Simplified probabilistic non-linear assessment of existing railway bridges

An objective of the European Commission's Sixth Framework Research Project, Sustainable Bridges, is to advance understanding of the behaviour of existing railway bridges and develop tools to assess their ability to safely handle future traffic demands and extend their service lives. This paper presents the findings of a study that reviews structural safety models applicable to the assessment of existing bridges. The study proposes the use of simplified probabilistic non-linear structural analysis methods to provide more accurate assessments of the load capacity of bridge systems than traditional methods. The simplified methods use the results of a limited number of deterministic non-linear structural analyses and apply these results into a reliability framework. The application of the proposed methods is illustrated by assessing the safety of an existing bridge. The accuracy and efficiency of the simplified methods are verified by comparing the results of the simplified methods to those obtained from full probabilistic non-linear analysis procedures.     

Reliability-based capacity design for reinforced concrete bridge structures

In the seismic design of reinforced concrete (RC) bridge structures, there should be no brittle failures, such as shear failures, in the components, and a plastic hinge should be formed at the bottom of the bridge pier. These are important concepts in capacity design to guarantee the safety of bridges subjected to severe earthquakes. These concepts can maximise post-event operability and minimise the cost of repairing bridges after a severe earthquake. In this article, a reliability-based methodology to carry out capacity design with partial factors is proposed and applied to the seismic design of RC bridge structures. This ensures that (i) all of the components undergo the desired ductile failure mode, (ii) the damage due to an earthquake is induced only at the bottom of the bridge pier and (iii) the probability of failure is at most equal to a specified value.     

轴向压缩下圆形和多边形钢管混凝土柱的统一公式

目前,不同截面钢管混凝土(CFST)柱的轴向承载力采用不同的公式计算。研究人员和设计师试图在柱的设计中找到一个适用于不同截面(包括实心、空心、圆形和多边形截面)的统一公式,这一直是他们面临的一个挑战,事实上也是十分重要的问题。为满足现代的设计要求,结构在材料的使用、结构构件的拓扑学方面不断优化,上述问题应运而生。作者之前研究了圆形空心和实心CFST柱轴向承载力的统一公式,该文将其拓展到正多边形截面空心和实心CFST柱,将圆形截面作为多边形边数为1的特殊情况。最后,给出用于计算圆形或多边形截面实心和空心钢管混凝土柱轴向承载力的统一公式。此外,对空心圆形和方形钢管混凝土柱进行了试验。这些试验结果对有限的公开发表的文献进行了补充,也验证了该分析公式。     

型钢加固钢筋混凝土梁的受力分析

通过对型钢加固钢筋混凝土梁的受力分析,依据所作的基本假定分析了加固前后梁截面的应变及应力变化,推导了加固前后梁的承载力、型钢与梁间剪应力以及加固梁抗弯刚度的计算式;得出型钢加固钢筋混凝土梁可大幅度提高梁的抗弯能力,同时也有效提高梁抗弯刚度的结论;最后提出对加固材料性能和加固前梁上荷载的定性要求。     

有压溶液作用下混凝土中氯离子浓度分布研究

为探索测定混凝土中钢筋锈蚀临界氯离子浓度的快速测定方法,本文对有压溶液作用下混凝土内部的氯离子浓度分布进行了测定。试验测定了0.65水灰比、1 MPa压强作用下混凝土的渗透系数以及不同加压时间条件下的自由氯离子浓度和总氯离子浓度,得到了不同加压时间下自由氯离子沿混凝土深度的浓度分布曲线。结果表明,随着加压时间的增长,在同一混凝土渗透深度处,自由氯离子浓度呈上升趋势。数值模拟的结果也较好的反映了这一规律。这为钢筋锈蚀临界氯离子浓度的快速测定方法的提出提供了理论及实验基础。     

Tactical capacity planning for semiconductor manufacturing: MILP models and scalable distributed parallel algorithms

A multiperiod stochastic mixed‐integer linear programming model is developed to address the tactical capacity planning of semiconductor manufacturing with considerations of complex routing of material flows, in‐process inventory, demand and capacity variability, multisite production, capacity utilization rate, and downside risk management. Both planning level decisions (i.e., capacity allocation and customer service level decisions) as well as operational level decisions (i.e., production, inventory, and shipment decisions) can be simultaneously determined based on the two proposed multiobjective optimization models. To address the huge number of scenarios needed to characterize the uncertainty and the large number of first‐stage integer variables in industrial scale applications, two novel scalable distributed parallel optimization algorithms are developed to mitigate the computational burden. The proposed mathematical models and algorithms are illustrated through two case studies from a major US semiconductor manufacturer. Results from these case studies provide key decision support for capacity expansion in semiconductor industry. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3930–3946, 2016     

湿法磷酸增产技改措施

针对云天化云峰分公司280 kt/a磷酸生产系统过滤和浓缩能力偏小制约产能发挥的问题,进行技改分析。通过新增消化槽、100 m~2转盘式过滤机,更换料浆泵和浓缩系统酸加热器,装置生产能力提高至320 kt/a,浓缩系统氟吸收率提升7~11百分点,达到了预期目的。     

搅拌热在苯甲酸发热量测试中的影响研究

为研究搅拌热在苯甲酸发热量测试中的影响,通过理论推导,得出搅拌热影响量近似计算公式,并进行了实例验证。研究表明,搅拌热发热量测试结果的影响与搅拌热、主期时间、试样质量相关。当搅拌热不参与计算时,表现出试样质量小则发热量偏高,试样质量大则发热量偏低。而当搅拌热参与计算时,得出的发热量测试结果无此明显现象。因此,搅拌热作为附加热参与计算有利于提高发热量测试结果的精密度和准确度。     

Loading of fibrous filter media and newly designed filter configurations by salt particles: An experimental study

Various fibrous filter media, including surface filter media, depth filter media, woven and nonwoven filter media, were tested and particle loading capacity was calculated using bench‐scale setup via a new estimation approach which was proposed and experimentally verified with Novick‐Kozeny model. Multi‐element structured arrays (MESAs) developed by our research group were evaluated as well for particle loading capacity and filter lifetime on 24″ × 24″ full scale test rig (based on ASHRAE 52.2 Standard). Effects of varying filter media type, filter depth, pleat count and MESAs' element count on salt particle loading performance were experimentally investigated. The experimental studies showed that nonwoven activated carbon fiber filter media have allowed significantly higher salt particle loading capacity and longer useful lifetime compared to woven or nanofiber entrapped media. Furthermore, MESAs were able to significantly enhance loading capacity for salt particles and useful lifetime due to higher filtration area and lower filtration velocity. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3739–3750, 2016     

微观孔隙结构与聚合物匹配性研究

大庆油田采油五厂在总结其动态变化特征及调整方法时发现,油层发育相似的井聚驱效果、增产措施效果会存在一定的差异,从杏十三区聚驱工业区沉积相带图看,大面积发育河道的层位,孔隙结构存在较大差异,因此针对孔隙结构进行室内入注能力的研究,通过分析聚合物与孔隙结构的匹配关系,结合室内研究成果,确定了微观空隙结构与聚合物的匹配模板.