钢筋混凝土的泊松系数

文章基于接近实物尺寸的钢筋混凝土构件复合受力试验和回归分析,提出钢筋混凝土组合材料泊松系数的新概念和回归方程。钢筋混凝土组合材料泊松系数与匀质弹性材料泊松系数不同,它不是一个常数。钢筋混凝土组合材料泊松系数分为受拉泊松系数和受压泊松系数,且受拉泊松系数常为负值。受拉泊松系数回归曲线存在上升段和下降段;受压泊松系数回归曲线分为混凝土开裂前、达到峰值应力前和峰值应力后３ 个阶段。     

钢筋混凝土柱壳的非线性分析

混凝土受拉开裂及多向压力作用下混凝土的非线性应力－应变关系是产生钢筋混凝土结构非线性反应的两个主要原因，据此建立混凝土破坏的一般准则，用这些准则建立非线性有限元分析的应力－应变增量关系，对于钢筋混凝土构件的有限元分析，文中介绍的方法可以直接考虑钢筋的作用，钢筋和混凝土两种不同材料的应力－应变关系可以分别考虑，便于有限元计算程序的编制。     

地下室底板的抗裂设计与施工

地下室底板往往都是大面积钢筋混凝土结构。由于岩石地基和基础的强大约束，当混凝土产生温度和收缩变形时，会有很大的拉应力，其拉应变甚至会大于混凝土的极限拉应变，从而导致底板开裂。本文从设计与施工两方面讨论了控制这种裂缝的有效措施。     

平面应变状态混凝土等效单轴应变本构模型研究

推导了平面应变状态下的等效单轴应力－应变关系，以应力－应变曲线试验值与计算值的误差达到最小为目标，反演出双向受压时相应于强度值的等效单轴应变值，并回归得到其计算公式；同时对一拉一压，双向受拉及一向开裂，双向开裂等受力状况提出了εic的计算方法；经对现有强度理论的分析比较，选择了适合平面应变状态的强度准则，从而得到了平面应变状态混凝土等效单轴应变本构模型。     

对ABAQUS中混凝土弥散开裂模型的静力特性的分析

为全面了解ABAQUS有限元软件中混凝土弥散开裂模型分析混凝土材料和构件的能力,用该模型对混凝土材料的单轴、双轴应力状态下力学性能以及构件的抗弯、抗剪性能进行模拟,并与试验结果进行对比分析.结果表明,混凝土弥散开裂模型能较精确地模拟单轴受拉和受压、双轴受压和双轴拉压应力状态下混凝土的力学性能,也能较好地预测钢筋混凝土构件的抗弯和抗剪性能及其相应的破坏形态,但不能很好地描述混凝土双轴受拉应力状态下材料的力学性能,也不能反映体积应变发展变化的规律.     

对ABAQUS中混凝土弥散开裂模型的静力特性分析

为全面了解ABAQU S有限元软件中混凝土弥散开裂模型分析混凝土材料和构件的能力,用该模型对混凝土材料的单轴、双轴应力状态下力学性能以及构件的抗弯、抗剪性能进行模拟,并与试验结果进行对比分析。结果表明,混凝土弥散开裂模型能较精确地模拟单轴受拉和受压、双轴受压和双轴拉压应力状态下混凝土的力学性能,也能较好地预测钢筋混凝土构件的抗弯和抗剪性能及其相应的破坏形态,但不能很好地描述混凝土双轴受拉应力状态下材料的力学性能,也不能反映体积应变发展变化的规律。     

平面应变混凝土强度变形试验与等效单轴应变本构模型

利用自行研制的三向强度变形试验装置,进行了应力比α=σ1/σ3=0:-1,0.05:-1,0.1:-1,0.2:-1和0.3:-1的拉-压平面应变状态强度与变形试验.试验结果表明:在拉压平面应变状态时,混凝土破坏形态主要分为受拉和受压2种,应力比α=σ1/σ3≤-0.1时为受拉破坏,应力比α>-0.1时为受压破坏;在混凝土开裂或屈服前,应力应变关系呈线性.同时,根据试验结果给出了拉-压平面应变状态的强度计算公式,完善了平面应变状态等效单轴应变本构模型.     

混凝土梁教学实验中的异常开裂机理探讨

针对钢筋混凝土简支梁剪压破坏性教学实验,在加载临近极限承载力时,梁端上部受压混凝土出现竖向开裂的异常现象,认定混凝土受压区出现拉应力;通过剪跨段上部混凝土应变测试,得到随荷载增加应变由压变拉的试验数据;根据实测应变分布,计算钢筋与混凝土在完全锚固情况下的粘结剪力,并与混凝土对钢筋的实际粘结强度进行比较,得出钢筋与混凝土粘结破坏并产生滑移的结论;认为剪跨段短,上部纵向应变梯度大,滑移引起的钢筋相对伸长在混凝土中产生拉伸效应,是导致剪跨段上部混凝土竖向开裂的主要原因,并提出验证实验方案。     

冻融循环下砼力学性能与相对动弹性模量关系

研究冻融循环作用后混凝土受拉峰值应力、受压峰值应力、受拉峰值应变、受压峰值应变、受压极限应变及受拉初始弹性模量与相对动弹性模量之间的关系.对经过0,25,50,75,100和125次冻融循环作用的C20,C30,C40和C50抗拉试件进行单轴拉伸试验,对经过0,25,50和75次冻融循环作用的C20棱柱体试件进行抗压试验,得出各力学性能随相对动弹性模量变化的规律,回归得出相关的计算公式.结果表明:冻融循环作用后,随着相对动弹性模量的降低,混凝土的受拉峰值应力、受压峰值应力及受拉峰值应变等力学性能指标逐渐减小,而受压峰值应变及受压极限应变却逐渐增大.     

铁路简支梁桥纵向连续加固模型试验研究

对和原型梁比例为１∶５的钢筋混凝土简支梁进行了纵向连续加固前、后的静载试验研究．通过对试验结果对比和分析，简支梁模型经过纵向连续加固后可有效的提高梁的承载能力，增加梁的抗弯刚度，减小梁跨中截面挠度和端截面转角，降低梁跨中截面受压区混凝土的最大压应力和受拉区最外层受拉钢筋的最大拉应力．     

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.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

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