碳纤维片材加固钢筋混凝土梁的问题探讨

碳纤维片材加固钢筋混凝土梁的问题包括碳纤维片材加固钢筋混凝土梁的应用前提、钢筋混凝土梁斜向贴碳纤维抗剪加固承载力计算和使用阶段加固梁的验算公式。这些问题是对现行规范的补充和完善,并提出有待进一步研究的问题。     

芳纶纤维加固钢筋混凝土梁锚固长度的简化计算方法

根据芳纶纤维(Aramid Fiber Reinforced Plastic,简称 AFRP)补强加固钢筋混凝土梁的粘结破坏的试验结果,分析AFRP加固钢筋混凝土抗弯构件粘结界面的剪应力的分布规律,即在纤维截断点处存在较高的应力集中,随着离截断点距离的增大剪应力分布逐渐趋于均匀.粘结锚固长度不足和过高的应力集中是造成AFRP加固钢筋混凝土构件早期破坏的主要原因.采用"齿"状块体力学计算模型和混凝土裂缝理论推导了AFRP加固钢筋混凝土梁所需要的有效锚固长度,并通过修正得出了AFRP加固钢筋混凝土受弯构件最小锚固长度的简化计算公式,提出了AFRP的容许应变值和避免AFRP早期破坏应采用的措施,可供AFRP加固工程设计和施工参考.     

火灾下CFRP加固RC梁高温抗弯承载力简化计算方法

火灾下粘贴碳纤维复材(CFRP)加固构件的承载力计算是对其进行抗火设计的关键。采用数值模拟手段进行了标准火灾下单面和三面受火的CFRP加固钢筋混凝土(RC)梁温度场分析,考虑温度场的主要影响因素(保护材料厚度和导热系数),提出了加固构件表面及内部温度简化计算公式,并与试验数据对比验证了简化公式的准确性。结合混凝土梁截面承载力极限状态分析方法、材料及界面性能高温退化模型,建立了在ISO 834标准火灾情况下不同时刻CFRP加固RC梁高温抗弯承载力简化计算方法,并与荷载效应进行对比,即可进行防火保护材料厚度的合理选择。该研究成果可用于建立CFRP加固钢筋混凝土梁的火灾保护设计方法,或判断已有保护措施的CFRP加固梁是否能达到要求的耐火极限,能够为CFRP加固构件的抗火设计和安全鉴定提供理论手段和方法。     

上海石化碳纤维首用于机场改扩建

<正>日前,中国石化上海石油化工股份有限公司碳纤维补强材料首次应用于南京机场改扩建项目,工程使用碳纤维编织布超过1×10~4m~2,创出该产品在单次工程项目中的最大用量纪录。项目建设单位在对机场航站楼改造加固工程中,针对航站楼的结构特点和改造要求,使用碳纤维编织布对其屋顶、梁、柱、楼板等主次承力结构进行加固补强,有效     

基于已有试验结果和理论公式预测加固钢筋混凝土箱梁碳纤维布剪力贡献

对于纤维布抗剪加固矩形梁和T形梁,中外学者已进行了大量的试验和理论研究,并且提出纤维布剪力贡献计算公式,部分公式被不同国家的规范收录。但对于加固钢筋混凝土箱形截面梁的纤维布剪力贡献计算鲜有文献记录,因此本研究在已有试验和理论公式的基础上预测箱形截面纤维布剪力贡献计算。本文讨论了5种不同规范计算纤维布剪力贡献公式,同时收集了现有文献的181片纤维布抗剪加固矩形梁和T形梁试验结果,通过采用5种计算公式计算181片梁的纤维布剪力贡献值与试验结果对比,发现所有计算公式均有不同程度的离散,但fib Bulletin 14能较准确地计算矩形梁和T形梁的纤维布剪力贡献。此外,同样收集已有文献中的碳纤维布加固钢筋混凝土箱梁试验结果,采用已讨论的5种计算公式计算剪力,与试验结果相比,其计算值均大于试验值,研究发现规范中的计算公式都高估了纤维布的有效应变,而fib Bulletin 14的计算结果接近于试验值。因此,通过纤维布有效应变的试验值和fib Bulletin 14计算值的比较,引入有效应变修正系数1.31,计算出加固箱形梁纤维布剪力贡献值,与试验值能够较好地吻合。     

碳纤维布加固钢筋混凝土结构的抗爆能力

碳纤维布加固修复结构技术作为一种结构加固修复新技术，具有显著的物理力学特点．近年来，在国内外得到了快速发展．国外的一系列实验研究成果均表明，粘贴CFRP能有效提高钢筋混凝土结构的抗爆能力。建议开展碳纤维布补强加固建筑物钢筋混凝土构件的抗爆研究工作．     

CFRP加固初始受载钢筋砼梁弯曲性能的试验研究

在对一组采用CFRP进行抗弯加固的初始受载钢筋混凝土梁土梁试验的基础上。研究了这些梁的裂纹扩展。载荷-挠度曲线。纵向钢筋和碳纤维布的应变，破坏载荷和破坏特征。     

CFRP加固初始受载钢筋砼梁抗剪性能的试验研究

在一组采用CFRP进行抗剪加固的初始受载钢筋混凝土梁试验的基础上，研究了这些梁的裂纹扩展。载荷-挠度曲线，碳纤维布的应变，箍筋应变，破坏载荷和破坏特征。     

粘贴CFRP板加固钢筋混凝土梁的长期变形性能试验研究与数值模拟

为了研究实际工程中粘贴CFRP板加固钢筋混凝土梁的长期变形性能,从而为加固梁在长期使用过程中是否满足结构的正常使用极限状态提供判断依据,并解决长期试验操作难度大、时间跨度长的问题,进行了粘贴CFRP板加固钢筋混凝土梁的加固以及粘贴CFRP板加固钢筋混凝土梁在持续荷载作用下的长期变形试验,建立了用于计算粘贴CFRP板加固钢筋混凝土梁的长期变形的非线性有限元模型。数值计算结果与试验结果吻合较好。利用该模型对粘贴不同厚度CFRP板的加固梁的长期变形进行了数值计算,结果表明CFRP板对加固梁的长期变形的影响不明显,其总变形的减小主要来源于CFRP板对瞬时变形的约束。     

不同锚固形式的钢筋在粉煤灰混凝土梁中的粘结性能研究

为了探究各种不同锚固形式的钢筋在RC梁中的抗弯与粘结性能,制作了3组3根钢筋混凝土梁,对其进行压载试验,试验结果表明:设计的两种新型锚固形式钢筋能显著提高钢筋与混凝土粘结性能。     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US

In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures (release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species (Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles from the southeastern region of the US.     

Methyl 2,4,6-decatrienoates Attract Stink Bugs and Tachinid Parasitoids

Halyomorpha halys (Stål) (Pentatomidae), called the brown marmorated stink bug (BMSB), is a newly invasive species in the eastern USA that is rapidly spreading from the original point of establishment in Allentown, PA. In its native range, the BMSB is reportedly attracted to methyl (E,E,Z)-2,4,6-decatrienoate, the male-produced pheromone of another pentatomid common in eastern Asia, Plautia stali Scott. In North America, Thyanta spp. are the only pentatomids known to produce methyl 2,4,6-decatrienoate [the (E,Z,Z)-isomer] as part of their pheromones. Methyl 2,4,6-decatrienoates were field-tested in Maryland to monitor the spread of the BMSB and to explore the possibility that Thyanta spp. are an alternate host for parasitic tachinid flies that use stink bug pheromones as host-finding kairomones. Here we report the first captures of adult and nymph BMSBs in traps baited with methyl (E,E,Z)-2,4,6-decatrienoate in central Maryland and present data verifying that the tachinid, Euclytia flava (Townsend), exploits methyl (E,Z,Z)-2,4,6-decatrienoate as a kairomone. We also report the unexpected finding that various isomers of methyl 2,4,6-decatrienoate attract Acrosternum hilare (Say), although this bug apparently does not produce methyl decatrienoates. Other stink bugs and tachinids native to North America were also attracted to methyl 2,4,6-decatrienoates. These data indicate there are Heteroptera in North America in addition to Thyanta spp. that probably use methyl 2,4,6-decatrienoates as pheromones. The evidence that some pentatomids exploit the pheromones of other true bugs as kairomones to find food or to congregate as a passive defense against tachinid parasitism is discussed.     

2005～2006年国外塑料工业进展

收集了2005年7月～2006年6月国外塑料工业的相关资料，介绍了2005—2006年国外塑料工业的发展情况。提供了世界塑料产量、消费量及全球各类树脂生产量以及各国塑料制品的进出口情况。作为对比，介绍了中国塑料的生产情况。按通用热塑性树脂（聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂）、工程塑料（聚酰胺、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚）、通用热固性树脂（酚醛、聚氨酯、不饱和树脂、环氧树脂）、特种工程塑料（聚苯硫醚、液晶聚合物、聚醚醚酮）的品种顺序，对树脂的产量、消费量、供需状况及合成工艺、产品开发、树脂品种的延伸及应用的扩展作了详细的介绍。     

2007～2008年世界塑料工业进展

收集了2007年7月～2008年6月世界塑料工业的相关资料,介绍了2007～2008年国外塑料工业的发展情况,提供了世界塑料产量、消费量及全球各类树脂的需求量及产能情况.按通用热塑性树脂(聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、ABS树脂)、工程塑料(尼龙、聚碳酸酯、聚甲醛、热塑性聚酯、聚苯醚)、特种工程塑料(聚苯·硫醚、液晶聚合物、聚醚醚酮)、通用热固性树脂(酚醛、聚氨酯、不饱和聚酯树脂、环氧树脂)不同品种的顺序,对树脂的产量、消费量、供需状况及合成工艺、产品应用开发、树脂品种的延伸及应用的进一步扩展等技术作了详细介绍.