Effects of Ultraviolet Radiation,High Temperature and Alkaline Chemicals on Ageing of Silicone Sealants Used in Ballastless Track Expansion Joints

Expansion joints silicone sealants used in high speed railway construction suffer from ultraviolet radiation（UV）, high temperature combined with the alkaline environment. To evaluate the durability and analyse the ageing mechanism, six one-component silicone sealants from different companies were selected and subjected to accelerated ageing tests including UV, thermal and alkali ageing treatments. The ageing effects on the performance of the sealants were evaluated via the appearance and the mechanical property changes. The changes in molecular structure were studied by means of Fourier transform infrared spectroscopy（FTIR）, differential scanning calorimetry（DSC） and thermogravimetry（TG）. This study revealed that different materials displayed different sensibilities to the ageing methods, in which 15 %-20 % decreases of mechanical properties could be observed under UV radiation test, owning the most significant effects. Structure analysis showed that the physical changes of aggregative states were the principal factors to the performance, along with the chemical slight changes. The glossiness dropped significantly in ageing test, which could be used as one of the effective evaluation parameters for ageing conditions in the field.

Damage alarming for bridge expansion joints using novelty detection technique based on long-term monitoring data

Damage alarming and safety evaluation using long-term monitoring data is an area of significant research activity for long-span bridges. In order to extend the research in this field, the damage alarming technique for bridge expansion joints based on long-term monitoring data was developed. The effects of environmental factors on the expansion joint displacement were analyzed. Multiple linear regression models were obtained to describe the correlation between displacements and the dominant environmental factors. The damage alarming index was defined based on the multiple regression models. At last, the X-bar control chart was utilized to detect the abnormal change of the displacements. Analysis results reveal that temperature and traffic condition are the dominant environmental factors to influence the displacement. When the confidence level of X-bar control chart is set to be 0.003, the false-positive indications of damage can be avoided. The damage sensitivity analysis shows that the proper X-bar control chart can detect 0.1 cm damage-induced change of the expansion joint displacement. It is reasonably believed that the proposed technique is robust against false-positive indication of damage and suitable to alarm the possible future damage of the expansion joints.

Design of Bridge Expansion Joints with Perforated Dowels Under Impact Loading

The expansion joints are expected to have movement capacity, bearing capacity for static and dynamic loading, water-tightness, low noise emission and traffic safety. In particular, the failure due to impact loading is the main reason for the observed damages. The problem of dynamic behavior of the expansion joints is so complex that we shall focus our attention on the impact factor for vehicle load that is governed by traffic impact. In order to overcome this difficulty, the cantilever-toothed aluminum joint (finger joint) is one of the promising joints under impact loading. In this study, from the viewpoint of design methodology, numerical studies for impact behavior were conducted for aluminum alloy expansion joints with perforated dowels. The design impact factor for the expansion joints with the perforated dowels against traffic impact loading was examined by using numerical simulations.

Numerical analysis of influence of expansion joints on welding residual stress of an EGR cooler

The influence of expansion joints on the welding residual stress at the tube-plate junction of an exhaust gas recirculation(EGR)cooler was studied by numerical simulation method.The simulation results show that the expansion joints set on the housing of the EGR cooler mainly for the sake of protecting the tube-plate joints from bearing additional heating stress can also reduce the welding residual tensile stress.The expansion joints set on the EGR cooler can mitigate the tensile force acting on the edges of the main plates through its elastic extension,and thus reduce the magnitude of welding residual tensile stress at the tube-plate junction.

Durability of Bridge Expansion Joints with Perforated Dowels Under Traffic Impact Loading

In design phases, expansion joints are required to have movement capacity, bearing capacity for static and dynamic loading, watertight, low noise emission and traffic safety. On the basis of the fact that failure due to dynamic loading is the main reason for the observed damages, attention is focused on the bearing capacity for dynamic loading governed by impact, because it differs from the static loading. In this study, from the viewpoint of durability, experimental studies for dynamic behavior were conducted for aluminium alloy expansion joints with perforated dowels. The validity of the perforated dowels against traffic impact loading was confirmed by both experimental and numerical studies.

Application Study on Elastomer Expansion Joint in Heavy Haul Railway

The article summarizes related research results and achievements of elastomer expansion device in railway bridge and puts forward a new idea of using polyurethane elastomer material to seal concrete bridge joints between adjacent spans in heavy haul railways. The new type expansion device is composed of polyurethane elastomer material and named TTXF （elastomer expansion joint）. In theory, researchers find out expansion joint deformation regularity between adjacent bridge spans through theoretical analysis and detection in heavy haul railways, such as Datong-Qinhuangdao Railway and Shenchi-Huanghua Port Railway. Fatigue tests prove that TTXF can adapt to permanent and dynamic deformation. On the other hand, it has been successfully applied in the test section of Central South of Shanxi Railway Passage and continuous monitoring has been conducted in extreme weather for over one year. The expansion joint has a good effect practically.

BASF and Sinopec Break Ground on $1.4 Billion Expansion of Nanjing Joint Venture Chemical Site

BASF and Sinopec began the construction for the expansion of their joint venture,BASF-YPC Co.,Ltd. (BYC). BASF and Sinopec plan to jointly invest approximately $1.4 billion

Characterization of the negative thermal expansion material Zr_(1-x)Hf_xW_2O_8

The oxide ZrW_2O_8 displays unusual property of isotropic negative thermalexpansion in a large wide temperature range, which makes it have a number of important potentialapplications. The cubic Zr_(1-x)Hf_xW_2O_8 (x velence 0,0.3, 0.5, 0.7, and 1.0) were synthesized bystandard solid state reaction technique. The high and low temperature X-ray diffraction analysisindicate that the substitution of the Hf^(4+) for Zr^(4+) only leads to reducing the latticeconstants, and the changes of negative thermal expansion coefficients are not obvious. The linearexpansion coefficients of Zr_(1-x)Hf_xW_2O_8 (x velence 0,0.3, 0.5, 0.7, and 1.0) are about -6 X 10^(-6) K^(-1) in the temperature range of 298 to 973 K, while that of Zr_(0.5)Hf_(0.5)W_2O_8 is -9.6X 10^(-6) K_(-1) from 83 to 298 K. The phase transition temperatures from alpha-ZrW_2O_8 tobeta-ZrW_2O_8 structure were also determined by X-ray diffraction method. Thermogravimetric analysis(TGA) exhibits that Zr_(1-x)Hf_xW_2O_8 is not hygroscopic in air.

电阻缝焊在多层波纹管膨胀节制造中的非典型应用

因薄壁多层的波纹管刚度小,补偿量大,寿命长而得到广泛应用。但薄壁多层的波纹管与其连接件的环缝焊接难度较大。为了方便多层波纹管的环缝焊接,多采用电阻缝焊将波纹管的直边段封焊在一起。电阻焊缝普遍存在2种状态,即熔合状态和塑性粘合状态。在生产实践中和通过试验研究发现,塑性粘合状态的电阻焊缝大量存在,但并没有显著影响环缝的焊接,采用分散热输入的多层焊是可以克服的。此种电阻缝焊的目的和要求与通常意义上的2层电阻缝焊不同,不要求有承压强度和密封性,只要将多层波纹管端部塑性粘合成整体,当波纹管与连接件焊接时,使下层起到对上层的衬垫作用,不致烧穿即可。此处电阻焊缝是工艺过程焊缝,不是终极焊缝,是在波纹管膨胀节制造过程中的非典型应用。生产实践中不分层的塑性粘合状态的电阻焊缝也可以满足环缝焊接。

关节镜联合肘管扩大成型术治疗肘关节骨性关节炎伴肘管综合征疗效观察

目的探讨关节镜联合肘管扩大成型术治疗肘关节骨性关节炎伴肘管综合征的临床疗效。方法选择2020年9月至2023年8月河北省沧州中西医结合医院骨外科收治的101例肘关节骨性关节炎伴肘管综合征患者为研究对象,按照手术方式不同将患者分为观察组(n=51)和对照组(n=50)。观察组患者采用关节镜联合肘管扩大成型术,对照组患者采用常规肘管扩大成型术。观察并记录2组患者的手术时间、术中出血量、住院时间、并发症发生情况。分别于术前、术后6个月时,采用Mayo肘关节功能评分(MEPS)评估2组患者的肘关节功能,采用日常生活活动能力评定表(ADL)评估2组患者的日常生活能力,采用视觉模拟评分(VAS)评估2组患者的疼痛程度;使用关节量角器测量肘关节旋前度数、旋后度数、屈伸度数,评估2组患者的肘关节活动度;使用Keypoint型肌电图仪检测小指展肌的复合肌肉动作电位(CMAP)、尺神经的神经传导速度(NCV)、运动诱发电位潜伏期(MEPLP),评估2组患者神经恢复情况。结果观察组患者的手术时间、住院时间显著短于对照组,术中出血量、并发症显著少于对照组(P<0.05)。术前,观察组和对照组患者的MEPS、ADL、VAS评分比较差异无统计学意义(P>0.05);术后6个月,观察组患者的MEPS、ADL评分显著高于对照组,VAS评分显著低于对照组(P<0.05)。术前,观察组和对照组患者的旋前度数、旋后度数、屈伸度数比较差异无统计学意义(P>0.05);术后6个月,2组患者的旋前度数、旋后度数、屈伸度数显著高于术前(P<0.05),观察组和对照组患者的旋前度数、旋后度数、屈伸度数比较差异无统计学意义(P>0.05)。术前,观察组和对照组患者的CMAP、NCV、MEPLP比较差异无统计学意义(P>0.05);术后6个月,观察组患者的CMAP、NCV显著高于对照组,MEPLP显著低于对照组(P<0.05)。结论常规肘管扩大成型术、关节镜联合肘关节扩大成型术均可改善肘关节骨性关节炎伴肘管综合征患者的肘关节活动度,但后者损伤更小,恢复更快,在提升肘关节功能及日常生活能力、减轻疼痛程度、调节肌电图检查指标等方面效果更佳,且并发症更少。

基于ANSYS的复式膨胀节强度和轴向刚度有限元分析

通过ANSYS有限元分析,研究了复式膨胀节在同时受内压及轴向位移时的强度和轴向刚度.建立了复式膨胀节的二维轴对称模型,并考虑了非线性对复式膨胀节的影响,将分析结果与EJMA工程近似法计算结果进行对比,表明ANSYS有限元结果更接近实际情况,采用工程近似法分析复式膨胀节时存在一定误差.

桥梁无缝伸缩缝树脂弹性体路用性能试验研究

无缝伸缩缝是一种新型的桥梁伸缩缝,为研究无缝伸缩缝树脂弹性体路用性能,探究应用于桥梁中小位移伸缩缝的可行性。该文通过60℃车辙试验、-10℃低温小梁弯曲试验、动态模量试验、泊松比试验和Overlay Test(OT)试验对树脂弹性体的高低温稳定性、变形性能和疲劳抗裂性能进行了对比研究。试验结果表明:树脂弹性体60℃动稳定度>31 000次/mm,-10℃低温弯曲应变>43 000×10^(-6),不同温度和荷载条件下动态模量为10~12MPa,拉伸/压缩泊松比为0.030~0.050,OT试验断裂能相对TST弹塑体提高59%。桥梁无缝伸缩缝树脂弹性体具有优异的高低温性能,对温度和荷载频率不敏感,是一种泊松比低、抗疲劳开裂能力较强的材料,更能满足桥梁中小位移伸缩缝的行车和变形要求。

膨胀节用接管法兰和波纹管焊接的工艺分析

膨胀节中的接管选用双相不锈钢S-03和波纹管选用奥氏体不锈钢316L材料的焊接,焊接工艺采用钨极氩弧焊。目的是为了得到强度高于奥氏体不锈钢316L的焊缝组织,保证膨胀节产品焊缝不再是强度薄弱点,提高膨胀节产品的耐压力,保证膨胀节产品的可靠性,延长膨胀节产品使用周期,使膨胀节产品满足工程需要。为了获得满足要求的焊缝组织,通过对双相不锈钢、奥氏体不锈钢及Ni基合金焊接性能分析,确定焊接方法、焊接工艺参数。采用S-659焊丝焊接双相不锈钢S-03与奥氏体不锈钢316L时,可以得到强度高于奥氏体不锈钢316L的焊缝组织,提高膨胀节产品的可靠性和使用周期。

桥梁拓宽中新旧桥梁连接方法和受力分析应用与研究

结合实际工程,研究了新旧桥梁之间的连接方法,研发了用于新旧桥梁连接的伸缩装置和沉降装置;采用有限元模型模拟新旧桥梁,分析了旧桥在拓宽后的内力变化,以及主梁位移变形的情况。结果表明:提出的新旧桥梁的连接方法在伸缩缝与沉降缝交点处可保持桥面平整,并有良好防水、防尘性能;老桥的主梁拓宽后在移动的车辆荷载作用下其内力较拓宽前减小很多,新桥的内力相应增加,说明新桥对旧桥的荷载起到了一部分的承担作用;新旧桥梁连接后,桥梁的整体性更好,受力更为均匀。

桥梁伸缩缝锚固区破坏机理及材料应用现状

伸缩缝锚固区是保障伸缩缝正常工作的重要组成部分,但受施工和交通荷载的影响易出现病害,严重影响了桥梁使用质量和行车安全。针对桥梁伸缩缝锚固区的结构和受力特点,介绍了伸缩缝锚固区材料的破坏形式,分析了锚固区破坏机理,总结了锚固区材料的性能需求,分析了目前各类锚固区材料应用现状,并为伸缩缝锚固区材料选取提出了建议。

伸缩缝及支座病害对简支梁桥车致动力响应的影响研究

中小跨径桥梁在中国公路桥梁中占比大,其伸缩缝服役环境恶劣,易发生损伤造成过往车辆剧烈振动、桥梁支座损伤等病害。为探明伸缩缝、支座参数对简支梁桥车致动力响应的影响,建立了车⁃伸缩缝⁃桥梁耦合动力响应(VBCV⁃J)数值分析方法,并通过实测数据验证了该方法,进而开展了伸缩缝、支座参数影响规律的研究。研究结果表明:车速与车辆的振动密切相关,在车速较高、路面状况“一般”时,伸缩缝、梁端的冲击效应会超出规范值。伸缩缝中梁高于路面会导致该部件的冲击效应增大明显,反之则有所减小;而伸缩缝中梁高于或低于路面,均会造成该桥梁端冲击效应增大。伸缩缝弹性支撑刚度的降低、主梁边支座脱空均会引起伸缩缝、主梁梁端的冲击效应增大。支座刚度降低则主要导致主梁整体的冲击效应增大。伸缩缝的破损不仅影响自身冲击效应,还会大幅增大简支梁桥梁端构件的冲击作用,在设计和养护中,应对伸缩缝及梁端构件给予足够的重视。

混合梁斜拉桥微膨胀UHPC灌注钢混结合段的时变效应

为明确微膨胀超高性能混凝土(Ultra-High-Performance Concrete,UHPC)灌注材料的收缩徐变对混合梁斜拉桥钢混结合段长期性能的影响,以湖北武穴长江公路大桥为工程背景,开展材性试验与结构反应实测。基于一种全桥杆系+局部空间网格的多尺度有限元建模方法,对不同灌注材料收缩徐变下钢混结合段的时变效应进行分析研究。研究结果表明:实桥所采用的微膨胀UHPC在测试龄期内膨胀应变呈现出先增后减且始终保持膨胀的趋势,在约5 d龄期时达到最大膨胀应变292.6με,至1 080 d时为83.8με;徐变系数在前50 d龄期内增长较快,至1 080 d时为1.63。灌注材料的收缩可在结合段内部产生显著的次应力,表现为内填混凝土的拉应力和钢格室的压应力;徐变则会导致混凝土应力松弛而使一部分恒载压应力向钢结构转移。运营20 a后,钢混结合段内填普通混凝土存在较高的开裂风险。未作收缩控制的普通UHPC虽亦出现拉应力,但未超过其抗拉强度,抗裂安全系数仍可达到1.5以上。而微膨胀UHPC处于受压状态,不存在开裂问题。微膨胀UHPC的应用,既可改善内填混凝土的抗裂性能,又有助于常规钢混结合段的结构优化,大幅减少材料用量和结构自重。

某试验台高温高压管道结构设计研究

针对某型号燃烧室压力模化试验台高温高压管道展开设计,管道试压过程发生膨胀节变形,根据现场实际变形情况开展原因分析,提出膨胀节及试验台管道优化改进方案,通过开展有限元分析,论证了方案的可行性。根据优化改进方案进行现场调整,并开展高温高压联调测试,验证了优化改进方案的可行性。

基于循环孔洞扩张模型的X型圆管节点超低周疲劳寿命预测

海洋工程钢结构在服役过程中,受风、浪、流或地震等极端循环载荷的影响,易发生超低周疲劳断裂破坏,造成人员伤亡及财产损失,因此超低周疲劳断裂分析及寿命预测对于海工结构安全性评估至关重要。然而,现阶段基于累积损伤理论提出的多种超低周疲劳寿命预测模型无法对多尺度节点实现统一预测,造成了实际工程应用的不便。因此文中基于循环孔洞扩张模型开展X型圆管节点超低周疲劳寿命预测。首先,开发了基于循环孔洞扩张模型的VUSDFLD程序,实现ABAQUS与FORTRAN子程序联合应用,利用有限元分析验证循环孔洞扩张模型在X型圆管节点超低周疲劳断裂分析中的有效性;其次,根据多组X型圆管节点超低周疲劳断裂有限元分析结果,在宏观层面提出了一种基于Manson-Coffin公式的超低周疲劳寿命预测公式;最后,依据Miner理论,将适用于等幅加载的超低周疲劳寿命公式扩展至变幅加载情况,验证了多种节点尺寸下超低周疲劳公式的适用性,为工程应用提供了理论依据。

高温烟气管道膨胀节稳定失效分析与设计优化

针对某甲醇制烯烃(MTO)装置再生烟气管道波纹管膨胀节稳定失效的故障,分析了管道支座布置和操作工况变化对膨胀节稳定性的影响,结合管道热位移、盲板力的计算,证明了管道支座的选型及合理布置是保证膨胀节安全、有效服役的关键。提出了膨胀节的改造应用方案和治理措施,为类似工况膨胀节的应用和失效预防提供了经验。