不同方式加固的榫卯节点木框架抗震性能试验研究

设计了竹斜撑、钢箍和钢支撑3种榫卯节点木框架加固方法,完成了4榀足尺单层单跨平面木框架拟静力试验。研究了不同加固方式对榫卯节点木框架抗震性能的加固效果,分析了未加固木框架和不同加固方式木框架的破坏特征、水平承载力、延性、刚度及承载力退化性能、耗能能力和榫头应变。结果表明:竹斜撑加固、钢箍加固和钢支撑加固木框架的正向峰值荷载较未加固木框架分别提高了105.2%、246.6%和68.1%,而反向峰值荷载仅分别提高了-8.7%、57.7%和12.4%;与未加固木框架相比,竹斜撑加固木框架和钢支撑加固木框架的初始刚度分别提高了82.4%和38.3%,钢箍加固木框架提高有限,仅为3.3%;在水平反复荷载作用下,各加固木框架的整体刚度均随位移及循环次数的增加而逐步下降,进入塑性阶段后,各加固木框架刚度下降较为平缓且与对比木框架差异较小;钢箍加固木框架的耗能能力显著大于未加固木框架,竹斜撑加固木框架和钢支撑加固木框架正向加载时的耗能较未加固木框架提高明显,但反向加载时基本没有增加。     

中国古建筑木结构榫卯节点加固的试验研究

通过对3个按照<营造法式>制作的二等材殿堂式木构架的缩尺模型,以及3个碳纤维布和2个扁钢加固榫卯节点的构架模型在水平低周反复荷载作用下的试验研究,得到了未加固构架、碳纤维布加固构架及扁钢加同构架的破坏特征、滞回曲线、骨架曲线、强度和刚度退化规律、变形及耗能等性能.试验结果表明:所有构架的梁、柱构件完好无损,破坏均发生在榫卯节点;未加固构架、碳纤维布加同构架及扁钢加固构架的滞回曲线有明显的不同;碳纤维布和扁钢加固后构架强度和刚度增加,而耗能能力却有所降低;木构架具有非常好的变形能力.扁钢加固适合于强度或刚度明显不足且较隐蔽的榫卯节点.而碳纤维布加固适合于破损程度较小的榫卯节点.     

碳纤维复材布和加腋角钢复合加固受损混凝土框架受力性能试验研究

碳纤维增强复合材料(CFRP)布和角钢复合加固钢筋混凝土结构,可以同时发挥两种加固材料的优势。针对两榀严重受损的钢筋混凝土框架,首先用CFRP布加固出现明显损伤的框架梁、柱和节点;而后在框架节点和框架柱固定端反粘由钢板焊接的加腋角钢并用螺栓固定。对加固后的框架试件进行模拟地震作用下的水平低周反复荷载试验,研究CFRP布和加腋角钢复合加固损伤混凝土框架的受力性能。试验结果表明:复合加固框架的刚度退化和承载力退化均较均匀,未发生突变,可以较好防止结构突然性倒塌;CFRP布的耗能能力较差,但加腋角钢的钢板可达到最大承载力;随着加腋角钢节点钢板肢长的增大,复合加固框架的耗能能力增强,加固框架的抗震能力提高。     

CFRP加固前后L形竖缝装配式耗能剪力墙抗震性能研究

设计2个L形竖缝装配式耗能剪力墙,对其进行低周往复加载试验,并对2个破坏后的试件使用CFRP加固后再进行同样的加载试验,研究加固前后试件的承载力、剐度退化、耗能能力以及延性等性能.结果 表明,L形竖缝装配式耗能剪力墙整体工作性能良好,随轴压比的增加试件的承载力增加,延性有所降低,但位移延性系数均大于或接近3,有较好的变形能力;腹板墙和L形翼墙均表现为弯剪破坏;在使用CFRP加固后,试件的延性、刚度及承载力有所下降,但部分墙肢能满足使用要求.加固前后试件均表现出了良好的耗能能力.     

低周反复荷载作用下钉节点性能试验研究

介绍了轻型木结构框架剪力墙结构中的面板与木框架钉节点在低周反复荷载作用下的试验研究;对采用不同OSB面板厚度、不同钉边距、顺纹或横纹受力的10组共100个钉节点试件的承载力、破坏模式、延性、刚度退化、强度退化和耗能性能作了比较分析。得到以下结论:钉边距影响钉节点的破坏模式;钉边距和面板厚度的增大有利于提高节点承载力、耗能和变形能力;板厚对顺纹受力试件承载力及横纹受力试件承载力相对关系影响较大,顺纹受力试件的延性与耗能能力相对横纹受力试件较差;钉边距增大使强度退化的速率逐渐降低;各因素对刚度退化的影响可忽略。     

碳纤维布加固混凝土梁柱节点抗震性能试验研究

通过7个足尺混凝土梁柱节点的低周反复加载试验,对应用碳纤维布的两种空间框架节点加固方法及一种平面框架节点加固方法进行了分析研究。试验结果表明,所采用的不同加固方法均能够有效地增强节点核心区的抗剪性能,改变节点的剪切破坏模式,提高节点的承载力与延性,使得加固节点的强度退化和刚度退化得以滞后,耗能能力得到大幅度提高,从而有效改善了梁柱节点组合体的抗震性能。     

碳纤维布加固震损装配整体式混凝土框架节点抗震性能试验研究

通过拟静力试验,研究碳纤维布加固震损装配整体式框架节点的抗震性能,分析了节点破坏形态、滞回曲线、骨架曲线、位移、延性、刚度和承载力退化等抗震性能指标,比较节点损伤程度对碳纤维布加固效果的影响,然后通过数值模拟对加固的影响因素进行分析,在此基础上建立了加固节点核心区抗剪承载力计算式。研究表明:碳纤维布加固节点试件极限承载力最大提高27.1%;极限位移最大提高23.8%;节点试件的耗能、延性增强,刚度退化、承载力退化减慢;轻度损伤节点加固后抗震性能得到有效提高;中度损伤节点加固后抗震性能可完全恢复;理论式计算结果与试验和模拟中的核心区抗剪承载力进行对比分析,误差在10%以内。     

古建筑榫卯节点抗震加固试验

为探究中国古代大木作结构抗震加固的有效方法,分别采用马口铁和CFRP加固榫卯节点,研究了节点加固前后构架的抗震性能.制作了1:8缩尺比例的木结构空间模型,通过进行低周反复加载试验,获得了构架加固前后的力-侧移曲线,并对比分析了相应的骨架曲线、耗能能力、刚度退化、变形能力等抗震指标.结果表明:马口铁和CFRP均可提高构架...     

碳纤维布-角钢组合加固混凝土框架节点抗震性能试验研究

在理论分析的基础上,提出了适用于混凝土框架节点抗震加固的碳纤维布-角钢组合加固方法,并通过2个节点试件的低周反复加载试验对该方法进行了检验。试验结果表明:碳纤维布-角钢组合加固体系能够有效地增强节点核心区的抗剪承载力,改变节点的剪切破坏模式,提高节点的承载力与延性,使得加固节点的强度和刚度退化得以滞后,耗能能力得到大幅度提高,从而显著改善了梁柱节点组合体的抗震性能。     

碳纤维布加固震损方钢管混凝土框架边节点抗震性能试验研究

为了研究碳纤维布加固震损钢管混凝土柱-钢梁框架节点的抗震性能,按1:2的缩尺比例设计并制作4个方钢管混凝土柱-钢梁框架边节点试件,进行了预损加载、碳纤维布加固和节点加固后的低周往复荷载破坏试验。研究了碳纤维布加固震损节点的有效性,探讨了不同震损程度对加固效果的影响。通过对节点试件的滞回曲线、骨架曲线、碳纤维布应变、延性、耗能能力、刚度退化及承载力退化等参数分析可知:碳纤维布加固方钢管混凝土柱-钢梁框架边节点,保证了"强柱弱梁"的抗震延性设计目标的实现,破坏形态均为钢梁弯曲破坏;碳纤维布加固提高了节点试件承载力,抗震性能得到明显改善;在一定损伤程度情况下,加固节点恢复并超过受损前的抗震性能。     

Dimensional stability of waterproofing bituminous sheets used in low slope roofs

Lap joints between waterproofing bituminous sheets, applied in either single or multiple layers, are one of the most critical areas of roofs, especially when the waterproofing systems comprise only a single sheet. In fact, the way how lap joints are executed is highly associated with the occurrence of anomalies in such systems. With this regard, the dimensional stability of the sheets is one of their most important characteristics, as it that can strongly influence the performance of the lap joints and the details on roof upstands. In this context, with the aim of contributing to improve the understanding of this characteristic of bituminous sheets, the present paper presents results of an experimental study on the dimensional changes suffered by bituminous sheets when subjected to temperature variations. Different types of traditional and non-traditional sheets, with various types of bituminous mixtures (oxidised bitumen and atactic polypropylene (APP) and styrene–butadiene–styrene (SBS) modified bitumen) and reinforcements (polyester, glass fibre and polyethylene) were tested according to EN 1107-1 standard. For most of the sheets, the isolated reinforcements were also subjected to dimensional stability tests in order to evaluate their influence on the overall performance of the waterproofing layer. The results of these experimental investigations confirm that sheets with polyester reinforcement are much less stable than sheets reinforced with glass fibre. In addition, it was concluded that the influence of the type of polymer–bitumen is negligible when compared to the influence of the type of reinforcement – in general, the dimensional stability of the sheets is worse than that of the corresponding reinforcement. Finally, it is shown that the dimensional stability performance of similar products produced by different manufacturers is similar, both for the isolated reinforcements and for the waterproofing sheets.     

Laboratory investigation of polyethylene sheeting as a friction reducer in deep foundation

A testing program was undertaken in which the effectiveness of polyethylene sheeting in mitigating downdrag in cohesionless soils was investigated using a direct shear apparatus and a rod shear test. A large number of concrete blocks were prepared in the laboratory and furnished with various arrangements of polyethylene sheets. These arrangements included samples with one or two sheets with fixed or free boundary conditions. The concrete-polyethylene-soil samples were tested in the laboratory under different temperatures and shearing rates. Based on the parameters used in this investigation, the obtained results demonstrated that the polyethylene sheets can be used as a friction reducer in piles. Using single layer of polyethylene sheeting reduced the skin friction by 62–67% depending on the soil type. The best arrangement was found in the two free 0·15 mm polyethylene sheets. This setup increased the effectiveness of the sheets to 77%. Lubricating the two sheet arrangement with mineral oil improved the effectiveness to 98%. Considering the effect of the shearing rate and the temperature on the behaviour of the lubricated sheets, a formula is suggested     

西北自然环境条件下浸润树脂耐久性对碳纤维片材耐久性能的影响

CFRP加固广泛应用于土木工程,对耐久性能的研究已得到了工程界的重视。通过对目前土木工程加固常用的两种CFRP及其配套树脂在西北地区自然环境条件下耐久性进行初步的对比试验研究。试验每组试件设为5件,进行了16组共80个试件的试验。通过2年初步试验,结果表明,碳纤维片材耐久性与浸润树脂耐久性有一定的相关性。     

Safety against formation of through cracks of profiled fibre-reinforced cement sheets for roofing

Loads due to wind, snow or traffic on a roof determine the requirements to the strength and stiffness properties of profiled sheets for roofing. Apart from these loads, locked-in stresses can occur due to differences in temperature and moisture strains in the profiled sheets and the wooden laths supporting the sheets. These tensile and compressive stresses are induced in the sheets if they are firmly fastened to the laths with fastening screws.The purpose of this investigation was to analyse the safety of the profiled sheets in transmitting these loads without the formation of through cracks.The analysis is based on an experimental and a theoretical investigation of the strength and stiffness properties of unexposed profiled fibre-reinforced cement sheets and of sheets that had been exposed on a roof in three years.     

华北自然环境条件下表面防护对碳纤维片材耐久性能的影响

碳纤维片材加固混凝土结构广泛应用于土木工程,关于其耐久性能的研究已得到了工程界的重视。通过对目前土木工程加固常用的碳纤维片材在华北地区自然环境条件下的耐久性能进行了试验研究,其中,对部分试件进行了遮挡防护,以期考察防护与否对碳纤维片材抗拉强度、伸长率和弹性模量等的影响。试验每组试件设为5件,目前试验时间截至2年,已进行了7组共35个试件的试验。经分析发现,无防护碳纤维片材拉伸性能比有防护碳纤维片材下降快。     

碳纤维布加固钢结构的黏结性能研究

与传统的钢结构加固方法相比,粘贴碳纤维布加固钢结构具有很大的优势和应用前景,如不会导致严重的应力集中、不会产生残余应力、施工方便、维护费用低等。碳纤维布与钢结构之间的黏结性能直接影响加固效果,但是目前国内对这方面的研究还未涉足。本文对粘贴碳纤维布加固钢板进行了静力拉伸试验,采用高强型和高模型碳纤维布及不同的端部锚固措施,考察了未损伤钢板和损伤钢板加固后的效果。得到了加固试件的屈服荷载和极限荷载,并对不同的破坏形式进行了分析。试验结果表明,粘贴碳纤维布加固能明显提高钢构件的屈服荷载。测量了碳纤维布的应变分布,得到了碳纤维布与钢板之间的黏结应力分布和碳纤维布的有效黏结长度,并与理论公式的计算结果进行了对比,二者吻合较好。     

Laboratory and industrial investigations on hybrid of acrylic and glass short fibers as an alternative for substituting asbestos in Hatschek process

Asbestos fibers have been used in cement based materials to improve tensile strength and controlling crack formation and propagation. Asbestos–cement sheets are produced by the Hatschek technique in a number of developing countries.Due to the health and safety issues in the asbestos products, attempts have been made to substitute other fibers using the Hatschek system for cement sheets. The quality and homogeneity of the products depend on the type of fibers and varies substantially in the Hatschek system during production.In this investigation acrylic and glass fibers in separate and hybrid forms were used for manufacture of flat and corrugated sheets. Higher strength and ductility were obtained for the sheets containing glass fibers. Performance was even better when hybrid system of acrylic and glass fibers was used. The hybrid system was used for production of fiber–cement sheets in factory. This system is proposed as an appropriate alternative for substituting asbestos in the Hatschek process.     

碳纤维布加固钢筋混凝土短梁受弯试验及承载力计算

通过11根不同跨高比碳纤维（carbon fiber reinforced polymer, CFRP）布加固钢筋混凝土梁的受弯试验,研究了跨高比、纵筋配筋率和CFRP布层数对钢筋混凝土梁极限荷载的影响。结果表明：CFRP布加固钢筋混凝土梁的受弯破坏主要有CFRP布拉断和受压区混凝土压碎两种模式;随跨高比的减小,CFRP布加固钢筋混凝土梁极限荷载显著增加;随纵筋配筋率和CFRP布层数的增加,CFRP布加固钢筋混凝土梁极限荷载显著提高。结合文中和已有文献的试验结果,提出了反映跨高比影响的CFRP布加固钢筋混凝土短梁受弯承载力计算方法,该方法既可用于CFRP布加固的钢筋混凝土短梁也可用于浅梁的受弯承载力计算。     

预应力CFRP片材抗剪加固钢筋混凝土T梁试验研究

针对外贴FRP片材抗剪加固钢筋混凝土梁存在材料利用率低、易发生剥离破坏等问题,开发了用于抗剪加固的CFRP片材预应力张拉和锚固系统,给出了相应的施工工艺和方法。为验证提出系统的有效性,进行了预应力CFRP片材抗剪加固钢筋混凝土T型截面梁试验。基于CFRP片材断裂的破坏模式,提出了预应力CFRP片材加固钢筋混凝土梁的抗剪承载力计算公式。结果表明,该文开发的预应力张拉和锚固系统能有效地对CFRP片材施加预应力,减少预应力损失。预应力CFRP片材抗剪加固梁均发生以受压区混凝土压碎为标志的受弯破坏模式,锚固装置能够确保CFRP片材在断裂之前不发生剥离破坏。预应力CFRP片材对混凝土梁斜裂缝的产生和发展有明显的抑制作用,加固后钢筋混凝土梁的抗剪承载力得到大幅提升。计算结果与试验值吻合较好,验证了加固梁抗剪承载力模型的有效性。     

用无机胶粘贴CFRP布加固混凝土板抗火性能试验研究

针对粘贴CFRP布用有机胶软化点过低的问题,研制出600℃时强度不低于常温强度的无机胶。为探索用无机胶代替有机胶粘贴CFRP布提高加固结构抗火性能的可行性,进行了5块用无机胶粘贴CFRP布加固混凝土板的抗火试验。考虑到高温时CFRP布在绝氧条件下强度降低较为缓慢的特点,试验前分别选用厚型隧道防火涂料和厚型钢结构防火涂料对其进行防火保护。试验板先按ISO 834标准升温曲线升温1.5h,再自然降温1.0h。各板底纵向CFRP布经历最高温度为90~300℃,火灾下跨中最大新增位移介于计算跨度的1/438~1/95。经历火灾后,CFRP布完好,无机胶与混凝土板可靠粘贴。试验结果表明:采用无机胶粘贴CFRP布加固混凝土板,厚型隧道防火涂料和厚型钢结构防火涂料均能达到对CFRP布进行控温和绝氧的目的,前者防火效果明显优于后者;用无机胶粘贴CFRP布加固混凝土板采用防火涂料保护后,火灾下和火灾后CFRP布与混凝土板均可有效共同工作。