裂缝扩展

• With this in minds , many researchers have proposed a variety of models for describing the nonlinear fracture of concrete for the past decades . amid them most take the critical stress intensity factor kic as the fracture toughness , a sign of ability to resist the crack extension
  对此，在过去的几十年里，众多研究人员提出了很多描述混凝土非线性断裂的模型，而其中的大多数断裂模型都以临界应力强度因子k _ ( ic )作为抵抗裂缝扩展阻力的断裂韧度。
• In spite of that , the cracks propagate stably in specimens for all types of tests . thus the paris formula can be used to describe the fatigue crack propagation , and the values of fatigue fracture parameters in the paris formula are regressed by using the results of fatigue damage and stress intensity factors computation
  尽管如此，不论对哪种疲劳试验，其试件疲劳裂缝扩展主要表现为稳定扩展，可以运用paris公式描述疲劳裂纹扩展阶段，并利用疲劳损伤数值模拟计算结果和裂缝扩展过程中的应力强度因子回归了疲劳裂缝扩展速率公式中的疲劳断裂参数。
• In this thesis , stress distribution , concrete cracking and its propagating , and failure mechanism of the orifice of the xiao wan arch dam , as well as the influence of reinforcing bars are studied by both experimental tests and nonlinear analysis . also , the improvement of the performance of the orifice in cracking control by using steel fiber reinforced concrete is studied . these works are useful for the design of the orifice in arch dams
  本文采用试验研究与计算分析相结合的研究方法，结合小湾工程，对拱坝底孔在不同工况下的应力分布、混凝土开裂、裂缝扩展和孔口破坏规律，以及配筋方式、数量对其影响进行了研究，并利用有限元方法对采用钢纤维混凝土提高孔口的抗裂性能和限裂性能进行有益的探讨，为安全可靠、经济合理地设计拱坝孔口提供理论依据。
• Through the research and analysis on the three aspects concerning the base interface of the pavement panel , crack accumulation , expansion in the pavement panel and interaction between spring plates on the road surface as well as its damage on the road fatigue , it is first brought forth that the process of fissures and breakage in the cement concrete pavement can be divided into three stages , i . e . stage of initial crack formation and damage in the bottom of the pavement slab , stage of accumulation , intensifying & expansion in ruptures from load during the time of use and stage of fissures & breakage in the pavement
  通过对路面板底界面开裂、路面板中裂缝积聚、扩展和路面表面车板相互作用及其对路面疲劳破坏的影响等三个层面的研究和分析，首次提出水泥混凝土路面的开裂和破坏过程可以分为三个阶段，即路面板底初始损伤西南交通大学博士研究生学位论文第11页和早期裂缝的形成阶段、使用期间荷载作用对路面造成的开裂损伤累计、加剧和裂缝扩展阶段以及路面断裂破坏阶段。
• Two different reinforcing methodologies are applied : modification of the overlay characteristics by adding chopped glass fibers to the hot mixture asphalt ( hma ) and reinforcing asphalt overlay with glass grids . theory of fracture mechanics ( fm ) is employed to determine crack growth rates for the suggested anti - cracking overlay systems . asphalt mixture designing tests , three point bending tests and fatigue crack propagation tests were carried out . the critical stress intensity factors kic are determined for plain and reinforced asphalt concrete . depending on the fatigue crack propagation , the crack growth rate is determined for each type of anti - cracking system and the cracking process is also analyzed . one of the significant points in this study is the attempt to give better understanding of the crack propagation for multilayer asphaltic overlay or what are suggested herein to be called composite structure anti - cracking overlay system . the results indicate that the reinforcing materials improve anti - cracking characteristics of the asphalt concrete . composite structure anti - cracking overlay gives a good solution for the reflective cracking phenomenon over old cracked pavements
  利用2种不同的方法加筋沥青罩面:在沥青混合料中加入短切玻璃纤维改善沥青混凝土的特性,采用玻璃格珊加筋沥青混凝土.应用断裂力学方法分析沥青路面裂缝扩展机理.采用沥青混合料设计试验、三点弯曲试验和疲劳裂缝扩展试验,确定加筋沥青混凝土的临界应力强度因子kic ,测量每一种沥青罩面抗裂系统的裂缝扩展速率.本研究的主要特点是提出复合型抗裂罩面系统,分析了多层加筋沥青罩面裂缝扩展过程,推荐了若干沥青路面抗裂系统.结果证明,加筋材料可以提高沥青罩面的抗裂特性,复合型抗裂罩面系统能够有效地阻止反射裂缝的扩展
• The analysis and research of meso - mechanics is one of the popular methods of current researching on the mechanic behaviors of concrete materials . in the meso - mechanic method , concrete is taken as a type of three - phase composite material comprising mortar matrix , aggregate and bond between matrix and aggregate . using nonlinear finite element method numerical simulation is executed to present the damage failure process of concrete specimens considering the heterogeneity of various phase of concrete
  混凝土细观力学方法将混凝土看作由粗骨料、硬化水泥胶体以及两者之间的界面粘结带组成的三相非均质复合材料,利用适当的混凝土细观结构模型,在细观层次上划分单元,考虑其各相介质单元材料力学特性的差异,利用数值方法计算模拟混凝土试件的裂缝扩展过程及破坏形态,直观地反映出试件的损伤断裂破坏机理。
• 4 ) three - dimensional nonlinear analysis of the bottom outlet of the xiao wan arch dam is presented using sub - model techniques . the structural characteristics and failure mechanism of the bottom outlet , under loading of concrete deadweight , hydraulic pressure , internal water pressure and temperature are studied . it is shown that the meshing of the structure becomes easy and the computing time is reduced by using sub - modeling method
  4 )对小湾拱坝的1 ~ #底孔进行了三维非线性分析，研究了孔口在坝体自重、库水压力、孔内水压力和库水温度影响等作用下的孔口应力分布、混凝土开裂、裂缝发展规律以及配筋对孔口开裂和裂缝扩展的影响。
• But , for the reflective cracking of asphalt pavement with half rigid base course and the cracking of the ac overlay above joints ( cracks ) in existing pcc pavement , the results of research show that the fatigue life of ac layer is mainly the life of the crack propagating stage . so the theory and method of fatigue destructive mechanics ( fatigue fracture mechanics and fatigue damage mechanics ) should be used to study and design the pavement structures instead of traditional fatigue mechanics
  而对于半刚性基层反射裂缝和旧水泥混凝土路面沥青混凝土加铺层接缝(裂缝)开裂，研究发现，沥青结构层的疲劳寿命主要为裂缝扩展阶段的寿命，此时不应采用传统的疲劳力学进行研究和结构层设计，而应采用疲劳破坏力学(疲劳断裂力学和疲劳损伤力学)理论与方法。