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排序方式: 共有297条查询结果,搜索用时 15 毫秒
281.
Carlos Marı́n Jesús Galindo-Zaldı́var Luı́s Roberto Rodrı́guez-Fernández 《Comptes Rendus Geoscience》2003,335(2):255-264
The Campo de Dal??as, located between the central and eastern Betic Cordilleras, shows an evolution determined by the overprinting of two main stress fields since Pliocene times. The first of these develops hybrid and tensional joint sets up to Pleistocene (100 000 yr) and is characterized by NNW–SSE horizontal trend of compression and an ENE–WSW horizontal extension. The second stress field has prolate to triaxial extensional ellipsoids, also with ENE–WSW horizontal extension, and continues to be active today. The most recent stresses produce the reactivation of previous joints as faults whose trends are comprised mainly from N120°E to N170°E and have a normal and transtensional regime, with dextral or sinistral components. The palaeostress evolution of this region is similar to that undergone by other basins of the Eastern Betic Cordilleras, although the Pliocene–Pleistocene transcurrent deformations in the Campo de Dal??as only develop joints and not strike-slip faults. 相似文献
282.
对用套管加强的T型管节点在平面外弯矩作用下的极限强度作了参数化分析。同时将相应的套管以及管节点的几何参数对极限强度的影响进行评估,并且和未加强的T型管节点作了比较。在计算结果中可以得出在管节点的弦管和撑管的连接处用合适的套管加强,可以将管节点在平面外弯矩作用下的极限强度提高到3倍多。 相似文献
283.
Gu Hongxin Chen Tieyun Senior Engineer Marine Design Research Institute of China Shanghai Professor Shanghai Jiao Tong University Shanghai 《中国海洋工程》1991,(3)
"The effect of interaction of loads on the ultimate static strength of tubular joints of offshore fixed platforms, is a practical problem. But there is still absence of rigorous theory to explain available experimental data and empirical criteria for the static strength of tubular joints. The idea of yield at hot spot of tubular joints is introduced in this paper. The interaction equations of plastic capacity for the tubular joints under combined loads (two and three different kinds) are derived. Thereafter the Yura's test data and empirical criteria of ultimate static strength for the tubular joints can be explained. The idea of classification of category of loads in accordance with experimental data and the present theory is suggested. Finally, the improved ultimate capacity equations for tubular joints are recommended. The physical significance of the coefficient of plastic reservation Qp is discussed. 相似文献
284.
Marine structures are mostly made of metals and always experience complex random loading during their service periods. The fatigue crack growth behaviors of metal materials have been proved from laboratory tests to be sensitive to the loading sequence encountered. In order to take account of the loading sequence effect, fatigue life prediction should be based on fatigue crack propagation (FCP) theory rather than the currently used cumulative fatigue damage (CFD) theory. A unified fatigue life prediction (UFLP) method for marine structures has been proposed by the authors’ group. In order to apply the UFLP method for newly designed structures, authorities such as the classification societies should provide a standardized load-time history (SLH) such as the TWIST and FALSTAFF sequences for transport and fighter aircraft. This paper mainly aims at proposing a procedure to generate the SLHs for marine structures based on a short-term loading sample and to provide an illustration on how to use the presented SLH to a typical tubular T-joint in an offshore platform based on the UFLP method. 相似文献
285.
岩石节理剪切变形对岩体工程的安全性和稳定性具有重要影响。为研究常法向应力下岩石节理剪切变形本构关系,采用RDS-200型岩石直剪仪对非规则砂岩节理进行了不同法向应力下的直剪试验。根据岩石节理剪切应力?位移全程曲线形状特征,将其依次划分为峰前压密阶段、线性阶段、屈服阶段和峰后软化阶段;根据剪切应力在峰后软化阶段降低幅度和速率大小,将岩石节理剪切应力?位移曲线划分为3种类型:峰后平台型、峰后缓降型和峰后跌落型。基于岩石节理剪切应力?位移曲线各阶段剪切变形特征,采用分段函数建立了岩石节理剪切变形本构模型。与其他模型相比,新提出的岩石节理剪切变形本构模型对试验数据拟合精度更高,更好地描述了岩石节理剪切应力?位移全程曲线。另外,在通过岩石节理直剪试验由经验公式确定模型参数之后,所提出本构模型可在不同法向应力下实现对不同粗糙度岩石节理剪切应力?位移曲线的预测。研究结果对岩石节理剪切变形的数值模拟和工程估计具有一定的实用价值。 相似文献
286.
钢管超高性能RPC短柱的轴压特性研究 总被引:5,自引:0,他引:5
本文用试验研究了钢管超高强混凝土RPC(后称钢管RPC)短柱在轴压荷载作用下的性能,从分析RPC与普通混凝土和高强混凝土性能上的差异着手,探讨了钢管RPC在轴压作用下的受力变形机理与破坏特点。基于对试验结果和相关文献资料的综合分析,得到了计算钢管RPC承载力的经验公式,并与相关现行规程的计算结果进行了比较。结果表明,国内现行的一些钢管混凝土设计规程不适用于计算钢管RPC的承载力。 相似文献
287.
This paper presents the feasibility of using an impedance‐based health monitoring technique in monitoring a critical civil facility. The objective of this research is to utilize the capability of the impedance method in identifying structural damage in those areas where a very quick condition monitoring is urgently needed, such as in a post‐earthquake analysis of a pipeline system. The basic principle behind this technique is to utilize high‐frequency structural excitation (typically greater than 30 kHz) through surface‐bonded piezoelectric sensors/actuators to detect changes in structural point impedance due to the presence of damage. Real‐time damage detection in pipes connected by bolted joints was investigated, and the capability of the impedance method in tracking and monitoring the integrity of the typical civil facility has been demonstrated. Data collected from the tests illustrates the capability of this technology to detect imminent damage under normal operating conditions and immediately after a natural disaster. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
288.
地下水不稳定混合抽水的模型及模拟方法 总被引:2,自引:0,他引:2
本文指出在混合井抽水量已知的情况下,不能预先分配各层的分流量,只能从刻画混合抽水的模型运转中获取。提出“窜流”是混合井孔的最基本特征,建立了符合混合抽水机理的渗流-管流耦合模型.文中提出“折算(层流)渗透系数K1”的概念及其表达式,解决了管流与渗流耦合的困难,并提出了混合井井流的模拟方法。 相似文献
289.
290.
Tests and model calibration of high‐strength steel tubular beam‐to‐column and column‐base composite joints for moment‐resisting structures 下载免费PDF全文
Performance‐based engineering (PBE) methodologies allow for the design of more reliable earthquake‐resistant structures. Nonetheless, to implement PBE techniques, accurate finite element models of critical components are needed. With these objectives in mind, initially, we describe an experimental study on the seismic behaviour of both beam‐to‐column (BTC) and column‐base (CB) joints made of high‐strength steel S590 circular columns filled with concrete. These joints belonged to moment‐resisting frames (MRFs) that constituted the lateral‐force‐resisting system of an office building. BTC joints were conceived as rigid and of partial strength, whereas CB joints were designed as rigid and of full strength. Tests on a BTC joint composed of an S275 steel composite beam and high‐strength steel concrete‐filled tubes were carried out. Moreover, two seismic CB joints were tested with stiffeners welded to the base plate and anchor bolts embedded in the concrete foundation as well as where part of a column was embedded in the foundation with no stiffeners. A test programme was carried out with the aim of characterising these joints under monotonic, cyclic and random loads. Experimental results are presented by means of both force–interstory drift ratio and moment–rotation relationships. The outcomes demonstrated the adequacy of these joints to be used for MRFs of medium ductility class located in zones of moderate seismic hazard. Then, a numerical calibration of the whole joint subassemblies was successfully accomplished. Finally, non‐linear time‐history analyses performed on 2D MRFs provided useful information on the seismic behaviour of relevant MRFs. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献