含钢率对GFRP管-钢骨混凝土组合构件抗冲击性能的影响

为了研究含钢率对GFRP(glass fiber reinforced polymer)管-钢骨混凝土组合构件抗冲击性能的影响,建立15个组合构件的数值模型,在验证模型正确的基础上,通过分析典型构件的冲击全过程、截面弯矩发展以及破坏时应变分布规律,研究构件在侧向冲击荷载作用下的破坏模式;通过分析构件冲击力时程曲线、侧移时程曲线以及能量变化情况,探究含钢率对不同长细比构件抗冲击性能的影响。结果表明:与未配置钢骨的构件相比,GFRP管-钢骨混凝土构件的抗冲击承载力提高了7%~134%,侧向位移减小了13%~68%。在侧向冲击荷载作用下,构件的破坏模式以弯曲破坏为主,同时伴随着GFRP管和混凝土冲击区域的局部破坏,抗弯刚度是影响构件抗冲击性能的主要因素之一。构件的抗冲击承载力随着含钢率的增高而提高,随着构件长细比的增大而降低。含钢率相差1.5%时,截面惯性矩较大的窄翼缘型钢对构件的抗冲击性能更有利。对于长细比大于20的构件,钢骨耗能是组合构件总能耗的主要组成部分。

内衬GFRP防护复合管壁原缺陷坑处应力重分布规律分析

为了深入研究内衬GFRP防护复合管壁在其原管道内腐蚀缺陷坑处的应力重分布状态以及其修复的效果,利用弹塑性力学中的平衡微分方程,建立了管道内腐蚀缺陷处的数学模型,采用有限单元法建立了含单个腐蚀缺陷的管道模型,并通过改变腐蚀缺陷坑的深厚比,将修复前后腐蚀缺陷坑处的应力状态进行对比分析。分析结果表明,腐蚀缺陷坑的深厚比对管道的应力分布有着显著的影响,所以在进行管道安全评估时应注意腐蚀坑深度的影响;在腐蚀缺陷坑深厚比0.1到0.8的分次增加的过程中,管壁腐蚀缺陷处的周向应力,径向应力,Mises应力都有增大的趋势;修复前腐蚀缺陷坑处的周向应力和Mises应力相近,径向应力较前两者小,三者中周向应力最大;在修复前后,管道腐蚀缺陷处的控制应力一般是周向应力,管道的失效可依据周向应力进行判断;修复后的内衬GFRP防护复合管壁,原始腐蚀缺陷坑处发生了应力重分布,其周向应力与Mises应力均有减小,修复效果明显。

两端简支GFRP管-钢骨混凝土构件抗侧向冲击性能有限元分析

目的 研究两端简支GFRP管-钢骨混凝土构件的抗侧向冲击性能,为该类构件的工程应用提供参考。方法 建立并验证侧向冲击荷载作用下两端简支GFRP管-钢骨混凝土构件有限元模型,分析了典型构件在侧向冲击荷载作用下的全过程、破坏形态、应力发展、相互作用力时程曲线和弯矩时程曲线等动态响应;研究了冲击能量、冲击冲量、钢材强度、GFRP管厚度以及截面含钢率对构件抗冲击性能的影响。结果 随着冲击能量及冲量的增大,冲击持时和构件弯曲变形增大;提高钢材强度、GFRP管厚度可以改善构件的抗冲击性能。结论 GFRP管对混凝土有较好的约束作用,构件在侧向冲击荷载作用下整体发生弯曲破坏,内部钢骨塑性变形发展充分,构件抗侧向冲击性能优越。

Seismic performance of recycled concrete-filled square steel tube columns

An experimental study on the seismic performance of recycled concrete-filled square steel tube （RCFST） columns is carried out. Six specimens were designed and tested under constant axial compression and cyclic lateral loading. Two parameters, replacement percentage of recycled coarse aggregate （RCA） and axial compression level, were considered in the test. Based on the experimental data, the hysteretic loops, skeleton curves, ductility, energy dissipation capacity and stiffness degradation of RCFST columns were analyzed. The test results indicate that the failure modes of RCFST columns are the local buckling of the steel tube at the bottom of the columns, and the hysteretic loops are full and their shapes are similar to normal CFST columns. Furthermore, the ductility coefficient of all specimens are close to 3.0, and the equivalent viscous damping coefficient corresponding to the ultimate lateral load ranges from 0.323 to 0.360, which demonstrates that RCFST columns exhibit remarkable seismic performance.

Effect of contact thermal resistance on temperature distributions of concrete-filled steel tubes in fire

To predicate the temperature distribution of concrete-filled steel tubes(CFSTs) being exposure to fire,a finite element analysis model was developed using a finite element package,ANSYS.A suggested value of contact thermal resistance was therefore proposed with the supporting of massive numbers of collected test data.Parametric analysis was conducted subsequently towards the cross-sectional temperature distribution of CFST columns in four-side fire,in which the exposure time,width of the cross section,steel ratio were taken into account with considering contact thermal resistance.It was found that contact thermal resistance has little effect on the overall temperature regulation with the exposure time,the width of cross-section or the change of steel ratio.However,great temperature dropping at the concrete adjacent to the contact interface,and gentle temperature increase at steel tube,exist if considering contact thermal resistance.The results of the study are expected to provide theoretical basis for the fire resistance behavior and design of the CFST columns being exposure to fire.

以水压试验分析纤维缠绕角度对GFRP管力学性能的影响

基于海洋环境中长期受压的钢筋混凝土桥梁墩柱易发生开裂和锈蚀的特点,工程中越来越多地应用纤维增强复合材料(FRP)对桥梁墩柱进行加固处理。实践表明FRP纤维缠绕角度的大小对其能起到的加固效果存在一定的差异。为更好地探究纤维缠绕角度与力学性能的关系,对45°、60°和80°三组不同缠绕角度的玻璃纤维复合材料(GFRP)圆管进行水压加载试验,通过收集应力-应变数据计算不同角度下GFRP圆管的环向弹性模量。结果表明:随着纤维缠绕角度的增大,GFRP管的环向弹性模量由8.85 GPa提高到38.16 GPa,对钢筋混凝土墩柱的加固效果更好。

Reliability analysis of circular concrete-filled steel tube with material and geometrical nonlinearity

Most of the previous research on concrete-filled steel tube is restricted to a deterministic approach. To gain clear insight into the random properties of circular concrete-filled steel tube, reliability analysis is carried out in the present study. To obtain the Structural nonlinear response and ultimate resistance capacity, material and geometrical nonlinear analysis of circular concrete-filled steel tube is performed with a three-dimensional degenerated beam ele- ment. Then we investigate the reliability of concrete-filled steel tube using the first-order reliability method combined with nonlinear finite element analysis. The influences of such parameters as material strength, slenderness, initial geo- metrical imperfection, etc. on the reliability of circular concrete-filled steel tube column are studied. It can be con- cluded that inevitable random fluctuation of those parameters has significant influence on structural reliability, and that stochastic or reliability methods can provide a more rational and subjective evaluation on the safety of CFT structures than a deterministic approach.

Behavior of eccentrically loaded concrete-filled GFRP tubular short columns

The glass fiber reinforced polymer (GFRP) tube is an effective material that can increase the bearing capacity and ductility of concrete.To study the mechanical behavior of this composite structure,twenty-one concrete-filled GFRP tubular short columns were tested under an eccentric load.The principle influencing factors,such as the eccentricity ratio,concrete strength and ratio of longitudinal reinforcement were also studied.In addition,the course of deformation,failure mode,and failure mechanism were analyzed by observing the phenomena and summarizing the data.The test results indicated that the strength and deformation characteristics of core concrete increase as a result of the addition of the GFRP tube.However,the gain in strength due to the addition of the GFRP tube decreases as the ratio of e /d increases.An increase in the longitudinal steel ratio can improve the bearing capacity of the composite short column effectively.Furthermore,the study showed that the constraint effect of the GFRP tube on high-strength concrete is not as effective as that on common concrete.The reason is that the lateral deformation of the high-strength concrete is less than that of the common concrete when the concrete column was tested under the same axial compression ratio.

Ductility and Ultimate Capacity of Concrete-Filled Lattice Rectangular Steel Tube Columns

A kind of concrete-filled lattice rectangular steel tube(CFLRST)column was put forward.The numerical simulation was modeled to analyze the mechanical characteristic of CFLRST column.By comparing the load-deformation curves from the test results,the rationality and reliability of the finite element model has been confirmed,moreover,the change of the section stiffness and stress in the forcing process and the ultimate bearing capacity of the column were analyzed.Based on the model,the comparison of ultimate bearing capacity and ductility between CFLRST column and reinforced concrete(RC)column were also analyzed.The results of the finite element analysis show that the loading process of CFLRST column consists of elastic stage,yield stage and failure stage.The failure modes are mainly strength failure and failure of elastoplastic instability.CFLRST column has higher bearing capacities in comparison with reinforced concrete columns with the same steel ratio.In addition,the stiffness degeneration of CFLRST column is slower than RC column and CFLRST column has good ductility.

内套GFRP管圆钢管混凝土组合柱的偏压力学性能分析

利用ABAQUS有限元软件建立了适用于内套GFRP管圆钢管混凝土组合柱的单向偏压模型,研究了影响该组合柱力学性能及失效模式的关键因素。结果表明:该组合柱的极限承载力随着偏心距的增大而降低,随着外置圆钢管和内套GFRP管壁厚的增加而提高。内套GFRP管壁厚对构件极限承载力的影响小于偏心距和外置圆钢管壁厚造成的影响。长径比对极限承载力的影响较小。基于影响系数法建立了适用于单向偏压构件的极限承载力计算方法,该计算方法可为相关工程提供参考。

Prediction of Axial Capacity of Concrete-Filled Square Steel Tubes Using Neural Networks

The application of artificial neural network to predict the ultimate bearing capacity of CFST （ concrete-filled square steel tubes） short columns under axial loading is explored. Input parameters consiste of concrete compressive strength, yield strength of steel tube, confinement index, sectional dimension and width-to-thickness ratio. The ultimate bearing capacity is the only output parameter. A multilayer feedforward neural network is used to describe the nonlinear relationships between the input and output variables. Fifty-five experimental data of CFST short columns under axial loading are used to train and test the neural network. A comparison between the neural network model and three parameter models shows that the neural network model possesses good accuracy and could be a practical method for predicting the ultimate strength of axially loaded CFST short columns.

GFRP管-灌浆料修复锈蚀钢管节点受压性能研究

圆钢管焊接节点应用广泛,长期服役后的腐蚀退化问题严重影响其安全性和剩余寿命。为研究GFRP管-灌浆料修复锈蚀钢管节点的效果,对6组未锈蚀、锈蚀未修复和GFRP管-灌浆料修复的锈蚀圆钢管T形节点开展了支管轴压力静载试验。试验结果表明:主管锈蚀导致的约10%重量损失会使节点承载力降低近20%;GFRP管-灌浆料有效地约束了锈蚀主管的侧向外凸变形,使节点的控制破坏模式由主管塑性化转变为主管冲剪,从而使锈蚀节点的受压承载力和初始刚度分别提升约100%和50%,且均高于未锈蚀的对比试件。基于验证的精细化有限元模型,进一步参数分析表明,支主管直径比、GFRP管厚度以及修复主管截面空心率是影响修复节点受压性能的关键参数,主管修复长度和灌浆料强度的影响较小;优化修复构造,可使主管重量损失28%的锈蚀节点承载力提升至锈蚀前的1.5倍以上。最后,基于修复节点承载力达到1.2倍未锈节点的目标,提出了适用于不同节点锈蚀率的修复建议,可为长期服役后锈蚀钢管结构的修复与性能提升提供参考。

极地低温下GFRP管-混凝土短柱循环轴压性能

为了推广GFRP管-混凝土柱在极地基础设施建设中的应用,开展了14个GFRP管-混凝土短柱在极地低温环境下的轴压试验,主要研究参数为温度和GFRP管的径厚比.试验结果包括试验现象与破坏模式、荷载-应变曲线、塑性应变、刚度退化和耗能能力等.试验结果表明:所有试件破坏模式均为GFRP管环向撕裂,发生脆性破坏;单调加载下组合柱的荷载-应变曲线与循环加载下组合柱的荷载-应变曲线的包络线基本吻合,但循环荷载作用下组合柱的极限荷载和峰值应变略低于单调荷载作用下的组合柱;随着温度的降低,组合柱的极限荷载逐渐增大,峰值应变逐渐减小;循环荷载作用下,GFRP管-混凝土短柱的塑性应变与卸载点应变呈线性关系,且温度影响不大,混凝土强度是影响两者关系的主要因素;随着竖向应变的增大,GFRP管-混凝土短柱的刚度逐渐降低,且降低速率逐渐减小;GFRP管-混凝土短柱的等效黏滞阻尼系数逐渐增大,且增大速率逐渐降低.综合以上分析,采用“最远点”法确定GFRP管-混凝土短柱的名义屈服点,并提出了GFRP管-混凝土短柱在低温下的设计方法和设计流程,分别从强度、变形和GFRP管利用率3个角度来衡量试件设计的安全储备,为GFRP管-混凝土短柱在极地低温环境下的安全设计提供参考,保障其在极地和寒区环境的服役安全.

冻融环境下GFRP管混凝土柱轴压性能试验研究

通过对21个玻璃纤维增强聚合物(GFRP)管混凝土柱和21个素混凝土柱分别在水溶液和质量分数为3.5%的氯化钠(NaCl)溶液中进行冻融循环试验及轴压试验,且对冻融后的GFRP管混凝土柱进行了超声波检测,研究冻融环境下不同冻融介质和冻融循环次数对GFRP管混凝土柱轴压性能的影响。结果表明,冻融介质相同的情况下,随着冻融循环次数的增加,质量损失率增大,相对动弹性模量降低,GFRP管混凝土柱内异常点增多,承载力下降,极限应变下降;冻融次数相同的情况下,经盐冻作用的GFRP管混凝土柱轴压极限承载力降低更为明显。GFRP管混凝土柱盐冻循环150次后极限承载力下降了29.45%,下降量是相同条件下水冻结果的2.19倍。盐冻循环后的GFRP管混凝土柱极限应变小于相同条件下的水冻循环极限应变。

GFRP管-配筋空心高强混凝土轴压短柱有限元分析

目的为提高PHC管柱在海洋环境中的耐腐蚀性和承载力,将PHC管柱置入GFRP管混凝土截面中,形成GFRP管-配筋空心高强混凝土柱,并研究其短柱的轴压性能。方法利用ABAQUS软件建立组合柱的有限元模型,验证模型可靠性,对典型构件的荷载-位移曲线、各组成部分的内力分担比例、纵向应力变化进行分析;研究GFRP管壁厚度、夹层混凝土抗压强度、普通钢筋直径对构件承载力与提高系数的影响。结果随着GFRP管壁厚度、夹层混凝土强度及普通钢筋直径的增加,构件的轴压承载力提高率分别在17.4%~44.7%、3.3%~9.7%以及3.8%~7.6%,极限轴向位移提高率分别在145.2%~182.8%、-1.2%~-8.4%以及3.3%~1.4%;构件提高系数随GFRP管壁厚度增加显著提高。结论GFRP管-配筋空心高强混凝土柱有较高的轴压承载力和轴向变形能力;在三种参数中,GFRP管壁厚度是影响构件的轴压承载力、轴向变形能力以及构件各组成部件间组合作用的重要参数。

硫酸盐环境下GFRP管混凝土柱轴压性能演化规律

硫酸盐长期腐蚀会导致混凝土结构性能退化,纤维增强聚合物(FRP)与混凝土组合结构具有良好的抗腐蚀性能。对玻璃纤维增强聚合物(GFRP)管混凝土短柱采用硫酸盐浸泡和干湿循环两种作用方式开展腐蚀试验,通过表观现象观察、质量损失测试、超声探测等,研究组合柱在硫酸盐作用下结构变化特征;开展轴压试验,测试极限承载力与荷载-应变曲线,对比分析GFRP管混凝土短柱轴压性能演化规律。结果表明:在硫酸盐环境中,GFRP管能抵抗硫酸盐的侵蚀,有效保护混凝土,确保组合柱抗压强度。硫酸盐溶液浸泡和干湿循环作用降低了GFRP管混凝土短柱的强度以及延性,且随着腐蚀时间的增加,硫酸盐干湿循环作用比浸泡作用下对GFRP管混凝土短柱造成的缺陷更多,GFRP管与混凝土协同作用略微降低。

Axial Bearing Capacity of Short FRP Confined Concrete-filled Steel Tubular Columns

The bearing capacity of FRP confined concrete-filled steel tubular （FRP-CFST） columns under axial compression was investigated. This new type of composite column is a concrete-filled steel tube （CFST） confined with fiber-reinforced polymer （FRP） wraps. Totally 11 short column specimens were tested to failure under axial compression. The influences of the type and quantity of FRP, the thickness of steel tube and the concrete strength were studied. It was found that the bearing capacity of short FRP-CFST column was much higher than that of comparable CFST column. Furthermore, the formulas for calculating the bearing capacity of the FRP-CFST columns are proposed. The analytical calculated results agree well with the experimental results.

基于空气激波管的GFRP层合板抗爆性能研究

基于激波管原理自制了80 mm口径的空气冲击波加载装置,并进行了冲击波峰值、速度等参数与破膜压力之间关系的标定。在此基础上,开展了GFRP层合板抗爆性能研究,并用3D全场应变测量系统获取了层合板的动态响应过程。结果表明:使用空气激波管产生的冲击波可以合理模拟爆炸波的加载过程;在冲击波峰值压力为0.93~3.93 MPa之间时,GFRP层合板在冲击波加载过程中的挠度随冲击波压力的增大有S形增大的趋势,卸载之后残余变形很小;预制2 mm小孔的层合板在峰值压力为3.5 MPa的冲击波作用下,发生了撕裂破坏,说明初始损伤严重影响了GFRP层合板的抗爆炸冲击能力。

GFRP缠绕管-木-钢筋混凝土组合柱轴压性能研究

本文通过试验研究了用玻璃纤维增强复合材料(GFRP)缠绕管约束的木-钢筋混凝土组合柱的轴向压缩性能,并与GFRP布包裹的木-钢筋混凝土组合柱进行比较,分析了各组成部分对组合柱失效模式、承载力、刚度和延性的影响。结果表明:添加木芯的GFRP管约束柱的刚度比添加木芯的外包GFRP布组合柱刚度高36.2%~49.2%,而不同GFRP约束形式对组合柱的承载力和延性无显著影响;木芯的引入使GFRP约束柱的延性提升了23.8%~27.0%;相比于无GFRP约束的组合柱,使用GFRP缠绕管约束组合柱可使柱的承载能力显著提高146.5%~208.6%,延性提高28.4%~56.4%。