Compressive Strength Estimation for the Fiber-Reinforced Polymer (FRP)-Confined Concrete Columns with Different Shapes Using Artificial Neural Networks

An evaluation of existing strength of concrete columns confined with fiber-reinforced polymer( FRP) was presented with extensive collection of experimental data. According to the evaluation results, artificial neural networks( ANNs) model to predict the ultimate strength of FRP confined column with different shapes was proposed. The models had seven inputs including the column length,the tensile strength of the FRP in the hoop direction,the total thickness of FRP,the diameter of the concrete specimen,the elastic modulus of FRP,the corner radius and the concrete compressive strength. The compressive strength of the confined concrete was the output data. The results reveal that the proposed models have good prediction and generalization capacity with acceptable errors.

Fiber-Reinforced Polymer Bridge Design in the Netherlands： Architectural Challenges toward Innovative, Sustainable, and Durable Bridges

This paper reviews the use of fiber-reinforced polymers （FRPs） in architectural and structural bridge design in the Netherlands. The challenges and opportunities of this relatively new material, both for the architect and the engineer, are discussed. An inventory of recent structural solutions in FRP is included, followed by a discussion on architectural FRP applications derived from the architectural practice of the author and of other pioneers.

Strengthening reinforced concrete beams using prestressed glass fiber-reinforced polymer-Part II:Analytical study

Strengthening reinforced concrete (R. C.) beams using prestressed glass fiber-reinforced polymer (PGFRP) was studied experimentally as described in Part I of this paper (Huang et al., 2005). In that paper, R. C. beams, R. C. beams with GFRP (glass fiber-reinforced polymer) sheets, and R. C. beams with PGFRP sheets were tested in both under-strengthened and over-strengthened cases. The test results showed that the load-carrying capacities (ultimate loads) of the beams with GFRP sheets were greater than those of the beams without polymer sheets. The load-carrying capacities of beams with PGFRP sheets were greater than those of beams with GFRP sheets. The objective of this work is to develop an analytical method to compute all of these load-carrying capacities. This analytical method is independent of the experiments and based only on the traditional R. C. and P. C. (prestressed concrete) theory. The analytical results accorded with the test results. It is suggested that this analytical method be used for analyzing and designing R. C. beams strengthened using GFRP or PGFRP sheets.

Deriving Tensile Properties of Glass Fiber Reinforced Polymers (GFRP) Using Mechanics of Composite Materials

This work addresses the tensile properties of glass fiber reinforced polymers (GFRP) and investigates the different ways of estimating them without the cost associated with experimentation. This attempt is achieved through comparison between experimental results, derived in accordance with the ASTM standards, and results obtained using the mechanics of composite materials. The experimental results are also compared to results derived from work by other researchers in order to corroborate the findings regarding the correlation of tensile properties of the GFRP material and the fiber volume fraction.

Acoustic emission responses and damage estimation of coal with carbon fiber-reinforced polymer confinement under uniaxial compression

Fiber-reinforced polymer(FRP)wrapping is a potential technique for coal pillar reinforcement.In this study,an acoustic emission(AE)technique was employed to monitor coal specimens with carbon FRP(CFRP)jackets during uniaxial compression,which addressed the inability to observe the cracks inside the FRP-reinforced coal pillars by conventional field inspection techniques.The spatiotemporal fractal evolution of the cumulated AE events during loading was investigated based on fractal theory.The results indicated that the AE response and fractal features of the coal specimens were closely related to their damage evolution,with CFRP exerting a significant influence.In particular,during the unstable crack development stage,the evolutionary patterns of the AE count and energy curves of the CFRPconfined specimens underwent a transformation from the slight shockemajor shock type to the slight shockesub-major shockeslight shockemajor shock type,in contrast to the unconfined coal specimens.The AE b-values decreased to a minimum and then increased marginally.The AE spatial fractal dimension increased rapidly,whereas the AE temporal fractal dimension fluctuated significantly during the accumulation and release of strain energy.Ultimately,based on the AE count and AE energy evolution,a damage factor was proposed for the coal samples with CFRP jackets.Furthermore,a damage constitutive model was established,considering the CFRP jacket and the compaction characteristics of the coal.This model provides an effective description of the stressestrain relationship of coal specimens with CFRP jackets.

FRP筋混凝土短梁抗剪性能试验研究及承载力计算

为分析梁高、剪跨比、腹筋率等参数对纤维增强聚合物(FRP)筋混凝土短梁抗剪承载力的定量影响,并验证前期基于拉杆拱模型提出的抗剪承载力计算方法的科学合理性,对11根玄武岩FRP筋混凝土短梁开展了剪切破坏试验,试验梁最大梁高为1.2 m.试验结果表明,梁高、剪跨比、水平腹筋率、竖向腹筋率均对FRP筋混凝土短梁的抗剪承载力有显著影响.当梁高由300 mm增大到1200 mm,试验梁的无量纲极限抗剪强度下降46.7%.当水平腹筋率由0增大至1.0%,试验梁的无量纲极限抗剪强度提高40.5%.基于拉杆拱模型提出的抗剪承载力计算式可以合理反映梁高、剪跨比、水平腹筋率等因素的影响规律,计算结果与本试验结果及搜集试验数据均吻合良好.

B/CFRP筋海水海砂活性粉末混凝土梁抗弯性能研究

为研究B/CFRP-SSRPC结构的抗弯性能,以配筋率及梁截面高度为研究因素,对5根B/CFRP-SSRPC梁开展四点弯曲试验研究,探究研究因素对B/CFRP-SSRPC梁极限承载力、跨中挠度及破坏模式等的影响规律.试验结果表明:增大配筋率仅对试验梁开裂后抗弯性能有明显提升,增大梁截面高度对试验梁开裂前及开裂后抗弯性能均有提升,且对试验梁开裂前抗弯性能的提升更明显;所有试验梁均为脆性破坏,破坏模式与配筋率密切相关;现行中国、美国两国FRP筋普通混凝土结构设计规范均低估了B/CFRP-SSRPC梁的抗弯承载力及抗剪承载力,计算误差分别受试验梁的破坏模式及剪跨比影响.

FRP布材增强钢筋混凝土桩水平承载性能研究

纤维增强复合材料(FRP)由于其轻质高强的优点被广泛应用于抗震加固、结构补强等实际工程中,但有关FRP增强混凝土桩水平承载性能的研究较少。为了研究不同FRP布材加固混凝土桩承载特性问题,通过室内模型试验对FRP布桩(普通钢筋混凝土桩身包裹FRP布材)的水平承载规律进行研究,探究了不同包裹层数、不同FRP布材类型、不同布材混合包裹对钢筋混凝土桩承载性能的影响。同时利用ABAQUS软件建立FRP布桩三维有限元模型,对每种工况进行数值模拟。结果表明,FRP布桩的水平承载性能随着包裹层数的增加而提升,提升效果与包裹层数之间并不存在正比例关系;不同布材类型的FRP布桩中,CFRP布对FRP布桩的水平承载性能提升效果最优;混合包裹(CFRP+GFRP)的提升效果要略优于包裹2层GFRP布。

Progressive Crushing of Polymer Matrix Composite Tubular Structures: Review

The present paper reviews crushing process of fibre-reinforced polymer (FRPs) composites tubular structures. Working with anisotropic material requires consideration of specific parameter definition in order to tailor a well-engineered composite structure. These parameters include geometry design, strain rate sensitivity, material properties, laminate design, interlaminar fracture toughness and off-axis loading conditions which are reviewed in this paper to create a comprehensive data base for researchers, engineers and scientists in the field. Each of these parameters influences the structural integrity and progressive crushing behaviour. In this extensive review each of these parameters is introduced, explained and evaluated. Construction of a well-engineered composite structure and triggering mechanism to strain rate sensitivity and testing conditions followed by failure mechanisms are extensively reviewed. Furthermore, this paper has mainly focused on experimental analysis that has been carried out on different types of FRP composites in the past two decades.

A Review on Strengthening of Timber Beams Using Fiber Reinforced Polymers

Fiber reinforced polymer(FRP)has been used in the construction industry because of its advantages such as high strength,light weight,corrosion resistance,low density and high elasticity.This paper presents a review of bonding techniques adopted to strengthen timber beams using FRP to achieve larger spans.Different methods of bonding between FRP and timber beams have been summarized with a focus on the influencing factors and their effects as well as relevant bond-slip models proposed for fundamental understanding.Experimental investigations to evaluate the flexural performance of timber beams strengthened by FRP bars,sheets and wraps have also been critically reviewed to identify key influencing parameters.Limited research available on the shear performance of FRP reinforced timber beams have been analyzed to determine the influencing factors of the shear performance in timber-FRP beams.The paper finally presents an overall summary of the current-state-of-the-art and proposes some future research directions in the field.

Experimental Investigation of Natural Fiber Reinforced Polymers

The potential usage of virgin Low density polyethelyne (LDPE) reinforced with different concentrations (2%, 5% and 6% by weight) of treated rice straw with different lengths (2 mm, 4 mm and 6 mm) is investigated to produce high value products that have technical and environmental demand. The two treatment methods used for rice straw are alkali and acidic treatments of rice straw. The removal of impurities and waxy substances from fiber surface avoid creation of rougher topography after treatment and improves the quality of fiber, also content of hemi cellulose and lignin decrease so increase effectiveness of fiber due to dispersing of fiber in matrix. The reinforcing material is embedded in the matrix material to enhance tensile and flexural behaviors of the synthesized composite. The result of investigating these two mechanical properties, using statistical analysis & design of experiments, showed an enhancement in the mechaniccal properties of the virgin polymer composite compared to the virgin polymer. The flexural stress of the composite increased three times the virgin flexural stress, while the tensile stress increased eight times the original tensile stress.

Nonlinear stability of timber column strengthened with fiber reinforced polymer

By taking into account the effect of the bi-modulus for tension and compression of the fiber reinforced polymer （FRP） sheet in the reinforcement layer, a general mathematical model for the nonlinear bending of a slender timber beam strengthened with the FRP sheet is established under the hypothesis of the large deflection deformation of the beam. Nonlinear governing equations of the second order effect of the beam bending are derived. The nonlinear stability of a simply-supported slender timber column strengthened with the FRP sheet is then investigated. An expression of the critical load of the simply-supported FRP-strengthened timber beam is obtained. The existence of postbuckling solution of the timber column is proved theoretically, and an asymptotic analytical solution of the postbuckling state in the vicinity of the critical load is obtained using the perturbation method. Parameters are studied showing that the FRP reinforcement layer has great influence on the critical load of the timber column, and has little influence on the dimensionless postbuckling state.

Flexure-Compression Testing of Bridge Timber Piles Retrofitted with Fiber Reinforced Polymers

The adequacy of using Fiber Reinforced Polymer (FRP) retrofit technique to restore the flexure-compression behavior of deteriorated bridge timber piles is examined experimentally in this paper. Sixteen specimens are tested monotonically under eccentric compressive loading. The specimens are first tested in their unretrofitted condition to determine their elastic properties. Each specimen is then cut and connected (posted) using the proposed FRP retrofit technique, and retested. The results show that the retrofitted specimens are capable of reaching same or higher strengths than that of the unretrofitted specimens with minimal reduction in their stiffness. Based on the experimental results, a design equation is presented to compute the volumetric ratio of FRP needed for retrofitting bridge timber piles under eccentric load.

预应力FRP网格加固空心板梁桥的病害修复效果分析

针对空心板梁桥存在的典型病害问题,采用预应力纤维增强复合材料(FRP)网格进行加固,通过数值模拟分析其对底板开裂及铰缝破损病害的修复效果,讨论了FRP网格种类、用量、布置方式等参数对桥梁承载性能的影响.结果表明:在底板开裂部位横向或纵向布置预应力FRP网格,均可有效控制底板开裂和梁体下挠;在跨中横向布置预应力FRP网格,可有效降低铰缝破损的不利影响;若两类病害均显著存在,可采用横向布置预应力FRP网格进行综合加固;在预应力水平与加固量相同的条件下,玄武岩纤维增强复合材料(BFRP)网格与碳纤维增强复合材料(CFRP)网格的加固效果基本相当.合理布置预应力FRP网格可有效改善空心板梁桥底板开裂和铰缝破损病害,有助于提升其长期受力性能.

Proposed numerical and machine learning models for fiber-reinforced polymer concrete-steel hollow and solid elliptical columns

This study employs a hybrid approach,integrating finite element method(FEM)simulations with machine learning(ML)techniques to investigate the structural performance of double-skin tubular columns(DSTCs)reinforced with glass fiber-reinforced polymer(GFRP).The investigation involves a comprehensive examination of critical parameters,including aspect ratio,concrete strength,number of GFRP confinement layers,and dimensions of steel tubes used in DSTCs,through comparative analyses and parametric studies.To ensure the credibility of the findings,the results are rigorously validated against experimental data,establishing the precision and trustworthiness of the analysis.The present research work examines the use of the columns with elliptical cross-sections and contributes valuable insights into the application of FEM and ML in the design and evaluation of structural systems within the field of structural engineering.

Superior Mechanical Behavior and Flame Retardancy FRP via a Distribution Controllable 1D/2D Hybrid Nanoclay Synergistic Toughening Strategy

The incorporation of commercial flame retardants into fiber-reinforced polymer(FRP)composites has been proposed as a potential solution to improve the latter’s poor flame resistance.However,this approach often poses a challenge,as it can adversely affect the mechanical properties of the FRP.Thus,balancing the need for improved flame resistance with the preservation of mechanical integrity remains a complex issue in FRP research.Addressing this critical concern,this study introduces a novel additive system featuring a combination of one-dimensional(1D)hollow tubular structured halloysite nanotubes(HNTs)and two-dimensional(2D)polygonal flake-shaped nano kaolinite(NKN).By employing a 1D/2D hybrid kaolinite nanoclay system,this research aims to simultaneously improve the flame retardancy and mechanical properties.This innovative approach offers several advantages.During combustion and pyrolysis processes,the 1D/2D hybrid kaolinite nanoclay system proves effective in reducing heat release and volatile leaching.Furthermore,the system facilitates the formation of reinforcing skeletons through a crosslinking mechanism during pyrolysis,resulting in the development of a compact char layer.This char layer acts as a protective barrier,enhancing the material’s resistance to heat and flames.In terms of mechanical properties,the multilayered polygonal flake-shaped 2D NKN plays a crucial role by impeding the formation of cracks that typically arise from vulnerable areas,such as adhesive phase particles.Simultaneously,the 1D HNT bridges these cracks within the matrix,ensuring the structural integrity of the composite material.In an optimal scenario,the homogeneously distributed 1D/2D hybrid kaolinite nanoclays exhibit remarkable results,with a 51.0%improvement in mode II fracture toughness(GIIC),indicating increased resistance to crack propagation.In addition,there is a 34.5%reduction in total heat release,signifying improved flame retardancy.This study represents a significant step forward in the field of composite materials.The innovative use of hybrid low-dimensional nanomaterials offers a promising avenue for the development of multifunctional composites.By carefully designing and incorporating these nanoclays,researchers can potentially create a new generation of FRP composites that excel in both flame resistance and mechanical strength.

An efficient improved Gradient Boosting for strain prediction in Near-Surface Mounted fiber-reinforced polymer strengthened reinforced concrete beam

The Near-Surface Mounted(NSM)strengthening technique has emerged as a promising alternative to traditional strengthening methods in recent years.Over the past two decades,researchers have extensively studied its potential,advantages,and applications,as well as related parameters,aiming at optimization of construction systems.However,there is still a need to explore further,both from a static perspective,which involves accounting for the nonconservation of the contact section resulting from the bond-slip effect between fiber-reinforced polymer(FRP)rods and resin and is typically neglected by existing analytical models,as well as from a dynamic standpoint,which involves studying the trends of vibration frequencies to understand the effects of various forms of damage and the efficiency of reinforcement.To address this gap in knowledge,this research involves static and dynamic tests on simply supported reinforced concrete(RC)beams using rods of NSM carbon fiber reinforced polymer(CFRP)and glass fiber reinforced polymer(GFRP).The main objective is to examine the effects of various strengthening methods.This research conducts bending tests with loading cycles until failure,and it helps to define the behavior of beam specimens under various damage degrees,including concrete cracking.Dynamic analysis by free vibration testing enables tracking of the effectiveness of the reinforcement at various damage levels at each stage of the loading process.In addition,application of Particle Swarm Optimization(PSO)and Genetic Algorithm(GA)is proposed to optimize Gradient Boosting(GB)training performance for concrete strain prediction in NSM-FRP RC.The GB using Particle Swarm Optimization(GBPSO)and GB using Genetic Algorithm(GBGA)systems were trained using an experimental data set,where the input data was a static applied load and the output data was the consequent strain.Hybrid models of GBPSO and GBGA have been shown to provide highly accurate results for predicting strain.These models combine the strengths of both optimization techniques to create a powerful and efficient predictive tool.

纤维增强复合材料(FRP)配筋混凝土结构研究综述

新型建材纤维增强复合材料(FRP)具有高抗拉强度、低密度和耐腐蚀性能优良等特性,是一种具有巨大潜力的工程材料。如今,传统的钢筋混凝土结构面临钢筋易锈蚀的问题,给社会造成了较大的经济损失,维护和修复成本高昂。通过在特定环境中将钢筋替换为FRP筋,不仅能够有效解决钢筋混凝土结构的耐久性问题,而且能够进一步优化其工作性能,延长使用寿命,降低维护成本。首先简述了FRP筋混凝土结构的国内外研究进展,随后对FRP筋、FRP筋混凝土及预应力FRP筋混凝土结构的特性进行了阐述,最后对FRP筋混凝土结构的重要发展问题进行了总结,并对其未来的发展前景进行了展望。

GFRP约束ECC短柱偏压试验研究

纤维增强复合材料(Fiber Reinforced Polymer,FRP)约束工程纤维增强水泥基复合材料(Engineered Fiber Reinforced Cementitious Composites,ECC)轴压柱可显著提高其承载能力和延性,但偏压作用下FRP约束ECC柱的性能提升程度和作用机理有待研究。基于此,以偏心距(0、10、30、50 mm)和FRP层数(0、2、4层)为试验变量,对玻璃纤维增强复合材料(Glass Fiber Reinforced Polymer,GFRP)约束ECC短柱展开了竖向加载试验,并对试验结果进行了分析。研究结果表明:小偏心破坏时受压侧FRP断裂、混凝土被压碎,大偏心破坏时受拉侧FRP撕裂与混凝土横向裂缝近乎同时出现。轴压作用下,轴向变形和抗压强度显著增大;偏压作用下,抗压承载力随着偏心距的增大而减小,而极限位移无明显变化规律。此外,承载力和延性都随着FRP层数的增加而增大。