Alternative closed‐form solutions for the mean rate of exceedance of structural limit states     

Xavier Romão  Raimundo Delgado  Aníbal Costa 《地震工程与结构动力学》2013,42(12):1827-1845

Two new closed‐form expressions representing the mean rate of exceedance of a given limit state are presented herein. These proposals overcome limitations that were identified with the original formulation of the well‐known SAC/FEMA approach. The new expressions involve new parametric functions for the modeling of the seismic hazard data and for the demand evolution for increasing values of the earthquake intensity measure. Given the carefully selected parametric form of these functions, mathematical tractability is able to be maintained to establish two new closed‐form solutions representing the mean rate of exceedance of a given limit state. The function proposed for the hazard exhibits nonlinear behavior in log‐log space and is able to represent the actual hazard data over a wider range of earthquake intensity levels. The function proposed for the demand evolution addresses issues related to the inadequate performance of the SAC/FEMA approach when force‐based demand parameters such as the shear force are considered. To illustrate the applicability of the new closed‐form solutions, the probability of occurrence of several limit states is determined for a reinforced concrete structure. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

预制钢筋混凝土剪力墙结构抗震性能研究进展（Ⅱ）：结构性能研究   总被引：2，自引：0，他引：2  

李爱群  王维  贾洪  潘志宏  吴晓莉 《地震学刊》2013,(6):736-742

阐述了预制钢筋混凝土剪力墙结构抗震性能研究的重要性和预制钢筋混凝土剪力墙结构抗震性能研究的最新进展。综述了国内外预制钢筋混凝土剪力墙结构设计规范以及设计方法的研究进展。指出常规预制装配式钢筋混凝土剪力墙结构的抗震性能较差,在地震作用下,主要靠结构构件连接处的损伤和结构构件损坏来消耗能量;无粘结后张拉预应力预制混凝土剪力墙结构,在地震作用下具有自恢复中心能力和良好的抗震能力,但该结构体系的耗能能力不足。认为在预制钢筋混凝土剪力墙结构中设置耗能减震元件,或将预制钢筋混凝土剪力墙结构设计成隔震结构,将有效提高预制钢筋混凝土剪力墙结构的抗震性能。该类预制装配式剪力墙结构的抗震性能有待于进一步研究。  相似文献   

Experimental study of hollow rectangular bridge column performance under vertical and cyclically bilateral loads     

Han Qiang  Du Xiuli  Yihui Zhou  George C. Lee 《地震工程与工程振动(英文版)》2013,12(3):433-445

To investigate the seismic performance of hollow reinforced concrete(RC) bridge columns of rectangular cross section under constant axial load and cyclically biaxial bending,five specimens were tested.A parametric study is carried out for different axial load ratios,longitudinal reinforcement ratios and lateral reinforcement ratios.The experimental results showed that all tested specimens failed in the flexural failure mode and their ultimate performance was dominated by flexural capacity,which is represented by the rupture/buckling of tensile longitudinal rebars at the bottom of the bridge columns.Biaxial force and displacement hysteresis loops showed significant stiffness and strength degradations,and the pinching effect and coupling interaction effect of both directions severely decrease the structural seismic resistance.However,the measured ductility coefficient varying from 3.5 to 5.7 and the equivalent viscous damping ratio varying from 0.19 and 0.26 can meet the requirements of the seismic design.The hollow RC rectangular bridge columns with configurations of lateral reinforcement in this study have excellent performance under bidirectional earthquake excitations,and may be considered as a substitute for current hollow RC rectangular section configurations described in the Guideline for Seismic Design of Highway Bridges(JTG/T B02-01-2008).The length of the plastic hinge region was found to approach one sixth of the hollow RC rectangular bridge column height for all specimen columns,and it was much less than those specified in the current JTG/T.Thus,the length of the plastic hinge region is more concentrated for RC rectangular hollow bridge columns.  相似文献   

动力输出系统(PTO)对集成波能转换装置式防波堤消波性能及波能捕获率影响研究     

毛艳军  马哲  程勇  翟钢军 《海洋工程》2019,37(4):45-53

针对波浪能转换装置(WEC)研究重点主要集中在能量捕获效率方面,而忽略其附带的消波功能的问题。基于Open FOAM程序,建立垂荡浮子式波浪能发电装置与桩式约束的浮式防波堤的集成系统(OBC-FB)。主要研究WEC中的重要组件动力输出系统(PTO)对集成系统波能捕获效率及消波性能的影响。分析流体黏性影响下线性PTO系统的最优PTO阻尼特性。开发非线性电磁阻尼模型与线性PTO系统性能进行比较。结果显示,考虑黏性影响下线性的最优PTO阻尼系数略大于无黏的理论值;适当增大PTO阻尼系数可以获得更大的波能捕获宽度比(CWR),从而可以保证装置单位特征尺寸的波能转换效率更高,同时可以在更宽波况范围保证消波性能;相较于线性PTO阻尼系统,非线性电磁PTO阻尼系统可以更好地兼顾波能捕获效率和消波性能。因此,在OBC-FB集成系统的优化设计中,PTO阻尼系统是一个重要的优化参数。  相似文献   

Penetration modeling of ultra-high performance concrete using multiscale meshfree methods     

Paul A. Sparks  Jesse A. Sherburn  William F. Heard  Brett A. Williams 《国际地质力学数值与分析法杂志》2019,43(14):2328-2351

Terminal ballistics of concrete is of extreme importance to the military and civil communities. Over the past few decades, ultra-high performance concrete (UHPC) has been developed for various applications in the design of protective structures because UHPC has an enhanced ballistic resistance over conventional strength concrete. Developing predictive numerical models of UHPC subjected to penetration is critical in understanding the material's enhanced performance. This study employs the advanced fundamental concrete (AFC) model, and it will run inside the reproducing kernel particle method (RKPM)-based code known as the nonlinear meshfree analysis program (NMAP). NMAP is advantageous for modeling impact and penetration problems that exhibit extreme deformation and material fragmentation. A comprehensive experimental study was conducted to characterize the UHPC. The investigation consisted of fracture toughness testing, the utilization of nondestructive microcomputed tomography analysis, and lastly projectile penetration shots on the UHPC targets. To improve the accuracy of the model, a new scaled damage evolution law (SDEL) is employed within the microcrack informed damage model. During the homogenized macroscopic calculation, the corresponding microscopic cell needs to be dimensionally equivalent to the mesh dimension when the partial differential equation becomes ill posed and strain softening ensues. To ensure arbitrary mesh geometry for which the homogenized stress-strain curves are derived, a size scaling law is incorporated into the homogenized tensile damage evolution law. This ensures energy-bridging equivalence of the microscopic cell to the homogenized medium irrespective of arbitrary mesh geometry. Results of numerical investigations will be compared with results of penetration experiments.  相似文献   

博物馆文化展演与城市记忆活化传承 ——基于旅游留言档案的文本分析     

文彤  刘璐 《热带地理》2019,39(2):267-277

通过对广州南越王博物馆2015年1月至2017年7月期间的1 294条旅游留言档案（线下留言207条，线上留言1 087条）的文本分析，发现建筑遗址、文物遗产、解说系统和游客参与共同构成了博物馆文化展演的“舞台”“道具”“演员”和“观众”维度因素体系，“建筑遗址”通过真实遗址和现代展馆构建了满足观众对历史文化想象的“舞台”，“文物遗产”和“解说系统”分别以静态和动态的方式将城市记忆内涵进行解构，最后“游客参与”使记忆主体发挥能动性，完成自身对记忆内涵的再编码，实现城市记忆的建构和传承，因此这4个因素在城市记忆构建过程中分别发挥了唤醒、强化、活化和传承作用，构建了博物馆城市记忆链，并进一步强调了记忆主体感知行为、博物馆文化原真特性对于文化展演和记忆传承效果的重要影响。  相似文献   

城市和区域多中心研究进展     

卓云霞  刘涛 《地理科学进展》2020,39(8):1385-1396

在城镇快速扩张和交通通信技术迅猛发展的背景下,许多城市和区域呈现出多中心的趋势;在城市和区域规划实践中,多中心也成为广泛应用的空间政策工具。论文回顾了国内外城市和区域多中心的研究进展,首先从研究尺度和中心重要性的界定出发,辨析了城市内和城市间、形态和功能多中心的内涵;而后分别从新中心的产生和既有中心一体化的角度解析了城市和区域多中心的形成和演化机制;进而总结了实证研究中多中心的识别和测量方法、城市和区域空间结构单中心化与多中心化的分异以及多中心绩效评估等领域的进展与不足。文章最后提出了多中心研究的拓展方向：明晰多中心概念并进行合理测度、比较空间结构演化的分异并剖析内在机制、对多中心的绩效进行多维度系统评估。  相似文献   

Ship performance monitoring dedicated to biofouling analysis: Development on a small size research catamaran     

《Applied Ocean Research》2019

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饲料中添加壳寡糖对花鲈(Lateolabrax japonicus)幼鱼的生长、消化和血清生化指标的影响     

胡晓伟  上官静波  黎中宝  杨敏  徐安乐 《海洋学报》2018,40(2):69-76

本试验旨在研究壳寡糖对花鲈（Lateolabrax japonicus）幼鱼生长，肠道消化，血清生化指标及肠道菌群的影响。本试验选用360尾规格一致的花鲈幼鱼（19.37 g左右）为研究对象。壳寡糖饲料添加浓度设为6组:0%、0.2%、0.4%、0.6%、0.8%、1.0%。设3个平行组，养殖周期45 d。结果显示:（1）生长性能:添加0.6%和0.8%两组的增重率、特定生长率与对照组相比有提高（P>0.05）；（2）肠道消化酶:添加0.6%~1.0%的壳寡糖显著（P<0.05）提高胰蛋白酶活性，0.4%~0.8%的壳寡糖显著（P<0.05）提高了脂肪酶活性；（3）肠道菌群:0.6%~1.0%的壳寡糖显著降低了沙门氏菌数量（P<0.05），大肠杆菌的数量在0.8%时显著降低（P<0.05），双歧杆菌的数量在0.2%~0.6%时显著增加（P<0.05）；（4）血清生化指标:壳寡糖显著提高血清总蛋白和高密度脂蛋白胆固醇含量（P<0.05）；（5）血清非特异性免疫:添加0.6%的壳寡糖显著降低丙二醛（P>0.05），0.2%的壳寡糖增强超氧化物歧化酶、碱性磷酸酶和过氧化物酶活性，添加壳寡糖使溶菌酶的活性显著增强（P<0.05）。研究结果表明:饲料中添加0.6%~0.8%的壳寡糖对花鲈幼鱼生长性能、血脂及肠道健康影响效果最佳。  相似文献   

水平轴潮流能发电装置结构对其水动力性能的影响     

王葛  潘京大  张兴东  李广建  王兵振 《海洋通报》2018,(4):475-480

为研究水平轴潮流能发电装置结构对其水动力性能的影响,运用格子玻尔兹曼(LBM)方法,建立水平轴潮流能发电装置的数值模拟分析模型,对水轮机在不同尖速比工况下的水动力性能进行模拟。将模拟结果与同工况水池拖曳实验得到的数据相对比,二者捕获能系数误差在2%左右,验证了LBM方法的可行性和准确性。在此基础上利用LBM方法研究机舱和立柱结构对水轮机特性的影响,得到其对水轮机捕获效率的影响规律。  相似文献