多次地震动作用下对桥梁圆端空心墩的位移响应研究

实际结构往往遭遇多次地震动作用,而目前国内抗震设计规范考虑的仅为单一地震事件影响,尚无法考虑多次地震动下桥梁结构的响应情况。针对上述现象,作者以秋末河大桥为工程背景,基于抗震分析软件OpenSees对铁路圆端空心墩进行传统及累积增量动力分析数值模拟,通过对比两种情况下位移响应情况来研究多次地震动的影响。结果表明：1)该铁路圆端空心墩较柔,高阶振型较为明显,结构最大位移及残余位移随峰值加速度的增加而增加;2)较单一地震作用而言,多次地震动下,结构的最大位移及残余位移均偏大;3)两种不同分析方法,对于结构最大位移响应,当结构处于弹性状态,其差异不明显,当结构处于弹塑性状态,其差异较大不可忽略;对于残余位移而言,其差异均较为明显,不可忽略。     

亚胺基二乙酸树脂对金属镍的静态吸附及连续逆流U形解吸系统

研究了亚胺基二乙酸型螯合树脂R604对模拟含镍废水中镍离子静态交换吸附性能的主要影响因素,包括废水浓度、pH值、温度等,还研究了吸附平衡态、吸附过程的动力学,热力学,并给出了相应的模型,这些模型均与实验结果有很好的符合度,最后研究了独创的U形解吸柱系统对吸附饱和树脂的解吸性能,探讨了树脂停留时间、解吸液树脂流量比对解吸率和金属浓缩液浓度在柱体内分布的影响.研究表明,亚胺基二乙酸型树脂在废水金属离子镍的去除中有着高效、独特的性能,连续逆流U形解吸系统能提高重金属浓缩液浓度,并大幅度节省解吸液用量,减少解吸时间.     

Performance-based seismic financial risk assessment of reinforced concrete frame structures

Engineering facilities subjected to natural hazards (such as winds and earthquakes) will result in risk when any designed system (i.e. capacity) will not be able to meet the performance required (i.e. demand). Risk might be expressed either as a likelihood of damage or potential financial loss. Engineers tend to make use of the former (i.e. damage). Nevertheless, other non-technical stakeholders cannot get useful information from damage. However, if financial risk is expressed on the basis of probable monetary loss, it will be easily understood by all. Therefore, it is necessary to develop methodologies which communicate the system capacity and demand to financial risk. Incremental dynamic analysis (IDA) was applied in a performance-based earthquake engineering context to do hazard analysis, structural analysis, damage analysis and loss analysis of a reinforced concrete (RC) frame structure. And the financial implications of risk were expressed by expected annual loss (EAL). The quantitative risk analysis proposed is applicable to any engineering facilities and any natural hazards. It is shown that the results from the IDA can be used to assess the overall financial risk exposure to earthquake hazard for a given constructed facility. The computational IDA-EAL method will enable engineers to take into account the long-term financial implications in addition to the construction cost. Consequently, it will help stakeholders make decisions.     

空腹式连续刚构桥抗震性能评价

以一座在建的空腹式连续刚构桥为研究对象,采用SAP2000软件建立三维有限元模型,以桥墩的位移延性比为损伤指标,采用IDA法对结构进行地震响应分析。在结构地震易损性分析中,同时考虑了地震动和结构材料参数的不确定性,采用拉丁超立方抽样法形成地震动-桥梁结构样本对,通过大量非线性计算得到了该桥在近场、远场地震作用下的易损性曲线。同时在此基础上进行了全桥在E1和E2水准抗震性能评价。     

DMTO装置基于IDA与节能潜力框架的能效分析

为全面分析技术和管理水平、负荷、生产结构、耗能工质等因素对装置能效、节能量和节能潜力的影响, 提出采用IDA指标分解的能源绩效分析和节能潜力分析的综合框架分析DMTO装置的能效。提出的分析框架能综合并且真实有效地反映出能源使用的活动水平、能源结构和能源强度等因素的影响, 并能量化装置的技术与结构对节能量的影响, 因而可以直观地揭示提高能效、降低能耗和节能的有效实施途径。DMTO装置的示例分析, 验证了IDA能效分析与节能潜力分析方法的一致性和实用性, 为提出方法广泛用于能效管理与节能的实践奠定了坚实的应用基础。     

Decision‐tree‐based methods for differential diagnosis of β‐thalassemia trait from iron deficiency anemia

Several discrimination indices have been proposed to distinct between β‐thalassemia trait (βTT) and iron deficiency anemia (IDA). This study is the first application of tree‐based methods for differential diagnosis of βTT from IDA. One hundred forty‐four patients with hypochromic microcytic anemia aged 18–40 years old from Ayat Hospital of Tehran were recruited. Classification and Regression tree, CHi‐squared Automatic Interaction Detector (CHAID), Exhaustive CHi‐squared Automatic Interaction Detector (E‐CHAID), Quick, Unbiased, Efficient Statistical Tree (QUEST), Classification Rule with Unbiased Interaction Selection and Estimation (CRUISE), and Generalized, Unbiased, Interaction Detection and Estimation (GUIDE) have been used to discriminate the diagnosis. Mean corpuscular volume (MCV) was found as the main predictor in discrimination. All the mentioned tree‐based methods showed acceptable sensitivity, specificity, accuracy, Youden's index, false positive and negative rate, positive and negative predictive values and AUC in differential diagnosis of βTT from IDA. However, Classification Rule with Unbiased Interaction Selection and Estimation revealed more precise classification with an area under the curve value of 0.99. Decision‐tree‐based methods can be used to develop sensitive and accurate diagnostic methods for differentiating βTT from IDA.     

Incremental dynamic collapse analysis of RC core‐wall tall buildings considering spatial seismic response distributions

Despite wide‐ranging studies on fragility analysis and collapse safety assessment of short to medium‐rise reinforced concrete (RC) structures, a new interest in the topic is still valuable and even necessary for tall RC buildings. This study aims at establishing fragility relationships as well as collapse probability of high‐rise RC core‐wall buildings under maximum considered earthquake ground motions. This study is carried out in a probabilistic framework on a case study of a fully 3‐dimensional numerical model developed to simulate seismic behavior of a 42‐story building having a RC core‐wall system. Proposing planar and vertical distributions of ductility and damage indices, the incremental dynamic analysis, and the multi‐direction nonlinear static (pushover) analyses were employed to reach the research goal. Median collapse‐level capacities were defined in terms of seismic responses (e.g., ductility/damage indices) as well as several intensity measures by employing statistical analyses and cumulative density functions. Available and acceptable collapse margin ratios were next estimated to quantify collapse safety at maximum considered earthquake shaking level. On an average basis, the statistics indicated 9%–10% and 5%–6% collapse probability of the building subjected to near‐ and far‐field ground motions, respectively.     

Seismic performance of MR frames protected by viscous or hysteretic dampers

This study concerns the behaviour of steel frames protected by different anti‐seismic devices (dampers). Typical hysteretic and viscous dampers are arranged in three steel moment‐resisting frames (MRFs) having different dynamical features but are designed to accomplish determined performance objectives. The proposed devices are selected following an iterative procedure based on the use of a suitable damage functional, which has been applied to control the behaviour of the protected structures under a specific seismic record. The outcomes obtained by implementing incremental dynamic analyses, carried out on the basis of seven historical records characterized by different features, allow to analyse the improvement of the structural performance due to the considered dampers and, therefore, to provide design information about their employment. The comparison of results is carried out taking into account the dampers capacity to protect the structures from damage, the inter‐storey drifts, the residual deformations and the possible amplification effects. In conclusion, the equivalent behaviour factors for each damper type are given, with the aim of providing useful design parameters for the implementation of simplified conventional linear analyses. Copyright © 2014 John Wiley & Sons, Ltd.     

Seismic performance of moment resisting steel frame subjected to earthquake excitations

This study presents static and dynamic assessments on the steel structures. Pushover analysis (POA) and incremental dynamic analysis (IDA) were run on moment resisting steel frames. The IDA study involves successive scaling and application of each accelerogram followed by assessment of the maximum response. Steel frames are subjected to nonlinear inelastic time history analysis for 14 different scaled ground motions, 7 near field and 7 far field. The results obtained from POA on the 3, 6 and 9 storey steel frames show consistent results for both uniform and triangular lateral loading. Uniform loading shows that the steel frames exhibits higher base shear than the triangular loading. The IDA results show that the far field ground motions has caused all steel frame design within the research to collapse while near field ground motion only caused some steel frames to collapse. The POA can be used to estimate the performance-based-seismic-design (PBSD) limit states of the steel frames with consistency while the IDA seems to be quite inconsistent. It is concluded that the POA can be consistently used to estimate the limit states of steel frames while limit state estimations from IDA requires carefully selected ground motions with considerations of important parameters.     

基于IDA的RC框架二层次延性关系

为考查强震作用下结构整体延性与局部延性的内在关系,设计了1榀6层3跨钢筋混凝土框架,基于OpenSees平台,选取2条地震波作增量动力分析(IDA)。分别考查了IDA基底剪力-顶点位移能力曲线的屈服点与极限点所对应的框架各杆端截面曲率延性系数。研究发现,梁铰破坏机制为主的框架,其整体延性主要由部分梁端及柱脚延性贡献,柱脚曲率延性系数大致为整体延性系数的2~4倍;框梁的梁端曲率延性系数最高可超过整体延性系数的6~9倍。