变形钢筋与高强轻骨料混凝土的黏结-滑移性能

研究变形钢筋与轻骨料混凝土间的黏结-滑移性能,完成了9组中心拉拔试验,分析了轻骨料混凝土强度、锚固长度、粗骨料类型及钢筋的直径对黏结应力的影响.结合试验结果,采用厚壁模型,给出了轻骨料混凝土黏结强度的解析解,并建立了钢筋与轻骨料混凝土间的黏结应力-滑移曲线本构模型.结果表明:轻骨料混凝土的黏结-滑移性能主要受砂浆强度影响,使得该类混凝土与变形钢筋间的黏结应力优于普通混凝土;黏结强度随着轻骨料混凝土的强度提高而增加,随着黏结长度的降低而增加;本文提出的本构模型能够较为准确地预测试验曲线.     

钢筋黏结滑移模型及OpenSees有限元模拟

基于钢筋混凝土构件端部锚固钢筋黏结-滑移机理,在Ustuner局部黏结应力-滑移关系的基础上推导出钢筋应力-滑移关系骨架曲线的计算方法.分析了配箍率、混凝土的有效约束宽度、钢筋延伸长度对钢筋应力-滑移关系的影响.将推导的钢筋应力-滑移关系曲线应用于OpenSees有限元软件中,对已有的2根既有钢筋混凝土构件进行有限元模拟,分析结果与试验结果符合良好.     

剪切波沿钢筋纵向入射时钢筋与混凝土间黏结力拟静力解析解

为研究钢筋与混凝土之间黏结应力分布以及黏结应力和滑移量之间关系的理论,基于拟静力假定,从剪切波沿钢筋纵向入射时钢筋混凝土的弹性响应入手,运用线性本构滑移模型及弹性复势方法获得钢筋与混凝土界面滑移量与黏结力的封闭形式解答,并通过算例分析钢筋直径、混凝士动剪切模量、混凝土保护层厚度、箍筋直径及间距对滑移量及黏结力的影响规律.研究结果表明:当选用的钢筋直径越小时,钢筋与混凝土间黏结力越大而滑移越小;当钢筋直径越大时,则恰好相反;当动剪切模量越大时,钢筋与混凝土间黏结力及滑移量都越大,动剪切模量越小,则钢筋与混凝土间黏结力及滑移量越小;当混凝土保护层越厚时,钢筋与混凝土间黏结力越大;当混凝土保护层越薄时,则反之,而滑移量却没有明显变化;箍筋间距对黏结力及滑移量的影响很微弱;箍筋直径越大,黏结力越大,箍筋直径越小,则钢筋与混凝土间黏结力及滑移量越小,而滑移量没有明显变化.所得结果与试验结果相吻合,该封闭形式解答可为钢筋混凝土结构设计提供理论依据.     

单轴受拉状态下混凝土非局部化细观损伤模型

以非局部化理论和随机损伤力学为基础,从细观机制出发考虑断裂和塑性滑移的影响,提出了非局部细观损伤模型.利用残余应力系数反映塑性滑移对损伤细观机制的影响;利用非局部化比例解决层数敏感性问题.结合细观和宏观两个尺度进行损伤本构模型建模,描述混凝土内部的应变发展、损伤演化以及沿受力方向任一高度处的应力-应变关系.基于非局部化比例分析得出的应力-应变关系与实验结果符合较好.     

再生混凝土与钢筋间黏结应力分布函数

通过改变箍筋间距,采用钢筋开槽内贴片方法,测试全天然骨料和全再生骨料共6组钢筋混凝土构件的平均黏结-滑移曲线及锚固段内不同位置处的钢筋应变。基于试验结果,计算不同锚固位置处钢筋与混凝土的黏结应力和相对滑移,得到相应位置的黏结-滑移曲线。分析箍筋约束对再生混凝土-钢筋黏结应力分布的影响机理,并建立再生混凝土与钢筋间黏结应力分布函数模型。研究结果表明:未配箍构件的加载端黏结应力大于自由端黏结应力;构件配箍筋后,平均极限黏结强度提高,峰值滑移显著增加,平均黏结-滑移曲线下降段变平缓,且随着箍筋间距减小,锚固段黏结应力分布逐渐均匀;再生粗骨料对钢筋混凝土的黏结应力分布影响较小。     

碳纤维板-混凝土界面黏结性能的试验研究与有限元分析

碳纤维板与混凝土的界面黏结性能是碳纤维加固混凝土结构的关键性能之一,对加固结构的力学行为和破坏形态等有着重要影响.进行了4个试件的碳纤维板-混凝土黏结双面剪切试验,研究了设置不同粘贴长度的试件的界面力学行为和破坏模式,分析了黏结长度对界面极限承载力和应力分布的影响.试验结果表明:加载点附近应力远大于端部应力,板端黏结界面剪应力沿板长方向大致呈指数衰减分布.在试验研究基础上,在ANSYS中采用正交弹簧单元组模拟界面黏结,建立了试件的有限元模型,并采用试验分析得到的局部黏结滑移曲线关系作为有限元模型中的界面弹簧单元刚度,计算发现有限元分析结果和试验结果比较吻合,从而验证了本文有限元模型的有效性.以本文试验得到的黏结滑移曲线关系为基础,通过拟合得到了基于几种经典黏结滑移本构形式的界面本构模型.试验及有限元分析表明:当拉伸应力超过碳纤维板强度的24%时,碳板已开始从混凝土表面剥离.为保证充分利用碳纤维板的强度,应采用可靠锚具对碳纤维板进行锚固.     

锈蚀钢筋与TRC约束混凝土黏结滑移本构关系

采用试验和理论分析相结合的方法,基于电化学锈蚀中心拉拔试验,研究在有无纤维编织网增强混凝土(TRC)约束下,对不同电化学锈蚀率变形钢筋与混凝土界面黏结性能的影响,并且对试件破坏形态以及黏结滑移曲线等进行了分析研究.研究结果表明:在无TRC约束的情况下,锈蚀钢筋与混凝土极限黏结应力随锈蚀率增加而降低,尤其是混凝土产生锈胀裂缝后极限黏结应力下降明显;TRC约束对锈蚀钢筋与混凝土的黏结性能尤其是锈蚀程度较大的试件有很好的改善作用;对于产生锈胀裂缝的试件,TRC约束具有良好的限制试件开裂以及提高极限黏结应力的作用,同时TRC约束对维持锈蚀钢筋与混凝土的黏结刚度也有明显效果;最后建立了TRC约束混凝土与锈蚀钢筋上升段的黏结滑移本构关系.     

钢筋-超高性能混凝土界面黏结性能试验

为研究轻薄UHPC构件内钢筋-UHPC界面间的黏结性能,以钢筋直径、黏结长度和保护层厚度为变量设计了多组配筋UHPC拉拔试验,并探讨各设计变量对钢筋-UHPC界面黏结性能的影响.基于试验结果,分析各设计参数对配筋UHPC试件破坏形式、黏结应力-滑移曲线、黏结锚固强度及其对应滑移量等因素的影响.研究表明：钢筋直径、黏结长度和保护层厚度的变化对配筋UHPC界面黏结性能影响较大;极限黏结强度及滑移量随黏结长度的减小而增加,随钢筋直径增加而先增加后降低;随保护层厚度变薄,极限黏结强度降低而滑移量增加.钢筋直径为12 mm和16 mm时,配筋保护层厚度和黏结锚固长度分别不宜小于1.5倍和4倍直径;直径为8 mm的钢筋黏结锚固长度不宜小于3.5倍直径.基于数理统计法归纳的配筋UHPC界面极限黏结强度及临界锚固长度计算式与试验结果误差较小.     

型钢轻骨料混凝土黏结滑移性能试验研究

通过推出试验,研究型钢轻骨料混凝土黏结滑移性能.采用正交试验设计,考虑了轻骨料混凝土强度、型钢埋置长度、保护层厚度、横向配箍率等因素对黏结滑移性能的影响.根据试验结果,统计回归了特征黏结强度和特征滑移值计算公式;提出了型钢轻骨料混凝土平均黏结应力于和加载端滑移SL的本构关系数学模型.研究结果表明:型钢埋置长度la与型钢截面高度d的比值和轻骨料混凝土强度对黏结强度影响较显著;型钢轻骨料混凝土相对于型钢普通混凝土有较小的黏结强度和较陡的荷载滑移下降段.     

单弹簧联结单元法的改进算法

单弹簧联结单元法是在实体单元与梁单元的切向设置单弹簧联结单元,模拟钢筋与混凝土切向的相互作用.其切向刚度是由钢筋与混凝土之间的粘结力与滑移量的关系确定,法向变形协调则通过建立法向自由度约束方程保证.在单弹簧联结单元法的基础上,提出了基于钢筋混凝土滑移关系全量曲线的非线性迭代解法,对单弹簧联结单元法进行了改进.在钢筋和混凝土之间直接引入粘结滑移本构关系,由钢筋和混凝土之间的全量滑移量直接求解相互作用力,不仅可以考虑本构关系曲线的下降段,而且受加载方式的影响较小,使得单弹簧联结单元法的求解速度和精度大大提高.     

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.     

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     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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