导　　师： 魏德敏

学科专业： 081405

授予学位： 博士

作　　者： ;

机构地区： 华南理工大学

摘　　要： GFRP筋混凝土桥面板的现行设计方法主要是通过修正钢筋混凝土桥面板设计方法获得的，并以简支弯曲试验的研究成果作为依据。然而，实际工程中发现混凝土桥面板中存在的拱效应使其工作性能远高于规范设计的结果。为了揭示GFRP筋混凝土板中拱效应的工作机理，在正常使用阶段和极限承载力中考虑拱效应的影响，推导更合理的设计方法，本课题进行了试验研究、有限元分析和设计方法推导，主要完成如下工作： 模拟单跨单向板在整体结构中的工作状态，设计一套试验装置对板带试件端部施加纵向和转动约束。加载试验研究表明，与配钢筋试件在筋材屈服后形成拱效应不同，开裂后GFRP筋试件在纵向约束作用下逐渐形成拱效应。由于GFRP筋的弹性模量较普通钢筋低，适筋试件中GFRP筋在正常使用阶段同拱效应的协同工作性能较钢筋优越。而配筋率相同时，适筋GFRP筋试件和钢筋试件的正常工作性能相似，可见拱效应弥补了GFRP筋刚度的不足。GFRP筋的配置对极限承载力的影响不明显，但直接决定试件的裂缝分布和破坏形态。少筋试件筋材断裂正截面混凝土压溃破坏。适筋试件和超筋试件均发生斜截面混凝土压溃，破坏时筋材应变远小于极限应变，这是因为拱效应提高了试件正截面的混凝土受压区高度，正截面承载力大于斜截面承载力。 建立非线性有限元数值模型，摸清板带拱效应在不同参数下工作性能的变化规律。研究表明，纵向约束刚度与板带纵向抗压刚度比为0.2~1时，拱效应将使板带具有良好的工作性能；刚度比过高，则板带端部约束接近固支，拱效应作用增长幅度减缓，过低则板带正常工作性能差；随着板带跨度或厚度变化，纵向约束作用增大时等效拱的高跨比减小，等效拱的高跨比增加时纵向约束作用下降，板的跨度和厚度适中时，拱效应作用最优；在满跨均布加载、1//4跨对称集中加载和跨中集中加载三种模型的对比分析中发现，满跨均布加载模型的等效斜压杆宽度最大，拱效应的作用更为明显。 基于试验研究及有限元分析的结果，推导建立考虑拱效应的GFRP筋桥梁面板设计方法。将开裂后的GFRP筋混凝土板带简化为三铰拱体系，纵向约束和底层筋材简化为拱脚的压簧和跨中的拉簧，定义等效三铰拱体系的关键参数，量化拱效应和筋材对板带力学性能的影响，结合虚功原理推导出GFRP筋混凝土板最大挠度的计算方法。在混凝土结构规范的基础上，以三铰拱体系的筋材应力代替受弯计算得到的筋材应力，修正体现筋材与混凝土粘结强度影响的系数，以及裂缝间混凝土伸长对裂缝宽度的影响系数，获得最大裂缝宽度的计算方法。进而，以三铰拱体系计算得到的混凝土受压区高度推导正截面极限承载力。假设斜裂缝的开展路径，以斜截面残余混凝土受压区高度推导斜截面极限承载力。板带极限荷载为两种极限承载力中的较小值。结合现有的针对钢筋混凝土桥面板设计研究的成果，将上述推导的板带设计方法应用到GFRP筋混凝土桥面板中，推导建立的理论分析方法与试验值吻合良好。 The present design methods of concrete bridge deck slabs reinforced with GFRP bars aremainly obtained by amending the design methods of concrete bridge deck slabs reinforcedwith steel reinforcement, basing on research results of experimental tests on simply supportedflexural components. However, it was found in practical engineering that structural behaviourof concrete bridge decks was underestimated by design codes, due to the existing archingaction. In order to investigate the working mechanisms of arching action in concrete bridgedeck slabs reinforced with GFRP bars, and to establish a reasonable design methodconsidering the influence of arching action on serviceability and ultimate states, a series ofexperimental study, finite element analysis and design method deduction were carried out.The main achievements were shown as follows: Simulating the behavior of a single span one-way slab strip in a global bridge deckstructure, a test device was designed to provide longitudinal and rotational restraints at eachend of test specimens. Arching action in specimens reinforced with GFRP bars occurred aftercracking, while arching action in specimens reinforced with steel bars became significant aftersteel bars yielded. The elastic modulus of GFRP bars was lower than that of steel bars, thecompatibility between GFRP and concrete was better than those of steel and concrete duringservice working stage in specimens with moderate reinforcement ratio. The low stiffness ofGFRP bars could not influence behaviors of GFRP reinforced concrete slabs compared tothose reinforced with steel bars, when the reinforcement ratio was similar and moderate. Inthe experimental tests, it was found that reinforcement configuration affected slightly onultimate bearing capacity, but determined direct the racking distribution and failure mode ofspecimens. In the test specimens of plane concrete and slabs with small reinforcementpercentages, concrete crushing in normal section at the failure loads. However, in the slabmodels with moderate to high reinforcement ratio, test specimens failed with concretecrushing in oblique section and strain of reinforcement was far less than the ultimate strain,for the depth of concrete compressive zone was increased due to arching action, and bearingcapacity in normal section was larger than that in oblique section. Nonlinear finite element models were set up to discover the law of arching action in slabstrips changed with structural parameters. It was found that the models performed well witharching action when the ratio of longitudinal restraint stiffness to longitudinal compressivestiffness of slab strips was0.2to1. With higher ratio, restraint at the ends was closer to fixedsupported, and the increased scope of influence of arching action decreased. If the ratio was lower, serviceability of the slab strips degraded. When the span or depth of the models werevaried, influence from longitudinal restraints grown with the decrease of ratio of depth to spanof the equivalent arching, otherwise, ratio of depth to span of the equivalent archingincreased with influence from longitudinal restraints decanted. When the span or depthreached moderate value, arching action worked well. Comparing the analysis of models underuniform loading, central symmetrical loading at one-fourth span and central loading atmid-span, the width of equivalent oblique strut in uniform loaded model was largest, and thearching action was most significant. Design method of concrete bridge deck slabs reinforced with GFRP bars was proposedconsidering arching action, on the base of the results of experimental researches and finiteelement analysis. After cracking, the slab strip was simplified to be a three-hinge arch system.Longitudinal restraints were regarded as compressive springs at arch feet, and tensilereinforcement was look as a tensile spring at mid-span. Critical parameters of the equivalentthree-hinge arch system were defined, and influence from arching action and reinforcementon the mechanism of slab strip were quantified. The max deflection was calculated with thevirtual work principle. Based on the code for design of concrete structures, calculation methodof the maximum crack width was proposed,in which strain of steel bars from flexuralcalculation was replaced by that calculated in the three-hinge arch system, and coefficientswere modified which reflecting the influence from bond strengths between reinforcement andconcrete, and from concrete deformation between cracks on crack widths. Further more,ultimate bearing capacity in normal section was deduced with depth of concrete compressivezone calculated in the three-hinge arch system. Development path of the oblique crack wassupposed, and ultimate bearing capacity in oblique section was derived with depth ofcompressive zone of remanent concrete in oblique section. The limit load was the smallerultimate bearing capacity. Design methods of concrete slab strips reinforced with GFRP barswere induced into the design of a global bridge deck slab reinforced with GFRP bars,combining the present research results of design method of concrete bridge deck slab withsteel reinforcement. The predictions by the proposed methods were validated by test resultswith a good collection.

关 键 词： 混凝土板 挠度 裂缝宽度 极限承载力 筋 拱效应

分 类 号： [U443.31]

领　　域： [建筑科学] [交通运输工程]