不同材料及加固方式对梁弯曲性能影响试验研究

为研究不同材料、不同加固量和不同加固方式对加固梁承载能力、挠度变化、破坏形态及裂缝发展的影响,通过四点弯曲加载试验,对11组试验梁进行抗弯试验研究。试验结果表明:不同加固筋材及加固方式对试验梁的开裂荷载、屈服荷载、极限荷载及跨中荷载-挠度曲线都有一定的影响。提升开裂荷载主要受加固方式的影响,内嵌螺旋肋筋鱼尾式及格栅式的加固梁开裂荷载提升明显,较直嵌式加固方式,最大提高了182%;相同加固量时,端部锚固方式的加固梁屈服荷载和极限荷载提升最明显;采用内嵌CFRP筋材加固梁的极限荷载最大,最大提高了113. 68%。加固材料对加固梁的抗弯刚度影响明显,内嵌CFRP筋加固梁的抗弯刚度最优;十字嵌入式、鱼尾嵌入式、格栅式及端部锚固式加固梁的抗弯刚度要明显优于直嵌式加固梁。     

损伤混凝土结构加固性能及加固后耐久性研究

混凝土诞生的一个多世纪以来,由于老化、环境侵蚀、自然灾害、人为因素的影响,混凝土构件存在着普遍的损伤问题。因此混凝土的发展史也是损伤混凝土的加固史,混凝土加固技术贯穿了混凝土发展的始终。但是在混凝土加固活动中加固主体一般比较重视加固后的混凝土结构强度,对混凝土结构加固以后的整体耐久性并不重视,这种现象让加固活动本身的积极意义大幅度削弱。针对这一现象,本文从混凝土结构加固性能和耐久性能出发,结合损伤混凝土加固和加固后的耐久性实际,对损伤混凝土结构加固性能及加固后耐久性进行简要分析。     

探讨市政路桥加固改造设计要点

相关部门需要及时做好市政路桥加固改造设计,保证城市交通的正常运作。基于此,本文从市政路桥加固改造设计中需要考虑的问题以及加固改造的重要性展开论述,详细阐述了市政路桥加固改造设计中预应力加固、路基沉降处理、扩大混凝土截面、钢板复合纤维加固、桥面加固改造等设计要点。     

土木工程建设中结构与地基加固技术的运用

文中首先分析了土木工程建设中结构与地基加固技术应用的重要性,其次,就土木工程建设中地基加固技术、结构加固技术两项技术进行了分析。再次,就土木工程建设中结构与地基加固技术应用的原因进行了探究,包括土木工程建设中结构存在问题、土木工程建设中质量存在缺陷两方面,随后,围绕土木工程建设中地基加固技术的运用进行了比较深入的分析,包括换填加固技术的具体运用、排水固结加固技术的具体应用、挤压加固技术的具体应用、化学加固技术的具体应用几项内容。最后开展了土木工程建设中结构加固技术的运用分析工作,包括截面加固技术的具体应用、碳纤维布加固技术的具体应用、钢筋植筋加固技术的具体应用几方面,旨在通过本文的研究,为土木工程建设质量提升起到促进作用。     

工程结构新型加固方法概述

既有混凝土结构受自然环境、使用环境等各种因素的影响,呈现出不同程度的承载力不足、变形过大等缺陷,国内外研究者针对工程结构受损情况提出了不同的维修加固方法。文章基于承载力加固、使用功能加固及耐久性加固等不同的加固性质,概述了各种新型加固方法的特点及工程应用实例,提出了不同加固性质较为理想的加固方法,为工程实际提供参考。     

钢筋混凝土梁抗剪加固方法研究

钢筋混凝土梁的抗剪加固问题是工程结构加固常见的难题之一,本文介绍了增加截面法、置换混凝土加固法、外贴钢板法、外包型钢加固法、增设支点加固法的设计方法和适用范围,以及国内外关于FRP加固法的设计规定,为相关研究及施工应用提供参考。     

论FRP在土木工程结构加固应用

FRP是新型的土木工程结构加固材料,并且其应用是近年来研究的热点,FRP的性能比较稳定,与传统的建筑加固材料相比,优势比较明显。FRP应用于土木工程结构加固具有施工方便、维修费用少、结构耐久性能好等优势,这种材料必将在未来的土木工程结构加固领域占据重要的位置。本问首先介绍了FRP材料的种类、特性及其优点,然后对FRP在土木工程结构加固中的应用进行了详细的阐述,主要包括:混凝土结构加固、抗剪抗弯加固、砌体结构的加固、混凝土梁和柱的加固、复杂环境下的下部结构加固。     

FRP加固木结构研究和应用综述

与传统加固方法相比,FRP加固技术具有轻质高强、操作简便、耐久性好等特点,在木结构加固中具有重要的应用前景。详细叙述了国内外FRP加固木结构受压、受弯和受剪性能的研究方法和得到的结论,介绍了FRP加固木结构技术在建筑和桥梁中的应用概况。在总结已有研究中缺乏FRP对木柱约束效应、考虑木结构实际应力应变模型的加固木梁受弯性能及FRP加固木梁受剪性能三个方面研究的基础上,提出针对这三个方面进一步研究不同加固方式和加固参数对FRP加固木结构受力性能影响的建议,为制定FRP加固木结构标准奠定基础。     

碳纤维加固法在桥墩加固工程中的应用技术

在混凝土加固工程通常采用钢板粘接加固法和碳纤维粘接加固法。钢板加固法目前用的较多,设计理论和施工技术较为成熟;碳纤维布加固法是近年来发展较快的加固方法,以强度高、质量轻、耐腐蚀、施工简单等特点备受关注。本文以日本首都高速道路公司承担的首都高速3号线高架桥桥墩抗震加固工程为例,讨论碳纤维在混凝土加固工程中的实用技术。     

防汛抗旱中水库加固施工存在的问题与应对措施

近年来在防汛抗旱的相关工作领域中,水库加固施工还存有很多问题、不足,严重影响加固施工效果、质量,并且在实际的加固施工工作中不能结合防汛抗灾的项目特点、要求和实际情况针对性的运用先进加固施工技术措施,缺少良好的加固方法、加固形式,难以通过合理性的手段提升加固施工效果,需要快速的应对和处理,确保加固施工水平。基于此,下文分析杨麻水库的情况,研究防汛抗旱过程中的水库加固施工问题,提出几点相关的问题应对建议、举措,旨在为增强水库加固施工效果、先进性程度提供一定的基础保障、切实的帮助。     

Pressure Reinforcement of Particulate Polymeric Composites Originated By Adhesive Debonding

Particulate elastomeric composites exhibit considerable reinforcement when they are extended under moderate superposed pressures. Numerous experiments have shown that this effect is provoked by pore formation and relevant matrix overstraining. The interfacial friction between the debonded matrix and filler has as well been shown to influence this phenomenon markedly. It seemed resonable first to study separately elastic and frictional contributions to reinforcement.

The paper examines the reinforcement effect caused by elastic pore suppression under superposed pressure without taking into account the frictional effect. The structural element has the form of a rubber neo-Hookean cylinder (matrix) with a rigid spherical inclusion (filler) at the center. Quantitative dependence of the reinforcement on the volume suppression, pressure, degree of extension, volume content of the inclusion and modulus of the matrix has been obtained in the framework of large deformation. The analysis of these data has shown that theoretical results were in good agreement with the available experimental evidence.

Some peculiarities of the phenomenon have been established such as the weakening of the extent of reinforcement with the extension, higher reinforcement under negative pressures, two different geometrical modes of the vacuole compression depending on the extension and the range of matrix moduli where the reinforcement effect becomes negligible.     

Comparison of the usage of nut shell,walnut shell,and pistachio shell as a reinforcement particle on the mechanical and wear performance of polypropylene

In this study, the usability of nutshell, pistachio, and walnut shell wastes as reinforcement materials in industrial applications and their comparisons with each other was examined. For this purpose, composite samples with a polypropylene (PP) matrix were produced and their mechanical and tribological characterizations were performed. As a result of the tensile tests, both the tensile strength and elastic modulus values of all composite specimens are higher than those of pure PP. On the other hand, the value of elongation at break is lower. The sliding wear resistance increases with increasing reinforcement with walnut and pistachio shell reinforcement, whereas the positive effect becomes negative when the nutshell reinforcement is over 3 wt%. All three types of reinforcement positively affected the scratch resistance. Pistachio shell reinforcement gives the best result. It has been determined that the relative cutting volume value of the samples increases with the reinforcement rate and the wear behavior changes from ductile to brittle. In light of these results, it has been seen that nut, pistachio, and walnut shells could be used as reinforcement materials in industrial applications instead of being waste or fuel.     

Factors affecting the premature failure of a reinforced concrete construction

The factors responsible for the premature failure of reinforcement in the Pumping Station at Manzala Lake in Egypt have been investigated. Concrete analysis indicated that the water used contained high concentration of salts. The total alkalinity of the cement showed that ordinary concrete has been used instead of dense concrete. General and pitting attack was observed microscopically on the reinforcement outside the building. Transgranular corrosion cracking was observed on the reinforcement of an external column carrying the building as well as on the reinforcement taken from two locations close to the pumps inside the building. The combined action of repeated stress due to the building vibration during pumps operation and the corrosive environment resulted in reinforcement cracking.     

碳纤维复合材料加固形式对棱柱体应力应变的影响

为了进一步研究碳纤维加固技术对棱柱体本构关系的影响,利用碳纤维增强复合材料(CFRP)以0、100、200 mm等不同加固间距对素混凝土棱柱体加固后进行轴压,以荷载、位移、环向应变和竖向应变等参数为判定依据,结果表明:未加固的素混凝土柱脚发生脆性破坏;CFRP加固间距为0的包裹试件被压碎,CFRP发生断裂;加固间距分别为100、200 mm时,非加固区混凝土出现比较分散的裂缝;CFRP能够有效约束加固柱的环向应变,且破坏时试件有一定的延性;CFRP加固间距为0的试件能够约束竖向位移,但只要有加固间距,竖向应变就不会发生太大变化。     

The Mechanism of Filler Reinforcement from addition of neutral polymeric bonding agents to energetic polar propellants

It has been demonstrated that addition of small amounts of the newly developed neutral polymeric bonding agents (NPBA's) to energetic propellants such as HMX/PEG/NG composites causes strong filler reinforcement. The mechanism of this reinforcement occurs through interfacial effects, and not because of an overall increase in the crosslink density of the binder. It has been demonstrated directly that the NPBA's have a favorable relative affinity for HMX and concentrate at the solid surface during mixing. All the experimental evidence supports the theory that highly crosslinked polymeric shells form around the HMX particles and chemically bond to the binder matrix during the cure, thus causing an increase in the initial modulus. Furthermore, these shells appear to eliminate the weak, soft layers around the particles, and hence filler reinforcement persists up to much higher elongation than without addition of NPBA. Based on the filler reinforcement observed, the simple one-step procedure of incorporating our NPBA is almost as effective as the more costly process of precoating the particles.     

Mechanical characterization of sol-gel alumina-based ceramics with intragranular reinforcement of multiwalled carbon nanotubes

Multiwalled carbon nanotubes (MWCNTs) have been widely considered for mechanical reinforcement of ceramic matrix composites. Nevertheless, the efficiency of this reinforcement strategy is under debate due to fabrication issues, such as a good homogenization or the location of the MWCNTs inside the matrix composite. Regarding this, the intragranular location of the MWCNTs has been deemed a crucial feature for optimizing the reinforcement compared to the typical intergranular placement achieved by conventional procedures. Recently, the sol-gel method has been reconsidered, as it promotes the intragranular placement of the MWCNTs. This work presents the mechanical characterization of these composites synthesized by the sol-gel method, where crack-bridging has been revealed as toughening mechanism. Finally, the conventional use of the bibliographical Young's modulus of pure alumina for the estimation of the fracture toughness is discussed, obtaining significant improvements of the fracture toughness when indentation measurements are treated by considering elastic moduli obtained by nanoindentation.     

二氧化硅气凝胶纳米网络骨架强化方法研究进展

二氧化硅气凝胶是一种具有高孔隙率、高比表面积、低热导率等诸多优异特性的纳米多孔材料,在航天、化工、建筑等众多领域有着广阔的应用前景。但是,二氧化硅气凝胶的网络骨架存在本征陶瓷脆性,限制了其实际应用。本文从气凝胶纳米颗粒颈部强化设计角度出发,介绍了液相强化法和气相强化法两类网络骨架强化策略的研究进展,并对以上两种强化策略的增强机理进行了阐释,最后对二氧化硅气凝胶网络骨架强化技术的发展方向提出了展望。     

PPO／PA合金研究

聚苯醚/尼龙(PPO/PA)合金综合了PPO的高耐热、韧性好及PA易成型、耐油性好的特点,在汽车工业领域,作为汽车外装件的优选材料得到广泛应用。针对PPO/PA合金的反应相容手段、共混工艺条件、复合阻燃体系及增强效效果进行了研究,制得了阻燃增强型PPO/PA合金。     

胶粘剂性能对复合材料加固损伤钢板性能影响研究

以海洋工程中含裂纹钢板为研究对象,通过虚拟裂纹闭合法建立有限元仿真模型,模拟塑性钢板加固前后的承载能力,并分析胶粘剂的剪切强度和延伸率对加固性能的影响。设计相应的加固试验模型,对比经过交变湿热、太阳辐射老化、盐雾等海洋环境试验前后的结构加固性能,并选用适合海洋环境的胶粘剂进行加固方案的优化。研究表明,改变胶粘剂的性能参数对加固结构的屈服点影响不大,但对复合材料加固的极限承载能力影响较大。海洋环境因素可导致胶粘剂的性能下降,选用适合海洋环境的优异胶粘剂后可提高加固的可靠性和耐久性。