Remote structural health monitoring with serially multiplexed fiber optic acoustic emission sensors     

陈仲裕  梁玉进  Farhad Ansari 《地震工程与工程振动(英文版)》2003,2(1):141-146

Development and testing of a serially multiplexed fiber optic sensor system is described. The sensor differs from conventional fiber optic acoustic systems, as it is capable of sensing AE emissions at several points along the length of a single fiber. Multiplexing provides for single channel detection of cracks and their locations in large structural systems. An algorithm was developed for signal recognition and tagging of the AE waveforms for detection of crack locations. Laboratory experiments on plain concrete beams and post-tensioned FRP tendons were performed to evaluate the crack detection capability of the sensor system. The acoustic emission sensor was able to detect initiation, growth and location of the cracks in concrete as well as in the FRP tendons. The AE system is potentially suitable for applications involving health monitoring of structures following an earthquake Supported by: National Science Foundation, Grant number CMS-9900338  相似文献   

Lateral load pattern in pushover analysis   总被引：9，自引：2，他引：7  

孙景江  Tetsuro Ono  赵衍刚  王威 《地震工程与工程振动(英文版)》2003,2(1):99-107

The seismic capacity curves of three types of buildings including frame, frame-shear wall and shear wall obtained by pushover analysis under different lateral load patterns are compared with those from nonlinear time history analysis. Based on the numerical results obtained a two-phase load pattern; an inverted triangle (first mode) load pattern until the base shear force reachesβ times its maximum value, V_max, followed by a (x/H)^α form, hereβ and α being some coefficients depending on the type of the structures considered, is proposed in the paper, which can provide excellent approximation of the seismic capacity curve for low-to-mid-rise shear type buildings. Furthermore, it is shown both the two-phase load pattern proposed and the invariant uniform pattern can be used for low-to-mid-rise shear-bending type and low-rise bending type of buildings. No suitable load patterns have been found for high-rise buildings.  相似文献   

大别山地震波速度剖面的重力拟合及花岗岩带   总被引：2，自引：1，他引：1       下载免费PDF全文

袁惟正徐新忠  雷江锁袁学诚 《中国地质》2003,30(3):235-239

笔者对穿越大别山造山带的六安—大冶宽角反射地震剖面进行了重力拟合。拟合结果表明严格按宽角反射地震速度换算成的密度剖面所产生的是一个重力高,它反映出大别山是一个穹隆,与实测大别山重力低大相径庭。只有将位于大别山山根上,南北大别之间设置一个从地表直达莫霍界面的巨大低密度体,重力曲线才能得到很好的拟合。这个低密度体应为近北西走向的花岗岩带。它与反射地震剖面上石镇透明反射地震带位置吻合,但宽度远较反射地震透明带为大。重力曲线的拟合进一步说明,在华北陆块与扬子陆块碰撞后的白垩纪时,大别山出现一个伸展期,在这个时期,大别山穹隆形成,并伴随有大规模花岗岩的侵入,超高压变质岩从地壳中下部折返到地表。研究说明,联合应用反射地震、宽角反射地震和重力,进行综合解释是必要的,可以得到更令人信服的地质结论。  相似文献   

基于BISQ模型双相各向同性介质中地震波数值模拟   总被引：11，自引：2，他引：9  

孟庆生  何樵登  朱建伟  王德利 《吉林大学学报(地球科学版)》2003,33(2):217-221

基于BISQ机制,推导了双相各向同性介质中弹性波数值模拟方程,并借助交错网格有限差分方法进行了波场模拟。证实了三种波(快纵波、慢纵波、横波SV)的存在和波场特征;在合成地震记录中,观测列三种波的反射,由于各种波相互之间的转换,转换波在地震记录中显示也很清楚,这使得波场变得更为复杂化。  相似文献   

Seismic Hazard and Risk Assessment for Tulbagh,South Africa: Part I – Assessment of Seismic Hazard     

Kijko  A.  Retief  S. J. P.  Graham  G. 《Natural Hazards》2002,26(2):175-201

In this part of our study the probabilistic seismic hazard analysis (PSHA) for Tulbagh was performed. The applied procedure is parametric and consists essentially of two steps. The first step is applicable to the area in the vicinity of Tulbagh and requires an estimation of the area-specific parameters, which, in this case, is the mean seismic activity rate, , the Gutenberg-Richter parameter, b, and the maximum regional magnitude, m_max. The second step is applicable to the Tulbagh site, and consists of parameters of distribution of amplitude of the selected ground motion parameter. The current application of the procedure provides an assessment of the PSHA in terms of peak ground acceleration (PGA) and spectral acceleration (SA). The procedure permits the combination of both historical and instrumental data. The historical part of the catalogue only contains the strongest events, whereas the complete part can be divided into several subcatalogues, each assumed complete above a specified threshold of magnitude. In the analysis, the uncertainty in the determination of the earthquake was taken into account by incorporation of the concept of `apparent magnitude'. The PSHA technique has been developed specifically for the estimation of seismic hazard at individual sites without the subjective judgement involved in the definition of seismic source zones, when the specific active faults have not been mapped or identified, and where the causes of seismicity are not well understood. The results of the hazard assessment are expressed as probabilities that specified values of PGA will be exceeded during the chosen time intervals, and similarly for the spectral accelerations. A worst case scenario sketches the possibility of a maximum PGA of 0.30g. The results of the hazard assessment can be used as input to a seismic risk assessment.  相似文献   

A Study of Seismicity and Earthquake Hazard at the Proposed Kalabsha Dam Site,Aswan, Egypt     

Fat-Helbary  Raafat E.  Tealb  Aly A. 《Natural Hazards》2002,25(2):117-133

High and Aswan Dams Authority (HADA) proposed a plan aiming at constructing a rockfill dam in the Kalabsha area, about 60 km south of Aswan High Dam. The aim of this dam is to restrain the overflow of water to the Kalabsha Valley for keeping one billion cubic meters from being lost due to seepage and evaporation. The safety of dams during earthquakes is extremely important because failure of such a structure may have disastrous consequences on life and property. Therefore, different factors were considered as part of a site assessment. Five seismic source zones, close enough to the site to give rise to potentially damaging earthquake ground motions, were identified. Seven active faults that have the potential for producing significant earthquakes and that pass through or near the dam site were also identified. The earthquake loading represented by ground motions at the site was evaluated. Probabilistic seismic hazard procedures were used for assessing the earthquake loading at six individual sites using Area-and Line-Source Models (ASM & LSM). The ASM is based on current observed seismicity, whereas the LSM is based on geological slip rates. The output represents the expected acceleration amplitude with 90 percent probability of not being exceeded in exposure times of 20, 50, and 100 years. The results from the two models appear to be different, the expected ground motions from ASM were twice as high as expected from LSM. This difference is due to the load of the Aswan reservoir (Nasser Lake) triggering earthquakes on those parts of the faults that lie under the lake at Kalabsha area. The hazard at the selected sites is given by the hazard curve that is represented by the relationship between the peak ground acceleration and its annual exceedance probability. By comparing the curves for the six individual sites for the same source model, it can be concluded that the potential ground acceleration level for all the sites is almost the same. Considering the mean results from the two models, the annual exceedance probability of the expected ground acceleration from ASM is approximately ten times higher than the annual exceedance probability from LSM.Since ASM is based on current seismicity, it is more appropriate forrepresenting the actual hazard for the dam site.  相似文献   

基于抗震性态的设防标准研究   总被引：11，自引：0，他引：11       下载免费PDF全文

谢礼立  马玉宏 《地震学报》2002,24(2):200-209

以基于性态的抗震设计为出发点,并以我国为例,针对目前国内外抗震设防标准的若干问题和不足,提出了基于性态抗震设计的三环节抗震设防方法．将现有的设防内容改为确定结构的抗震设计类别、确定设计烈度或设计地震动参数、确定建筑的重要性等级３个方面,并分别在每一方面进行具体深入的研究,从而形成了一套完整的基于性态的抗震设防标准确定的原则、方法和框架,可以直接用来编制规范供抗震设计使用．   相似文献   

利用高频地震波检测混凝土构件完整性的方法   总被引：2，自引：0，他引：2  

单娜琳  朱德兵  黄锡柳 《CT理论与应用研究》2002,11(2):1-4

大型混凝土构件（如高层建筑基础的地梁,桩承台等）在施工过程中可能造成局部松散,空洞,蜂窝或离析等质量问题。为检测混凝土构件的的完整性,采用地震勘探方法中的地震映象法（又称地震共偏移距法）。通过在模拟裂缝,空洞模型上的试验,获得了存在异常体时,地震映象时间剖面的波形特征;测得偏移距,点距等参数变化时,对地震映象时间剖面的影响。模型实验和实测工作证明;在合理选择震源各种测量参数条件下,高频地震映象方法可有效检测混凝土构件完整怀,实现对混凝土构件质量新的监测。  相似文献   

福建省地震重点监视防御区城市防震减灾体系工程简介     

杜运连  吕至环 《福建地震》2002,(1)

福建省地震重点视防御区城市防震减灾体系工程以中国地震局关于建立健全地震监测预报、震灾预防和紧急救援三大体系为主要目标 ,以国家和福建省确定的地震重点监视防御区为主要目标区 ,尤以切实加强重点监视防御内城市的防震减灾措施 ,强化城市对地震灾害的综合防御能力为主要建设内容。该项目得到中国地震局、福建省委、省政府和有关地市大力支持 ,已列为福建省“十五”重点项目 ,省委、省政府为民办实事重点项目  相似文献   

Effect of near-fault earthquake on bridges: lessons learned from Chi-Chi earthquake   总被引：4，自引：1，他引：3  

Chin-Hsiung?LohEmail author  Wen-I?Liao  Juin-Fu?Chai 《地震工程与工程振动(英文版)》2002,1(1):86-93

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 earthquake. Much 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 examined. To study the near-fault ground motion effect on bridge seismic design codes, a two-level seismic design of bridge structures was developed and implemented. This design code reflects the near-fault factors in the seismic design forces. Finally, a risk assessment methodology, based on bridge vulnerability, is also developed to assist in decisions for reducing seismic risk due to failure of bridges. Director of Center for Research on Earthquake Engineering. Supported by: the Science Council, Chinese Taipei, under grant no. SC 90-2211-E-002-028.  相似文献