旧水泥混凝土路面沥青加铺层疲劳断裂分析

在道路的使用过程中,沥青加铺层一直经历着交通荷载及温度变化的循环作用,沥青加铺层结构中的裂缝扩展呈现为疲劳断裂特征.沥青加铺层的使用寿命（从开始承载直至破坏所经历的车辆荷载及温度循环次数或作用时间）可分为疲劳裂缝形成寿命和疲劳裂缝扩展寿命两部分.疲劳裂缝形成寿命为由微观缺陷发展到宏观可检裂缝所对应的寿命,目前仍由传统疲劳理论的方法确定;而疲劳裂缝扩展寿命则为由宏观可检裂缝扩展到临界裂缝而发生破坏这段区间的寿命,用疲劳断裂力学方法确定.论文着重对沥青混合料与沥青路面的疲劳断裂进行分析.     

高等级公路沥青路面裂缝病害的预防性养护

针对高等级公路沥青路面出现的裂缝病害,分析了传统养护方法的不足,并且着重介绍了目前比较流行的稀浆封层及红外热处理等沥青路面的预防性养护技术,从而避免路面结构的破坏,减少维修养护的总成本,为施工单位提供了良好的预防性养护技术.     

Prediction of fracture behavior of beam-to-column welded joints using micromechanics damage model

Moment-resisting steel frames often fail by fracture failure of beam-to-column welded joints during a strong earthquake. This paper provides a numerical methodology based on micromechanics damage model instead of traditional fracture analytical methods to investigate the crack initiation and propagation of welded beam-to-column joints subjected to monotonic loading and ultra low cycle loading conditions. Firstly, parameters used in the micromechanics damage model for steel base metal, heat affected zone and weld metal were calibrated, respectively, against uniaxial tension test results and cycle test results of notched specimens. The evolution of void growth in the notched specimens under different loading conditions was compared. Secondly, fracture process of the welded joints subjected to tensile loading was simulated based on the micromechanics damage model. The predicted load displacement response agrees well with the other researcher's test results. Finally, the micromechanics damage model was applied numerically to investigate the ultra low cycle fatigue fracture behavior of the welded joints under constant amplitude as well as variable amplitude inelastic cyclic loading. According to the distribution and evolution of void in the welded joints obtained from finite element analysis, crack initiation and propagation were presented and the number of cycles to fracture was predicted. It is shown that the fatigue life predicted from finite element analysis based on micromechanics damage model agrees well with the other's test results.     

大理岩三点弯曲梁弹塑性损伤破坏研究

在应变空间内,推导出弹塑性损伤增量本构方程,通过自编程序实现该本构方程,同时将此程序实现了并行算法;建立了三点弯曲梁二维及三维细观尺度数值试样,分别进行相应地弹塑性损伤破坏数值模拟,作了相应的对比分析,在数值模拟中,提出破坏单元网格消去法,模拟裂纹扩展。研究发现:数值试验同物理试验较吻合,且与理论分析是一致的;由于三维试样细观单元的非线性比二维在空间上更为离散,由三维细观单元弹塑性损伤非线性反映宏观试样的非线性,更能深入地研究细观破坏机理;提出的破坏单元网格消去法为有限元清晰模拟裂纹开辟了新的途径;并行算法程序的实现为应用于大型三维水利水电工程奠定了基础。     

沥青路面低温抗裂性能研究

介绍了沥青路面低温开裂的类型,并对影响沥青路面低温开裂的因素进行了分析,提出了提高沥青路面抗裂性能的措施,以提高沥青混合料的低温抗裂性能,达到减少温缩裂缝的目的,从而改善沥青路面的路用性能。     

Numerical fracture analysis on the specimen size dependency of asphalt concrete using a cohesive softening model

Cracking in asphalt concrete is one of the major causes of structural and functional deterioration of pavement systems. Various experimental and numerical approaches with typical specimen size have been applied to analyze the fracture mechanism of asphalt concrete but the specimen size dependency on the fracture has an important role. Herein, the clustered discrete element method (DEM) approach was applied into the investigation of size effect on fracturing of asphalt concrete based on a disk-shaped compact tension (DC(T)) test. A bilinear cohesive softening model was implemented into the DEM framework to enable simulation of crack initiation and propagation in asphalt concrete. The laboratory tests were conducted for specimen sizes of asphalt concrete varying from 100 to 450 mm. Micromechanical fracture modeling approach was also applied to investigate the heterogeneous fracture behaviors for different specimen sizes. Image processing procedure was conducted to determine the microstructure of asphalt specimen and to project it into the numerical mesh. The specimen size dependency of asphalt concrete was captured by the developed experimental fracture test and the clustered DEM fracture model was able to accurately predict the size-dependent fracture behavior when considering viscoelasticity and heterogeneity.     

平头塔式起重机起重臂疲劳损伤寿命分析

由于塔式起重机工作的特殊性,对于其安全可靠性能的研究尤为重要。本文利用高周疲劳损伤理论及数值模拟的方法对平头塔式起重机起重臂进行了疲劳损伤寿命分析并得出了平头塔式起重机起重臂焊缝允许的最大初始裂纹及裂纹的扩展寿命,为平头塔式起重机的疲劳设计提供了理论依据及判别方法。     

高速公路沥青路面裂缝的成因及防治

介绍了沥青路面裂缝的种类,分析了沥青路面裂缝形成的原因,同时提出了沥青路面裂缝的防治措施,从而最大限度地降低沥青路面裂缝的产生,提高了沥青路面的使用寿命。     

半刚性基层沥青路面疲劳裂缝扩展与寿命预估研究

以疲劳断裂力学理论和材料试验为基础,对半刚性基层沥青路面裂缝的扩展行为进行系统研究,分析了裂缝尖端的应力强度因子变化规律和偏荷载作用下各影响因素对疲劳寿命的影响;结合路面结构初始状态的荷载响应,回归得到了路面的疲劳寿命预估方程。结果表明,路面疲劳主要是由偏荷载作用于横向裂缝导致,疲劳寿命随面层整体模量和轴载增长而递减,随基层模量、路基模量、中面层厚度、基层厚度增长和车速而递增,随下面层厚度的增长先减后增。回归得到的疲劳寿命预估方程考虑的影响因素更加全面,为我国路面结构设计和科研提供了理论支持和补充。     

浅谈沥青路面温缩裂缝

分析了沥青路面温缩裂缝产生的原因,为研究沥青混合料的低温抗裂性能,介绍了六种实验测试方法,根据不同地区气候的不同,提出降温争剧程度的自然区域划分,据此选择合适的沥青混合料,从而更好地解决沥青路面低温缩裂的问题。     

浅谈沥青混凝土路面的早期破坏与预防措施

沥青路面裂缝产生的原因是由多种因素造成的,它的防治自然就成为一个综合治理的问题。主要介绍了沥青混凝土路面早期破坏的分类和产生的主要原因,然后从早期破坏的预防和维修方面进行了探讨,设计施工、选用材料中,充分考虑防虑防裂问题,对根除沥青路面裂缝的发生有着重要意义。     

浅谈沥青路面早期破坏

从设计和施工两方面对省道长神线薄弱路段路面改造工程施工前的路况损坏原因进行了探讨，并对裂缝破坏的几种主要表现形式进行了分析，指出应从设计、施工、养护方面防止裂缝的产生，从而延长沥青路面的使用周期，提高投资效益。     

随机变幅荷载作用下焊接节点海水腐蚀疲劳裂纹扩展试验

本工作采用国产海上平台用钢的T型和十字形板状焊接节点试件,模拟导管架臂节点的弯曲受力状态,在随机变幅荷载下进行了海水腐蚀疲劳裂纹扩展试验,分别测得在海水自由腐蚀和阴极保护条件下的(~—da/dN)-AK~(NM)关系曲线。对于十字型焊接节点试件,根据试验测得的裂纹扩展速率曲线,用断裂力学方法对其海水腐蚀疲劳裂纹扩展寿命(有阴极保护)进行了估算,估算得到的裂纹扩展寿命曲线与试验数据,以及用线性累积损伤理论估算的寿命曲线,进行了分析比较和讨论。     

沥青路面裂缝处理新技术开槽灌缝技术的应用

指出传统裂缝处理方式只能对沥青路面裂缝进行暂时处理,不能治本,而开槽灌缝技术却能实现对裂缝的有效处理,从设备、灌缝材料的选用、裂缝的开槽、清理、灌缝等方面,对开槽灌缝技术的应用情况进行了论述。     

PVC土工格栅在沥青路面中的应用

探讨了半刚性基层沥青路面的特性，详细地阐述了PVC土工格栅在沥青路面中的补强作用，结合试验路工程介绍了PVC土工格栅的施工顺序和施工方法，以提高路面材料抗疲劳强度和抗车辙能力，从而提高沥青路面的使用品质。     

索承式桥梁吊索钢丝腐蚀疲劳寿命评估

根据吊索镀锌钢丝腐蚀疲劳破坏特点,把镀锌钢丝腐蚀疲劳纹形成和扩展过程分解成镀锌层腐蚀失效、蚀坑萌生、蚀坑形成、短裂纹扩展、长裂纹扩展和断裂破坏等阶段,建立各阶段时间表达式,得到镀锌钢丝疲劳寿命表达式,提出基于断裂力学的吊索钢丝腐蚀疲劳寿命评估研究结果方法。通过算例分析复杂运营条件下腐蚀环境和应力幅等因素对吊索钢丝腐蚀疲劳寿命的影响,研究结果表明:吊索钢丝腐蚀疲劳寿命主要由钢丝镀锌层腐蚀、蚀坑发展和短裂纹扩展等3个阶段组成,为了准确地评估吊索腐蚀疲劳寿命,需要掌握大桥的运营环境和交通荷载。     

高速公路沥青路面早期破坏原因分析

我国高速公路的路面广泛采用半刚性基层沥青路面,而这种路面出现早期破坏的现象比较普遍。针对我国高速公路设计和施工的实际情况,分析了目前沥青路面产生早期破坏的主要原因,提出了防止路面早期破坏的方法和建议。     

Analysis of fatigue crack growth behavior in asphalt concrete material in wearing course

Fatigue crack is a main form of structural damage in flexible pavements. Under the action of repeated vehicular loading, deterioration of the asphalt concrete materials in pavements, caused by the accumulation and growth of micro and macro cracks, gradually takes place. The indirect tensile fatigue testing (ITFT) was carried out on three types of asphalt concrete materials comprising a high stiffness Gilsonite modified wearing course (GM-ACWC), stone mastic asphalt (SMA) and conventional asphalt concrete wearing course (ACWC) to establish fatigue damage model and failure criteria. Fatigue damage model, based on continuum damage approach, to describe the formation of micro-cracks and crack propagation was developed for the wearing course materials. With the fatigue damage model, finite element analysis was carried out to study the crack resisting performance of the three wearing course materials in a flexible pavement structure.     

陕西省农村公路路面主要病害成因及解决措施

文章主要探讨了陕西省农村公路——沥青路面和水泥混凝土路面的主要病害成因及解决措施。其中,沥青路面着重分析了龟网裂、裂缝、推移、泛油、翻浆、松散和坑槽等6种主要病害;水泥混凝土路面则主要分析了裂缝、破碎、断板、错台、磨光露骨等5种主要病害。针对不同的病害成因,提出了具体的解决措施。     

浅谈沥青路面损坏及结构层设计

对沥青路面结构层从设计、路面施工、养护等方面进行了分析,并就如何防治沥青路面结构层的损坏,提出了增强结构层抗滑系数及提高路面抗搓性的建议,以延长沥青路面的使用寿命,同时提高了经济效益和社会效益。