水平低周反复荷载下预应力砌体墙抗震承载力试验研究

通过对不同类型的预应力混凝土小型空心砌块砌体墙进行水平低周反复荷载试验,研究了预应力砌体的破坏形态、滞回特征、延性等抗震性能。试验结果表明:在墙顶施加预应力可以提高墙体的抗剪强度和变形能力,改善墙体的抗震性能。     

浅析多层砌体房屋中构造柱的设置与作用

砌体结构是我国使用最为广泛的一种结构形式。在民用及公共建筑中占有很大的比重。但由于其所使用材料的脆性性质，因而决定了它的抗震性能较差。为增强砌体的整体性，提高其抗震能力，通过大量的试验研究和多年的工程实践证明，在多层砌体房屋中设置构造柱，是一种很有效的抗震措施。构造柱与圈梁共同组成砌体结构的“弱框架”。使结构物遭受大震时．可以有较大的非弹性变形．这种变形应控制在规定的范围内，使结构不发生危及安全甚至猝然倒塌的可能；而遭受设防烈度的地震时，结构部分地进入非弹性阶段，其损坏控制在可以修复的范围内。构造柱在多层砌体房屋中起着至关重要的作用，切不可因其为“构造”柱而忽视它。让它在地震时抗震．非地震时承重。用构造柱来加强集中荷载较大的部位．或一些薄弱的部位；与砌体混合承重，解决了一些一般要采用框架．而用构造柱承重后。则仍采用砌体结构。由于砌体结构较框架结构经济，施工速度也快．所以这种抗震、承重构造柱经济效益明显。     

FRP布加固砌体结构界面粘结性能的研究进展

砌体结构存在着承载力低、抗震能力差等问题,所以对砌体结构的加固尤为重要。近些年在国内外兴起的纤维增强复合材料(简称FRP)以其轻质高强、耐久性好、施工方便等优点为砌体结构的加固提供了新的方向。FRP与砌体间的界面粘结性能是影响加固效果的关键因素之一。总结了国内外学者关于FRP加固砌体结构界面粘结性能的研究现状,通过收集到的试验数据对FRP加固砌体结构的极限承载力计算公式进行了校核,并对今后拟开展的研究工作提出了建议。     

风化砂岩中压力型锚索孔周边岩体动应力数值分析

为了更加精确地研究风化砂岩中压力型锚索的抗震性能,通过FLAC3D软件数值模拟研究了地震荷载作用下风化砂岩中锚索孔周边岩体的动应力。研究结果表明:垂直锚索距离与锚索孔周边砂岩应力分布曲线和应力峰值之间存在负相关关系,而地震荷载峰值加速度与锚索孔周边砂岩应力分布曲线和应力峰值之间存在正相关关系,它们的影响幅度均较大;预应力荷载与锚索孔周边砂岩应力分布曲线和应力峰值之间存在正相关关系,在地震初期预应力荷载对锚索孔周边砂岩剪应力影响较大。研究结果丰富了压力型锚索的抗震性能内容,可给工程提供一定参考。     

关于砌体结构的震害分析与思考

砌体结构在现在以及将来很长一段时期仍然是我国城镇建设中民用建筑的主要结构类别。历次震害表明:砌体结构房屋受地震破坏最为严重,因此做好砌体结构的抗震减灾工作在我们现阶段抗震工作中尤为重要。文章结合近些年来我国近年来在历次地震中的震害分析,提出如何在空间布置上和构造上加强砌体结构房屋的整体抗震性能。     

FRP加固砌体结构的应用研究进展

本文简要阐述了FRP(Fiber Reinforced Polymer)复合材料在砌体结构加固领域中应用的重要意义,详细介绍了FRP加固砌体结构抗剪、抗震以及FRP与砌体粘结性能等方面的研究进展,期望为FRP材料的应用以及砌体结构加固的设计、施工和实际加固改造提供应用参考。     

大开间约束砖砌体结构的抗震性能与设计方法

提出对大开间砖砌体结构采取在砖砌体中设置钢筋混凝土墙中柱和水平条带的加强措施。通过大比例模型试验 ,探讨其抗震性能 ;采用非线性有限元法对约束砌体横墙进行全过程分析 ,采用弹塑性时程分析法对原型结构进行地震反应分析 ;在此基础上提出了相应的设计建议和构造措施。试验与理论分析结果表明 ,在 7度区采用大开间约束砖砌体结构建造 7层住宅 ,可满足抗震设防要求。     

BFRP复合材料增强钢筋混凝土柱抗震性能试验研究

我国地震灾害频发,建筑结构抗震性能对工程抗震减灾具有重要意义.为研究玄武岩纤维复合材料(BFRP)加固钢筋混凝土柱结构构件的抗震性能,室内展开了不同混凝土等级、未加固和BFRP加固的钢筋混凝土构件振动试验,深入研究了BFRP材料对钢筋混凝土柱结构抗震性能的影响.结果表明:(1)相较于普通未加固钢筋混凝土柱,振动荷载下B...     

FRP筋加固砌体结构界面粘结性能的研究现状

表面嵌入式(NSM)加固法为纤维增强塑料筋(FRP筋)加固砌体结构常用的方法,FRP筋脱粘破坏为其首要的破坏形态,研究FRP筋与砌体间的粘结性能和脱粘机理成了这项加固技术的关键。综述了国内外学者关于拉拔试验、界面剪切试验、弯曲试验以及数值模拟的研究进展,对NSM-FRP筋加固砌体结构的界面粘结性能进行了研究。研究发现加固砌体结构的变形能力、能量耗散能力和延性得到了显著增加,增加FRP筋的埋设深度可以有效提高脱粘荷载。最后使用收集到的试验数据对各种粘结性能相关公式进行了校核,对今后拟开展的研究提出了建议。     

多层砖混结构房屋的抗震设计探讨

砖混结构由于选材方便、施工简单、工期短、造价低等特点,多年来砖混房屋是我国当前建筑中使用最广范的一种建筑形式;其中民用住宅建筑中约占90％以上。砖混结构多采用粘土砖和混合砂浆砌筑,通过内外砖墙的咬砌达到具有一定整体连接性的目的。在地震设防地区,多层砖混砌体房屋由于组成的基本材料和连接方式决定了其脆性性质,变形能力小,导致房屋的抗震性能较差;因此改善砌体结构延性,提高房屋的抗震性能具有极其重要意义。根据现行建筑抗震设计规范、砌体结构设计规范,结合自身设计的实践经验,我认为,在多层砖混房屋抗震设计上应注意以下几方面。     

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.     

Many Drugs of Abuse May Be Acutely Transformed to Dopamine,Norepinephrine and Epinephrine In Vivo

It is well established that a wide range of drugs of abuse acutely boost the signaling of the sympathetic nervous system and the hypothalamic–pituitary–adrenal (HPA) axis, where norepinephrine and epinephrine are major output molecules. This stimulatory effect is accompanied by such symptoms as elevated heart rate and blood pressure, more rapid breathing, increased body temperature and sweating, and pupillary dilation, as well as the intoxicating or euphoric subjective properties of the drug. While many drugs of abuse are thought to achieve their intoxicating effects by modulating the monoaminergic neurotransmitter systems (i.e., serotonin, norepinephrine, dopamine) by binding to these receptors or otherwise affecting their synaptic signaling, this paper puts forth the hypothesis that many of these drugs are actually acutely converted to catecholamines (dopamine, norepinephrine, epinephrine) in vivo, in addition to transformation to their known metabolites. In this manner, a range of stimulants, opioids, and psychedelics (as well as alcohol) may partially achieve their intoxicating properties, as well as side effects, due to this putative transformation to catecholamines. If this hypothesis is correct, it would alter our understanding of the basic biosynthetic pathways for generating these important signaling molecules, while also modifying our view of the neural substrates underlying substance abuse and dependence, including psychological stress-induced relapse. Importantly, there is a direct way to test the overarching hypothesis: administer (either centrally or peripherally) stable isotope versions of these drugs to model organisms such as rodents (or even to humans) and then use liquid chromatography-mass spectrometry to determine if the labeled drug is converted to labeled catecholamines in brain, blood plasma, or urine samples.     

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.     

Novel polyurethane coating technology through glycidyl carbamate chemistry

Glycidyl carbamate chemistry combines the excellent properties of polyurethanes with the crosslinking chemistry of epoxy resins. Glycidyl carbamate functional oligomers were synthesized by the reaction of polyfunctional isocyanate oligomers and glycidol. The oligomers were formulated into coatings with several amine functional crosslinkers at varying stoichiometric ratios and cured at different temperatures. Properties such as solvent resistance, hardness, and impact resistance were dependent on the composition and cure conditions. Most coatings had an excellent combination of properties. Studies were carried out to determine the kinetics of the curing reaction of the glycidyl carbamate functional oligomers with multifunctional and model amines. Detailed kinetic analysis of the curing reactions was also undertaken. The results indicated that the glycidyl carbamate functional group is more reactive than a glycidyl ether group. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, on October 27–29, 2004, in Chicago, IL.