Parameters of static response of carbon fiber reinforced polymer(CFRP) suspension cables

The feasibility of longer spans relies on the successful implementation of new high-strength light weight materials such as carbon fiber reinforced polymer(CFRP). First, a dimensionless equilibrium equation and the corresponding compatibility equation are established to develop the cable force equation and cable displacement governing equation for suspension cables, respectively. Subsequently, the inextensible cable case is introduced. The formula of the Irvine parameter is considered and its physical interpretation as well as its relationship with the chord gravity stiffness is presented. The influences on the increment of cable force and displacement by λ2 and load ratio p′ are analyzed, respectively. Based on these assumptions and the analytical formulations, a 2000 m span suspension cable is utilized as an example to verify the proposed formulation and the responses of the relative increment of cable force and cable displacement under symmetrical and asymmetrical loads are studied and presented. In each case, the deflections resulting from elastic elongation or solely due to geometrical displacement are analyzed for the lower elastic modulus CFRP. Finally, in comparison with steel cables, the influences on the cable force equation and the governing displacement equation by span and rise span ratio are analyzed. Moreover, the influences on the static performance of suspension bridge by span and sag ratios are also analyzed. The substantive characteristics of the static performance of super span CFRP suspension bridges are clarified and the superiority and the characteristics of CFRP cable structure are demonstrated analytically.

Strengthening an in-service reinforcement concrete bridge with prestressed CFRP bars

Carbon fiber reinforced polymer (CFRP) bars were prestressed for the structural strengthening of 8 T-shaped rein-forced concrete (RC) beams of a 21-year-old bridge in China. The ultimate bearing capacity of the existing bridge after retrofit was discussed on the basis of concrete structures theory. The flexural strengths of RC beams strengthened with CFRP bars were controlled by the failure of concrete in compression and a prestressing method was applied in the retrofit. The field construction processes of strengthening with CFRP bars-including grouting cracks, cutting groove, grouting epoxy and embedding CFRP bars, surface treating, banding with the U-type CFRP sheets, releasing external prestressed steel tendons-were introduced in detail. In order to evaluate the effectiveness of this strengthening method, field tests using vehicles as live load were applied before and after the retrofit. The test results of deflection and concrete strain of the T-shaped beams with and without strengthening show that the capacity of the repaired bridge, including the bending strength and stiffness, is enhanced. The measurements of crack width also indicate that this strengthening method can enhance the durability of bridges. Therefore, the proposed strengthening technology is feasible and effective.

Rapid repair of severely earthquake-damaged bridge piers with flexural-shear failure mode

An experimental study was conducted to investigate the feasibility of a proposed rapid repair technique for severely earthquake-damaged bridge piers with flexural-shear failure mode. Six circular pier specimens were first tested to severe damage in flexural-shear mode and repaired using early-strength concrete with high-fluidity and carbon fiber reinforced polymers （CFRP）. After about four days, the repaired specimens were tested to failure again. The seismic behavior of the repaired specimens was evaluated and compared to the original specimens. Test results indicate that the proposed repair technique is highly effective. Both shear strength and lateral displacement of the repaired piers increased when compared to the original specimens, and the failure mechanism of the piers shifted from flexural-shear failure to ductile flexural failure. Finally, a simple design model based on the Seible formulation for post-earthquake repair design was compared to the experimental results. It is concluded that the design equation for bridge pier strengthening before an earthquake could be applicable to seismic repairs after an earthquake if the shear strength contribution of the spiral bars in the repaired piers is disregarded and 1.5 times more FRP sheets is provided.

Aerodynamic stability of cable-supported bridges using CFRP cables

To gain understanding of the applicability of carbon fiber reinforced polymer (CFRP) cable in cable-supported bridges, based on the Runyang Bridge and Jinsha Bridge, a suspension bridge using CFRP cables and a cable-stayed bridge using CFRP stay cables are designed, in which the cable’s cross-sectional area is determined by the principle of equivalent axial stiffness. Numerical investigations on the aerodynamic stability of the two bridges are conducted by 3D nonlinear aerodynamic stability analysis. The results showed that as CFRP cables are used in cable-supported bridges, for suspension bridge, its aerodynamic stability is superior to that of the case using steel cables due to the great increase of the torsional frequency; for cable-stayed bridge, its aerodynamic stability is basically the same as that of the case using steel stay cables. Therefore as far as the wind stability is considered, the use of CFRP cables in cable-supported bridges is feasible, and the cable’s cross-sectional area should be deter-mined by the principle of equivalent axial stiffness.

预应力CFRP布加固混凝土梁受弯试验

目的 研究不同加固方法下预应力碳纤维布加固混凝土梁的受弯性能,解决桥梁加固缺陷的问题。方法 制作了5根试验梁,其中一根为对比梁,不做任何加固处理,其余4根分别采用不同的锚固方式、不同的初始张拉力及不同的加固位置进行加固,通过控制变量,进行加载试验,分析其受弯性能的差异。结果 经加固后的试验梁承载能力与刚度明显增加,与对比梁相比,极限荷载分别提升了25%、22.06%、30.78%及36.76%;各试验梁达到屈服荷载时,经加固的试验梁挠度均小于对比梁产生的挠度,且模腔自锁式锚具锚固的试验梁挠度小于穿孔式自锁锚具锚固的试验梁挠度,相同锚固方法下初始张拉力较大的试验梁挠度要小于初始张拉力较小的试验梁挠度。结论 使用预应力碳纤维布加固混凝土梁能够有效提高混凝土梁的抗弯性能,提升效果与加固位置、锚固方式及初始张拉力大小有关。

A low-cost and high-strength basalt/carbon fiber reinforced polymer improved by imitating tree-root micro/nano aramid short fiber

The high-strength Basalt Carbon Fiber Reinforced Polymer(BCFRP)composites had been manufactured by guiding Imitating Tree-root Micro/Nano Aramid Short Fiber(ITMNASF)into the interlayer of Basalt Fiber(BF)and Carbon Fiber(CF)plies to form thin interleaving,and various mass proportions of IT-MNASF were designed to discuss the reinforcing effect on the BCFRP heterogeneous composites.The results of three points bending tests showed that flexural strength and energy absorption of 4wt%IT-MNASF reinforced BCFRP heterogeneous composites had been improved by 32.4%and 134.4%respectively compared with that of unreinforced specimens.The 4wt%IT-MNASF reinforced BCFRP specimens showed both a greater strength and a lower cost(reduced by 31%around)than that of plain CFRP composites.X-ray micro-computed tomography scanning results exhibited that the delamination-dominated failure of plain BCFRP composites was changed into multi-layer BF and CF fabrics damage.The reinforcing mechanism revealed that the introduced IT-MNASF could construct quasi-vertical fiber bridging,and it was used as"mechanical claws"to grasp adjacent fiber layers for creating a stronger mechanical interlocking,and this effectively improved resin-rich region and interfacial transition region at the interlayers.The simple and effective IT-MNASF interleaving technique was very successful in low-cost and high-strength development of BCFRP heterogeneous composites.

熔丝制造3D打印CFRP层内损伤破坏机理与模型研究

为将3D打印技术应用到桥梁工程中,以熔丝制造3D打印碳纤维复合材料锚环为研究对象,开展了材料层内损伤失效机理的基础性研究工作.首先,对锚环进行了张拉锚固破坏试验,明晰材料的损伤失效模式.其次,测试分析了材料的弹性参数及强度参数值,供后续仿真分析使用.最后,通过VUMAT子程序构建了材料的损伤失效本构关系,利用ABAQUS仿真分析软件模拟熔丝制造3D打印碳纤维复合材料锚环的渐进损伤失效全过程,分析其层内损伤失效机理.结果表明:熔丝制造3D打印碳纤维复合材料具有显著的层内损伤现象;选用Hashin损伤起始判据与刚度瞬间退化模型作为熔丝制造3D打印碳纤维复合材料损伤力学模型偏于安全,具有一定的可行性;锚环在高度方向产生纵向裂纹是由纤维拉伸失效导致的.

碳纤维格栅网-UHPC 增强RC 连续梁 负弯矩区裂缝性能研究

为研究碳纤维格栅网-UHPC(Ultra-High Performance Concrete)增强RC(Reinforced Concrete)连续梁负弯矩处的抗裂性能,设计7根配置不同的UHPC及碳纤维格栅网的试验梁,进行五点弯曲加载试验,分析碳纤维格栅网和UHPC的掺入、碳纤维格栅的网格尺寸、格栅的层数以及UHPC的铺设厚度等参数对负弯矩区开裂荷载和裂缝性能的影响,提出了适合碳纤维格栅网-UHPC增强的钢筋混凝土梁平均裂缝间距、裂缝宽度计算公式。试验结果表明:对照组试验梁的裂缝呈细且密的特点,有别于普通RC梁的裂缝少,宽度大;与普通RC梁相比,单独设置碳纤维格栅网、UHPC增强的试验梁负弯矩区段的开裂荷载分别提升了28.6%、85.7%,同时设置碳纤维格栅网和UHPC增强的4个试验梁分别提升了114.3%、128.6%、142.9%、171.4%;碳纤维格栅网格尺寸的减小、碳纤维格栅层数的增加、UHPC铺设厚度的增加均可以提高抗裂性能,并且使裂缝数量显著增加,裂缝间距和裂缝宽度明显减小。本文基于现有的国内外规范提出的适合碳纤维格栅网-UHPC联合加固的钢筋混凝土梁的平均裂缝间距、裂缝宽度计算值与试验值吻合较好,验证了计算公式的准确性。

装配式PC箱梁负弯矩锚固区加固设计

以某在建桥梁负弯矩区缺少受力钢筋加固设计为例,采用全过程分析方法,对桥梁锚固区承载能力进行验算、并对承载能力不满足工况进行加固处理得出:粘贴钢板和粘贴碳纤维布均能提高桥梁承载能力并满足规范要求,鉴于桥梁加固区为预制箱梁负弯矩锚固区,桥梁成桥后再实施更换加固材料或选择其他加固方法困难,因此在加固材料、方案的选择上需要择优考虑;桥梁设计、施工过程中需重视结构的全寿命周期,减少或者避免建设阶段结构缺陷。

基于桥梁改造的新旧混凝土结构粘接加固复材改性研究

试验制备了一种聚乙烯醇(PVA)纤维水泥基复合材料(ECC),并将该材料与碳纤维布(CFRP)结合,对新旧钢筋混凝土梁进行复合加固处理,研究材料性能。结果表明,制备的ECC材料具备较好综合性能,粘接效果和抗裂效果良好,可以与CFRP结合,对桥梁混凝土进行粘接加固;相对于普通钢筋混凝土梁,经过ECC/CFRP复合加固后,钢筋混凝土梁的刚度提高,极限荷载明显提升;随着ECC/CFRP复合加固层厚度的增加、CFRP长度的增加,粘接加固效果越好,极限荷载最大值分别达到30.17、29.73 kN。ECC/CFRP复合加固可以提高旧危桥梁混凝土的性能,粘接加固效果较好。

某公路立交火烧桥承载能力评估及加固设计

某拉载汽车化油器清洗剂的半挂车在经过桥下时发生燃烧,引燃装载物发生爆炸,对该桥第4孔、第5孔上部结构、下部结构、桥面系造成较大损伤。该桥进行外观检测及荷载试验,结果承载能力满足原设计要求,但火灾高温对桥梁有一定程度的影响,受火灾影响严重的空心板梁安全储备有所降低。因此提出了通过粘贴碳纤维板+嵌入碳纤维筋的加固方法,使结构承载能力安全储备得到提高,从而达到桥梁满足安全通行的要求。

碳纤维复合材料在桥梁加固中的设计应用研究

总结了碳纤维复合材料在桥梁加固中应用的优势,深入分析碳纤维复合材料在桥梁加固中的施工工艺,从加强结构设计、重视材料选择、优化施工工艺、加强施工管理等方面探讨碳纤维复合材料在桥梁加固中的设计与应用策略。

碳纤维粘贴材料在桥梁结构加固中的应用研究

针对当前使用的有关桥梁结构加固方法存在的问题,提出了在桥梁结构加固中粘贴碳纤维材料的应用方法。通过分析任意截面上的法向应力分量、剪应力分量,结合莫尔-库伦强度理论,判断莫尔圆与抗剪强度线的相对位置判断相交点的状态。根据莫尔圆与抗剪强度线几何关系,确定极限平衡条件,由此确定贴碳纤维材料的单位面积用量。以X大桥的K225+150-K225+500断面为研究对象,通过工程实例加固效果可知,所研究方法分析的K225+150-K225+500断面加固容许安全系数均在容许范围内,且最大安全系数为0.98,具有安全加固效果。

采用碳纤维布加固的在役小箱梁承载力效果分析

基于某特大桥中的预制小箱梁段的典型病害,使用有限元软件进行了正截面、斜截面、极限承载力等验算,并提出不同维修加固方法的比选,得出对结构损伤小,施工工期短,且承载力提升多的方案。对加固后桥梁的承载力提升进行有限元模拟验算可知,加固后,小箱梁外边梁边跨跨中及中跨跨中截面、正截面抗弯承载能力提高约6%,满足正常使用要求。

预应力碳纤维板在预应力桥梁加固中的应用

结合工程实例,从设计角度介绍了预应力碳纤维板加固方法在预应力桥梁加固中的应用,并通过有限元计算软件,对比分析加固前后桥梁正常使用极限状态的应力情况和承载能力极限状态下的承载能力,验证了此种加固方法在控制桥梁开裂和提升结构承载能力方面效果显著,在预应力桥梁加固中是一种有效的方法。

钢筋混凝土过渡墩盖梁开裂成因分析及加固处治

G42沪蓉高速公路湖北省境内某大桥全长668.04 m,全宽24.5 m。上构预应力混凝土T梁采用先简支后结构连续,下构桥墩盖梁横桥向长10.90 m,顺桥向宽2.20 m,悬臂长度1.75 m。19号桥墩盖梁由于混凝土保护层厚度偏厚,混凝土浇筑养生质量不佳,导致盖梁的两侧立面、底面均出现了网状裂缝,裂缝宽度超限且数量多,同时盖梁顶面出现了一条贯通的横向裂缝。结合工程实例,介绍了该桥墩盖梁加固采用的张拉预应力碳纤维板法、张拉预应力钢筋法、粘贴钢板法等加固方法。

桥梁加固维修施工技术及质量管控研究

桥梁是重要的基础设施,与人们的日常生活有着紧密的联系;但随着社会的发展,车辆行驶的密度逐渐增大,桥梁交通设施逐渐出现了一定的问题,桥梁老化问题日益凸显。因此,需要重视桥梁加固维修工作,加强对施工技术和质量的管控,只有这样才能保证桥梁的安全运行。文章主要对桥梁加固维修施工技术进行了详细的分析,并提出了一系列质量管控措施,旨在为相关人员提供一定的参考意见。

碳纤维增强聚合物在桥梁工程中的应用

碳纤维增强复合材料在桥梁工程领域具有重要的应用前景。该文介绍了碳纤维增强材料在桥梁中的高强度、轻质化、耐久性和抗腐蚀性等方面的优势,概述了碳纤维增强材料在斜拉桥拉索、桥梁梁板、桥墩和桥梁加固等桥梁中的应用,指出碳纤维增强材料有望实现桥梁工程向更安全、更耐久和更可持续方向应用与发展。

铁路桥墩病害分析及加固方法研究

文章以赤大白铁路桥墩病害检测及维修加固工程为背景,就铁路桥墩病害进行了现场检测及理论检算,综合分析桥墩病害成因,并根据分析结果提出了灌胶封闭综合粘贴碳纤维布法的加固设计方案。加固完成并连续运营数年后,对加固后的桥墩再次进行检测,结果显示桥墩无新增病害,原病害位置无开裂。实践证明,桥墩病害分析结果合理,加固效果良好,可以为同类铁路桥墩维养工程提供参考。

既有空心板梁桥横向预应力碳纤维板加固技术研究

铰缝破坏会削弱装配式空心板的整体性能,影响结构的承载能力,因此,对于出现铰缝病害的空心板桥进行加固尤为必要。文章首先分析了装配式空心板桥常见铰缝病害,然后根据病害成因研究了加固方案及施工工艺,最后通过荷载试验进行了加固效果评价。结果显示,偏载工况下,8#梁横向分布系数改善8.9%;正载工况下,5#梁横向分布系数改善9.3%。