Practical aspects of demand and capacity evaluation of RC members in the context of EC8‐3     

Xavier Romo  Raimundo Delgado  Aníbal Costa 《地震工程与结构动力学》2010,39(5):473-499

The structural safety assessment procedures proposed in Part 3 of Eurocode 8 (EC8‐3) for the case of reinforced concrete structures are addressed. The practical evaluation of the member chord rotation demand according to EC8‐3 is examined in detail along with several alternative formulations. The need for these formulations is demonstrated by presenting example situations where the EC8‐3 proposal is difficult to apply. The effectiveness of the proposed approaches is assessed through an example application and recommendations for their practical use are defined. Given the importance of the shear span in this context, a sensitivity analysis of the EC8‐3 capacity models with respect to this parameter is carried out and discussed in a later section. This analysis aims to assess the validity of the simplifications proposed by a previous research study for the quantification of the EC8‐3 capacity values. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Turbidite system architecture and sedimentary processes along topographically complex slopes: the Makran convergent margin     

JULIEN BOURGET  SEBASTIEN ZARAGOSI  NADINE ELLOUZ‐ZIMMERMANN  NICOLAS MOUCHOT  THIERRY GARLAN  JEAN‐LUC SCHNEIDER  VALENTINE LANFUMEY  SIGFRIED LALLEMANT 《Sedimentology》2011,58(2):376-406

This study investigates the morphology and Late Quaternary sediment distribution of the Makran turbidite system (Makran subduction zone, north‐west Indian Ocean) from a nearly complete subsurface mapping of the Oman basin, two‐dimensional seismic and a large set of coring data in order to characterize turbidite system architecture across an active (fold and thrust belt) margin. The Makran turbidite system is composed of a dense network of canyons, which cut into high relief accreted ridges and intra‐slope piggyback basins, forming at some locations connected and variably tortuous paths down complex slopes. Turbidite activity and trench filling rates are high even during the Holocene sea‐level highstand conditions. In particular, basin‐wide, sheet‐like thick mud turbidites, probably related to major mass wasting events of low recurrence time, drape the flat and unchannellized Oman abyssal plain. Longitudinal depth profiles show that the Makran canyons are highly disrupted by numerous thrust‐related large‐scale knickpoints (with gradients up to 20° and walls up to 500 m high). At the deformation front, the strong break of slope can lead to the formation of canyon‐mouth ‘plunge pools’ of variable shapes and sizes. The plunge pools observed in the western Makran are considerably larger than those previously described in sub‐surface successions; the first insights into their internal architecture and sedimentary processes are presented here. Large plunge pools in the western Makran are associated with large scoured areas at the slope break and enhanced sediment deposition downstream: high‐amplitude reflectors are observed inside the plunge pools, while their flanks are composed of thin‐bedded, fine‐grained turbidites deposited by the uppermost part of the turbidity flows. Thus, these architectural elements are associated with strong sediment segregation leading to specific trench‐fill mechanisms, as only the finer‐grained component of the flows is transferred to the abyssal plain. However, the Makran accretionary prism is characterized by strong along‐strike variability in tectonics and fluvial input distribution that might directly influence the turbidite system architecture (i.e. canyon entrenchment, plunge pool formation or channel development at canyon mouths), the sedimentary dynamics and the resulting sediment distribution. Channel formation in the abyssal plain and trench‐fill characteristics depend on the theoretical ‘equilibrium’ conditions of the feeder system, which is related closely to the balance between erosion rates and tectonic regime. Thus, the Makran turbidite system constitutes an excellent modern analogue for deep‐water sedimentary systems with structurally complex depocentres, in convergent margin settings.  相似文献   

The absorption of water color components and spectral modes in the Pearl River estuary     

席红艳  丘仲锋  何宜军  简伟军 《中国海洋湖沼学报》2007,25(4):359-366

In-situ data from cruises in the Pearl River estuary and adjacent marine areas were collected during March to May 2001. The absorption coefficients of the water color components were studied in detail containing total suspended matter (TSM), chlorophyll-a (chl-a), colored dissolved organic matter (CDOM), and de-pigment particles. For absorption coefficient of TSM, ap, and that of de-pigment particles, ad, correlations of ap(440)-TSM, ad(440)-TSM, ap(440)-chl-a and ad-chl-a were done (the italicized term means the concentration). There was a good correlation between ap(440) and chl-a concentration. An empirical relationship model between aph(675) and chl-a was developed showing a strong correlation of 0.93. Based on the two models the chl-a and aph(λ) were correlated. The values of calculated empirical spectral slope for CDOM absorption coefficients and that of de-pigment particles, 0.017 0 and 0.011 6 respectively, both are within a relative standard error of 10.0%.  相似文献   

边坡稳定性的神经网络预测研究   总被引：21，自引：0，他引：21  

贺可强  雷建和 《地质与勘探》2001,37(6):72-75

根据神经网络法的基本原理，结合38个实际边坡工程稳定实例，应用VB5．0可视化编程语言，建立了边坡稳定性的神经网络预测模型，并运用该模型对部分边坡工程的稳定性进行预测，预测结果与边坡实际稳定状态相吻合，从而表明了神经网络法在边坡稳定性预测中的有效性。  相似文献   

边坡岩体质量分类体系的CSMR法及应用   总被引：7，自引：0，他引：7  

李胜伟  李天斌  王兰生 《地质灾害与环境保护》2001,12(2):69-72

详细、系统地介绍边坡岩体质量评分类的CSMR法，并结合西南某水电站进水口边坡工程的实例，讨论运用CSMR系统进行边坡岩体质量分类的改进意见。实践证明，此法具有简便性和可行性，值得进一步推广。结合工程实践，并指出此法的不足之处。  相似文献   

龙塘山2号大桥岸坡破坏模式的离散元模拟     

詹志峰  谢强  赵文 《地质灾害与环境保护》2001,12(4):67-70,79

以龙塘山 2号大桥为工程背景 ,在综合考虑桥基岸坡的工程地质条件尤其是岩体结构的基础上 ,建立了数值分析模型 ,采用离散元法对该桥 10 #墩所处岸坡的破坏模式进行了模拟。模拟结果表明 :( 1)龙塘山 2号大桥 10 #墩所处岸坡基本稳定 ;( 2 )施工时 ,应对既有公路上方岸坡坡顶及坡面可能崩滑岩块进行预清除与加固 ;( 3)根据岸坡破坏趋势可得其稳定坡角为 5 0°  相似文献   

柔索桩护坡技术     

蒋天涛 《岩土工程技术》2001,(1):1-7

柔索桩是一种新型的护坡桩。在基坑外围将钢筋、铜棒或钢管等柔索材料按网格状平面布置，竖向植入土体内，周围灌浆或灌砂与土体紧密结合，桩端进入基坑底面标高下一定深度或计算的滑裂面下的稳固土体内，桩顶用混凝土梁或锚板将成排的桩群联成整体。这种上下紧箍的钢筋、铜棒或钢管等柔索材料与周围土体形成一个良好的三维高强复合土体。  相似文献   

Engineering-Geological Problems in the Moravian Karst,Czech Republic     

Milena AMALIKOVA 《《地质学报》英文版》2001,75(3):303-307

The Moravian karst belongs to one of the famous karst regions in Central Europe. It is situated in Moravia in the eastern part of the Czech Republic. According to the geology it is of Devonian age and the main rocks are of different types of limestones. The process of karstification is still active. They are many caves with rich stalagmites and stalactites and the Macocha abyss, the depth of which is 138.5 m. The underground Punkva River flows through the main part of the karst, forming beautiful underground lakes. Typical karst phenomena, such as sinkholes and deep canyons, may be observed on the surface of the terrain. Because of the karstification, water erosion and frost weathering, many steep unstable slopes and walls originated. To solve the stability from a geotechnical point of view is not easy. This requests a special engineering-geological knowledge and experience.  相似文献   

Kinematic and Block Theory Analyses for Shiplock Slopes of the Three Gorges Dam Site in China     

Jeongi-Gi Um  Pinnaduwa H. S. W. Kulatilake 《Geotechnical and Geological Engineering》2001,19(1):21-42

The granitic rock mass that exists in the shiplock region of the Three Gorges dam site contains a number of major discontinuities and about four sets of minor discontinuities. One hundred and thirty three major discontinuities have been mapped around the shiplock covering an area of 1740×600 m. These major discontinuities were used to perform rock slope kinematic and block theory analyses. Kinematic analyses were performed under the following two cases: (1) assuming all the mapped discontinuities cross the shiplock; (2) using only discontinuities that actually intersect the shiplock. Under case (1) and case (2) the shiplock faces in the proposed permanent shiplock region in fresh rock were found to be stable up to a cut slope of about 45° and 58°, respectively. Block theory was applied to identify different block types that exist on the shiplock faces and to estimate the maximum safe slope angles on the shiplock faces. The orientations of the major discontinuities that actually intersect the shiplocks were considered in this analysis. The total length of the shiplock (1750 m) was divided into 50 m segments. From the stereo-plots, the key blocks (Type I) and/or potential key blocks (Type II) were found for only five segments of the shiplock slopes. It was found that the dip of the cut slope should be less than about 60° to avoid creation of a key block on the proposed shiplock slopes. However, it is important to keep in mind that these conclusions are based on the kinematic analyses performed using only the major discontinuities. Further kinematic as well as kinetic analyses are recommended incorporating minor discontinuities, water forces, earthquake forces etc. before making the final conclusions about the maximum safe slope angle for the shiplock region.  相似文献   

北大某工程基坑支护     

李钟 《水文地质工程地质》2001,28(2):《水文地质工程地质》-2001年28卷2期-61-62.7页-《水文地质工程地质》-2001年28卷2期-61-62.7页

本文根据工程实例了软弱地层的基坑边坡支护方法，防止周边建筑物沉降变形的控制措施，邻潮防渗技术及残留 滞水的处理方法。  相似文献