Fatigue Behavior of Plain Concrete Under Biaxial Compression: Experiments and Theoretical Model     

ZHU  Jin-song 《中国海洋工程》2003,17(4):617-630

The effects of different lateral confinement stress on the fatigue behavior of and cumulative damage to plain concrete are investigated experimentally. Eighty 100 mm x 100 mm x 100 mm specimens of ordinary strength concrete are tested under constant- or variable-amplitude fatigue loading and lateral confinement pressure in two orthogonal directions. A fatigue equation is developed by modifying the classical Aas-Jakobsen S-N equation for taking into account the effect of the confined stress on fatigue strength of plain concrete. The results of variable-amplitude fatigue tests indicate that the linear damage theory proposed by Palmgren and Miner is unreasonable in the biaxial stress state. A nonlinear cumulative damage model that could model the effects of the magnitude and sequence of variable-amplitude fatigue loading and lateral confinement pressure is proposed on the basis of the evolution laws of the residual strains in the longitudinal direction during fatigue tests. The residual fatigue life predic  相似文献   

Documenting hurricane impacts on coral reefs using two-dimensional video-mosaic technology     

Arthur C. R. Gleason  Diego Lirman  Dana Williams  Nuno R. Gracias  Brooke E. Gintert  Hossein Madjidi  R. Pamela Reid  G. Chris Boynton  Shahriar Negahdaripour  Margaret Miller  & Philip Kramer 《Marine Ecology》2007,28(2):254-258

Four hurricanes impacted the reefs of Florida in 2005. In this study, we evaluate the combined impacts of hurricanes Dennis, Katrina, Rita, and Wilma on a population of Acropora palmata using a newly developed video‐mosaic methodology that provides a high‐resolution, spatially accurate landscape view of the reef benthos. Storm damage to A. palmata was surprisingly limited; only 2 out of 19 colonies were removed from the study plot at Molasses Reef. The net tissue losses for those colonies that remained were only 10% and mean diameter of colonies decreased slightly from 88.4 to 79.6 cm. In contrast, the damage to the reef framework was more severe, and a large section (6 m in diameter) was dislodged, overturned, and transported to the bottom of the reef spur. The data presented here show that two‐dimensional video‐mosaic technology is well‐suited to assess the impacts of physical disturbance on coral reefs and can be used to complement existing survey methodologies.  相似文献   

随机载荷下的疲劳损伤计算公式     

伍义生 《海洋工程》1994,(1)

本文推导了随机载荷下的疲劳损伤计算公式。数值计算结果表明：Ｐ．Ｈ．Ｗｉｒｓｃｈｉｎｇ给出的公式在宽带情况下与实际情况不符；Ｇ．Ｃｈａｕｄｈｕｒｙ给出的公式在窄带情况下与实际不符；本文绘出的公式不仅适合于窄带，也适合于具有各种不同带宽的宽带随机载荷。  相似文献   

Damage Detection Methods for Offshore Platforms Based on Wavelet Packet Transform     

李东升张兆德  王德禹 《中国海洋工程》2005,19(4):701-710

1 .IntroductionInthe whole service period of the platforms ,some damage is unavoidable due to the corrosion,impact ,fatigue and so on.The damage whould cause the structures’ultimate capacity and safety de-crease .Presently,it is generally acceptedthat the detection of damage involes considerable statisticaluncertainties,thus lot of efforts is made for the damage probalility model ,for example Song and Lu(1996) usedthefuzzy-settheoryto estimatethe humanerrorsthroughthe definitionof inspection…  相似文献   

Risk Assessment for Tuzla Naval Base Breakwater   总被引：5，自引：0，他引：5  

Can Elmar BALAS 《中国海洋工程》2003,17(3)

1 .IntroductionTurkeywasstruckbytwomajorearthquakeeventsonAugust 1 7thandNovember 1 2th ,1 999,namedIzmit (Mw=7.4 )andD櫣ｚｃｅ (Mw=7.2 )earthquakes,respectively .ThestationsoperatedbytheGeneralDirectorateofDisasterAffairs,theKandilliObservatoryandEarthquakeResearchInstituteofIstanbulTechnicalUniversitymeasuredatleast 2 7stronggroundmotionsfortheIzmitearthquakewithin 2 0 0kmofthefault.AsignificantsegmentofthefaultrupturedintheareabetweenthewestofGolcukandtheeastofLakeSapanca .Inthesou…  相似文献   

汶川抗震救灾的基础地理信息综合应急服务     

陈军  何超英  朱武  彭震中  金舒平 《测绘软科学研究》2008,(6):7-11

在5．12汶川特大地震抗震救灾中,国家测绘部门设计和组织实施了以数据成果服务、专用系统服务和专题制图服务为核心的基础地理信息综合应急服务。其是针对汶川震区地形特点和抗震救灾主体工作需求,快速整合和提供震区已有的基础测绘成果和最新遥感影像资料;快速搭建集震区海量数据集成管理为一体并具备3维影像浏览、对比分析等功能的专用地理信息系统,为灾情评估分析和重建规划研究提供地理空间数据集成展示和分析平台;应需地制作反映受灾范围、受灾程度、救灾响应、规划思路等的各类专题地图和地图集,有效地表达地震灾害的时空分布、重建规划布局等。  相似文献   

汶川地震山地灾害遥感快速提取及其分布特点分析   总被引：12，自引：0，他引：12  

苏凤环  刘洪江  韩用顺 《遥感学报》2008,12(6)

针对泥石流滑坡灾害体特有的物质组成与活动特点,通过比较分析其在不同遥感影像的光谱特征差异,选择ETM+影像作为主要数据源,提取湿度指数与绿度指数,利用ETM+的穗帽变换、影像差值增强、密度分割和掩膜技术建立了泥石流滑坡山地灾害快速提取模型,并用于汶川地震.通过灾害体的提取,分析了本次地震山地次生灾害的分布规律,利用空间叠加进行了成因的分析.本次地震山地灾害具有如下特点:(1)沿主要地表破裂带分布;(2)山地灾害主要出现在8度-9度地震烈度区,随着烈度的降低,山地灾害的总面积也相应的减少;(3)山地灾害主要发生在海拔高度1000-2500m的地带;(4)主要发生在坡度20°-50°之间的边坡上;(5)地震及余震期间以崩塌滑坡滚石为主,后期以泥石流滑坡为主;(6)具有河流左右两岸呈不对称分布等特点.结果表明,利用ETM+影像建立基于湿度指数与绿度指数的快速提取模型,对于大规模泥石流滑坡提取效果较好,进行大区域山地灾害的遥感快速提取是可行的.  相似文献   

Impact of the tsunami and earthquake of 26th December 2004 on the vital coastal ecosystems of the Andaman and Nicobar Islands assessed using RESOURCESAT AWiFS data   总被引：2，自引：0，他引：2  

Anjali Bahuguna  Shailesh Nayak  Dam Roy 《International Journal of Applied Earth Observation and Geoinformation》2008,10(2):229-1

Tsunami waves struck the Indian coast on 26th December 2004 affecting the Andaman and Nicobar group of islands. A quick assessment of the status of the vital coastal ecosystems has been made using pre- and post-tsunami Advance Wide Field Sensor (AWiFS) data of Indian satellite RESOURCESAT with an accuracy of 87–90% and the Kappa ranging from 0.8696 to 0.9053. Among the coastal ecosystems the coral reefs have suffered the maximum with the Nicobar reefs (69% eroded and 29% degraded) bearing the brunt more than the Andaman reefs (54% eroded and 22% degraded). Significant improvement to the condition of the reef damaged due to backwash has been noted. About 41% of the Sentinel reef area has undergone significant improvement. The continuance of the erosion of the southwestern Andaman reefs is due to the impact of recurring earthquakes. The impact on mangroves of both the groups of islands has been due to uprooting as well as inundation of seawater and resulting stagnation. Changes are expected in community structure of mangroves as a result of tsunami.  相似文献   

区域地质灾害危害程度等级划分探讨     

王昌平 《中国地质灾害与防治学报》2008,19(2):142-146

区域性地质灾害危害程度等级尚无比较科学的划分方法。通过福建省区域地质灾害危害程度等级划分的探讨,采用单位面积地质灾害造成的人员死亡数、财产损失值作为“地质灾害模数”,对区域地质灾害危害程度等级进行划分,判别不同区域地质灾害严重程度,为区域地质灾害防治决策提供科学依据。  相似文献   

汶川特大地震中山岭隧道变形破坏特征及影响因素分析   总被引：22，自引：0，他引：22  

李天斌 《工程地质学报》2008,16(6):742-750

汶川大地震造成位于震中附近的都江堰-汶川公路多座隧道严重受损。本文通过现场调研、资料收集与分析,将地震区山岭隧道变形破坏的基本类型概括为洞口边坡崩塌与滑塌、洞门裂损、衬砌及围岩坍塌、衬砌开裂及错位、底板开裂及隆起、初期支护变形及开裂等。分析其影响因素,认为发震断裂的次级断层、基覆界面、洞口不稳定斜坡、高地应力环境下的软弱围岩对隧道强烈震害具有控制作用。以汶川地震给予隧道抗震的启示,建议强震区的山岭隧道应将洞口边坡防护、洞口明洞和洞门结构作为一个系统进行综合设计,在条件允许的情况下尽可能采用削竹式洞门结构;隧道穿越活动断裂带的次级断层时在其两侧一定范围内二次衬砌应采用钢筋混凝土结构;基覆界面、围岩软岩与硬岩之间的过渡地带、围岩质量突变地带等应采用改善围岩力学性质且让其渐变的措施进行处理。  相似文献