Mechanical Behavior of a Glass-fiber Reinforced Composite to Steel Joint for Ships

The use of a glass-fiber reinforced composite in marine structures is becoming more common, particularly due to the potential weight savings. The mechanical response of the joint between a glass-fiber reinforced polymer （GRP） superstructure and a steel hull formed is examined and subsequently modified to improve performance through a combined program of modeling and testing. A finite-element model is developed to predict the response of the joint. The model takes into account the contact at the interface between different materials, progressive damage, large deformation theory, and a non-linear stress-strain relationship. To predict the progressive failure, the analysis combines Hashin failure criteria and maximum stress failure criteria. The results show stress response has a great influence on the strength and bearing of the joint. The Balsawood-steel interface is proved to be critical to the mechanical behavior of the joint. Good agreement between experimental results and numerical predictions is observed.

Flexural behavior of steel reinforced engineered cementitious composite beams

In order to enhance the durability of steel encased concrete beams, a new type of steel reinforced engineered cementitious composite(SRECC) beam composed of steel shapes, steel bars and ECC is proposed. The theoretical analyses of the SRECC beam including crack propagation and stress-strain distributions along the depth of the composite beam in different loading stages are conducted. A theoretical model and simplified design method are proposed to calculate the load carrying capacity. Based on the proposed theoretical model, the relationship between the moment and corresponding curvature is derived. The theoretical results are verified with the finite element analysis. Finally, an extensive parametric study is performed to study the effect of the matrix type, steel shape ratio, reinforced bar ratio, ECC compressive strength and ECC tensile ductility on the mechanical behavior of SRECC beams. The results show that substitution concrete with ECC can effectively improve the bearing capacity and ductility of composite beams. The steel shape and longitudinal reinforcement can enhance the loading carrying capacity, while the ductility decreases with the increase of steel shape ratio. ECC compressive strength has significant effects on both load carrying capacity and ductility, and changing the ultimate strain of ECC results in a very limited variation in the mechanical behavior of SRECC beams.

THE EFFECT OF POLYMER IN STEEL FIBER REINFORCED CEMENT COMPOSITES

Three kinds of polymers, polymethyl acrylate emulsion (POLYVINYLformal solution (PV- FO), styrene acrylate copolymer emulsion (SA)are chosen To study the effect of polymer in steel fiber rein forcedce- Ment composites (SFRCC). The experimental results show That thebonding properties in SFRCC are remarkably im- Proved after theaddition of three kinds of polymer.

Fatigue tests of composite beam by steel fiber reinforced self-stressing concrete in the hogging bending

Through the experiments of 7 T-section composite beams, steel fiber reinforced self-stressing concrete （SFRSC） as the composite beam in the composite layer was studied under the hogging bending. The tests simulated composite layer tensile strain under the hogging bending of inverted loading composite beams, giving the relationship under the different fatigue stress ratios between fatigue cycles and steel bar’s stress range, crack width, stiffness loss and damage, etc., in composite layer. This article established fatigue life equation, and analyzed SFRSC reinforced mechanism to crack width and stiffness loss. The results show that SFRSC as the composite beam concrete has excellent properties of crack resistance and tensile, can reinforce the fatigue crack width and stiffness loss of composite beams, and improve the durability and in normal use of composite beams in the hogging bending zone.

Study on Interface mechanical behavior of steel tube reinforced concrete composite pile

Currently for the steel tube reinforced concrete composite pile research, although predecessors make a comprehensive research on the composite pile beating performance, design technology, but there are still many problems have not been solved, such as the steel tube reinforced concrete pile composite interracial force learn performance research is still in the initial stage. In this paper, we mainly discuss the research methods of several interface mechanical properties and propose the possibility of studying the mechanical properties of the steel tube reinforced concrete composite pile by using the principle of ultrasonic speckle.

Experimental and analytical study on seismic behavior of steel-concrete multienergy dissipation composite shear walls

In this paper, a steel-concrete multi-energy dissipation composite shear wall, comprised of steel-reinforced concrete （SRC） columns, steel plate （SP） deep beams, a concrete wall and energy dissipation strips, is proposed. In order to study the multi-energy dissipation behavior and restorability after an earthquake, two stages of low cyclic loading tests were carded out on ten test specimens. In the first stage, test on five specimens with different number of SP deep beams was carried out, and the test lasted until the displacement drift reached 2%. In the second stage, thin SPs were welded to both sides of the five specimens tested in the first stage, and the same test was carried out on the repaired specimens （designated as new specimens）. The load-bearing capacity, stiffness, ductility, hysteretic behavior and failure characteristics were analyzed for both stages and the results are discussed herein. Extrapolating from these results, strength calculation models and formulas are proposed herein and simulations using ABAQUS carried out, they show good agreement with the test results. The study demonstrates that SRC columns, SP deep beams, concrete wall and energy dissipation strips cooperate well and play an important role in energy dissipation. In addition, this study shows that the shear wall has good recoverability after an earthquake, and that the welding of thin SP＇s to repair a deformed wall is a practicable technique.

Electromagnetic Shielding and Absorption Properties of Fiber Reinforced Cementitious Composites

In order to investigate the electromagnetic shielding effectiveness （SE） and absorbing properties of fiber reinforced concrete, steel fiber, carbon fiber and synthetic polyvinyl alcohol （PVA） fiber reinforced concrete were researched. The results show that with the increase of fiber Volume fraction, the SE and trend of frequency change of corresponding fiber reinforced concrete are enhanced. When the volume content of steel fiber is 3%, the SE of concrete is above 50 dB and its frequency is above 1.8 GHz. Moreover, in the range of 8-18 GHz, steel fiber, carbon fiber and PVA fiber all can improve the microwave absorption properties of concrete. The concrete with 0.5% carbon fiber can achieve the best absorbing property, the minimum reflectivity is about -7 dB; while steel fiber optimal volume fraction is 2%. The reflectivity curve of PVA fiber reinforced concrete fluctuates with the frequency, and the minimum value of the reflectivity is below -10 dB. The results show that fiber reinforced concrete could be used as EMI（electromagnetic interference） prevention buildings by attenuating and reflecting electromagnetic wave energy.

Fatigue properties of special kind of reinforced concrete composite beams

The special reinforced concrete composite beam consists of a steel fiber reinforced self-stressing concrete composite layer and a reinforced concrete T-beam, and constructional bars are set up at their bonding interface. Fatigue properties of the composite beam under the action of negative moment were experimentally studied. Through inverted loading mode the load-beating state of a composite beam was simulated under the action of negative moment. With the ratios of constructional bars being 0, 0.082% and 0.164% respectively as parameters, the effects of constructional bars on the properties of composite beam, such as fatigue life, crack propagation, rigidity loss as well as damage behavior of bonding interface, were studied. The mechanism of the constructional bars on the fatigue properties of the composite beams and the restriction mechanism of crack widths and rigidity loss were analyzed. The test results show that the constructional bars can enhance the shear resistance of the bonding interface between composite layer and old concrete beam and restrict expanding of steel fiber reinforced self-stressing concrete, which are beneficial to synergistic action of composite layer and old concrete beam, to reducing the stress amplitude of bars and the crack width of composite layer, and to increasing the durability and fatigue life of the composite beam.

配筋PVA-钢混杂纤维增强水泥基复合材料梁柱边节点抗震性能试验研究

改善工程材料韧性和耐久性,提高框架梁柱节点抵抗变形和破坏的能力,是提高框架结构抗震韧性的有效途径之一。采用PVA-钢混杂纤维增强水泥基复合材料代替普通混凝土应用到梁柱边节点,考虑轴压比和加密区体积配箍率的影响,设计6个配筋PVA-钢混杂纤维增强水泥基复合材料、1个配筋单掺PVA纤维增强水泥基复合材料和1个钢筋混凝土梁柱边节点试件进行拟静力试验,分析其破坏形态、滞回曲线、骨架曲线、延性、耗能能力、钢筋应变和梁端塑性铰区转角,探讨混杂纤维的加入对梁柱边节点抗震性能的影响。结果表明:与钢筋混凝土节点和单掺PVA纤维增强水泥基复合材料节点相比,PVA-钢混杂纤维增强水泥基复合材料节点的承载力高、变形能力大、延性好、耗能能力强,抗震性能显著提升。当试验轴压比从0.12增加到0.24,梁端塑性铰区产生一定的外移,塑性性能发挥更充分,同时试件的变形能力、延性、耗能能力增加。在加密区体积配箍率减小的情况下,试件仍表现出良好的抗震性能。

圆钢管型钢再生混凝土组合柱滞回性能非线性有限元分析

基于圆钢管型钢再生混凝土组合柱低周反复荷载试验研究,采用OpenSees软件对该组合柱进行了滞回性能数值分析,获取了组合柱的滞回曲线及抗震性能指标,并与试验结果进行了比较,验证了组合柱数值模型的合理性。在此基础上,对组合柱的滞回性能开展了参数影响分析。结果表明:再生骨料取代率从0增大到100%,组合柱的峰值荷载下降了7.78%,延性略有降低;提高再生混凝土强度、型钢强度及圆钢管强度,对于提升组合柱的承载力及刚度是有利的,但却使组合柱的脆性增大;随着轴压比的增大,组合柱的承载力呈现先上升后下降的趋势,而延性逐渐变差;型钢配钢率从5.54%增至9.99%,组合柱的峰值荷载提高了24.34%,但对于改善组合柱的延性不明显;增大钢管壁厚对组合柱的承载力和延性均是有利的。

GFRP布无损加固输电铁塔角钢受力性能研究

针对现役输电铁塔在覆冰、风荷载、边坡变形等作用下可能存在承载力不足的问题,研究玻璃纤维增强复合材料(GFRP)布无损加固铁塔角钢的受力性能。首先,利用文献中的物理试验对加固钢材数值试验方法进行验证;其次,以铁塔角钢为研究对象,基于验证的数值试验方法建立72组有限元分析模型,探讨长细比、GFRP布粘贴层数、粘贴长度等因素对角钢极限承载力的影响;最后,推导并改进GFRP布角钢复合构件理论承载力计算方法。结果表明:不同长细比对构件极限承载力影响较大,当角钢长细比大于70时,加固后的承载力提升不明显;增加GFRP布粘贴层数,角钢承载力大幅提升,粘贴8层GFRP布的承载力提升率最高达41.03%;柱中GFRP布粘贴长度为75%与粘贴长度为100%的角钢极限承载力相比提升不大,仅为0.27%~2.10%;对推导的GFRP布角钢复合构件理论承载力计算方法引入修正系数后,数值试验与理论计算值相对误差缩小至-2.70%~1.77%,有效提升理论解计算精度。在对现役铁塔加固时,只需对角钢全长的75%粘贴6~8层GFRP布进行加固,且对于长细比λ≤70的角钢加固效果更好。

装配式型钢混凝土复合墙抗震性能研究

为研究铸钢节点连接装配式型钢混凝土复合墙的破坏机理和抗震性能,对1∶2缩尺的型钢混凝土复合墙试件进行了拟静力试验,通过改变墙体的内置型钢类型,对比分析其在低周往复荷载作用下的破坏过程、破坏模式、滞回特性、抗剪承载力、变形能力、墙体损伤以及耗能能力等,试验结果表明:焊接结构用铸钢节点强度和刚度大、安全性高,可以应用于型钢混凝土复合墙的现场装配式连接中;型钢混凝土复合墙均发生整体剪切破坏,其抗剪承载力、耗能和变形能力较钢筋混凝土复合墙均有较大程度的提高.结合工程实际,给出了型钢混凝土复合墙的现场装配方案.

装配式型钢混凝土叠合框架梁连接节点构造设置与安全分析

住房和城乡建设部印发《“十四五”建筑业发展规划》提出大力发展装配式建筑、推动生产和施工智能化升级的主要任务。而国内目前采用的预制叠合框架梁存在着跨度大自重大吊装成本高、预制梁柱节点位置易发生钢筋碰撞吊装定位难度大等问题,限制了装配式建筑结构的发展。结合实际工程项目,提出一种新型的装配式型钢混凝土叠合框架梁,并对该叠合梁的构造设置、连接方式及安全性进行分析,从而为装配式框架结构、框架—剪力墙结构等装配式建筑中框架梁的深化设计提供一种新的拆分方案。

钢纤维细石混凝土-钢组合板抗弯性能试验研究

钢纤维细石混凝土是一种具有优异力学性能和良好工作性的高性能混凝土复合材料。本试验针对正交异性钢桥面铺装层裂缝病害问题,对4组采用不同钢筋配筋率和保护层厚度的横桥向钢纤维细石混凝土-钢组合桥面板进行了抗弯破坏试验,研究了组合板的荷载-挠度关系与裂缝开展特征;用等效截面法计算了开裂应力、裂缝宽度和钢筋应力,验证了钢纤维细石混凝土-钢组合板的抗裂性能。结果表明:60 mm厚钢纤维细石混凝土铺装层在小配筋率(2.6%)和低于规范要求的保护层厚度(15 mm)条件下呈现出多缝开裂的破坏形态,具备较高的延性和开裂应力,满足规范和工程应用的要求。

配筋率对钢箱-UHPC组合梁裂缝特征的影响

为研究钢箱-超高性能混凝土(UHPC)组合梁负弯矩区裂缝特征,设计制作了3根配筋率分别为1%、2%和3%的UHPC翼板部分充填砼窄幅钢箱组合梁,通过对不同配筋率的试验梁进行反向加载试验研究组合梁的裂缝发展特征,并对最大裂缝宽度、裂缝间距及开裂荷载进行对比分析。研究结果表明:试验梁在不同配筋率条件下,UHPC面层裂缝发展明显不同,配筋率越高最大裂缝宽度越小,裂缝越密集,开裂荷载越大;与配筋率为1%的试验梁相比,配筋率为2%和3%的试验梁的开裂弯矩分别提高了30.3%和65.2%;可根据《公路钢筋混凝土及预应力混凝土桥涵设计规范》(JTG 3362—2018)中的裂缝宽度计算公式乘以0.78的修正系数,来计算窄幅钢箱-UHPC组合梁负弯矩区的裂缝宽度。

CFRP-PCPs复合筋加固钢-混组合梁负弯矩区抗裂试验与理论计算

为解决钢-混组合梁负弯矩区混凝土板易开裂而造成刚度减弱的行业难题,以预制的CFRP-PCPs(carbon fibre reinforced polymer-prestressed concrete prisms)复合筋作为中支座的腹筋,并以复合筋的数量、预应力张拉水平和截面尺寸为主要参数设计制作了五根复合筋钢-混组合连续梁和一根普通组合连续梁,研究其在单跨单点荷载下负弯矩区的抗裂性能。结果表明:复合筋能显著增强中支座截面刚度,对负弯矩区的裂缝控制能力提升显著;与普通组合梁相比,复合筋梁的开裂荷载提高近30%,裂缝数量与裂缝宽度减少近50%;复合筋面积是提高裂缝控制能力的主要因素,预应力水平和截面尺寸对开裂荷载的影响较弱;复合筋的开裂荷载与预应力水平、面积正相关,其中预应力水平是影响复合筋效用时长的关键因素。基于现有理论和试验数据,本文提出CFRP-PCPs复合筋钢-混组合梁负弯矩区开裂荷载和复合筋的开裂荷载计算公式,计算结果与试验值较为吻合,可为复合筋在钢-混组合梁桥实际工程中应用提供参考。

长材轧机热轧钢筋类产品生产概述

结合国家标准对长材轧机热轧钢筋类产品的生产工艺、产品特点等进行解读,并介绍高强螺纹钢筋的几种生产工艺。可供工程技术人员、产品用户等理解各类热轧钢筋的生产工艺、产品特点等。

正交异性钢-钢纤维混凝土组合桥面板疲劳极限状态研究

为了解正交异性钢-钢纤维混凝土(Steel Fiber Reinforced Concrete,SFRC)组合桥面板的疲劳性能及失效机理,以川南城际铁路临港长江大桥为背景,设计、制作正交异性钢-SFRC组合桥面板足尺模型进行疲劳试验,采用ANSYS软件建立试件有限元模型,研究关键细节的疲劳应力和开裂等情况。基于有限元模型,分析不同设计参数(钢顶板厚度、栓钉布置、SFRC抗拉强度及层厚)下组合桥面板疲劳极限状态的失效模式,并提出了主要控制参数取值建议。结果表明:200万次疲劳加载后足尺模型的实测最大裂缝宽度为0.136 mm,出现在SFRC层上缘,钢结构未开裂,组合桥面板疲劳性能良好;组合桥面板疲劳极限状态主要由SFRC层开裂控制,钢顶板厚度、栓钉布置对组合桥面板疲劳性能的影响较小,SFRC抗拉强度和层厚对组合桥面板疲劳性能影响较大,为主要控制参数;在常规正交异性钢桥面板上铺设薄层(厚度不超过50 mm)SFRC时,SFRC抗拉强度不应小于5 MPa,在常规正交异性钢桥面板上铺设普通SFRC(钢纤维体积含量不高于1%,抗拉强度不高于3 MPa)时,SFRC层厚不宜低于100 mm。

浅谈建筑结构加固工艺

我国在基础建设快速发展的阶段,进一步加大了对基础设施建设的投入,从而加快了建筑业的发展,充分发挥国家科技力量的支撑作用,相继修建了各种类型的道路、桥梁、高楼、会展中心、重大水利工程等。由于受到自然灾害、空气影响等,这些建筑的结构往往出现过早老化的情况。据相关统计数据显示,全国城镇需要开展加固工作的民用建筑有30亿平方米,其中亟待修复加固处理的建筑有10亿平方米。如何对这些老旧建筑检测加固,需要进行研究探讨。

带钢筋桁架楼承板的PRC连梁抗震性能试验研究及数值分析

为适应超高层建筑以及现代工业化住宅建筑体系迅速发展的需要,提出了一种带钢筋桁架楼承板的新型钢板-混凝土组合(plate-reinforced composite,PRC)连梁。通过拟静力试验,分析了不考虑楼板作用、带普通钢筋混凝土(reinforced concrete,RC)楼板及带钢筋桁架楼承板PRC连梁的破坏形态、承载能力、变形能力和耗能能力等。在此基础上,采用ABAQUS软件分析在不同峰值荷载作用下钢筋桁架楼承板PRC连梁的混凝土、钢板和钢筋骨架的应力发展情况。研究结果表明:钢筋桁架楼承板的设置能显著提高小跨高比PRC连梁的受剪承载力、耗能能力和延性,设置楼板能显著提高连梁的峰值荷载,且带钢筋桁架楼承板对PRC连梁承载力的提升比带普通RC楼板更强,其连梁试件PRC-S3的正向峰值荷载比不带楼板连梁PRC-NS1和带普通RC楼板连梁PRC-S2分别提升了31%和18%,但带楼板连梁在梁板交界处产生通缝之后连梁的刚度退化较为严重;带钢筋桁架楼承板的PRC连梁具有优越的耗能能力,在连梁跨度范围内均出现了显著的对角压杆,主压杆及其衍生压杆共同构成桁架作用来承受剪力;楼承板桁架上下弦钢筋以及连梁纵筋均在连梁根部位置出现应力集中,且连梁试件PRC-S3破坏点对应的累积耗能是不带楼板试件PRC-NS1的1.39倍。