钢丝网复合砂浆加固混凝土受弯构件非线性分析

对用钢丝网复合砂浆加固的钢筋混凝土梁进行了正截面抗弯试验研究.试验包括16根用钢丝网加固的梁和两根未加固的对比梁,采用U形三面的加固方式(钢丝网复合砂浆包裹了梁的受拉面及两个侧面).试验中对比了加固与未加固构件的裂缝开展情况、跨中挠度以及极限荷载.试验结果表明,钢丝网复合砂浆薄层可以明显地提高钢筋混凝土梁的抗弯承载力,提高抗裂性能,增强构件的抗弯刚度.理论部分采用非线性的方法得到加固构件的荷载-挠度曲线,与试验结果比较,有较好的吻合.     

二次受力下自密实混凝土加固RC梁受弯性能研究

为模拟实际工程中加固构件的真实承载能力,实验在原混凝土构件持续受荷状态下,采用自密实混凝土对构件进行加固、养护。共进行了7根二次受力下自密实混凝土加固钢筋混凝土梁和2根对比梁的受弯性能试验,研究了不同初始受力水平、不同加固厚度及不同界面处理方式对加固钢筋混凝土梁抗弯承载力和截面刚度的影响。试验量测了构件裂缝分布形态、荷载-挠度曲线、钢筋应变发展规律等。结果表明：采用自密实混凝土加固钢筋混凝土梁,能有效地提高钢筋混凝土梁的抗弯承载力、截面刚度等性能;二次受力下自密实混凝土加固梁抗弯承载力随着初始受力水平的增大而降低。在试验结果的基础上,基于平截面假定,提出了二次受力下自密实混凝土加固梁钢筋滞后应变及抗弯承载力计算式,计算结果与试验结果吻合良好。     

高强钢绞线网--聚合物砂浆加固混凝土及预应力混凝土梁的抗弯性能试验研究

该文侧重研究了采用高强钢绞线网--聚合物砂浆加固技术三面加固普通钢筋混凝土(RC)梁和预应力混凝土(PRC)梁的抗弯性能.进行了6 片RC 梁及5 片PRC 梁的抗弯静载试验,探讨了不同初始损伤程度、有效预应力大小和加载方式等对高强钢绞线网--渗透性聚合物砂浆加固梁的抗弯性能影响.结果表明：采用高强钢绞线网--聚合物砂浆加固技术加固RC/PRC梁能够有效抑制裂缝的开展,能有效地提高RC/PRC 加固梁的抗弯承载能力和抗弯刚度;重复加载会导致加固梁刚度一定程度的退化,初始损伤程度大小不会显著改变加固后RC/PRC梁的抗弯承载力;该文研究对于大量既有RC/PRC梁的抗弯加固具有一定的参考价值.     

钢筋钢丝网砂浆加固混凝土柱的抗震性能试验研究

为更有效提高抗震加固效率, 提出采用钢筋钢丝网砂浆加固混凝土柱的思路。制作钢筋钢丝网砂浆加 固、钢筋网砂浆加固和未加固钢筋混凝土方柱三类共9个试件, 进行各柱在竖向恒定轴力和水平向低周反复加载作用下的抗震性能对比试验研究, 测试了各柱的抗震承载力、延性、破坏形态及其滞回特性, 讨论了配箍率、加固形式和轴压比对构件抗震性能的影响。结果表明：相对钢筋网加固柱, 钢筋钢丝网加固柱的耗能能力有大幅度的提高。     

加固层厚度对PVA-RFCC加固梁弯曲性能的影响

为了提高加固构件的抗裂性能和极限承载力,提出一种聚乙烯醇纤维增强钢丝网水泥基复合(PVA-RFCC)新型加固材料,是由钢筋网和钢丝网作为增强材料,聚乙烯醇纤维水泥基复合材料(PVA-ECC)作为基体构成.设计7根加固梁和1根对比梁进行四点弯试验,重点探讨了加固层(CRL)厚度对加固梁抗弯性能的影响.同时,对最佳CRL厚度计算表达式进行推导.结果得出:当CRL仅为PVA-ECC或仅含钢丝网(SM)时,试验梁弯曲性能随着CRL厚度增大而降低;当CRL中包含钢筋网(RM)或SM-RM时,试验梁弯曲性能随着CRL厚度的增大而增强.CRL厚度与极限荷载呈二次函数关系,SM-RM是最优加固方式,SM主要提高试验梁延性,RM主要提高试验梁的承载力和刚度.结合试验和理论计算结果,得出CRL为PVA-ECC或仅含SM时,试验梁的最佳CRL厚度为40 mm;仅加RM或SM-RM时,最佳CRL厚度为60 mm.     

复合砂浆钢筋网加固抗弯RC梁的非线性分析

复合砂浆钢筋网薄层加固是一种有效的加固方法,能够显著地提高钢筋混凝土梁的抗弯承载力、变形能力以及抗裂性能。以8根复合砂浆钢筋网加固RC梁的试验研究结果为参考,通过非线性有限元分析广泛地研究了加固梁纵向配筋率、配箍特征值、梁高宽比对极限荷载提高幅度的影响,并初步分析了少筋梁和超筋梁加固后的荷载-跨中挠度曲线的变化规律。根据分析和试验结果,通过等效假定给出了复合砂浆钢筋网加固RC梁的极限承载力计算公式和抗弯刚度计算公式。     

钢绞线(丝)网-聚合砂浆加固钢筋混凝土梁受弯性能研究

钢绞线(丝)网-聚合砂浆加固技术是一项新型加固工艺,具有耐火、耐腐蚀、耐老化、施工速度快等优点,已被逐渐应用于钢筋混凝土结构的加固补强中。采用该技术抗弯加固钢筋混凝土梁的受力性能可分为三个阶段：未裂阶段、裂缝阶段和破坏阶段。已有研究多数集中于加固混凝土梁正常使用阶段的抗弯性能分析,对受力纵筋屈服后破坏阶段的抗弯性能分析则鲜有涉及。该文在以往试验研究的基础上,采用换算截面法计算加固钢筋混凝土梁屈服阶段和极限阶段的等效刚度,对加固梁在集中荷载作用下抗弯性能全过程进行受力分析,并通过10根加固梁的试验数据对其验证,吻合良好。     

钢筋钢丝网砂浆加固混凝土圆柱的抗轴压性能

为大幅度提高加固效率,提出用钢筋钢丝网砂浆加固混凝土圆柱的思路。分别用钢筋钢丝网(SW)、钢筋网(S)、单一纤维复合材料(FRP)和混杂纤维复合材料(HFRP)加固混凝土圆柱共36根,进行轴压对比试验,探讨不同加固方法对试件承载能力和延性的影响。结果显示:SW加固柱保护层砂浆剥落与内部核心混凝土破坏几乎同时发生;且保护层砂浆裂缝间距基本与钢丝网格间距相等(11mm左右),因而裂缝又多又密;故SW加固柱与S加固柱相比,在承载力提高30%的前提下,延性仍达S加固柱的2倍左右。FRP或HFRP加固柱的承载力提高幅度最大,但两种加固柱的延性和变形能力明显低于SW加固柱。该文给出了SW加固混凝土圆柱的极限承载力计算公式。     

水泥砂浆加固RC梁的抗冲击性能模拟分析

为研究高强钢绞线网-聚合物改性水泥砂浆(简称聚合物砂浆)加固钢筋混凝土梁的抗冲击性能,在3根未加固梁和4根加固梁的落锤冲击试验的基础上,采用显式有限元分析软件ANSYS/LS-DYNA,建立了包括混凝土梁、冲击锤头在内的有限元模型,对在冲击荷载作用下加固前、后混凝土梁的抗冲击性能进行了数值分析。之后,对采用不同直径钢绞线和不同厚度聚合物砂浆加固层的钢筋混凝土加固梁进行了参数分析。研究结果表明:高强钢绞线网-聚合物砂浆加固能显著提高钢筋混凝土梁的抗冲击性能;合理增加砂浆加固层厚度有利于改善梁身裂缝和破坏模式;选用恰当直径的钢绞线加固钢筋混凝土梁有助于钢绞线承载能力的发挥;工程实际中,需合理考虑砂浆层厚度和钢绞线直径对加固效果的影响。     

碳纤维布加固已承受荷载的钢筋混凝土梁抗弯性能试验研究及抗弯承载力计算

进行了6根碳纤维布加固已承受荷载的钢筋混凝土梁和2根对比混凝土梁的抗弯性能试验研究,分析了碳纤维布加固已承受荷载的钢筋混凝土梁的破坏机理,研究了荷载历史对加固梁极限荷载的影响.试验结果表明,粘贴碳纤维布可以有效地提高加固梁的抗弯承载能力.无论荷载历史如何,只要梁承受的初始荷载相同,梁破坏时的极限荷载基本相同.梁端锚固对加固梁的极限荷载影响不明显.根据不同的破坏模式,提出了碳纤维布加固已承受荷载的钢筋混凝土梁的承载力计算方法,给出了工程实用计算公式.     

锚贴钢板加固RC锈蚀梁承载力计算方法与试验研究

基于桁架理论模型,定量考虑锈蚀钢筋力学性能、加固钢板厚度、粘胶层粘结强度、保护层厚度对承载力的影响,建立了RC梁锈蚀锚贴加固后极限承载力的计算公式。通过对9片锚贴钢板加固锈蚀梁、3片锈蚀梁以及3片不锈蚀加固梁的试验研究,验证了理论模型的正确性。试验研究和公式计算表明在锈蚀率接近和保护层厚度相同的情况下,钢板厚度每提高1mm,承载力大小提高15kN~20kN,在锈蚀率大小不同的情况下,锈蚀率增加2%~3%,承载力降低大约10kN。     

预应力钢绞线网加固钢筋混凝土柱恢复力模型研究

基于16根采用新型预应力钢绞线网张拉锚固技术加固的钢筋混凝土柱和2根对比柱在反复荷载作用下的试验结果, 进行了恢复力模型研究。结合之前相关试验研究, 确定出材料的本构关系, 建立了预应力高强钢绞线网约束加固钢筋混凝土的应力-应变关系方程;考虑构件轴力的二次矩效应, 提出了在反复荷载下预应力加固钢筋混凝土柱骨架曲线的计算方法, 建立了相应理论模型;结合Clough滞回规则, 建立了相应的恢复力模型。研究表明：对试验的材料本构关系适当简化, 通过合理的假定, 由基本的内外力平衡方程和简单的滞回规则, 可得到构件从加载到破坏全过程与试验吻合良好的骨架曲线和滞回曲线, 由此建立的恢复力模型简单、适用, 可为预应力高强钢绞线网加固钢筋混凝土柱设计和施工提供参考。     

Effective strain of RC beams strengthened in shear with FRP

The failure modes of Reinforced Concrete (RC) beams strengthened in shear with Fiber Reinforced Polymer (FRP) sheets or strips are not well understood as much as those of RC beams reinforced with steel stirrups. When the beams are strengthened in shear with FRP composites, beams may fail due to crushing of the concrete before the FRP reaches its rupture strain. Therefore, the effective strain of the FRP plays an important role in predicting the shear strength of such beams. This paper presents the results of an analytical and experimental study on the performance of reinforced concrete beams strengthened in shear with FRP composites and internally reinforced with conventional steel stirrups. Ten RC beams strengthened with varying FRP reinforcement ratio, the type of fiber material (carbon or glass) and configuration (continuous sheets or strips) were tested. Comparisons between the observed and calculated effective strains of the FRP in the tested beams failing in shear showed reasonable agreement.     

Reliability and adaptability of the analytical models proposed for the FRP systems to the Steel Reinforced Polymer and Steel Reinforced Grout strengthening systems

The paper presents a theoretical prediction of the structural behavior of reinforced concrete (RC) beams externally strengthened to flexure by using a unidirectional ultra-high tensile strength steel (UHTSS) reinforcing mesh embedded in an inorganic matrix (Steel Reinforced Grout, SRG) or in an organic matrix (Steel Reinforced Polymer, SRP).For these innovative composite materials are not yet available in literature specific standard documents, guidelines or analytical models capable to predict the structural behavior of the strengthened elements. Therefore, in order to evaluate the flexural strength of the strengthened beams some analytical models to predict the maximum axial strain developed in Fiber Reinforced Polymer (FRP) systems at the onset of intermediate debonding failure, have been used.The goal is to assess the effectiveness of current analytical models used, up to day, to FRP strengthening systems to the SRG and SRP strengthening systems. For this aim, a database of experimental results on RC beams strengthened in bending by bonded SRG and SRP systems has been collected.The comparisons between the theoretical predictions and the experimental data, in terms of debonding strain values, load carrying capacity, load-midspan deflection curves, have highlighted the reliability and adaptability of the current analytical models.Finally, in order to evaluate the effectiveness of the SRG and SRP systems for strengthening RC beams a parametric study was also carried out.     

Performance of reinforced concrete beams strengthened by hybrid FRP laminates

In the last two decades, the use of advanced composite materials such as Fiber Reinforced Polymers (FRP) in strengthening reinforced concrete (RC) structural elements has been increasing. Research and design guidelines concluded that externally bonded FRP could increase the capacity of RC elements efficiently. However, the linear stress–strain characteristics of FRP up to failure and lack of yield plateau have a negative impact on the overall ductility of the strengthened RC elements. Use of hybrid FRP laminates, which consist of a combination of either carbon and glass fibers, or glass and aramid fibers, changes the behaviour of the material to a non-linear behaviour. This paper aims to study the performance of reinforced concrete beams strengthened by hybrid FRP laminates.

This paper presents an experimental program conducted to study the behaviour of RC beams strengthened with hybrid fiber reinforced polymer (HFRP) laminates. The program consists of a total of twelve T-beams with overall dimensions equal to 460 × 300 × 3250 mm. The beams were tested under cyclic loading up to failure to examine its flexural behaviour. Different reinforcement ratios, fiber directions, locations and combinations of carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP) laminates were attached to the beams to determine the best strengthening scheme. Different percentages of steel reinforcement were also used. An analytical model based on the stress–strain characteristics of concrete, steel and FRP was adopted. Recommendations and design guidelines of RC beams strengthened by FRP and HFRP laminates are introduced.     

高强钢丝绳网片-聚合物砂浆加固RC板抗爆性能试验研究

为了研究高强钢丝绳网片-聚合物砂浆对钢筋混凝土(RC)板的抗爆加固效果,对5块加固RC板和1块未加固RC板进行了野外现场爆炸试验,研究了砂浆强度、钢丝绳间距、钢丝绳预应力和界面增设销钉等因素对试件的破坏形态、裂缝分布及发展、跨中位移、钢筋应变等影响规律,并对爆炸试验后的试件进行了剩余承载力试验和爆炸损伤评估.研究表明:...