Factors Analysis of Affecting Loading and Reinforcing Scheme of Large Goods in Railway

Large goods transported in railway are kinds of special goods and they are very important in national construction. In order to transport safely, loading and reinforcing schemes must be made first. How to design a reasonable scheme will be affected by many factors. This paper presents the characteristic of the large goods, summarizes the process of designing a loading and reinforcing scheme of large good, then probes the factors of affecting the loading and reinforcing scheme and gives a detail analysis. It’s considered that those out-of-gauge and overweight degree of goods, center-of- gravity height of a loaded wagon, position of center-of-gravity of goods, type of wagon for using, reinforcement material and reinforcement method, transport expense and transport organization could affect a scheme in the aspects of safety, economy, rapidity and convenience. This conclusion will instruct and help to make a good scheme.

Stability behavior of the Lanxi ancient flood control levee after reinforcement with upside-down hanging wells and grouting curtain

The stability of the ancient flood control levees is mainly influenced by water level fluctuations, groundwater concentration and rainfalls. This paper takes the Lanxi ancient levee as a research object to study the evolution laws of its seepage, displacement and stability before and after reinforcement with the upside-down hanging wells and grouting curtain through numerical simulation methods combined with experiments and observations. The study results indicate that the filled soil is less affected by water level fluctuations and groundwater concentration after reinforcement. A high groundwater level is detrimental to the levee's long-term stability, and the drainage issues need to be fully considered. The deformation of the reinforced levee is effectively controlled since the fill deformation is mainly borne by the upside-down hanging wells. The safety factors of the levee before reinforcement vary significantly with the water level. The minimum value of the safety factors is 0.886 during the water level decreasing period, indicating a very high risk of the instability. While it reached 1.478 after reinforcement, the stability of the ancient levee is improved by a large margin.

Coupling effects of influence factors on probability of corrosion initiation time of reinforced concrete

The coupling model of major influence factors such as environmental relative humidity,load-induced crack and stress state affecting the chloride diffusion process in concrete is discussed.The probability distributions of the critical chloride concentration CC,the chloride diffusion coefficient D,and the surface chloride concentration Cs were determined based on the collected natural exposure data.And the estimation of probability of corrosion initiation considering the coupling effects of influence factors is presented.It is found that the relative humidity and curing time are the most effective factors affecting the probability of corrosion initiation before and after 10 years of exposure time.At the same exposure time,the influence of load-induced crack and stress state on the probability of corrosion initiation is obvious,in which the effect of crack is the most one.

Seismic design factors for RC special moment resisting frames in Dubai,UAE

This study investigates the seismic design factors for three reinforced concrete （RC） framed buildings with 4, 16 and 32-stories in Dubai, UAE utilizing nonlinear analysis. The buildings are designed according to the response spectrum procedure defined in the 2009 International Building Code （IBC＇09）. Two ensembles of ground motion records with 10% and 2% probability of exceedance in 50 years （10/50 and 2/50, respectively） are used. The nonlinear dynamic resPonses to the earthquake records are computed using IDARC-2D. Key seismic design parameters are evaluated; namely, response modification factor （R）, deflection amplification factor （Cd）, system overstrength factor （Ωo）, and response modification factor for ductility （Rd） in addition to inelastic interstory drift. The evaluated seismic design factors are found to significantly depend on the considered ground motion （10/50 versus 2/50）. Consequently, resolution to the controversy of Dubai seismicity is urged. The seismic design factors for the 2/50 records show an increase over their counterparts for the 10/50 records in the range of 200%-400%, except for the D~ factor, which shows a mere 30% increase. Based on the observed trends, perioddependent R and Cd factors are recommended if consistent collapse probability （or collapse prevention performance） in moment frames with varying heights is to be expected.

Reinforcing Effect of Organo-Modified Fillers in Rubber Composites as Evidenced from DMA Studies

The use of organically enhanced kaolin clay as reinforcing filler for NR(natural rubber)and blends of NR with NBR(nitrile-butadiene rubber)and poly BR(butadiene rubber)system were investigated on the basis of DMA(dynamic mechanical analysis).Kaolin clay was modified using a chemical complex of HH(hydrazine hydrate)and SRSO(sodium salt of rubber seed oil).Intercalation of SRSO into kaolin under optimized condition showed an inter-lamellar layer expansion to 4.668 nm,compared to the characteristic d001 XRD(X-ray diffraction)peak of pristine kaolin at 0.714 nm.The morphology,visco-elastic behavior,modulus property,polymer miscibility and Tg(glass transition temperature)of nano-kaolin filled NR and its blend with synthetic rubbers have been studied in detail.DMA showed a diminution in tanδpeak height and a modulus shift in correspondence with increased CLD(crosslink density).Pure NR shows only~1%increase in storage modulus(E′)while adding nanoclay rather than micron sized pristine clay under experimental conditions,because of the feeble interaction between filler and matrix,as compared to blend.An increment of~76%and~117%in E′was recognized by the addition of 4 wt%nanoclay in blends such as BR mK and NBR mK.With loss modulus(E″)pure NR shows only~7%decrease while adding nanoclay,compared to blend.A decrement of~54%and~55%in E″by the addition of 4 wt%nanoclay in BR mK and NBR mK blends were observed.As a whole,DMA was performed to figure out the effect of surface modification enabling to materialize composite.

Characteristic of Fresh and Harden Properties of Polyvinyl Alcohol Fibre Reinforced Alkali Activated Composite

Fibre can enhance the mechanical properties of cement-based composites,but fibre also degrades their workability.However,the quantitative effects of fiber content and length-diameter ratio on alkali-activated materials are still unclear.Various aspect ratio,volume fraction of polyvinyl alcohol fibre(PVAF),and various water-binder ratio were employed to prepare a total of 26 groups of fibre reinforced alkali-activated composite(FRAAC).The influence of PVAF fibre factor(product of fiber volume fraction and length-diameter ratio)on flowability,compactness,strength,and crack fractal dimension of FRAAC was researched.The influence of water-binder ratio on the plastic viscosity of FRAAC was more significant than that on the yield stress.When fibre factor was lower than critical value of 150,the influence of fibres could be overlooked.The reason was that the space between fibres was distant,so the flowability of FRAAC was not impacted by PVAF.At this time,fibres were challenging to restrict the cracks in matrix and increase their mechanical properties.When fibre factor was higher than critical value 150 and lower than density packing value 450,the flexural strength,compressive strength and crack fractal dimension of FRAAC were considerably enhanced,and the FRAAC could still flow easily under dead weight.When fibre factor were above 450,noteworthy fibre balling considerably decreased the flowability,leading to poor solidity and reduced compressive strength.Hence,the ideal content of PVAF in alkali activated composite is between 150/(l/d)and 450/(l/d).

针刺捻转补泻手法对自发性高血压大鼠神经递质及炎症因子的影响

目的通过观察针刺捻转补泻手法对自发性高血压大鼠(SHR)下丘脑室旁核(PVN)中神经递质γ-氨基丁酸(GABA)、谷氨酸(Glu)含量以及血清中炎症因子白细胞介素-6(IL-6)、肿瘤坏死因子-α(TNF-α)水平表达的影响,探寻针刺调控血压的作用机制。方法27只雄性SHR大鼠随机分配到补法组、泻法组和模型组中。9只Wistar-Kyoto(WKY)大鼠作为空白组。空白组和模型组只进行捉抓固定不做针刺干预,补法组和泻法组均取双侧的太冲穴进行针刺干预。各组每日上午干预1次,周期为14 d,2周之间休息1 d。于针刺第0、3、7、14日定期测量大鼠尾动脉收缩压并记录。实验第14日取材,采用ELISA法检测大鼠PVN中GABA、Glu的含量,以及检测血清中炎症因子IL-6、TNF-α的含量,最后使用HE染色法观察PVN组织病理学改变。结果与模型组相比,补法组和泻法组均能显著降低SHR大鼠血压(P<0.01),且泻法组降压效果更为显著(P<0.05)。针刺后,与模型组相比,补法组和泻法组PVN组织中GABA含量显著增加,Glu含量显著降低(均P<0.01);补法组和泻法组血清中IL-6、TNF-α水平相比模型组显著下降(P<0.05或P<0.01)。HE染色结果显示:与模型组相比,补法组和泻法组可改善病变情况,细胞总数增多。结论针刺捻转补泻手法可明显降低SHR大鼠血压,且捻转泻法降压效果更为显著,其作用机制可能与PVN中神经递质GABA含量升高、Glu含量降低,以及炎症因子IL-6、TNF-α水平下降相关。

GFRP布无损加固输电铁塔角钢受力性能研究

针对现役输电铁塔在覆冰、风荷载、边坡变形等作用下可能存在承载力不足的问题,研究玻璃纤维增强复合材料(GFRP)布无损加固铁塔角钢的受力性能。首先,利用文献中的物理试验对加固钢材数值试验方法进行验证;其次,以铁塔角钢为研究对象,基于验证的数值试验方法建立72组有限元分析模型,探讨长细比、GFRP布粘贴层数、粘贴长度等因素对角钢极限承载力的影响;最后,推导并改进GFRP布角钢复合构件理论承载力计算方法。结果表明:不同长细比对构件极限承载力影响较大,当角钢长细比大于70时,加固后的承载力提升不明显;增加GFRP布粘贴层数,角钢承载力大幅提升,粘贴8层GFRP布的承载力提升率最高达41.03%;柱中GFRP布粘贴长度为75%与粘贴长度为100%的角钢极限承载力相比提升不大,仅为0.27%~2.10%;对推导的GFRP布角钢复合构件理论承载力计算方法引入修正系数后,数值试验与理论计算值相对误差缩小至-2.70%~1.77%,有效提升理论解计算精度。在对现役铁塔加固时,只需对角钢全长的75%粘贴6~8层GFRP布进行加固,且对于长细比λ≤70的角钢加固效果更好。

氯氧镁水泥混凝土中涂层钢筋的锈蚀劣化模型研究

为了推进钢筋氯氧镁水泥混凝土(magnesium oxychloride cement reinforced concrete,MOCRC)在西部地区的深度应用,设计模拟西部地区盐渍土环境、气候环境的室内加速破坏试验,研究涂层在多因素破坏试验环境下对钢筋的保护效果。利用电化学工作站测试试件的极化曲线和腐蚀电流密度,选用腐蚀电流密度作为Wiener随机退化过程的退化指标,建立随机退化过程的可靠度函数预测模型。结果表明:涂层在多因素试验环境下对钢筋的保护效果弱于纯浸泡试验环境下对钢筋的保护效果;通过可靠度函数寿命预测模型能够确定,MOCRC在不同浓度2%、4%、6%、8%氯化钠盐溶液室内多因素加速破坏试验环境下达到中等腐蚀破坏的时间分别为4000、3500、1400、400d。

UHPC直拉试验方法与本构关系研究

超高性能混凝土(Ultra-high performance concrete, UHPC)单轴拉伸(直拉)试验是分析UHPC抗拉性能和直拉本构关系的基础性试验,经过对其试件形状与尺寸的优化,试验成功率已得到了较大提升。但由于试件连接方式和局部加强方式的差异,各机构试验成功率参差不齐。为进一步保证直拉试验成功率,采用试验研究和数值模拟的方法系统分析了常见的四种试件连接方式和三种试件局部加强方式对试验成功率的影响,比选出最优试验方法。结果表明:面内夹持装置具有连接可靠、操作简单的优点,适合推广。但夹具的尺寸加工误差或微变形可能导致其与试件的接触面变窄、加剧夹持引发的试件应力集中,致使主裂纹位于测距范围之外;试件与夹具的接触区域进行柔性加强(粘贴碳纤维布)和刚性加强(粘贴铝片)均能有效解决上述问题,提高试验成功率。此外,采用比选的直拉试验方法,探究了钢纤维长径比和体积率对UHPC直拉损伤本构关系的影响。通过声发射(Acoustic emission, AE)监测探究了UHPC在直拉荷载作用下的损伤演化规律,利用声发射参数(累积计数比)构建损伤因子,得到了考虑钢纤维影响的UHPC直拉损伤本构关系。

牧草的重金属胁迫效应及修复机制研究进展

土壤重金属污染是造成生态环境质量下降、农作物重金属含量超标以及危害人类健康的主要因素。植物修复兼具生态和经济效益,是目前重金属治理的重要方式之一,但多数植物品种修复能力有限,不能达到良好的重金属去除效果。与之相比,牧草易栽培、生物量大、生长周期短,在重金属污染土壤治理中表现出较强的修复能力,具有良好的应用前景和开发价值。结合牧草植物修复重金属污染土壤的研究现状,系统阐述了重金属胁迫下牧草的响应特征及其对重金属的富集效果和修复机制,旨在为高效利用牧草治理重金属污染土壤提供参考。

基于深度强化学习的任务分析方法

针对任务分析中任务协同交互耦合度高、影响因素繁多等问题,提出了基于序列解耦与深度强化学习的任务分析方法,实现了复杂约束条件下的任务分解及任务序列重构。设计了基于任务信息交互的深度强化学习环境,基于目标网络与评估网络损失函数间的差值改进SumTree算法,实现任务间的优先级评估;将激活函数运行机制引入深度强化学习网络,提取任务特征,提出贪婪激活因子,优化深度神经网络参数,确定智能体最优状态,从而进行智能体状态转换。通过经验回放生成多目标任务执行序列图。仿真实验结果表明,该方法能生成最佳调度下的可执行任务图;且相对于静态情景,该方法对动态情景有较好的自适应性,在领域任务筹划中具有良好的推广应用前景。

轴压下FRP管-混凝土-钢管组合柱可靠性分析

以85个FRP管-混凝土-钢管双壁空心柱(double-skin tubular column,DSTC)轴压试验数据作为统计样本,评估了几种现有FRP约束混凝土强度模型,最终选择Teng模型进行可靠性分析,并确定了强度模型误差和构件抗力的最佳概率分布.运用JC法对DSTC进行可靠度计算.结果表明:可靠指标随着钢管强度、中空率和含钢率的提高而升高,而对混凝土强度的变化不敏感.FRP约束应力的增加会导致可靠指标的下降.基于可靠指标目标3.7,提出一个适用于DSTC的抗力分项系数表达式.

钢纤维混凝土的断裂损伤过程分析

为探究钢纤维的掺入在混凝土断裂中发挥的作用,通过应变片电测法和数字图像相关(DIC)法对楔入劈拉试件进行加载试验,分析了素混凝土和钢纤维混凝土两种材料的裂纹扩展行为。利用应变片电测法得到断裂损伤区内虚拟裂纹张开位移随荷载的变化和不同荷载时的张开位移分布的变化,绘制成曲线;由DIC法得到试件的应变场变化云图,并计算出张开位移,与应变片电测数据对比分析。结果表明:钢纤维能阻挡裂缝贯通发展,钢纤维试件在破坏过程中承载能力变化更为平缓;DIC法的运用在试件达到峰值荷载前是可靠的。另外,基于双K断裂准则计算了试件的最大承载力,与试验结果基本吻合;通过非线性断裂的裂纹黏聚模型及损伤因子计算法,结合试验数据,给出黏聚裂纹张开位移与损伤变量在断裂过程区的分布规律。

循环荷载作用下土工格栅加筋黄土动力特性研究

【目的】由于黄土所具有的结构疏松、抗剪性低,以及对水、力及震动都十分敏感等工程特性,故探究采用双向土工格栅对西宁地区黄土加筋前后土体动力性能的改善效果。【方法】采用GDS双向动三轴测试系统开展不同加筋层间距、不同围压、不同动应力幅值工况条件下加筋黄土的动三轴试验,分析循环荷载作用下加筋层间距对黄土动强度、动剪切模量、阻尼比等动力响应特性的影响,探讨分析加筋黄土动力响应特性的演化规律。【结果】结果显示:黄土动应变随着动应力的增大而增大,骨干曲线呈现应变强化型,并且骨干曲线随加筋层间距的减小逐渐由曲线型过渡为直线型;随着加筋层间距的减小,黄土强度随之增大,随着围压和加筋层间距的增加,黄土幅值剪应力明显增大,动剪应变减小,阻尼比明显减小。【结论】结果表明:围压和加筋层间距对加筋黄土的动力特性具有显著的增强作用,且存在一个最优加筋层间距。研究成果可为西宁地区加筋黄土道路设计提供参考依据。

强化学习框架中因果推断研究进展

因果推断在科学领域备受关注。近年来,因果关系的确定方法有所创新。强化学习作为一种机器学习方法,主要关注智能体如何在环境中采取行动,以最大化累积奖励。将因果推断方法嵌套在强化学习框架中的思想是因果推断领域以及强化学习方法论中重要的学术进展。基于此,首先,梳理了深度强化学习算法的背景和发展,介绍了基于值函数、基于策略梯度和基于模型的3类强化学习算法框架,以及与因果推断相结合的方向;其次,从5个技术应用角度,对强化学习思想在因果推断和因果识别中的应用研究进行了综述;最后,强调了强化学习框架中因果推断的数据驱动效率、稳定性及应用研究的必要性,并对未来的研究方向进行了展望。

基于值函数分解的多智能体深度强化学习方法研究综述

多智能体深度强化学习方法是深度强化学习方法在多智能体问题上的扩展,其中基于值函数分解的多智能体深度强化学习方法取得了较好的表现效果,是目前研究和应用的热点。文中介绍了基于值函数分解的多智能体深度强化学习方法的主要原理和框架;根据近期相关研究,总结出了提高混合网络拟合能力问题、提高收敛效果问题和提高算法可扩展性问题3个研究热点,从算法约束、环境复杂度、神经网络限制等方面分析了3个热点问题产生的原因;根据拟解决的问题和使用的方法对现有研究进行了分类梳理,总结了同类方法的共同点,分析了不同方法的优缺点;对基于值函数分解的多智能体深度强化学习方法在网络节点控制、无人编队控制两个热点领域的应用进行了阐述。

济南地区土岩二元结构边坡加固设计及稳定性研究

我国城市化建设不断发展,出现了大量覆盖土+下覆风化岩的二元结构边坡,但对于此类结构边坡的整体稳定性分析及支护设计理论体系方面研究较少。为此,以济南地区蒋山山体加固项目为研究对象,在分析现场施工条件、边坡高度及周边环境的基础上,提出了桩板式挡墙+预应力锚索+岩石锚喷的组合结构工程设计,成功地解决了济南地区土岩组合边坡土体易失稳、支挡结构变形较大和施工过程安全性差等支护难题。同时结合MIDAS/GTS有限元软件,对既有边坡的稳定性进行了分析,并从应力场、位移场及整体稳定性系数3个方面研究了土岩二元结构边坡滑移面位置及破坏机理。研究结果表明:既有边坡整体稳定性系数为1.22,属于基本稳定状态;随着施工工况进行,下覆灰岩薄弱面发生应力集中现象,边坡潜在滑移面的工程规模则随着加固措施的进行得到了有效的抑制;坡顶及坡脚位置处位移逐渐减小,而最大位移量位于边坡中部的土岩交界面附近,位移值14.64mm;通过边坡加固设计方案,土岩二元结构边坡整体稳定性系数提高至1.55,属于稳定状态,达到了规范要求。

暴雨下红粘土边坡稳定性分析与植被加固方案优化

为研究植被加固对暴雨下红粘土边坡安全性的影响,采用FLAC3D建立红粘土边坡开挖稳定性数值计算模型,对植被加固条件下红粘土边坡的放坡率进行了优化分析。结果表明,无支护条件下其岩土体最大位移在放坡率为1:1.1、1:1.3、1:1.5和1:1.7时分别达到1500、158.0、42.0和40.9mm。暴雨无支护条件下红粘土边坡稳定性安全系数值与其边坡系数呈线性关系,要满足《建筑边坡工程技术规范》的要求,其放坡率不能高于1:1.76。采用植被加固方案后,红粘土边坡潜在滑动面的位置和形状基本不发生变化,但其稳定安全系数则相比无支护条件会提高16.7%~18.5%。稳定性安全系数值与其边坡系数呈指数关系,红粘土边坡放坡率取1:1.3较合适。

地基工程框架锚索加固抗滑桩试验研究

文中结合志丹压气站施工实践,分析了框架锚索预应力、抗滑桩宽度和柱距对桩受力和变形特性的影响。结果表明,随着桩宽的增加,桩宽40mm的最大土压力分别比桩宽32mm和27mm的最大土压力高出17.3%和22.1%。当锚索拉力在1200~1600 kN时,桩身位移较小,应力分布较为均衡。当张拉力为1400 kN时,桩身锚固点与自由段底部最大正负剪应力之差约为最大剪应力的27%,桩身最大位移仅为5.5 mm,远小于预应力框架锚索的一般弹性变形范围。