浅埋暗挖大跨风道临时支撑拆除技术

西南风道具有地质条件及周围环境复杂、开挖跨度大(开挖跨度9.9 m)、埋深浅(结构上覆土厚度约10 m)、覆跨比较小(约为1)、路面外荷载作用频繁、穿过地下管线等显著特点。风道采用CRD法开挖支护,其中,临时支撑拆除是CRD法的关键技术,若施工不当易引起大的地表沉降,影响地下管线和地面交通运行安全,为了保证施工安全及周围环境的安全,采取分段、逐层拆除的方法,主要介绍CRD法临时支撑拆除施工,并通过对地层变位的监控量测,对临时支撑拆除施工效应进行分析。研究表明:1)临时支撑拆除范围原则上取隧道跨度,当环境要求严格时,应减小拆撑的范围;2)拆撑施工引起的地表沉降值比较小,占地表总沉降值的5.86%～18.49%;3)制定和完善了临时支撑拆除控制标准,包括临时支撑拆除时机的确定、位移的控制基准等。     

厦门马新大桥索梁锚固区的优化设计

运用现代有限元方法分析了某斜拉桥索梁锚固区局部应力的分布规律及索力的扩散规律。结果表明,索力引起主梁顶板内局部较大的横桥向拉应力,与锚块固结的横隔板和箱梁腹板则传递和承受了大部分的垂直索力分量。     

刚构-连续组合梁桥临时固结拆除顺序的研究

刚构-连续组合梁桥需经历墩梁临时固结拆除的体系转换过程,该种桥型属于超静定体系,临时固结的拆除会对桥梁结构成桥后位移和应力产生影响.探索该桥临时固结的拆除顺序对结构的影响,以达到优化合龙方案的目的,为今后该类桥梁的临时固结拆除方案提供相应的参考.     

裂纹尖端塑性区三维有限元分析

裂纹尖端塑性区的大小与其三维约束状态有关,而三维约束状态不仅与板厚还与外载荷、材料性质有关.因此不论是薄板还是厚板,用平面应力或者平面应变来模拟其状态都有局限性.现阶段对于三维约束状态下的裂纹还没有一个公认的可以准确计算塑性区大小的公式.文章用有限元对小范围屈服下,含Ⅰ型中心穿透裂纹板裂纹尖端的三维塑性区进行了研究,分析了硬化指数、屈服强度以及泊松比对塑性区大小的影响.计算从平面应力逐渐过渡到平面应变,结果与现有理论的预测结果进行比较,进而给出了一个计算裂纹尖端塑性区大小的计算公式.     

邻近既有污水管道新建接驳井与原管封堵技术研究

以某车站基坑范围内存在一大直径污水管道为背景,研究横跨基坑污水管道改迁技术。现状工作井内不具备潜水作业条件,且无法实施临排,其接驳施工难度极大,常规的迁改技术不能满足现场需求。经研究,通过采用在现状污水管道工作井旁新建工作井、在新建污水管道内设置临时闸板、合理选择上下游洞门破除时机及破除方式、现状污水工作井内安装临时闸板等方法,顺利完成了污水管道改迁中新管接驳与原管道封堵施工,综合效益显著。同时,也可为类似工程施工提供参考。     

Variable speed limit control for severe non-recurrent freeway bottlenecks

Variable speed limit (VSL) schemes are developed based on the Kinematic Wave theory to increase discharge rates at severe freeway bottlenecks induced by non-recurrent road events such as incidents or work zones while smoothing speed transition. The main control principle is to restrict upstream demand (in free-flow) progressively to achieve three important objectives: (i) to provide gradual speed transition at the tail of an event-induced queue, (ii) to clear the queue around the bottleneck, and (iii) to discharge traffic at the stable maximum flow that can be sustained at the bottleneck without breakdown. These control objectives are accomplished without imposing overly restrictive speed limits. We further provide remedies for (a) underutilized bottleneck capacity due to underestimated stable maximum flow and (b) a re-emergent queue at the bottleneck due to an overestimated stable maximum flow. We analytically formulate the reductions in total delay in terms of control parameters to provide an insight into the system performance and sensitivity. The results from the parameter analysis suggest that significant delay savings can be realized with the proposed VSL control strategies.     

PROLIFERATION AND MIGRATION OF EPENDYMAL CELLS IN THE BRAIN OF ADULT RATS AFTER PERMANENT FOCAL CEREBRAL ISCHEMIA

Objective Ependymal cells are thought to be the primary source of neural stem cells in the adult central nervous system. The purpose of this study is to examine spatial and temporal profiles of ependymal cell proliferation and migration after focal cerebral ischemia. Methods Eighty male Sprague Dawley rats underwent permanent middle cerebral artery occlusion after injection of 10/μL of 0.2% Dil into the lateral ventricle. Rats were sacrificed and brain sections were acquired for pathological evaluation and laser confocal imaging at day 1,3,7,11,14,21 and 28 after ischemia. Results The density of Dil-labeled cells in the ischemic ipsilateral subventricular zone was significantly higher than that in the control group and these labeled cells dispersed in the ischemic ipsilateral subventricular zone and/or were located in ependyma from day 1 to 11. In the ischemic ipsilateral cortex, some Diilabeled cells occurred in peri-infarction and infarction of parietal region at day14 and peaked at day 21 when some Dil-labeled cell nodules were found in this region. During postischemic day 14--28, a significant decrease in labeled celldensity in the ischemic ipsilateral subventricular zone was coincident with a significant increase in labeled cells density in the cortex (peri-infarction and infarction). Conclusion The results indicate that ependymal cells proliferate and migrate after focal cerebral ischemia in the adult rat brain.     

斜拉桥190m主塔锚固区U形预应力管道摩阻试验研究

针对斜拉桥190m主塔塔身锚固区U形预应力管道摩阻试验的过程,没有像传统的斜拉桥做此试验时制作足尺模型,而是直接利用塔身位置上的设计孔道,采用2台千斤顶对拉进行摩阻试验,并对整个过程进行了总结,形成科研成果。该方法简单、方便,既节省了成本,又能达到试验目的,可供同类桥梁施工借鉴。     

用“桥上桥”解决323t重载通过16m梁桥的设计与实践

“桥上桥”是大件运输中通过中小跨径桥梁的一种方法.介绍了运输323 t甲醛交换塔通过长寿区宴家化工园区跨度16m斜交梁桥,应用“桥上桥”结合原桥共同受力解决原桥承载力不足的问题,节省了大量加固费用和时间,取得了显著的技术经济效益.详细论述了“桥上桥”设计的计算过程和实践效果.     

均布荷载作用下双面组合梁的滑移效应分析

利用基本力学方法对钢．混凝土双面组合梁在均布荷载作用下的滑移效应进行分析，推导得到了负弯矩区上、下交界面滑移沿梁长方向的表达式，并通过算例比较了双面组合梁与传统单面连续组合梁的滑移特点。计算表明，与传统单面连续组合梁相比，钢-混凝土双面组合连续梁不仅在负弯矩区提高了截面承载力，也使截面刚度得到了提高。