粘钢加固RC梁剥离的有限元分析

介绍粘钢加固梁的剥离分析方法,提出了外粘钢板加固受弯钢筋混凝土梁的非线性有限元模型,并用ANSYS软件对试验梁的剥离荷载进行了仿真分析,仿真结果与实验结果的一致性证明了所建有限元模型与提出的方法的正确性与适用性。     

钢筋混凝土梁粘钢加固承载力设计分析

通过对粘钢加固的破坏机理分析 ,分析了钢筋混凝土梁粘钢加固的计算方法。粘钢加固有粘钢板加固和粘型钢加固两种形式。粘钢板加固时 ,钢板的宽厚比、胶层厚度和锚固方式决定了加固梁的两种典型破坏模式 :弯曲破坏和钢板剥离破坏。粘型钢加固在梁高不受限制时 ,能大幅提高梁的极限承载力 ,粘胶和植筋能保证型钢和钢筋混凝土梁共同工作     

基于ABAQUS的粘钢加固混凝土梁的有限元分析

为深入探讨粘钢加固法对钢筋混凝土梁受力性能的因素,采用ABAQUS有限元软件对粘钢加固钢筋混凝土梁进行了非线性有限元数值模拟计算,通过建立8个分析模型,对比分析了加固钢板长度和钢板厚度对钢筋混凝土梁加固后的极限承载力和刚度的影响。结果表明:大于梁纯弯区长度的加固钢板能够显著提高加固后钢筋混凝土梁的极限承载能力,并有助于提升梁加固后的初始刚度及刚度退化率。在粘钢加固长度一定的情况下,适当增加钢板厚度,可以使加固后梁的极限承载力、刚度及其变化有所提升,为进一步探究粘钢加固钢筋混凝土梁的工程实践提供一定的参考。     

碳纤维布兜贴钢板抗弯加固钢筋混凝土梁探索性试验

提出了对钢筋混凝土梁先贴钢板再用混锚碳纤维布兜住的抗弯加固新方法,完成了3根不同方式加固梁的四点弯曲对比试验。探索性试验结果表明:与基准梁相比,各加固梁的极限荷载得到了不同程度的提升,兜贴加固法的提升幅度明显大于碳纤维布和钢板单独粘贴的效果之和;加固梁破坏模式均为剥离破坏,纯粘钢板加固梁的破坏脆性明显,兜贴加固有利于防治钢板剥离,改善破坏延性。     

基于ABAQUS的钢板混凝土板平面外弯剪性能的非线性有限元分析

以钢板混凝土板的平面外弯剪性能试验研究为基础,采用有限元软件ABAQUS建立了钢板混凝土板的非线性有限元模型,模拟弯剪破坏、剪切破坏、钢板剥离破坏3种破坏形态下构件的受力性能。模型考虑了材料的非线性、钢板与混凝土的接触和栓钉的滑移模型,计算结果与试验结果吻合良好。利用有限元模型,对影响钢板混凝土板面外受力性能的主要参数进行了分析,包括栓钉间距、钢板厚度。结合试验现象和有限元分析结果,指出了钢板混凝土板面外受力性能随参数变化的原因,并提出了在一定情况下不同破坏形态之间转化的参数临界值。结果表明:可以通过对栓钉间距与钢板厚度的控制来使得钢板屈服,从而保证无抗剪钢筋的钢板混凝土板在平面外可以达到弯剪破坏形式。     

钢筋混凝土T梁HB-FRP抗剪加固试验和数值模拟

基于室内模型试验,开展了混合黏结纤维增强复合材料(HB-FRP)抗剪加固钢筋混凝土T梁的受力性能研究.对未加固、外贴纤维增强复合材料(EB-FRP)加固及HB-FRP加固T梁进行了破坏性对比试验,并采用Abaqus软件建立了精细化有限元模型,对比分析了试验和数值计算结果,验证了有限元模型的准确性;在此基础上进行参数分析,研究了混凝土强度、箍筋间距、FRP条带数量及FRP厚度对加固梁抗剪承载能力的影响.结果 显示:HB-FRP抗剪加固梁的剪切裂缝间距要小于EB-FRP加固梁的裂缝间距;EB-FRP加固梁发生黏贴区域大面积剥离,而HB-FRP加固梁仅在相邻钢扣件间有裂缝的区域出现了剥离,钢扣件有效抑制了裂缝剥离扩展;HB-FRP抗剪加固梁的FRP应变水平为EB-FRP抗剪加固梁的2倍,表现出了较好的延性.综合考虑未加固梁、EB-FRP加固梁及HB-FRP加固梁的参数分析结果,对钢筋混凝土T梁抗剪承载能力的影响因素按照重要性降序为:混凝土强度、箍筋间距、FRP间距、FRP厚度.     

胶层厚度对梁底粘钢加固的剥离影响仿真研究

为研究粘钢法加固胶层厚度对钢板剥离的影响,本文针对梁底粘钢板加固混凝土梁正截面,建立了同一钢筋混凝土梁用不同胶层厚度粘贴相同钢板的有限元模型,进行了仿真分析。通过对胶层和混凝土粘贴界面的应力场分析,发现胶层厚度对胶层端部的应力集中有影响,对界面胶层中间区域应力无影响,说明胶层厚度对钢板的端部剥离有一定的影响。     

锚焊U形钢板加固钢筋混凝土梁的抗弯性能研究

设计了3根锚焊U形钢板加固的混凝土梁试件,并进行了四点弯曲加载试验,获得试件的破坏形态、荷载-挠度曲线、钢板和混凝土界面滑移情况以及各材料在加载过程中的应变发展情况,分析了加固梁的受力模式.采用有限元软件ABAQUS分析配筋率、抗剪螺栓间距、抗屈曲螺栓数量和钢板厚度对加固梁性能的影响特征和变化规律.试验结果表明,锚焊U形钢板加固混凝土梁的破坏模式属于延性的弯曲破坏,且整体性良好.有限元分析结果表明,配筋率越高的构件,加固效果越差;增加翼缘抗剪螺栓间距、梁底抗剪螺栓间距和腹板抗屈曲螺栓数量可以限制钢板的滑移和屈曲失稳,一定范围内能增加梁的极限承载力;加固钢板越厚,加固梁的刚度和承载力越大,并且钢板厚度的不同对梁的屈服变形和极限变形均有一定的影响.     

锚杆锚固钢板法加固钢筋混凝土梁的试验研究

试验研究了锚杆锚固钢板法加固钢筋混凝土梁的抗弯力学性能,以及不同的锚杆布置方式对梁破坏形式的影响,并与外粘钢板加固钢筋混凝土梁进行了比较。试验结果表明:适量的锚杆可以保证外加钢板与混凝土梁的联合工作直至破坏,从而明显提高梁的抗弯承载力和抗弯刚度,达到与外粘钢板加固混凝土梁相当的加固效果。     

粘钢加固钢筋混凝土梁斜截面承载能力的试验研究

通过10根外部粘钢加固钢筋混凝土梁的斜截面抗剪试验,研究了外贴U型钢板、梁侧竖直钢板、梁侧斜钢板和梁侧钢丝网对梁的加固效果.试验结果表明:梁侧钢板角度对粘钢加固效果有明显的影响,采用45°斜向粘钢效果最好;由于锚固长度较短,易产生锚固破坏,应用时必须采取可靠的附加锚固措施;外部粘贴钢丝网无论是对提高抗裂能力还是承载能力都有明显的效果.通过理论分析,提出了粘钢加固梁斜截面的抗剪计算公式,与试验值吻合较好.     

Numerical simulation of steel-plate strengthened concrete beam by a non-linear finite element method model

Strengthening with epoxy bonded steel plate is one of the most widely used techniques for flexural upgrading of reinforced concrete (RC) beams. However, debonding failure at the plate cut-off zone and or in the vicinity of flexure and shear cracks leads to catastrophic failure of the upgraded beams. This particular failure depends on several factors such as the distance of plate curtailment from the support, plate thickness and the provision of end anchors. Since the conventional beam theory cannot predict the debonding failure of such beams, a finite element model capable of predicting the overall behavior of strengthened beams including different failure modes accurately is developed. This paper presents the formulation of finite elements and material models and simulation results of some RC beams tested for flexural strengthening with epoxy bonded steel plates.     

碳纤维布加固RC梁试验研究及有限元分析

通过试验分析了布厚度、箍筋强度和布端到支座距离等因素对CFRP布底板加固RC梁布端剥离破坏的影响，并应用ANSYS软件进行有限元分析。分析比较试验结果和有限元模拟结果表明，计算所采用的有限元模型及必要的简化方法是合理的。     

Finite element modelling of concrete cover separation failure in FRP plated RC beams

The technique of bonding fibre reinforced polymer (FRP) composites to the tension face or sides of reinforced concrete (RC) beams has become very popular for strengthening or retrofitting purposes. A distinct characteristic of such strengthened RC beams is that they very often fail due to various premature debonding failures. This paper presents a fracture mechanics based finite element analysis of debonding failures. Numerical results for an experimental beam are presented. Initial findings show that the method can successfully simulate the concrete cover separation failure mode in FRP strengthened RC beams.     

铝合金筋加固混凝土梁界面黏结性能与剥离承载力研究

通过试验研究与有限元模拟计算,分析了铝合金筋嵌入式加固混凝土梁的破坏模式和承载能力,对比了不同的剥离承载力计算模型,获得了铝合金筋应力和应变以及界面黏结应力沿梁跨度方向的分布曲线,推导出界面黏结-滑移关系和剥离承载力计算公式。结果表明:铝合金筋加固混凝土梁界面剥离破坏模式分为界面剥离破坏和混凝土保护层剥离破坏,混凝土梁加固后,抗弯性能和变形性能均得到改善; 界面剥离破坏是由跨中弯曲裂缝引起的局部界面黏结失效,最终延伸至加固筋一端从而造成加固筋剥离; 混凝土保护层剥离破坏是由于加固筋端部应力集中,造成周围混凝土保护层发生剥离脱落; 沿着梁的跨中至梁端方向,铝合金筋的应力和应变逐渐降低,界面黏结应力先增大后减小且应力最大值随荷载的增加而增加; 铝合金-结构胶界面和结构胶-混凝土界面的黏结-滑移关系曲线可分为4个阶段,即弹性阶段、弹性软化阶段、弹性软化剥离阶段和软化剥离阶段; 建议的计算模型可以较准确地预测铝合金筋加固混凝土梁的剥离承载力。     

Shear strengthening of RC beams with web-bonded continuous steel plates

This paper presents the results of an experimental program and a parametric study conducted on RC beams strengthened in shear with web-bonded continuous steel plates. An experimental investigation was conducted to assess the effectiveness of web-bonded continuous steel plates for shear strengthening of RC beams having internal stirrups. A two-dimensional nonlinear finite element model was developed to simulate the overall behavior of beams with epoxy bonded steel plates. In order to develop a design methodology for beams with web-bonded steel plates, a parametric study was conducted. Main parameters considered were concrete strength, plate thickness, plate depth-to-beam depth ratio, yield strength of steel plates, beam size and the internal shear reinforcement ratio. A formula to compute the shear strength of such beams was proposed by adding up the concrete contribution, shear reinforcement contribution and the contribution of steel plates. The validity of proposed formula was checked against the results from parametric study and the experiments. It was found that the proposed formula predicts the ultimate shear strength of RC beams with web-bonded continuous steel plates very well.     

Evaluation of debonding failure of reinforced concrete girders strengthened in flexure with FRP laminates using finite element modeling

The use of Fiber-Reinforced Polymer (FRP) materials dates back to the early 1940s when they were used in aerospace and naval applications. During the 1970s and early 1980s, FRP started being used in civil engineering applications for new construction, but more importantly for repair and strengthening of existing structures. However, experimental research showed that the typical failure mode of reinforced concrete (RC) structures strengthened with FRP composite materials is due to the debonding that occurs at the interface between concrete and FRP. The bond between FRP and concrete is therefore the key factor controlling the behavior of these structures since it limits the full use of the FRP strength. The paper evaluates the effect of the debonding failure on the response of FRP-strengthened RC beams. A nonlinear RC beam element with bond-slip between the concrete and the FRP laminates is developed and used to analyze several test specimens and to investigate their corresponding failure mode. The model was also used to study the reduction factor of FRP tensile strength of simply supported strengthened RC girders due to debonding failure. This reduction factor proved to be affected by several parameters: (a) the bond strength between FRP and concrete interface; (b) the concrete strength; (c) the thickness of FRP; (d) the modulus of FRP; (e) the width of FRP laminate; and (f) the development length of the FRP sheet. A large number of beam specimens were analyzed in order to conduct a thorough evaluation of debonding failure of RC beams strengthened with FRP laminates. Based on these studies, new equations that account for the aforementioned parameters were proposed to address the reduction in FRP strength due to debonding failure.     

预载水平及剪/弯承载力比对剥离破坏的影响

通过碳纤维片材加固钢筋混凝土简支梁的受弯试验及文献中相关试验,研究了预载水平及剪/弯承载力比对纤维片材初始剥离荷载的影响。对本文试验及文献中发生剥离破坏的碳纤维片材加固钢筋混凝土梁的试验研究,分析结果表明:(1)随剪/弯承载力比的增大,加固梁纤维片材的初始剥离荷载也随之增大;但当剪/弯承载力比值较小,即受剪承载力富裕度较小的情况下,纤维片材可能会在低于设计极限承载力时发生剥离破坏;(2)加固时预载水平的大小对碳纤维片材加固钢筋混凝土梁的极限荷载和CFRP片材初始剥离时的荷载影响不大。因此加固设计时必须充分考虑加固构件的受剪承载力对剥离破坏的影响,以避免纤维剥离这一脆性破坏模式的发生。     

A simple and rational beam segment model for analyzing intermediate crack-induced debonding in FRP-strengthened beams

Intermediate crack (IC) induced debonding failure of fibre reinforced polymer (FRP) plate strengthened reinforced concrete (RC) beams is one of the common debonding modes, in which debonding initiates at a major flexural crack and then propagates toward a plate end. Finite element (FE) method has been used to analyze the IC debonding failure and a whole strengthened beam has been taken as a mechanical model in existed researches. In view of that it is difficult to appropriately simulate all the cracks in an entire strengthened beam and consequently to carry out a parameter study, a beam segment between two major adjacent flexural cracks in a flexural-shear zone of a strengthened beam was taken as a new simple mechanical model. The new simple “beam segment model” was validated to be rational by using Saint–Venant Principle and a numerical study. In the light of this, a parameter study was performed through a three dimensional nonlinear FE analysis of the proposed beam segment model. The influences of the load level, the bond-slip (δ–τ) relationship of FRP-to-concrete interface, and the geometry of the beam segment on the IC induced debonding were investigated. The numerical analysis shows that the influence of δ–τ relationship of FRP-to-concrete interface on debonding is fairly more significant than that of crack spacing of strengthened beams. Comparisons between analytical and experimental results show that the proposed beam segment model is appropriate for estimating the IC induced debonding.     

CFRP板加固钢筋混凝土梁的分离式有限元模型

利用有限元方法对用外粘碳纤维复合材料(CFRP)板加固的钢筋混凝土梁的受弯性能进行了分析。在分析中采用了分离式非线性有限元模型,在模型中考虑了钢筋与混凝土、CFRP板与混凝土的联结滑移对梁受弯性能的影响,并用试验验证了该模型的正确性。最后,用该模型对考虑二次受力时CFRP板加固梁受力机理进行了非线性有限元分析。