基于已有试验结果和理论公式预测加固钢筋混凝土箱梁碳纤维布剪力贡献

对于纤维布抗剪加固矩形梁和T形梁,中外学者已进行了大量的试验和理论研究,并且提出纤维布剪力贡献计算公式,部分公式被不同国家的规范收录。但对于加固钢筋混凝土箱形截面梁的纤维布剪力贡献计算鲜有文献记录,因此本研究在已有试验和理论公式的基础上预测箱形截面纤维布剪力贡献计算。本文讨论了5种不同规范计算纤维布剪力贡献公式,同时收集了现有文献的181片纤维布抗剪加固矩形梁和T形梁试验结果,通过采用5种计算公式计算181片梁的纤维布剪力贡献值与试验结果对比,发现所有计算公式均有不同程度的离散,但fib Bulletin 14能较准确地计算矩形梁和T形梁的纤维布剪力贡献。此外,同样收集已有文献中的碳纤维布加固钢筋混凝土箱梁试验结果,采用已讨论的5种计算公式计算剪力,与试验结果相比,其计算值均大于试验值,研究发现规范中的计算公式都高估了纤维布的有效应变,而fib Bulletin 14的计算结果接近于试验值。因此,通过纤维布有效应变的试验值和fib Bulletin 14计算值的比较,引入有效应变修正系数1.31,计算出加固箱形梁纤维布剪力贡献值,与试验值能够较好地吻合。     

箱型简支梁在荷载作用下剪力滞效应研究

近些年,箱型梁在大跨度桥梁建设中得到了广泛的应用。箱型梁的结构决定了其在承受荷载时必然存在着剪力滞效应,这使得箱型梁有出现局部开裂的可能,为进一步明确剪力滞效应对简支箱梁的影响,本文针对箱型梁存在的剪力滞效应,以箱型梁单箱单室的截面形式制作有机玻璃模型,进行荷载实验,探究了不同荷载工况下梁剪力滞效应的变化规律,为实际工程中简支箱梁的设计提供参考。     

U型梁的剪力滞效应分析

以上海某轨道交通线延伸段U型梁1∶1静载试验为背景,借助Ansys有限元软件建立实体分析模型,并与实验所得数据对比,验证有限元模型的正确性。U型梁剪力滞效应的理论分析方法过于复杂和粗糙,为此利用有限元实体模型,分析U型梁段在跨中弯矩最大和近支座剪力最大两种车辆布置工况下,U型梁1/4跨、1/2跨和3/4跨的剪力滞效应。根据计算分析结果,提出了合理的修正方案。     

夹层复合材料的弯曲理论分析与计算方法研究

对夹层梁弯曲理论进行了深入研究,并用解析的方法计算了夹层梁的弯曲应力和挠度。在高阶夹层梁理论假设的基础上,假设夹芯只存在剪切变形,根据经典的梁弯曲理论,通过对夹层梁微元的受力分析,确定各层、层间的内力分布和各层间的变形协调关系,从而求出夹层梁各层的正应力、层间剪应力和弯曲挠度的解析表达式。最后,用三维有限元计算结果验证了解析算法结果的准确性。研究结果表明,此方法计算公式简单且精度较高。     

内埋碳纤维砂浆调节混凝土梁承载能力的试验研究

基于碳纤维水泥基材料的电热效应,通过内埋碳纤维砂浆块对普通混凝土梁进行变形调节,获得了相应的温度-变形规律.在此基础上实施了对混凝土梁预加反向变形,使混凝土梁内部产生预应力,从而提高了混凝土梁达到相同挠度时的承载能力.     

粘贴CFRP板加固钢筋混凝土梁的长期变形性能试验研究与数值模拟

为了研究实际工程中粘贴CFRP板加固钢筋混凝土梁的长期变形性能,从而为加固梁在长期使用过程中是否满足结构的正常使用极限状态提供判断依据,并解决长期试验操作难度大、时间跨度长的问题,进行了粘贴CFRP板加固钢筋混凝土梁的加固以及粘贴CFRP板加固钢筋混凝土梁在持续荷载作用下的长期变形试验,建立了用于计算粘贴CFRP板加固钢筋混凝土梁的长期变形的非线性有限元模型。数值计算结果与试验结果吻合较好。利用该模型对粘贴不同厚度CFRP板的加固梁的长期变形进行了数值计算,结果表明CFRP板对加固梁的长期变形的影响不明显,其总变形的减小主要来源于CFRP板对瞬时变形的约束。     

水泥净浆梁通电时的变形效应

研究了水泥净浆梁在通电时的变形效应,即电力效应.研究表明:在水泥净浆梁厚度方向通电时梁上下表面出现温度差.接电源正极的表面温度总高于接电源负极的表面.由于温度差的存在,梁朝向温度高的一面(即接电源正极的一面)变形;电力效应是电致温度差和水泥孔隙中电解质溶液产生电渗的共同结果.在水泥净浆中加入氯化钠电力效应会更明显.     

梁变形特殊求解方法综述

梁是保证楼板的作用力传递给柱的重要组成部分。梁承受荷载的形式主要有受压,受剪,受弯,受扭。这些形式的荷载使得梁发生不同程度的变形。对梁变形的研究是一个热点问题,目前梁变形求解的方法主要有积分法和叠加法,这两种方法在实际工程中得到了广泛的应用。然而,对于多荷载作用的简单梁,多跨梁及超静定梁,积分计算过程十分繁琐,叠加法虽然可以弥补积分计算的不足,但是叠加法需要借助大量的记忆。本文主要从梁变形理论分析,算例研究两个方面入手,综述各种关于梁变形的特殊求解方法,最后基于快速发展的有限元法提出了梁变形特殊求解方法的展望,以期对进一步的研究工作提供参考。     

正交对称层合悬臂板计入横向剪应变的弯曲弹性解

本文提出了正交对称层板悬壁位移和应力法计入横尖变时的计算方法，从自由边边界条件和自由廨点条件导出了虚结点位移表达式。计算了（０／９０）。层合悬臂板的挠度和应力，计算了固支边上的剪力和弯矩，且验证了它们能十分精确地满足权作为整体的平衡条件。     

钢筋混凝土梁中碱-硅反应的控制

介绍国外用F级低钙粉煤灰控制钢筋混凝土梁结构变形的试验数据。试验数据表明 ,粉煤灰具有控制砼梁变形和防止由碱 硅反应引起的强度损失双重作用     

Effect of shear deformation on interfacial stresses in plated beams subjected to arbitrary loading

Bonding a fibre reinforced polymer (FRP) composite or metallic plate to the soffit of a reinforced concrete (RC), timber or metallic beam can significantly increase its strength and other aspects of structural performance. These hybrid beams are often found to fail due to premature debonding of the plate from the original beam in a brittle manner. This has led to the development of many analytical solutions over the last two decades to quantify the interfacial shear and normal stresses between the adherends. The adherends are subjected to axial, bending and shear deformations. However, most analytical solutions have neglected the influence of shear deformation of the adherends. For the few solutions which consider this effect in an approximate manner, their applicability is limited to one or two specific load cases. This paper presents a general analytical solution for the interfacial stresses in plated beams under an arbitrary loading with the shear deformation of the adherends duly considered. The shear stress distribution is assumed to be parabolic through the depth of the adherends in predicting the interfacial shear stress and Timoshenko's beam theory is adopted in predicting interfacial normal stress to account for the shear deformation. The solution is applicable to a beam of arbitrary prismatic cross-section bonded symmetrically or asymmetrically with a thin or thick plate, both having linear elastic material properties. The effect of shear deformation is illustrated through an example beam. The influence of material and geometric parameters of the adherends and adhesive on the interfacial stress concentrations at the plate end is discussed.     

Theoretical and finite element studies of interfacial stresses in reinforced concrete beams strengthened by externally FRP laminates plate

The paper presents the results of an analytical and numerical solution for interfacial stresses in carbon fiber reinforced plastic (CFRP)–reinforced concrete (RC) hybrid beams studied by the finite element method. The analytical analysis is based on the deformation compatibility approach where both the shear and normal stresses are assumed to be invariant across the adhesive layer thickness. The adherend shear deformations are taken into account by assuming a parabolic shear stress through the thickness of both the concrete beam and the bonded plate. In numerical analysis, the mesh sensitivity test shows that the finite element results for interfacial stresses are not sensitive to the finite element mesh. The finite element analysis then is used to calculate the interfacial stress distribution and evaluate the effect of the structural parameters on the interfacial behavior. It is shown that both the normal and shear stresses at the interface are influenced by the material and geometry parameters of the composite beam. Numerical results from the present analysis are presented both to demonstrate the advantages of the present solution over existing ones and to illustrate the main characteristics of interfacial stress distributions. We can conclude that this research is helpful for the understanding the mechanical behavior of the interface and design of the FRP–RC hybrid structures.     

Interfacial stresses in FRP-plated RC beams: Effect of adherend shear deformations

A recently popular method for retrofitting reinforced concrete (RC) beams is to bond fibre reinforced polymer (FRP) plates to their tensile faces. An important failure mode of such plated beams is the debonding of the FRP plates from the concrete due to high level of stress concentration in the adhesive at the ends of the FRP plate. This paper presents an improved solution for interfacial stresses in a concrete beam bonded with the FRP plate by including the effect of the adherend shear deformations. The analysis is based on the deformation compatibility approach where both the shear and normal stresses are assumed to be invariant across the adhesive layer thickness. In the present theoretical analysis, the adherend shear deformations are taken into account by assuming a parabolic shear stress through the thickness of both the concrete beam and the bonded plate. Numerical results from the present analysis are presented both to demonstrate the advantages of the present solution over existing ones and to illustrate the main characteristics of interfacial stress distributions.     

含分层损伤复合材料组合层合梁的屈曲性态

本文基于Ｍｉｎｄｌｉｎ假定推导了考虑剪切的组合层合梁的有限元列式,并在此基础上计算出含分层损伤的各种层合梁在受轴向压力情况下的屈曲模式。从中得出梁的屈曲性态与铺设角,梁的几何形状,分层位置及分层大小等因素的关系,所得结论具有普遍意义。     

外贴预应力玻璃钢板加固混凝土梁试验研究

本文针对外贴复合材料加固混凝土梁存在的不足,将玻璃纤维材料(GFRP)先施加预应力,再将其外贴到混凝土梁受拉面以提高混凝土梁的承载能力.针对GFRP板横向抗剪切挤压强度低的缺点,研究对GFRP板的预应力施加方法,在此基础上完成了9根不同预应力度,不同混凝土强度等级混凝土梁的抗弯试验;同时完成了4根预应力GFRP板在梁侧立面不同粘贴方式抗剪试验研究.试验结果表明,外贴预应力GFRP板加固混凝土梁可大幅度提高混凝土梁的开裂弯矩、极限承载力及GFRP板的强度利用率,改善梁的裂缝开展情况及提高梁的抗变形能力.     

A Theoretical Improved Adhesively Bonded Bi-material Beam Model for FRP–RC Hybrid Beams

In this paper we present an improved bi-material beam theory with adhesive interface, which has been applied to the study of the interfacial behavior in a concrete beam reinforced by an externally bonded fibre reinforced polymer (FRP) plate. The work explicitly considers the interfacial slip effect on the structural performance by including the effect of adherend shear deformations. This new method needs only one differential equation to determine both shear and normal interfacial stress whereas the others solutions in the literature need two differential equations. Compared with previously published analytical results, this one improves the accuracy of predicting the interfacial stresses and the solution is in a closed form. This research is helpful in the understanding of the mechanical behavior of the interface and design of FRP–reinforced concrete (RC) hybrid beams.     

芳纶纤维加固钢筋混凝土梁界面粘结应力分析

本文根据弹性梁理论和部分组合截面假定,并且考虑了钢筋混凝土梁和芳纶纤维剪切变形的影响,对两点集中加裁情况下的芳纶纤维加固钢筋混凝土梁的界面粘结剪应力和正应力进行了推导分析,由纤维端部边界条件得出了两种应力的解析解,根据试验梁的基本参数绘出了界面应力的分布曲线,找到了界面应力的分布规律,由此提出了降低纤维布端部应力集中的方法,可供施工参考使用.     

Repair technique of pre-cracked reinforced concrete (RC) beams with transverse openings strengthened with steel plate under sustained load

This paper presents a repairing technique of the steel plate that effectively strengthen RC members, control both the failure modes and the stress distribution around the beam chords and enhance the serviceability of pre-cracked RC beams with openings. Furthermore, to evaluate the usage of a temporary pre-stressed force that was applied on the RC beam so as to close all of the presence shear cracks before the steel plate application. Two un-strengthened control beams, five beams that were pre-cracked before the application of the steel plate, and one beam that was strengthened without pre-cracking were tested. Cracking was first induced, followed by repair using various strengthening technique, and then the beams were tested to failure. The advantages of the shear strengthening of RC beams that were obtained using this technique are based on the closing of all the existing cracks around the openings via epoxy injection. The results show that both the pre-existing damage level and the steel plate strengthening have a significant effect on strengthening effectiveness and failure mode at the ultimate strength. An analytical equation for predicting the shear strength of pre-damaged RC beams with circular openings was then proposed, and the obtained results later compared with those from the tests, results were in accordance.     

FRP增强胶合木梁弯曲变形的解析分析

在胶合木梁的受拉区设置纤维增强复合材料(FRP)是提高胶合木(glulam)梁结构性能的有效方法。通过力学模型分析,给出了FRP glulam简支梁变形的解析解。根据相关的力学机理并结合试验数据,对解析解进行了修正;修正系数是通过对某些参数进行回归分析得到的,将其与已有的试验结果进行对比,证实了模型具有较高精度,可以很好地模拟梁的全过程变形与刚度变化。此外,模型还广泛适用于多种常见简支梁的变形分析或刚度分析。