated. In this paper, we propose a new ‘Discrete‐Optimizing Control Method’ for vibration control. The control forces are determined analytically which makes the ‘discrete‐index function’ minimum. Through numerical simulation, the Discrete‐Optimizing Control Method is proved to be an effective control method. The response reduction effects are best when the control devices are concentrated on the adjacent three floors of the vibration source. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

Non‐linear‐Maxwell‐element‐type hysteretic control force     

Kazuhiko Yamada 《地震工程与结构动力学》2000,29(4):545-554

A simple non‐linear control law is proposed for reducing structural responses against seismic excitations. This law defines control force dynamics by one differential equation involving a non‐linear term that restrains the control force amplitude. If non‐linearity is neglected, the control force becomes the force in a Maxwell element, so it is called the non‐linear‐Maxwell‐element‐type (NMW) control force. The NMW control force vs. deformation relation plots hysteretic curves. The basic performance of an SDOF model with the NMW control force is examined for various conditions by numerical analyses. Furthermore, the control law is extended to fit an MDOF structural model, and an application example is shown. The computational results show that the NMW control force efficiently reduces structural responses. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

Finite element consolidation analysis of soils with vertical drain     

Guofu Zhu  Jian‐Hau Yin 《国际地质力学数值与分析法杂志》2000,24(4):337-366

This paper presents a finite element procedure for the analysis of consolidation of layered soils with vertical drain using general one‐dimensional (1‐D) constitutive models. In formulating the finite element procedure, a Newton–Cotes‐type integration formula is used to avoid the unsymmetry of the stiffness matrix for a Newton (Modified Newton) iteration scheme. The proposed procedure is then applied for the consolidation analysis of a number of typical problems using both linear and non‐linear soil models. Results from this simplified method are compared with those from a fully coupled consolidation analysis using a well‐known finite element package. The average degree of consolidation, excess porewater pressure and average vertical effective stress are almost the same as those from the fully coupled analysis for both the linear and non‐linear cases studied. The differences in vertical effective stresses are tolerable except for the values near the vertical drain boundaries. The consolidation behaviour of soils below a certain depth of the bottom of vertical drain is actually one‐dimensional for the partially penetrating case. Therefore, there are not much differences in whether one uses a one‐dimensional model or a three‐dimensional model in this region. The average degree of consolidation has good normalized feature with respect to the ratio of well radius to external drainage boundary for the cases of fully penetrating vertical drain using a normalized time even in the non‐linear case. Numerical results clearly demonstrate that the proposed simplified finite element procedure is efficient for the consolidation analysis of soils with vertical drain and it has better numerical stability characteristics. This simplified method can easily account for layered systems, time‐dependent loading, well‐resistance, smear effects and inelastic stress–strain behaviour. This method is also very suitable for the design of vertical drain, since it greatly reduces the unknown variables in the calculation and the 1‐D soil model parameters can be more easily determined. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

The timing of runoff response in design flood analysis     

A Ashfaq  P Webster 《水文研究》2000,14(7):1217-1233

This study presents an investigation of the time to peak of unit response functions for design flood studies. It is based on an empirical analysis of observed rainfall–runoff data for 49 basins in the UK and explores the relationship between unit response time to peak (t_p) and flood peak magnitude (Q_p). The results show that t_p varies significantly between events but suggest a systematic relationship between t_p and Q_p. The relationships which have been developed suggest that t_p decreases with flood magnitude and approaches to an asymptotic value for very large values of Q_p. These findings confirm numerous physical and field investigations and also support the reduction in response time for probable maximum flood (PMF) recommended in the Soil Conservation Services method, the Flood Studies Report method and the Flood Estimation Handbook. The findings also suggest that t_p should be modified in unit hydrograph methods of design flood analysis for return periods that differ from those used in deriving unit hydrographs. A simple correction curve has been developed for adjusting t_p according to the design flood return period. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献