圆砾地层深基坑地下连续墙变形特性分析

地下连续墙作为深基坑围护结构已经用于多种地质情况,但圆砾地层中地下连续墙的变形特性研究甚少。本文依托南宁轨道交通2号线苏卢站基坑工程,采用Midas/GTS对圆砾地层深基坑开挖过程中标准段和盾构收发井段的地下连续墙的变形情况进行数值模拟分析,并结合现场监测结果对圆砾地层基坑变形情况进行理论分析。分析结果表明圆砾地层基坑采用地下连续墙作为围护结构效果良好,侧向位移值较小,整体变形呈“弓”字形。盾构收发井段由于基坑宽度大,地下连续墙侧向位移比标准段侧向位移大。因此在圆砾地层基坑开挖应控制基坑开挖宽度。模型计算结果与现场监测结果均表明侧向位移在0.7H处地下连续墙变形增长最快,因此圆砾地层深基坑开挖采用地下连续墙支护应在0.7H处设置横向支撑。     

悬索桥主缆与索鞍间侧向力分布模式的模型试验研究

为明确主缆与索鞍间侧向力分布模式并为理论研究提供支撑,需开展针对性试验研究。通过在模型设计、加载方式及测试方法等方面的探索实践,形成了可行的侧向力试验方案。根据测试结果,研究了侧向力的分布模式及变化规律,并验证了理论研究成果的准确性。研究表明：侧向力与索力间基本呈线性变化关系,即在通常范围内增加索力所引起的接触挤压力的增大对鞍槽内离散体间的接触关系及传力机理并无明显影响;侧向力在层间分布差异明显,且不同高度处的侧向力随索力的变化率不同,说明侧向力与径向力间并非Janssen公式所述的固定比值关系;侧向力发展具有单向不可逆性;钢丝排列高宽比越大,其对应高度处的侧向力越小,但沿全高范围内的侧向合力越大;试验结果与理论结果吻合较好,证明所建立的主缆侧向力理论计算方法与公式是准确的。     

防屈曲支撑-钢筋混凝土框架结构基于能量平衡的抗震塑性设计

为确定防屈曲支撑在结构中的布置方式以使结构抗震性能充分发挥,提出了基于能量平衡的防屈曲支撑 钢筋混凝土框架结构抗震塑性设计方法。构建了结构的“强柱弱梁”整体屈服机制,采用侧力比将总结构体系离散为防屈曲支撑体系和纯框架体系,并建立了结构的双线性能力曲线。基于能量平衡方法计算结构的设计基底剪力并分别得到支撑体系和框架体系的设计侧向力,进而完成支撑的截面设计。按照塑性内力分配机制和考虑支撑屈服后性能,计算梁柱构件内力需求。以一幢5层结构为例,分别设计了不同侧力比的14个结构模型,对比了基底剪力、防屈曲支撑面积和梁柱钢筋用量等。通过22条地震波下的弹塑性时程分析,研究了不同侧力比结构的最大层间位移角、屈服机制、楼层剪力比、支撑最大位移延性、累积位移延性和结构残余层间位移角。分析结果表明：所提出的方法能实现结构的预期失效模式,并满足结构的抗震性能要求,并建议设计侧力比选取在0.3~0.5之间。     

Salmonella detection in powdered dairy products using a novel molecular tool

In this study, we developed a rapid, specific, and sensitive loop-mediated isothermal amplification technique combined with a lateral flow dipstick (LAMP-LFD) method to detect Salmonella targeting the siiA gene in powdered infant formula (PIF). The specificity of the detection method (LAMP-LFD) approached 100% using 21 Salmonella and 31 non-Salmonella bacterial strains. This detection method exhibited high sensitivity limits for pure cultures at 3.7 cfu/mL and in PIF at 2.2 cfu/g without enrichment. To evaluate the applicability of the LAMP-LFD method, we detected 60 positive PIF samples and 20 negative PIF samples. The results showed that the method of LAMP-LFD had a high diagnostic specificity of 100% for detection of Salmonella in PIF. To reduce incidence of LAMP contamination, we applied propidium monoazide (PMA) to eliminate carryover contamination of LAMP. At the same time, we found that PMA does not affect observation of LFD for measurement of LAMP signal. The results verified that the method of LAMP-LFD targeting the siiA gene is rapid, accurate, and sensitive for Salmonella detection in PIF, and that PMA shows great potential to be widely used to eliminate the amplicon contamination risk generated by the highly sensitive LAMP reaction in the detection process.     

带锥斗筒仓中稻谷的密度与应力分布模型

采用LHT-1粮食回弹模量仪测定稻谷堆的压缩密度,建立带锥斗筒仓中稻谷堆的密度、应力与粮层深度关系的微分方程组,用数值方法计算带锥斗筒仓中稻谷密度、应力与粮层深度关系,由积分法计算出筒仓中稻谷的储藏总质量。试验结果表明,淮稻5号(含水率为10.38%~18.30%w.b.)的密度随竖直应力(0.495~245.892 kPa)增大而增大(582.772~696.593 kg/m~3)。模型计算结果表明,在带锥斗筒仓的筒体部分,稻谷堆密度随着粮层深度的增加而增大;到锥斗部分,稻谷堆密度随着粮层深度的增加而逐渐减小。在带锥斗筒仓的筒体部分,稻谷堆的竖直应力随着粮层深度的增加而增大;在锥斗部分,稻谷堆的竖直应力则随着粮层深度的增加而减小。在带锥斗筒仓中的筒体部分,稻谷堆的侧向应力随着粮层深度的增大而增大;在筒体与锥斗结合处,稻谷堆的侧向应力突然增加;到了锥斗部分,稻谷堆的侧向应力随着粮层深度的增大先稍增大再逐渐减小。     

Practical modelling issues for masonry building retrofitted with squat shear wall

Damage observed following moderate to large earthquakes has shown masonry buildings are vulnerable to lateral shaking. The results of statistical analyses in Iran show that 90% of schools in the retrofitting list are unreinforced masonry buildings. A Practical Guideline for Seismic Rehabilitation of Masonry Schools has been published in Iran. This guideline proposed 2 retrofitting methods for retrofitting masonry schools: use of shear wall and shotcreting the perimeter of building. In the case of shear wall, their construction is usually expensive; there are less projects retrofitted by shear walls, and in most retrofitting masonry schools projects, perimeter shotcrete is used. The main aim of this study is offering recommendation to improve this guideline, resulting in more economical approaches. This study proposes including lateral resistance of masonry walls in resisting seismic loads and in the case of shear wall foundation proposes strip shallow foundation for concrete shear walls by including effect of rocking, sliding, and settlement response. It has been shown that with including masonry walls in lateral resistance of building, a considerable reduction in maximum drift occurred. Interaction of soil and structure by considered strip shallow foundation reduces the base shear and increases maximum drift of the building.     

Calculation model of the lateral stiffness of high‐rise diagrid tube structures based on the modular method

High‐rise diagrid tube structures are widely used in high‐rise buildings because of their strong lateral stiffness and flexible arrangement of plane layout. The lateral stiffness of rectangular diagrid tube structures is studied by many researchers, but it seldom attracts attention for arbitrary polygonal ones. Therefore, it is necessary to propose a calculation model for lateral stiffness of arbitrary polygonal diagrid tube structures. First, the basic concept of modular method is defined. Assuming that diagonals are only subjected to axial force, a calculation model of lateral stiffness of arbitrary polygonal diagrid tube structures is presented. The lateral displacements of structures are calculated by modular method. Then the accuracy of modular method and calculation model of lateral stiffness are verified by finite element method. Intersection law of structural lateral displacement curves is achieved. Taking the top displacement of structures as the reference index and based on the principle of equivalent material, diagonal angle optimization method is proposed, whose rationality is validated by finite element method. Based on the design method of top displacement control, preliminary design method of cross section of diagonals is suggested. Results in this paper are expected to provide a theoretical reference for preliminary engineering design.     

悬索桥主缆与索鞍间侧向力理论计算方法与公式研究

为解决主缆与索鞍间侧面抗滑摩擦力难以准确计算及充分利用的问题,需开展主缆侧向力方面的相关研究。通过探究既有侧向力计算公式的理论基础,揭示其应用局限性;基于离散体接触关系,提出鞍槽内相互作用力的计算模型,建立侧向力理论计算方法,并分析误差影响;基于最小二乘准则进行分区间多元非线性回归分析,提炼出便于工程应用的实用计算公式;探讨了参数影响,并对比既有公式、理论方法及实用公式的计算结果;利用实用公式计算某实桥主缆抗滑摩擦力,并阐明其组成机理。研究表明：由Janssen公式演化而来的既有公式不适用于主缆抗滑计算;鞍槽宽度正偏差对侧向力存在有限的增大效应;增加钢丝列数,侧向力迅速增大并趋于稳定、侧向力分布曲线由负指数收敛型渐变为近线性;侧向力与摩擦系数呈负相关关系;实用公式与理论方法的结果吻合较好;两块竖向隔板贡献了24.5%的摩擦力,说明设置竖向隔板是充分利用侧面抗滑贡献潜力的有效措施。     

全装配式钢筋混凝土框架-剪力墙结构抗震性能试验研究

为研究采用预制剪力墙、预制框架的全装配式RC框架-剪力墙结构的抗震性能,对2榀1/2比例两层两跨RC框架-剪力墙结构子结构模型试件（其中1榀为全装配试件PCFW2,1榀为全现浇对比试件RCFW）进行了低周反复荷载试验,分析了结构的破坏机制、破坏形态、塑性铰开展、滞回性能、位移延性、刚度退化和耗能能力等。结果表明：全装配式试件PCFW2与全现浇对比试件RCFW的开裂荷载相当,破坏过程和最终破坏形态基本相同;灌浆套筒、约束浆锚可有效传递钢筋应力;全装配式试件PCFW2整体性良好,其屈服荷载、峰值荷载、极限荷载均略大于全现浇对比试件RCFW的相应值,但相差不超过13.0%,位移延性系数较全现浇试件RCFW的略低。在大部分受力阶段,试件PCFW2耗能优于试件RCFW。建议全装配式框架-剪力墙结构中剪力墙的边柱（或边缘）纵筋,采用灌浆套筒连接,其余部分采用约束浆锚搭接连接,而框架湿节点处的后浇混凝土采用微膨胀混凝土。     

配筋方式对自升式钻井平台悬臂梁屈曲性能影响研究

自升式钻井平台悬臂梁的稳定性能是衡量其承载能力的重要指标。以某122 m(400英尺)自升式平台悬臂梁为研究对象,采用有限元分析方法,研究了在不同的工况下主梁配筋方式和侧向抗弯刚度比对悬臂梁线性屈曲性能的影响。使用弧长法得到了悬臂梁非线性屈曲过程的载荷-位移曲线,校核了中国船级社海上移动平台入级规范中的屈曲安全系数,得出了规范中的屈曲安全系数偏保守的结论。该结论可为悬臂梁的抗失稳设计提供理论依据。