钢筋混凝土结构的病害

钢筋混凝土结构是目前应用最为广泛的土木工程结构,其在服役过程中容易受到各种因素影响而发生多种病害,从而提前退出使用.研究各种病害对钢筋混凝土结构的影响对于确保钢筋混凝土结构的安全有着重要意义.本文采用拟人的方法将钢筋混凝土结构所受的各种病害(包括:钢筋锈蚀、混凝土碳化、化学侵蚀、冻融破坏、碱集料反应、疲劳破坏、开裂等)归结为几种病症,以此来分析各种病害导致钢筋混凝土的劣化机理,为减轻混凝土病害的影响,确保钢筋混凝土结构的健康提供帮助.     

近海环境氯离子侵蚀劣化下RC桥墩抗震分析

本文以一多跨钢筋混凝土连续梁桥为例,在考虑氯离子侵蚀劣化的影响,建立钢筋直径及屈服强度和混凝土材料劣化模型;研究结果表明:仅箍筋劣化,桥墩截面延性降低速度快;仅纵筋劣化,桥墩截面抗弯能力变小而延性变大;纵箍筋共同劣化时的桥墩截面延性和抗弯能力都明显下降趋势,对结构的抗震性能最不利。     

氯离子侵蚀环境下钢筋混凝土箱梁的弯曲行为试验研究

氯离子引起的钢筋锈蚀是钢筋混凝土箱梁性能劣化的主要原因之一.以氯离子对钢筋混凝土的侵蚀机理为基础,开展单室箱梁氯离子侵蚀的试验研究,制作了钢筋混凝土简支箱梁模型,主要分析了荷载作用下氯离子侵蚀对钢筋混凝土箱梁弯曲行为的影响程度.结果表明,钢筋混凝土箱梁经氯离子侵蚀并开裂后顶板处钢筋应力曲线变缓,应力增长较快,相反的底板处钢筋应力曲线变陡,应力增长较慢;通过荷载作用下腹板裂缝对比分析得出氯离子侵蚀加速了腹板裂缝的产生.     

混凝土裂缝产生的原因及应对措施

钢筋混凝土的质量一直建筑工作者需要面对的主要问题,钢筋混凝土的裂缝是建筑施工中最难解决的问题之一,这些裂缝不仅影响建筑物的美观,而且影响建筑物的使用功能,大大降低了建筑物结构的耐久性;破坏其整体性、降低其刚度;引起钢筋腐蚀。因此如何解决这种常见的混凝土裂缝,是设计者和施工者都不应忽视的问题     

建筑物外墙涂层的劣化分析及对策

介绍了建筑物外墙涂层劣化的主要表现、原因及防治对策。     

道砟抗破碎性能变化规律的冲击试验研究

道砟铺设于轨枕之下用于传递列车荷载,其抗破碎性能对于铁路的安全运营具有重要的影响.道砟在实际服役过程中会产生劣化,且雨水会显著改变其含水状态,该含水状态又会反作用于道砟,影响道砟的抗破碎性能.为研究劣化及劣化后饱和含水状态对道砟抗破碎性能影响规律,本文采用洛杉矶磨耗产生不同劣化程度的道砟,运用综合图像分析量化道砟劣化的...     

钢筋混凝土表面修补砂浆性能研究

混凝土建筑物常常存在耐久性、延长建筑物的使用寿命等问题,研制、推广应用新型修补及防护混凝土材料具有十分重要的现实意义.经试验研究分析了不同组分对修补砂浆性能的影响及作用机理,给出了修补砂浆的综合性能测试结果.新制钢筋混凝土修补砂浆抗拉压强度高,吸水率低,各项指标均满足使用要求.     

瞬时高温混凝土性能的测试方法

混凝土经历高温作用后的性能劣化对火灾后钢筋混凝土结构的稳定性与耐久性具有重要意义,而混凝土高温性能测试方法是确定混凝土高温性能劣化程度的基础.根据混凝土高温性能劣化的特征,提出一种新型测试方法:在800℃,以所设计的混凝土钢筋保护层厚度(50 mm)处温度达到250℃的时间确定为耐火极限.然后以该耐火极限为基准,根据混凝土试件内部温度场的变化、高温处理后的物理力学性能、混凝土试件的超声波检测、爆裂程度等参数,测试不同混凝土达到耐火极限时,其性能的劣化程度.通过对3组C50混凝土进行测试,结果表明:本测试方法具备简便易行,结果可靠,测试全面的特点.     

钢筋混凝土框架结构填充墙体裂缝的预防分析

随着建筑行业的蓬勃发展,各式各样的建筑物被开发建造。以框架结构为主的建筑结构并以钢筋混凝土填充墙体的建筑物越来越多,尤其是供给人们居住的楼房多是此类建筑构造。以此类框架结构为主的填充墙体会出现不同程度的倾斜,而且墙体裂缝是这类建筑物的通病,裂缝严重影响墙体的稳固性和完整性,使其使用过程存在安全隐患,并且影响建筑美观度。所以,本文围绕裂缝问题展开研究,分析了建筑物裂缝的类别,探究了钢筋混凝土墙体裂缝产生的主要原因,并针对裂缝原因给出了一些预防措施。     

双组分湿面混凝土防腐涂料的研制

采用双酚F环氧树脂、酚氨基醇固化剂为成膜物质,研制应用于表湿区钢筋混凝土桥梁、桥墩的初始涂装及表湿区钢筋混凝土桥梁劣化后的重新涂装和维护性涂装的防腐蚀涂料。     

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.     

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.     

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。