A Study on the Estimation of Prefabricated Glass Fiber Reinforced Concrete Panel Strength Values with an Artificial Neural Network Model

In this study,artificial neural networks trained with swarm based artificial bee colony optimization algorithm was implemented for prediction of the modulus of rapture values of the fabricated glass fiber reinforced concrete panels.For the application of the ANN models,143 different four-point bending test results of glass fiber reinforced concrete mixes with the varied parameters of temperature,fiber content and slump values were introduced the artificial bee colony optimization and conventional back propagation algorithms.Training and the testing results of the corresponding models showed that artificial neural networks trained with the artificial bee colony optimization algorithm have remarkable potential for the prediction of modulus of rupture values and this method can be used as a preliminary decision criterion for quality check of the fabricated products.

Strain coordination of quasi-plane-hypothesis for reinforced concrete beam strengthened by epoxy-bonded glass fiber reinforced plastic plate

The testing of thirteen reinforced concrete （RC） beams strengthened by epoxy-bonded glass fiber reinforced plastic plate （GFRP） shows that the RC beam and the GFRP plate with epoxy bonding on it can work fairly well in coordination to each other. But there is relative slipping between RC beam and GFRP plate. And the strain of GFRP and steel rebar of RC beam satisfies the quasi-plane-hypothesis, that is, the strain of longitudinal fiber that parallels to the neutral axis of plated beam within the scope of effective height （h0） of the cross section is in direct proportion to the distance from the fiber to the neutral axis. The strain of GFRP and steel rebar satisfies the equation: ε GFRP =Kε steel .

Structural Glass Fiber Reinforced Concrete for Slabs on Ground

This paper aims to contribute to the classification and specification of glass fiber reinforced concrete (GFRC) and to deal with the question if structural glass fiber reinforced concrete as a special kind of glass fiber reinforced concrete is suited for use in load-bearing members. Despite excellent material properties, the use of glass fibers in a concrete matrix is carried out so far only in non- structural elements or as a modification for the prevention of shrinkage cracks. The aim of re- search at the University of Applied Sciences in Leipzig is the use of alkali-resistant macro glass fibers as concrete reinforcement in structural elements as an alternative to steel fiber reinforcement. Slabs on ground, as an example for structural members, provide a sensible application for the new material because they can be casted as load bearing and non-load bearing and are mostly made of steel fiber reinforced concrete. In the future, structural glass fiber reinforced concrete shall provide a simple and visually appealing alternative to conventional steel bar or steel fiber reinforced concrete. The glass fibers can also be used in combination with conventional reinforcing bars or mat reinforcements. Initial investigations have announced some potential.

Seismic retrofitting of reinforced concrete frame structures using GFRP-tube-confined-concrete composite braces

This paper presents a new type of structural bracing intended for seismic retrofitting use in framed structures. This special composite brace, termed glass-fiber-reinforced-polymer （GFRP）-tube-confined-concrete composite brace, is comprised of concrete confined by a GFRP tube and an inner steel core for energy dissipation. Together with a contribution from the GFRP-tube confined concrete, the composite brace shows a substantially increased stiffness to control story drift, which is often a preferred feature in seismic retrofitting. An analysis model is established and implemented in a general finite element analysis program - OpenSees, for simulating the load-displacement behavior of the composite brace. Using this model, a parametric study of the hysteretic behavior （energy dissipation, stiffness, ductility and strength） of the composite brace was conducted under static cyclic loading and it was found that the area ratio of steel core to concrete has the greatest influence among all the parameters considered. To demonstrate the application of the composite brace in seismic retrofitting, a three-story nonductile reinforced concrete （RC） frame structure was retrofitted with the composite braces. Pushover analysis and nonlinear time-history analyses of the retrofitted RC frame structure was performed by employing a suite of 20 strong ground motion earthquake records. The analysis results show that the composite braces can effectively reduce the peak seismic responses of the RC frame structure without significantly increasing the base shear demand.

Experimental Investigation on the Properties of Recycled Concrete Using Hybrid Fibers

Due to the inherent property of concrete being very weak in tension, efforts have been made to overcome this deficiency by adding various type of fibers like carbon fiber reinforced polymer (CFRP), glass fiber reinforced polymer (GFRP), polypropylene fiber (PPF) and stainlesssteel fiber (SSF) smeared into the concrete mix. The present study involves experimental investigation on the use of GFRP, CFRP and SSF fibers alone or as combination to improve the mechanical properties of concrete. Furthermore, concrete cylinders were cast and tested for compression and tension using 10% fly ash as cement replacement in all specimens. Besides fiber material types, fiber reinforcement ratios of 1% and 1.5% were tested to investigate the mechanical properties of concrete. In all concrete cylinder tests, the fiber reinforcement ratio of 1% had a significant contribution in increasing the tensile strength as oppose to compressive strength. As a result, the tensile and compressive strengths were increased by 26% and 11%, respectively as compared to the control specimen. Increasing the fiber reinforcement ratio from 1% to 1.5%, resulted in diminishing the mechanical properties of concrete. However, reduction in concrete compressive strength was more prominent than the tensile strength. Furthermore, it was observed that, the crack propagation was decreased with the increase of fiber content when compared to the control specimen.

装配式桥梁板玻璃纤维混凝土-U形钢筋湿接缝受力与变形分析

为解决装配式桥梁板体系湿接缝处力学性能不稳定、易变形的问题,提出采用玻璃纤维混凝土-U形钢筋加强方案优化湿接缝性能,以雄安新区荣乌高速荣乌主线桥为背景进行研究。选取主线桥2个试验段(试验段A湿接缝采用普通混凝土-U形钢筋方案,钢筋点焊;试验段B湿接缝采用玻璃纤维混凝土-U形钢筋加强方案,钢筋满焊)进行梁板体系湿接缝性能试验,监测湿接缝处搭接钢筋力学响应及混凝土接触面变形特征,同时对长期运载及强降雨影响下的钢筋受力与混凝土变形进行监测。结果表明:长期运载下,试验段B横筋受力约为试验段A的一半,其中部纵筋承受外力远大于试验段A,边缘纵筋承受外力较少,试验段B稳定性更优;试验段B较试验段A在湿接缝部位变形量小,其稳定性及耐久性更优;强降雨阶段,试验段B较试验段A变形及力学响应波动程度更低,其抗渗能力、耐久性更优。由此可知基于玻璃纤维混凝土-U形钢筋加强方案的湿接缝构造在外力传导、抵抗变形方面具有较强稳定性,不易受恶劣环境影响。

玻璃纤维增强聚合物管约束高强混凝土柱轴压试验研究

为研究玻璃纤维增强聚合物管约束高强混凝土柱的轴压性能,设计了6个不同长细比的试件并对其进行了轴心受压试验,分析了其破坏过程及破坏形态、承载力、位移、荷载-位移曲线、骨架曲线、荷载-应变曲线。研究表明:玻璃纤维增强聚合物管约束混凝土柱轴压承载性能优异,随着长细比的减小,试件的轴压承载力提升显著;加载后期,该组合结构的破坏模式为玻璃纤维增强聚合物管发生环向破坏,内部混凝土被压溃;玻璃纤维增强聚合物空管轴压承载力相对较低,破坏时脆性特征明显;随着长细比的减小,玻璃纤维增强聚合物管约束高强混凝土柱的承载力和刚度逐步增加,长细比对结构的承载能力影响显著。研究结果对玻璃纤维增强聚合物管约束高强混凝土柱的理论研究和工程应用具有一定的指导意义。

木丝水泥填充墙-RC框架抗震性能试验研究

为研究木丝水泥填充墙-钢筋混凝土(RC)框架的抗震性能和破坏机理,共制作五个试件进行低周反复试验,其中一个试件为普通砖填充墙-RC框架对比试件,两个试件为开窗洞的木丝水泥填充墙-RC框架,另外两个试件为添加玻璃纤维网格布的木丝水泥填充墙-RC框架,并分析试件的滞回曲线、骨架曲线、延性系数、耗能情况与刚度退化等指标。试验结果表明,木丝水泥填充墙-RC框架的抗震性能良好,刚度退化速度远小于普通砖填充墙-RC框架,耗能能力在试件开裂后超过普通砖填充墙-RC框架;在木丝水泥填充墙-RC框架上开窗洞后会削弱其承载力,但破坏时裂缝只是沿四个窗角分别向四个填充墙角扩展,最终形成“X”形裂缝,而木丝水泥填充墙-RC框架与混凝土之间的粘结面未被破坏,在木丝水泥填充墙-RC框架表面加入玻璃纤维网格布后可以减少墙面裂纹的产生,且提高了极限承载力和延性系数,并抑制了刚度的快速下降。

Numerical simulation and experimental study on electrothermal properties of carbon/glass fiber hybrid textile reinforced concrete

Carbon/glass fiber hybrid textile reinforced concrete is a relatively new composite material with good mechanical capacity and excellent electrical conductivity.Both small-scale slab heating experiments and numerical simulation are presented in this paper.Temperature variation curves obtained during heating indicate the effects of environmental temperature,heat-conducting layer thickness and electric heating power.Comparison of temperature rising between the situations with and without thermal isolation layer is given as well.The results indicate that the textile can form a good conductive heating network and generate enough heat to raise the temperature in the concrete when connected to a power supply,while the resistance of the slab remains stable during the heating.Numerical results are in good accordance with the experiments.Real time snow-melting experiment was conducted to verify the feasibility of deicing.The electrothermal properties of textile can be utilized for deicing and snow melting in a safe,environmentally friendly and efficient way.

Mechanical behavior of concrete filled glass fiber reinforced polymer-steel tube under cyclic loading

The mechanical behavior of concrete-filled glass fiber reinforced polymer(GFRP)-steel tube structures under combined seismic loading is investigated in this study. Four same-sized specimens with different GFRP layout modes were tested by a quasi-static test system. Finite element analysis(FEA) was also undertaken and the results were presented. Results of the numerical simulation compared well with those from experimental tests. Parametric analysis was conducted by using the FE models to evaluate the effects of GFRP thickness, axial compression rate, and cross sectional steel ratio. The experimental and numerical results show that the technique of GFRP strengthening is effective in improving the seismic performance of traditional concrete-filled steel tubes, with variations related to different GFRP layout modes.

Experimental Study of the Shear Capacity of Glass Fiber Reinforced Polymer Reinforced Concrete Beam with Circular Cross Section

In order to research the shear behavior of glass fiber reinforced polymer (GFRP) reinforced concrete beam with circular cross section, based on the test results of 36 concrete beams subjected to four-point loading up to failure, the shear capacity and mechanical properties of deformation were analyzed comparatively between GFRP reinforced concrete (GFRP-RC) beams and steel reinforced concrete (steel-RC) beams. Furthermore, influencing factors of shear capacity of GFRP-RC beam with circular cross section were also investigated. The test results indicate that the failure modes of GFRP-RC and steel-RC beams are the same, but the crack patterns are slightly different. And, the shear capacity of GFRP-RC beam firstly increases with the reduction of shear span ratio, and then decreases. In addition, it was found that the influencing coefficient of GFRP on concrete increases with shear span ratio reducing.

有效高度对GFRP筋混凝土板冲切性能的影响

相比于传统的钢筋混凝土板,玻璃纤维增强聚合物(Glass fiber reinforced polymer,GFRP)筋混凝土板具有较高的耐腐蚀性能和较长的使用寿命,被广泛应用于水利工程和港口工程中。有效高度是影响GFRP筋混凝土板冲切承载力的重要因素,为量化其影响规律,完成了3块不同有效高度GFRP筋混凝土板的冲切试验。通过分析板的破坏形式、荷载—变形曲线、GFRP筋应变和混凝土应变,获得了GFRP筋混凝土板有效高度与冲切承载力之间的定量关系。试验结果表明:3块板均被冲切破坏,当有效高度分别增大23%和57%时,虽然抗冲切承载力分别对应提高51%和116%,但是GFRP筋应变和混凝土压应变反而比例减小;增大有效高度虽然一定程度上会减小板的变形,但不是决定极限挠度的唯一因素,在实际设计中应适当考虑有效高度的影响。

玻璃纤维增强复合材料筋与超高性能混凝土之间粘结-滑移本构模型

为研究玻璃纤维增强复合材料(GFRP)筋与超高性能混凝土(UHPC)之间的粘结性能,故基于相关文献中153个拉拔试验和42个梁式试验的数据,系统分析了FRP筋直径、相对粘结长度、相对保护层厚度、超高性能混凝土抗压强度、FRP筋表面形态和试验方法对玻璃纤维增强复合材料筋粘结强度的影响规律,通过回归分析和区间预测提出了超高性能混凝土中玻璃纤维增强复合材料筋与粘结强度和锚固长度的计算公式。对比分析了已有FRP筋与普通混凝土之间的粘结-滑移本构模型,基于CMR模型提出了绕肋玻璃纤维增强复合材料筋与超高性能混凝土之间粘结-滑移本构模型的计算公式。上述公式计算结果与试验结果均吻合良好,并可为工程设计及后续研究提供依据。

混凝土环境中GFRP筋性能衰退的规律及机理

为了探究玻璃纤维增强复合材料(GFRP)筋在模拟和真实混凝土环境中性能衰退的规律及机理,设置了碱溶液(AS)和混凝土包裹GFRP筋后置于自来水中(CS)2种侵蚀环境,采用短梁剪切法分析了GFRP筋力学性能的衰退规律,并借助扫描电子显微镜、差示扫描量热法分析了GFRP筋的微观结构和玻璃化转变温度(T_(g)).结果表明:随着温度的升高,GFRP筋层间剪切强度衰退的速率加快;GFRP筋在60℃的AS中老化183 d后层间剪切强度保留了48.6%,T_(g)降低了9.2%,部分纤维与树脂脱黏,树脂出现孔洞;相同条件下CS中GFRP筋的层间剪切强度保留了61.4%,T_(g)降低了3.4%,纤维产生浅坑.基于Arrhenius方程建立了北京地区GFRP筋的性能预测模型.

P-TRC板加固梁抗弯性能的有限元模拟分析

提出了一种内嵌预应力纤维织物增强混凝土板(P-TRC板)加固混凝土梁的方法,为了减少现场湿作业,板梁之间采用射钉连接。通过有限元建模分析,对比既有试验数据,验证了混凝土本构与纤维织物本构的准确性和数值方法的可靠性。在此基础上,分析了预应力水平、混凝土强度、纵筋配筋率和P-TRC板配网率等因素对加固梁抗弯性能的影响。有限元分析结果表明:纵筋配筋率与P-TRC板配网率的提高降低了织物的利用率;加固梁的屈服荷载随预应力和配网率的提高分别增加了7.2%~22.3%和5.4%~22.4%;极限荷载随预应力水平和配网率的提高分别增加了11.6%~21.7%和12.3%~34.3%。使用射钉将P-TRC板与梁底部连接,此种施工方法快捷方便,契合了建筑工业化的趋势。

5组不同合成纤维加固混凝土柱的轴压性能研究

共设计了5组纤维加固混凝土柱试件,研究了无纤维加固、玻璃纤维加固(GFRP)、碳纤维加固(CFRP)和碳纤维+玻璃纤维加固(JFRP、NFRP)混凝土柱的破坏形貌和轴压性能。结果表明,经过碳纤维、玻璃纤维和合成纤维加固处理后,混凝土柱的峰值应力、最大拉应变和纵向最大压应变都出现不同程度增大;合成纤维加固混凝土柱的峰值应力相较无加固试件明显增大,且合成纤维加固试件的最大拉应变和纵向最大压应变明显高于其他试件。由于纤维加固后,纤维可以对混凝土起到环向约束作用而增加钢筋应变,且合成纤维和碳纤维对混凝土柱的约束作用相近,而玻璃纤维对混凝土的约束作用相对较弱。纤维布加固混凝土柱有助于提升混凝土柱的环向约束,且混凝土柱的横向变形受到明显抑制,纤维对混凝土柱的纵向约束效果从高至低顺序依次为:JFRP、NFRP、GFRP、CFRP,且都高于未加固混凝土柱。

三维针织/机织混合聚氨酯基复合材料的压缩性能研究

为解决间隔织物增强复合材料存在强度低、抗压性差的问题,选用经编间隔织物和玻纤机织物或经编间隔织物和碳纤维布作为增强体,聚氨酯浆料作为基体材料,使用手糊法制备一款新型三维针织/机织混合聚氨酯基复合材料,探究经编间隔织物表层组织结构、间隔织物的厚度、是否添加机织物、机织物种类对三维针织/机织混合聚氨酯基复合材料性能的影响。实验结果表明,织物厚度相同的情况下,间隔织物的间隔梳栉针背横移针距数较小的复合材料具有较好的压缩性能。表面结构相同的情况下,织物厚度较大的三维针织/机织混合聚氨酯基复合材料的压缩性能较好。贴附机织物布的复合材料的压缩应力提升了49.2%,压缩模量提升了27.34%。

玻璃纤维增强塑料筋混凝土框架抗震性能的试验研究

为了研究玻璃纤维增强塑料筋混凝土框架的抗震性能,设计几何相似比为1∶4的结构缩尺模型,进行模拟地震振动台试验,采用4个不同强度水平地震作用进行单向、双向以及三向的地震波激励,得到模型的损伤和位移等宏观地震响应。结果表明:在罕遇地震作用下,玻璃纤维增强塑料筋结构达到中等破坏程度,但仍保持良好的整体性,基本符合“小震不坏,中震可修,大震不倒”的抗震设防标准;玻璃纤维增强塑料筋结构在竖向刚度突变位置出现较为严重破坏;为推迟构件开裂并提高承载能力,可使柱端弯矩增大系数增大并根据截面等效模量增大玻璃纤维增强塑料筋面积;在八度罕遇地震时,玻璃纤维增强塑料筋结构的层间位移角超过钢筋混凝土框架结构层间位移角限值,但仍具备一定的承载能力。

三维针织/机织聚氨酯基复合材料的力学性能

为解决间隔织物增强复合材料存在强度低、抗压性差的问题,选用经编间隔织物和玻璃纤维机织物作为增强体,聚氨酯泡沫作为基体,制备系列三维针织/机织聚氨酯基复合材料,并测试材料的拉伸、弯曲和压缩性能。结果表明:将经编间隔织物/玻璃纤维机织物以三维夹芯结构形式嵌入复合材料中,能够提高间隔织物增强复合材料的拉伸性能和压缩性能;在表面组织结构相同的情况下,经编间隔织物厚度大的三维针织/机织聚氨酯基复合材料的力学性能较好;在织物厚度相同的情况下,填充大六角形网孔的间隔织物的复合材料具有较好的力学性能。

GFRP管约束竹筋细石混凝土组合杆力学性能试验

在当前绿色发展、“双碳”目标、科技创新的多元化发展中,工程建设行业要实现“双碳”目标,需寻找合适的钢制品替代产品。竹材作为重要工程结构用材应时而发,很有必要研发“以竹代钢”的创新技术和产品。依据实际工程需求,提出一种玻璃纤维复合材料(GFRP)管约束大截面竹筋细石混凝土组合(GBCC)构件,替代薄壁钢管用作围栏承载立杆。GBCC构件力学性能良好、制作工艺简单、产品绿色低碳。为研究GBCC的基本受力性能和不同材料的协同工作状态,进行了12根GBCC短杆轴压破坏试验、7根长杆轴压稳定试验和10根长杆抗弯试验,并研究了GBCC杆力学性能的影响规律。结果表明:GBCC短杆轴压胀裂压溃破坏,长杆轴压失稳,长杆抗弯脆性断裂破坏;GBCC材料构成、含竹率、细石混凝土密实性、试件受力方向、竹筋缺陷均影响GBCC杆的受力性能;含竹率20%左右的GBCC试件能够达到甚至超过薄壁空心钢管试件的承载力和变形能力;GBCC长杆具有很好的弹性变形能力,基于试验结果构建了GBCC长杆抗压失稳极限承载力公式。