钢框架结构中钢筋混凝土双向板火灾下的声发射特性

利用自行研制的火灾试验炉，对1栋3层3×3跨足尺钢框架结构中的钢筋混凝土双向板进行火灾试验，开展了将声发射技术用于火灾下整体结构中钢筋混凝土双向板的破坏监测研究。考察了火灾作用下板的声发射事件数、能量率和b值的变化，分析了各参数与板的裂缝开展、炉温及竖向位移等的关系。结果表明：利用事件数、能量率、b值等参数可以准确区分火灾下钢筋混凝土双向板的裂缝早期开展阶段、裂缝集中出现阶段以及裂缝缓慢扩展阶段；火灾下板的声发射参数产生突变时，如能量率突然升高、b值突然下降等，表征结构可能出现破坏，在建筑结构的消防安全指导方面应给予足够关注。     

钢筋混凝土梁火灾下抗剪性能的试验研究

对5根足尺钢筋混凝土简支梁进行了标准火灾试验,研究了钢筋混凝土梁火灾下的抗剪性能,得到了火灾中梁内混凝土的温度分布、纵筋和箍筋的温度变化、梁的竖向挠度、梁端的轴向变形以及梁的破坏模式,对比分析了不同混凝土保护层厚度、剪跨比对梁耐火极限的影响。结果表明:与常温下不同,提高混凝土保护层厚度可以显著提高钢筋混凝土梁火灾下的抗剪性能。受火条件下,随着剪跨比的减小,梁发生斜截面剪切破坏的耐火极限逐渐增加,但破坏时的脆性特征更加明显。     

双跨门式刚架钢结构火灾下倒塌模式

采用有限元模型对双跨门式刚架钢结构的火灾试验进行了模拟,表明有限元模型可以准确预测火灾下双跨门式刚架钢结构的倒塌行为与倒塌模式。采用经试验验证的有限元模型,对火灾下双跨门式刚架钢结构的倒塌过程进行了数值模拟,归纳出双跨门式刚架钢结构的6种典型倒塌模式,并与单跨门式刚架钢结构的倒塌模式进行了对比,说明了中柱的存在对双跨门式刚架钢结构倒塌机制的重要影响。最后,通过大量的参数分析,研究了升温工况、柱脚刚性、中柱柱顶连接形式、荷载比、防火保护、温度梯度、跨高比和柱距等因素对火灾下双跨门式刚架钢结构倒塌模式的影响。参数分析结果表明,升温工况对双跨门式刚架钢结构的倒塌模式有显著影响,柱脚刚性、中柱柱顶连接形式、荷载比、跨高比和柱距对边柱倒塌模式和整体倒塌模式有一定影响,防火保护对中柱倒塌模式有一定影响,截面温度梯度对倒塌模式影响较小。结果可为双跨门式刚架钢结构在火灾下的倒塌预警提供参考。     

火灾下钢筋混凝土柱非线性有限元分析

采用合理的钢材和混凝土的热-力耦合本构模型,针对火灾下钢筋混凝土截面可能出现卸载和反向再加载情形,提出高温下混凝土单轴应力-应变滞回关系。根据火灾下U.L列式虚功增量方程和分层非线性梁单元方法,建立火灾下钢筋混凝土柱非线性有限元分析理论并编制相应的全过程分析程序NARCLF。对典型火灾下钢筋混凝土柱的试验资料进行双重非线性有限元分析。研究结果表明：采用材料应力一应变滞回关系的有限元分析方法的计算结果与实验结果较吻合,证明采用该方法可合理反映火灾下钢筋混凝土柱的变形特性和耐火性能。     

火灾下钢筋混凝土梁桥高温场形变分析

利用数值模拟程序分析了火灾高温下钢筋混凝土矩形截面简支梁任意时刻的温度场分布,研究了保护层厚度、荷载等级对火灾下的钢筋混凝土简支梁高温场时程形变的影响规律,建立了钢筋和混凝土的内力积分模型,以等比数列推导了非线性加速迭代方程.研究表明:截面温度分布与测点至梁体表面距离相关;保护层厚度对钢筋混凝土简支梁跨中挠度影响较大;火灾场钢筋混凝土简支梁跨中挠度时程曲线随荷载等级的增加呈非线性增长趋势,挠度时程曲线增大的程度随保护层厚度增加而减小;增加混凝土保护层厚度,可有效提高火灾场钢筋混凝土梁桥的耐火极限,控制其变形.     

RC框架结构抗连续倒塌研究

为研究钢筋混凝土结构在中柱失效工况下的抗连续倒塌性能,对移除中柱后的钢筋混凝土双跨梁结构进行pushdown加载,并对试件的破坏模式及承载能力进行观测。试验结果表明:中柱失效的钢筋混凝土双跨梁结构的压拱效应和悬链线效应可以抵抗连续倒塌的发生。采用有限元软件DIANA建模对试验结果进行了数值模拟分析,证明了数值模型的合理性。基于可靠的有限元模拟进行拓展参数分析,结果表明混凝土强度增加及跨高比减小有利于提高压拱效应的影响,配筋率的增大则降低压拱效应的影响。采用现有经典公式对第一峰值荷载进行分析,理论分析结果表明:Park模型的计算结果与有限元模拟结果较为接近,进一步证明了有限元模拟的可靠性。     

钢筋混凝土框架结构火灾反应分析

在钢筋混凝土框架模拟火灾试验和混凝土高温上本构关系试验基础上，根据不稳定抛弃讯理论和非线性直接刚度法，对钢筋混凝土框架在火灾进程中的温度反应和结构反应进行了非线性有限元分析。其中，考虑了钢筋的存在对温度分布的影响以及混凝土和钢筋在高温下的卸载规律对结构内力重分布所起的重要作用和高温瞬时徐主的影响。     

火灾时隧道截面形状对临界风速和烟气分布影响的数值研究

模拟分析了某地铁实际工程中三种区间隧道断面(单线盾构圆形断面、单跨矩形断面和双跨矩形断面)对临界风速的影响,结果表明单线盾构圆形隧道的临界风速最大,双跨矩形隧道对应的临界风速最小.拟合得出了纵向通风速度和逆流层长度的变化关系式,计算得出了10 MW火灾强度下三种隧道的临界风速,并在临界风速条件下对三种截面形状隧道对烟气的温度和浓度分布的影响进行了模拟分析,验证了拟合得出的通风速度和逆流层长度变化关系式的准确性,为地铁区间隧道火灾烟气扩散控制和通风系统设计提供了一定的参考依据.     

火灾后混凝土短柱的滞回性能和损伤评定

基于7根明火加热后钢筋混凝土短柱和1根未受火的对比试件的拟静力试验结果,分析受火时间、轴压比和剪跨比对火灾后钢筋混凝土短柱滞回性能的影响情况.结合强度退化分析各试件的损伤发展过程,采用Park损伤模型对受火后短柱和未受火的对比试件的抗震性能进行损伤评定,提出一种能反映火灾高温对柱式构件抗震性能损伤影响加大的评价指标.研究结果表明:火灾后钢筋混凝土短柱在低周往复荷载作用下的滞回曲线和滞回规则与未受火对比件的相似,但受火后滞回环的稳定性较未受火的差;钢筋混凝土短柱的累积滞回耗能随着受火时间的增加,轴压比的减小,以及剪跨比的减小而减小;同一位移角下的强度退化随着受火时间的增加,轴压比的增大,以及剪跨比的增大而加快.此外,Park损伤评价模型对受火前后钢筋混凝土短柱的抗震性能损伤指数均存在超前估计的不足.     

RC梁冲击破坏机理试验研究与残余变形预测方法探讨

进行了3根剪跨比为3.58钢筋混凝土梁的落锤冲击试验和1个静力对比试验,重点研究钢筋混凝土梁在冲击荷载作用下的破坏机理和冲击能量对钢筋混凝土梁残余变形的影响规律.试验结果表明,在静力下发生弯曲破坏的梁在低速冲击下的裂缝形态以弯曲裂缝、弯剪裂缝为主,在高速冲击荷载作用下以腹剪裂缝为主.试验测试了冲击力、支座反力、跨中位移和跨中纵筋应变等动态时程曲线,通过分析其动态时程曲线结果,获得了钢筋混凝土梁的冲击破坏机理,即冲击作用下梁的破坏过程分为局部响应阶段和整体响应阶段.同时,还统计了国内外相关文献冲击试验结果,通过比较分析钢筋混凝土残余变形-冲击能量关系实验数据,探讨了冲击荷载作用下钢筋混凝土梁残余变形的经验公式的适用性和存在的问题.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the