FRP约束方形混凝土柱轴心受压强度模型

FRP约束方形混凝土柱的侧向约束力受截面形状的影响较大,与圆形柱相比,由于拐角的应力集中导致的侧向约束应力不均匀等,使得FRP包裹方形柱的侧向约束效果明显降低。基于FRP约束圆柱体的强度公式,考虑方形柱的有效核心区、拐角效应以及等间距包裹的影响,引入对应的影响系数,建立了FRP约束方形混凝土柱轴心抗压强度新模型并与试验数据对比分析,结果表明,该模型具有良好的精度。

FRP-OFBG智能复合筋及其在加筋混凝土梁中的应用

结合纤维增强聚合物(FRP)的强度特性和光纤光栅(OFBG)的感知特性,研制开发出了FRP-OFBG智能复合筋,研究了它的力学、微观结构、感知等特性.通过FRP-OFBG加筋混凝土梁静载试验,监测了FRP筋的应变和混凝土开裂,研究了FRP筋与混凝土的滑移和混凝土梁的应变分布.结果表明,FRP-OFBG智能复合筋克服了光纤光栅在混凝土中埋设的工艺难题,是集感知和受力、功能材料和结构材料于一体的新型土木工程材料,既可以方便地作为混凝土结构的内部传感元件,也可以作为结构受力筋,具有很好的应用前景.

CFRP加固RC简支T梁桥受力性能试验研究

为深入研究粘贴碳纤维布加固钢筋混凝土T梁桥的加固效果,结合某桥梁大修工程,通过在简支T梁梁底粘贴4层碳纤维布以提高其正截面承载能力.为检验加固效果,分别在加固前后对试验孔进行荷载试验,加固前后均采用两辆重约330kN的同型号三轴载重汽车作为试验荷载,重点检测了加固前后主梁跨中挠度、梁底混凝土及碳纤维布应变以及裂缝扩展情况.荷载试验结果表明,在简支钢筋混凝土梁桥上粘贴碳纤维布可有效抑制混凝土开裂,增加破损主梁的抗弯刚度,提高上部结构整体受力的能力.

Seismic performance and global ductility of RC frames rehabilitated with retrofi tted joints by CFRP laminates

This paper presents a new FRP retrofi tting scheme to strengthen local beam-column joints in reinforced concrete(RC) frames.The new retrofi tting scheme was proposed following a preliminary study of four different existing retrofi tting schemes.A numerical simulation was conducted to evaluate the effectiveness of FRP-strengthened reinforced concrete frames by bridging behavior of local joints to the whole structure.Local confi nement effects due to varying retrofi tting schemes in the joints were simulated in the frame model.The seismic behavior factor was used to evaluate the seismic performance of the strengthened RC frames.The results demonstrated that the new proposed retrofi tting scheme was robust and promising,and fi nite element analysis appropriately captured the strength and global ductility of the frame due to upgrading of the local joints.

Effect of Cycling Low Velocity Impact on Mechanical and Wear Properties of CFRP Laminate Composites

The mechanical and wear properties of CFRP laminate were investigated using a method of cycling low velocity impact, to study the trend and mechanism of impact resistance of the CFRP laminate under repeated impact during its service process. The interface responses of CFRP laminate under di erent impact kinetic energy during the cycling impact process were studied were studied experimentally, such as impact contact duration, deformation and energy absorption. The worn surface morphologies were observed through optical microscopy and a 3?D surface profiler and the cross?sectional morphologies were observed through SEM to investigate the mechanism of impact material dam?age. Based on a single?degree?of?freedom damping vibration model, the normal contact sti ness and contact damp?ing of the material in di erent wear stages were calculated. It shows the failure process of CFRP laminate damaged by accumulated absorption energy under the cycling impact of di erent initial kinetic energy. The results indicate that the sti ness and damping coe cients will change at di erent impact velocities or cycle numbers. The damage mechanism of CFRP laminates under cycling low kinetic energy is delamination. After repeated experiments, it was found that there was a threshold value for the accumulated absorption energy before the failure of the CFRP laminate.

RELIABILITY ANALYSIS OF FRP LAMINATED PLATES WITH CONSIDERATION OF BOTH INITIAL IMPERFECTION AND FAILURE SEQUENCE

A probabilistic progressive failure analyzing method is applied to estimating the reliability of a simply supported laminated composite plate with an initial imperfection under bi-axial compression load. The initial imperfection and the strength parameters are considered as random variables. Ply-level failure probability is evaluated by the first order reliability method (FORM) together with the Tsai-Wu strength criterion and Tan criterion. Current stresses in the laminated structure are calculated by the classical lamination theory with the stiffness modified based on the last step ply failure. Probabilistically dominant ply-level failure sequences leading to overall system failure are identified, based on which the system failure probability is estimated. A numerical example is presented to demonstrate the methodology proposed. Through parameter studies it is shown that the deviation of the initial imperfection and some of the strength parameters largely influence the system reliability.

A FATIGUE FAILURE CRITERION OF NOTCHED GFRP LAMINATES

A fatigue failure criterion for predicting the fatigue life of notched orthotropic fiber reinforced plasties (FRP) plates based on the concept of stress field intensity (SFI) near the notch root is subjected to further experiments. The investigation is accomplished by obtaining experimental data on the notched specimens of glass fiber reinforced plastics (GFRP) with edged notches under tension tension cyclic loading. The process of initiation and growth of fatigue damage near the notch root is measured by means of the optic system with a computer controlled display (CCD) camera. The experimental results show that the number of loading cycles required to initiate fatigue damage is governed by the stress field intensity.

FRP约束混凝土轴心抗压强度研究

受FRP材料约束的混凝土的轴心抗压强度是这种复合材料组成的结构构件的基本力学性能之一，许多学者对FRP约束混凝土圆柱体轴心抗压强度进行了试验研究和理论分析，提出各自的计算模型。各种计算模型有各自的特点，但用于计算时，计算结果与试验存在较大的差异。本文简要介绍了其中具有代表性的研究成果，对其计算结果进行对比分析，并和试验数据比较。在此基础上，提出了改进的FRP约束混凝土圆柱轴心抗压强度计算的简单模型，模型计算结果与大量试验结果吻合，研究成果可供工程技术人员参考。

Free-Form Laminated Doubly-Curved Shells and Panels of Revolution Resting on Winkler-Pasternak Elastic Foundations: A 2-D GDQ Solution for Static and Free Vibration Analysis

This work presents the static and dynamic analyses of laminated doubly-curved shells and panels of revolution resting on Winkler-Pasternak elastic foundations using the Generalized Differential Quadrature (GDQ) method. The analyses are worked out considering the First-order Shear Deformation Theory (FSDT) for the above mentioned moderately thick structural elements. The effect of the shell curvatures is included from the beginning of the theory formulation in the kinematic model. The solutions are given in terms of generalized displacement components of points lying on the middle surface of the shell. Simple Rational Bézier curves are used to define the meridian curve of the revolution structures. The discretization of the system by means of the GDQ technique leads to a standard linear problem for the static analysis and to a standard linear eigenvalue problem for the dynamic analysis. Comparisons between the present formulation and the Reissner-Mindlin theory are presented. Furthermore, GDQ results are compared with those obtained by using commercial programs. Very good agreement is observed. Finally, new results are presented in order to investtigate the effects of the Winkler modulus, the Pasternak modulus and the inertia of the elastic foundation on the behavior of laminated shells of revolution.

Effect of Thermal Treatment on CFRP Parts Before and After Adhesive Bonding

Numerous non-destructive techniques are being investigated for assuring quality of the adhesive bonds.The research presented here is focused on non-destructive assessment of carbon fibre reinforced polymer(CFRP)parts.The surface condition directly influences the performance of adhesive bonds.The structural joints should ensure safe usage of a structure.However,some modifications of the surface may lead to weak bond that cannot carry the desired load.This is why there is a search for methods of surface assessment before bonding.Moreover,reliable techniques are required to allow to verify the integrity of the adhesive bond after manufacturing or bonded repair.We focus on the laser induced fluorescence(LIF)method for assessing the surface state.The LIF is a noncontact measurement method.In the context of adhesive bond assessment the electromechanical impedance(EMI)method is studied.The EMI uses surface bonded piezoelectric sensors for excitation and sensing.The investigated samples were made of CFRP layers.The samples were treated at elevated temperatures.The influence of the thermal treatment was studied using LIF.The thermal treatment at 220℃could be clearly distinguishedrom the rest of the considered samples.The thermally treated plates were bonded to untreated plate and then they were measured with the EMI method to study the influence of the treatment on the adhesive bond.The changes of EMI spectra were significant for the treatment at 280 ℃ and for some thermally treated samples that were later contaminated with de-icing fluid.

Residual Characteristic of High-Velocity Steel Fragments Penetrating UHMWPE FRP Laminates

The mechanical performance of ultra-high molecular weight polyethylene fiber (UHMWPE) and its composites were proposed. Penetrated properties of different thicknesses UHMWPE FRP laminates (URP) impacted by 3.3g cubic high velocity fragments were studied. According to the ballistic experimental results and theoretical analysis, the linear relation between ballistic limit vBL and area density AD was confirmed. The relative parameters of showing experientially residual velocity vr were expressed by the function of AD. In the end, versatile experiential expression between vr and AD was found. Prediction of vr and vBL using obtained expressions under the above stated condition of impacting URP was consistent with the experimentaled results. Consequently, the two experiential relations can be used to predict the residual velocity and ballistic limit of cubic high velocity fragments impacting URP. The residual characteristic of high-velocity steel fragments penetrating UHMWPE FRP laminates can be more exactly forecasted by the two derived experiential formulas.

Nonlinear Free Vibrations of C-C-SS-SS Symmetrically Laminated Carbon Fiber Reinforced Plastic (CFRP) Rectangular Composite Plates

The purpose of this paper is to apply the theoretical model developed in References [1] 08D0C9EA79F9BACE118C8200AA004BA90B02000000080000000E0000005F005200650066003400310032003700320039003100350035000000 -[6] 08D0C9EA79F9BACE118C8200AA004BA90B02000000080000000E0000005F005200650066003400310032003700320039003100360030000000 in order to analyze the geometrically nonlinear free dynamic response of C-C-SS-SS rectangular CFRP symmetrically laminated plates so as to investigate the effect of nonlinearity on the nonlinear resonance frequencies, the nonlinear fundamental mode shape and associated bending stress patterns at large vibration amplitudes. Various values of the plate aspect ratio and the amplitude of vibrations will be considered, and useful numerical data also are provided.

带肋FRP筋与混凝土的粘结强度预测方法

目前有关带肋纤维增强复合材料(FRP)筋粘结性能的研究不足。收集粘结纤维肋FRP筋(简称粘结肋FRP筋)和机械刻槽肋FRP筋(简称刻槽肋FRP筋)的试验数据,探究各参数对粘结性能的影响。结果表明:两种带肋FRP筋的宏观破坏模式都是拔出破坏,在细观上粘结肋FRP筋主要为FRP筋肋的剪切剥落,而混凝土损伤较轻微,大部分刻槽肋FRP筋表现为混凝土肋剪切破坏,二者的粘结强度随混凝土强度的增加而增大;增加保护层厚度可增强混凝土对FRP筋的约束效果,有助于提高粘结肋FRP筋的粘结强度,但对刻槽肋FRP筋几乎没有影响;增加相对肋高hrd和FRP筋肋宽比FR可提高粘结肋FRP筋的粘结强度;而刻槽肋FRP筋几乎不受hrd的影响,主要受混凝土肋宽比C_(R)的影响,其粘结强度随C_(R)的增加而增大;建立的粘结强度公式计算值与试验结果吻合较好,预测精度高于设计规范,主要原因在于该公式准确考虑了FRP筋肋成型工艺和几何特征对粘结强度的影响。

Exponential Decay of Laminated Beam with Nonlinear Time-varying Delay and Microtemperature Effect

This research paper addresses a topic of interest to many researchers and engineers due to its effective applications in various industrial areas.It focuses on the thermoelastic laminated beam model with nonlinear structural damping,nonlinear time-varying delay,and microtemperature effects.Our primary goal is to establish the stability of the solution.To achieve this,and under suitable hypotheses,we demonstrate energy decay and construct a Lyapunov functional that leads to our results.

一种新的宏、细观变形全场测量方法(英文)

基于光学干涉和衍射理论,提出了一种新的用于宏、细观面内变形测量的光学方法。利用三束准直相干光之间的干涉,分别得到面内位移U+V和U-V的两幅耦合条纹图。借助于FFT相移技术,直接计算出全场的U和V分布。本实验系统中包含有长距离显微镜,三光束系统,数字图像采集和处理系统等。它具有光路简单,避开条纹级次的确定,直接计算得到U、V场等优点。将它用于热塑性复合材料 56层板AS4/PEEK[0/±45/90]7S三点弯曲梁位移场的宏、细观测量。得到了层间的变形规律。本文还利用三维各向异性弹性有限元法对AS4/PEEK[0/±45/90]7S三点弯曲梁进行了数值计算,得到了自由表面的位移场和应变场的数值解。定量分析了层间的变形传递规律,有助于进一步分析AS4/PEEK[0/±45/90]7S层合板宏、细观变形。

Recent Advances in Hole Making of FRP/Metal Stacks:A Review

Weight reduction is a key driving force for materials development in aerospace industry,which leads to extensive usage of lightweight structural materials such as fiber reinforced polymer(FRP),titanium alloy,aluminum alloy,etc.Hole making is indispensable to assembling these lightweight components by riveted or bolted joints.However,hole making of FRP / metal stacks is always the most challenging task due to differences of material properties between FRP and metals.A comprehensive literature review on hole making of FRP/metal stacks in the last decade is given with a focus on four main aspects including drilling operation,drilling damages and machining parameter optimization,tool performance and wear,and developments in hole making technology.Finally,in order to ensure the precise and efficient hole making of FRP/metal stacks,an idea of low frequency vibration assisted drilling(LFVAD)FRP/metal stacks based on material removal characteristics is put forward by fully exploiting the unique advantages of LFVAD technology.

纤维增强聚合物（FRP）筋的设计与应用

1设计原则 FRP材料的特点是各向异性和高抗拉强工、配筋方向缺乏塑性变形(yielding).各向异性影响抗剪强度与FRP筋的连接作用以及与混凝土的粘结性能.为此提出的设计程序就要对混凝土采用FRP筋缺乏延性作出解释和说明.根据1995年版的ACI318有关规定,强度与工作应力设计方法可继续采用.FRP配筋、混凝土构件的设计以所需强度为基础,然后再根据可操作性能以及有关极限标准(如裂缝宽度、挠度、疲劳强度和蠕变破坏等)进行校核.在很多情况下,设计必须按使用标准进行控制.

FRP加固钢结构轴心受压构件的弹性稳定分析

钢结构中存在大量的受压构件,由于失稳而导致破坏。与传统的钢结构加固方法相比,FRP加固钢结构具有明显的优势。目前国内外对FRP加固钢结构技术的研究主要限于受拉构件和受弯构件加固,对受压构件的加固几乎还未涉足。采用能量法得到了FRP加固轴心受压钢管的弹性屈曲荷载,并与有限元计算结果进行了对比。

FRP-ECC加固对钢筋混凝土方柱轴压性能影响的研究

对常见钢筋混凝土方柱的FRP-ECC加固方案开展轴向抗压的力学性能研究。引入混凝土塑性损伤(CDP)和钢筋三折线等特征模型建立构件有限元模型,通过数值计算,明确了加固后钢筋混凝土破坏时的应力分布状态,探究了FRP的厚度和布置间距、ECC厚度及构件配筋率等因素对加固后承载力的影响规律。研究结果表明:方柱最终以核心混凝土束进入塑性状态而破坏,而FRP加固条仍处于弹性状态。随着FRP片材、ECC黏结层厚度的增加和加固条中心距的减小,加固效果逐渐凸显。FRP厚度达到20 mm或加固条宽度与间距的比值达到0.4时,极限承载力幅值提升分别达到11.29%和5.12%,同时,对于配筋率较高的方柱,FRP-ECC加固效果更明显。