Hybrid experimental performance of a full‐scale two‐story buckling‐restrained braced RC frame

This paper proposes a novel implementation of buckling‐restrained braces (BRB) in new reinforced concrete (RC) frame construction. Seismic design and analysis methods for using a proposed steel cast‐in anchor bracket (CAB) to transfer normal and shear forces between the BRB and RC members are investigated. A full‐scale two‐story RC frame with BRBs (BRB‐RCF) is tested using hybrid and cyclic loading test procedures. The BRBs were arranged in a zigzag configuration and designed to resist 70% of the story shear. The gusset design incorporates the BRB axial and RCF actions, while the beam and column members comply with ACI 318‐14 seismic design provisions. Test results confirm that the BRBs enhanced the RCF stiffness, strength, and ductility. The hysteresis energy dissipation ratios in the four hybrid tests range from 60% to 94% in the two stories, indicating that BRBs can effectively dissipate seismic input energy. When the inter‐story drift ratio for both stories reached 3.5% in the cyclic loading test, the overall lateral force versus deformation response was still very stable. No failure of the proposed steel CABs and RC discontinuity regions was observed. This study demonstrates that the proposed design and construction methods for the CABs are effective and practical for real applications. Copyright © 2016 John Wiley & Sons, Ltd.     

西北太平洋和汤加俯冲地区深震特殊聚簇的特性及成因探究

对比研究了具有不同热参数、不同俯冲形态的西北太平洋俯冲地区和汤加俯冲地区的深震特殊聚簇的地震学特性和成因.利用单键群方法探测到两个特殊的深震聚簇G1N和G1T.聚簇G1N位于地震空区下方,具有极低的b值（~0.54）,完全不同于具有高b值（~1.04）的汤加俯冲地区聚簇G1T.通过对聚簇地区板块形态、地震主应力轴、地震深度分布特征的分析,以及和汤加典型的板片折曲处地震活动性的对比,我们认为深震聚簇G1N附近的板块表现出板片折曲的特征,板块俯冲到地幔过渡带底部受到下地幔的黏性阻力,板片局部向上凸起发生折曲,产生局部的拉张应力,叠加在俯冲造成的压缩构造背景上,应力状态发生改变,从而影响该深震聚簇的地震活动性.汤加地区G1T聚簇深震的成因则完全不同,没有体现出板片折曲、应力变化的特征;相反,这些深震发生在较冷的Vitiza-Fiji俯冲板块上,该板块在5~8 Ma年前先行俯冲到G1T区域并与Tonga板块发生拆离,G1T聚簇深震就发生在这些温度依然很低、滞留于~500 km深度处的高速板片残留体上.     

盖层水岩相互作用研究及其油气地质意义——以黔中隆起及周缘为例

盖层封闭条件是南方海相碳酸盐岩沉积区寻找油气的关键,本文通过黔中隆起及周缘地区泥岩和灰岩盖层的水岩相互作用实验研究,模拟了泥岩、灰岩盖层在地表雨水、盐水和在不同温度下岩石的主要离子的溶解特征和质量损失特征。通过实验认为水岩相互作用对盖层的保存与破坏至关重要。不同水介质和不同流动状态下,盖层岩石在水介质中的溶解度和离子含量变化特征和幅度不同,泥岩与灰岩特征不同。表现在:天然雨水下,泥岩盖层阴、阳离子浓度均降低,并随时间趋于稳定,灰岩与泥岩略有差别;盐水环境下,盖层阴、阳离子溶解均受到抑制,浓度变化复杂,并随时间趋于稳定,灰岩与泥岩略有差别,温度升高溶解特征复杂化。下古生界在加里东运动暴露期间,黔中隆起及周缘盖层化学损失量巨大。     

A coupled CFD-DEM investigation of suffusion of gap graded soil: Coupling effect of confining pressure and fines content

Suffusion involves fine particles migration within the matrix of coarse fraction under seepage flow, which usually occurs in the gap-graded material of dams and levees. Key factors controlling the soil erodibility include confining pressure (p′) and fines content (F_c), of which the coupling effect on suffusion still remains contradictory, as concluded from different studies considering narrow scope of these factors. For this reason, a systematical numerical simulation that considers a relative wide range of p′ and F_c was performed with the coupled discrete element method and computational fluid dynamics approach. Two distinct macroresponses of soil suffusion to p′ were revealed, ie, for a given hydraulic gradient i = 2, an increase in p′ intensifies the suffusion of soil with fines overfilling the voids (eg, F_c = 35%), but have negligible effects on the suffusion of gap-graded soil containing fines underfilling the voids (eg, F_c = 20%). The micromechanical analyses, including force chain buckling and strain energy release, reveal that when the fines overfilled the voids between coarse particles (eg, F_c = 35%) and participated heavily in load-bearing, the erosion of fines under high i could cause the collapse of the original force transmission structure. The release of higher strain energy within samples under higher p′ accelerated particle movement and intensified suffusion. Conversely, in the case where the fines underfilled the voids between coarse particles (eg, F_c = 20%), the selective erosion of fines had little influence on the force network. High p′ in this case prevented suffusion.     

A lateral global buckling failure envelope for a high temperature and high pressure (HT/HP) submarine pipeline

Submarine pipelines are the primary component of an offshore oil transportation system. Under operating conditions, a pipeline is subjected to high temperatures and pressures to improve oil mobility. As a result, additional stress accumulates in pipeline sections, which causes global buckling. For an exposed deep-water pipeline, lateral buckling is the major form of this global buckling. Large lateral displacement causes a very high bending moment which may lead to a local buckling failure in the pipe cross-section. This paper proposes a lateral global buckling failure envelope for deep-water HT/HP pipelines using a numerical simulation analysis. It analyzes the factors influencing the envelope, including the thickness t, diameter D, soil resistance coefficient μ, calculating length L_f, imperfection length L and imperfection amplitude V. Equations to calculate the failure envelope are established to make future post-buckling pipeline failure assessment more convenient. The results show that (1) the limit pressure difference p_max (the failure pressure difference for a post-buckling pipeline when it suffers no difference in temperature) is usually below the burst pressure difference p_b (which is the largest pressure difference a pipeline can bear and is determined from the strength and sectional dimensions of the pipeline) and is approximately 0.62–0.75 times the value of p_b and (2) thickness t has little influence on the normalized envelopes, but affects p_max. The diameter D, soil resistance coefficient μ, and calculating length L_f influence the maximum failure temperature difference T_max (the failure temperature difference for a pipeline suffering no pressure difference). The diameter D also significantly affects the form of the normalized envelope.     

深水无粘结柔性管抗拉伸层屈曲问题研究进展

随着我国海洋石油工业不断向深水发展,深水柔性管即将获得广泛应用。深水柔性管结构形式复杂,其抗拉层螺旋钢缆在铺管安装和弯曲过程中可能受到轴向压载荷,产生鸟笼现象和侧向屈曲失效,是当前柔性管开发中的研究热点。介绍了国外在柔性管抗拉层钢缆受压载荷失稳的数值模拟和试验研究现状,为我国开展柔性管开发提供参考。     

海底埋设高温管道隆起屈曲数值模拟研究

高温是引发海底管道整体屈曲失效的主要因素,而海床上存在的局部隆起使得高温埋设管道更加容易发生隆起屈曲。这里重点研究海底埋设高温管道发生隆起屈曲的临界温度载荷及其影响因素,提出了一种简化的数值模拟分析模型,同已有的相关实验结果比较表明,本方法可以较好地近似计算高温管道的隆起屈曲。基于本方法开展的参数分析,得到了管道覆土高度、混凝土配重层厚度、海床不平整对海底高温管道发生隆起屈曲的影响趋势。     

海底管道止屈器形式与设计方法研究概述

海底管道的屈曲传播特性对于其整体安全性是极其不利的,一旦发生屈曲传播,会使整个海底管道结构发生失效破坏,为了解决屈曲传播问题同时兼顾经济性的考虑,可以在海底管道上安装止屈器。通过对国外已有止屈器资料的广泛深入调研,首先对止屈器的主要形式进行了总结和对比分析,然后对止屈器的设计方法和流程进行了简要总结。为我国深水海底管道铺设过程中止屈器的选择和设计提供有益的参考。     

Buckling‐restrained brace using steel mortar planks; performance evaluation as a hysteretic damper

The authors developed a buckling‐restrained brace that enables increased design freedom at both ends of the core plate and strict quality control while providing stable hysteresis characteristics even under high strains. The buckling‐restrained brace can be formed by welding a core plate covered with unbonded material to a pair of mortar‐filled channel steels (steel mortar planks) as a restraining part. The use of this approach enables visual confirmation of the status of the mortar filling and also facilitates standardizing structural members and member‐by‐member quality control. Specimens of a buckling‐restrained brace with different steel mortar plank heights are fabricated to adjust the restraining force, along with specimens with different core plate width‐to‐thickness ratios. The tests were conducted to reveal the hysteretic characteristics of the braces, as well as their cumulative plastic strain energy, elastoplastic properties, and stiffening properties. A performance evaluation formula as well as a buckling‐restrained brace design method using the test results is proposed. Copyright © 2006 John Wiley & Sons, Ltd.     

沪蓉西高速公路贺家坪段顺层边坡结构稳定性分析

顺层边坡是工程实践中经常遇到也是较容易产生破坏的一类边坡,其失稳问题一直是工程界极为瞩目和急需解决的问题之一。从地质力学角度分析了顺层边坡的形成机制,抽象出了顺层边坡溃屈破坏的力学模型。利用结构力学的基本理论,推导出了相应的计算公式,并利用文中的理论方法,分析了沪蓉西高速公路贺家坪段顺层边坡(桩号k63-k64)的稳定性,结果与实际情况吻合较好。