Locking‐free discontinuous finite elements for the upper bound yield design of thick plates

This work investigates the formulation of finite elements dedicated to the upper bound kinematic approach of yield design or limit analysis of Reissner–Mindlin thick plates in shear‐bending interaction. The main novelty of this paper is to take full advantage of the fundamental difference between limit analysis and elasticity problems as regards the class of admissible virtual velocity fields. In particular, it has been demonstrated for 2D plane stress, plane strain or 3D limit analysis problems that the use of discontinuous velocity fields presents a lot of advantages when seeking for accurate upper bound estimates. For this reason, discontinuous interpolations of the transverse velocity and the rotation fields for Reissner–Mindlin plates are proposed. The subsequent discrete minimization problem is formulated as a second‐order cone programming problem and is solved using the industrial software package MOSEK . A comprehensive study of the shear‐locking phenomenon is also conducted, and it is shown that discontinuous elements avoid such a phenomenon quite naturally whereas continuous elements cannot without any specific treatment. This particular aspect is confirmed through numerical examples on classical benchmark problems and the so‐obtained upper bound estimates are confronted to recently developed lower bound equilibrium finite elements for thick plates. Copyright © 2015 John Wiley & Sons, Ltd.     

一类新的能够渐进达到Gilbert-Varshamov界的Alternant子类码

本文基于Maximum Distance Separable(MDS)码的Hamming重量分布提出一类新的二元Alternant子类码.分析表明这类新的子类码包含整个BCH码类,并且可以渐进达到Gilbert-Varshamov(GV)界.     

彩超引导下微创经皮肾穿刺治疗上尿路结石

目的 总结彩超引导下微创经皮肾穿刺取石术（MPCNL）治疗上尿路结石的经验.方法 选取彩超引导下MPCNL治疗的上尿路结石患者200例,将其临床资料进行回顾性分析.结果 200例患者均采用彩超引导一次性穿刺成功,取净结石168例,残留小结石32例.有1例术中出血病例.手术时间60～200 min,平均130 min.肾造瘘管留置5～8 d,平均5.8 d.合并慢性肾功能不全及尿毒症者术后均获不同程度的改善.5例术后出血予输血等对症治疗后（其中3例行数字减影血管造影）,均止血成功.12例术后高热（其中3例出现感染性休克）,持续2～3巴d,经过抗感染、抗休克及对症治疗后均缓解.结论 彩超引导下MPCNL治疗上尿路结石成功率高,创伤小,减少了出血的可能性,且安全有效.     

腔镜下腋窝淋巴结清扫与传统手术的对比研究

目的 探讨腔镜下腋窝淋巴结清扫术的安全性、可行性,并对患者术手上肢功能状况进行评价.方法 比较32例乳腺癌腔镜下腋窝淋巴结清扫术（腔镜组）与35例乳腺癌传统腋窝淋巴结清扫术（传统组）的术中出血量、手术时间和淋巴结清扫数目;术后3个月随访上肢情况,比较2组患侧上肢的感觉、运动功能和水肿情况.结果 腔镜组术中出血量为（36.25±6.96）mL,显著少于传统组的（68.29±17.45）mL（P＜0.01）;腔镜组手术时间为（186.41±13.81）min,显著长于传统组的（158.86±16.09）min（P＜0.01）;2组手术淋巴结清扫数目差异无统计学意义[（16.00±3.47）枚比（16.86±2.94）枚,P＞0.05].术后3个月随访患侧上肢情况,感觉异常、运动受限和上肢水肿发生率腔镜组分别为18.75%、6.25%和9.37%,传统组分别为65.71%、28.57%和28.57%,腔镜组患侧上肢感觉异常、运动受限及上肢水肿者明显少于传统组（P＜0.01或P＜0.05）.结论 腔镜下腋窝淋巴结清扫手术安全、可行,具有微创、美观、上肢功能好等优点.     

神农大剧院钢结构外壳与混凝土结构共同工作分析研究

神农大剧院采用上部大跨度空间钢结构外壳,下部混凝土结构。本文采用通用结构分析与设计软件SAP2000V14,分别建立了混凝土结构、钢结构外壳单独模型和混凝土结构与钢结构外壳整体模型进行分析。分析结果反映了上、下部结构的相互影响的程度,了解了在温度、地震作用下整体结构的反应以及连接界面结构构件的实际受力状态,验证了钢结构外壳和混凝土结构组成的大跨度空间结构体系单独设计存在的隐患。     

山西某大型工业厂房的结构设计

结合工程实例,对大型工业厂房设计中应注意的问题进行分析研究。针对下层吊车起重吨位较小的特点,采用格构柱悬臂牛腿的做法,有效地减小钢柱在厂房内部的占地面积;针对超宽厂房的横向温度变形进行分析,采用单下柱、双上柱的格构柱形式,经与传统的双列柱的形式对比,可有效提高厂房内部使用空间,并降低用钢量;针对厂房纵向超长的特点进行温度应力计算,通过适当增强柱间支撑,合理布置屋面水平支撑等技术措施形成空间整体刚度体系,既满足厂房变形要求,确保了结构安全,又能节约一榀刚排架及基础。     

Prediction of central bursting defects in rod extrusion process with upper bound analysis method

The prediction of central bursting defects in the rod extrusion process through conical dies using the upper bound analysis is investigated. A kinematically admissible velocity field, including the radial and angular velocity components, is proposed. A new criterion is presented to predict the occurrence of the central bursting defects. Parameter b_obt, which represents the risk probability of cracking, is proposed. It is calculated using the shape of the boundary at the entrance by minimizing the total power dissipation during the extrusion process. When b_obt is equal to or greater than b_cr, central bursting occurs. Furthermore, the quantitative relationships between central bursting defects and process parameters (semi die angle, reduction in area and frictional factor) are studied. The results show that the central bursting defects are affected primarily by the reduction in area and the friction factor. The presented criterion is verified by comparing with the FEM simulation data and the results of the published paper.     

基于物联网的分布式电气连接点在线测温系统

为提高各种分布式电气设备运行的安全性和可靠性,降低因常规检修引起的人力和物力浪费,研制出一种基于物联网的分布式电气连接点在线测温系统。通过物联网技术将分布式电气连接点与主控室连接,在上位机软件系统中实现温度的监测,在高、低压电气设备领域形成统一的在线测温平台。系统经过试运行,效果良好,达到了预期要求。     

考虑土体强度不均匀性时宽窄基坑坑底隆起稳定研究

在基坑坑底隆起稳定性分析中,准确的破坏模式及滑动面是确定安全系数的基础。然而,基坑坑底隆起破坏模式种类繁多且形式各异。传统的经典基坑坑底隆起稳定分析以及规范分析方法在破坏模式及滑动面的选取上均存在差异和局限性。基于不连续布局优化法,首先研究了土体强度不均匀性对不同宽度基坑坑底隆起稳定性的影响。结果表明,软土层厚度较大且土体强度沿深度逐渐增长时,宽基坑坑底隆起滑动面并不覆盖整个坑底,即相当于软土层下部存在一硬土层,限制了滑动面向下延伸。进一步,分析了围护结构长度及抗弯强度对破坏模式及安全系数的影响,并提出以滑动面触碰围护结构来区分宽窄基坑。在宽基坑中,当围护结构嵌固深度较小时,失稳破坏滑动面并不通过桩底,此时应用绕最下道支撑的圆弧滑动模式时应适当修正滑动面半径。对于窄基坑,应用圆弧滑动模式时需修正坑内滑动面,以考虑窄基坑的空间效应对安全系数的提高作用。