Theoretical analysis on bending behavior of functionally graded composite beam crack-controlled by ultrahigh toughness cementitious composites

Ultrahigh toughness cementitious composites (UHTCC) obviously show strain hardening property under tensile or bending loading. The failure pattern of the UHTCC components exhibits multiple fine cracks under uniaxial tensile loading with prominent tensile strain capacity in excess of 3%, with merely 60 μm average crack width even corresponding to the ultimate tensile strain state. The approach adopted is based on the concept of functionally-graded concrete, where part of the concrete, which surrounds the main longitudinal reinforcement in a RC (reinforced concrete) member, is strategically replaced with UHTCC with excellent crack-controlling ability. Investigations on bending behavior of functionally-graded composite beam crack controlled by UHTCC has been carried out, including theo- retical analysis, experimental research on long composite beams without web reinforcement, validation and comparison between experimental and theoretical results, and analysis on crack control. In addition to improving bearing capacity, the results indicate that functionally-graded composite beams using UHTCC has been found to be very effective in preventing corrosion-induced damage compared with RC beams. Therefore, durability and service life of the structure could be enhanced. This paper discusses the development of internal force and crack propagation during loading process, and presents analysis of the internal force in different stages, moment-curvature relationship from loading to damage and calculation of mid-span deflection and ductility index. In the end, the theoretical formulae have been validated by experimental results.     

Theoretical analysis and experimental investigation on flexural performance of steel reinforced ultrahigh toughness cementitious composite (RUHTCC) beams

UHTCC (ultrahigh toughness cementitious composite), which is a kind of ultrahigh toughness cemen- titious composites material, exhibits pseudo strain hardening feature when subjected to tension load, and has enormous ductility and prominent crack dispersal ability. Accordingly, UHTCC can improve mechanical behavior of ordinary concrete structure especially its durability, and has been regarded as historical breakthrough to traditional cementitious materials. In this paper, the study focuses on flexure behav...     

功能梯度Timoshenko梁的静力弯曲分析

基于Timoshenko梁变形理论,建立功能梯度材料梁在均布载荷作用下的弯曲控制方程,寻找均匀梁和非均匀梁的控制方程的相似性,将功能梯度材料梁的弯曲求解转化为均匀梁的弯曲求解与相似转换系数的计算。通过理论推导和相似性分析证明,功能梯度Timoshenko梁的弯曲解与同样尺寸、边界条件和载荷条件下的均匀材料Timoshenko梁的弯曲解成正比,这个比例常数完全由材料的非均性质参数确定。     

CFRP筋钢筋混凝土剪力墙自复位性能试验研究

通过对1片钢筋混凝土剪力墙和4片配有碳纤维增强聚合物(CFRP)筋的剪力墙的低周反复荷载试验,在分析试验中测得的裂缝宽度、裂缝的发展和分布形态、侧向变形的基础上,研究了在钢筋混凝土剪力墙的适当位置部分或全部配置CFRP筋对剪力墙的残余裂缝和残余变形等自复位性能的影响规律。研究结果表明:与普通钢筋混凝土剪力墙相比,配有CFRP筋的剪力墙的开裂荷载较低,裂缝较多,裂缝分布分布范围较广,墙体的最大裂缝宽度、残余裂缝宽度和侧向残余变形分别降低了60%、70%和90%,说明在剪力墙中合理配置CFRP筋能使剪力墙具有优异的自复位性能。     

地表变形引起钢框架结构附加内力和变形的试验研究

为了揭示地表变形对钢框架结构的影响规律,根据地下开采引起的地表变形规律,采用物理相似模型试验,研究了单一地表变形和组合地表变形影响下,平面钢框架结构的附加内力和附加变形的演化规律,得出了单一地表变形和组合地表变形均会引起钢框架结构产生附加内力和附加变形,而且地表组合变形对钢框架结构的影响远大于单一地表变形,在组合地表变形中,水平变形主要引起钢框架结构产生附加内力,竖向变形主要引起钢框架结构产生附加变形。组合地表变形是引起平面钢框架结构破坏的主要因素。     

一种新型网壳结构节点的试验研究与有限元分析

结合工程实际，提出了一种用于单层网壳结构的新型毂形节点，对这种节点进行了足尺试验研究，并用有限元软件ANSYS对这种节点的极限承载力进行了非线性有限元计算，并将二者结果进行比较．分析了节点直径和壁厚对节点受压承载力的影响．对具有不同壁厚和直径的节点进行了数值计算，提出了节点受压极限承载力的计算公式根据试验结果提出了改进节点受拉性能的措施，可供工程设计人员和研究人员参考．     

进出口水温对大温差洗浴废水热泵机组性能的影响

洗浴废水中含有大量废热,为最大限度地回收洗浴废水热能,提出了双机串联大温差热泵机组。机组额定设计工况为：蒸发器侧洗浴废水进出口温度分别为30℃和6℃,冷凝器侧自来水进口温度为10℃,制取热水出口温度为45℃。通过实验研究了自来水进口温度、热水出口温度及洗浴废水入口温度对热泵机组制热性能（COP）的影响。实验结果表明,当自来水进口温度从5℃升高到15℃时,整体机组COP从5.0降低到3.85;当热水出口温度从40℃变化到50℃时,整体机组COP降低了7.5%;当洗浴废水进口温度从30℃升高到35℃时,整体机组COP提高了3.1%。在无辅助热源时,若洗浴废水温度从30℃降低到6℃,热水出水温度为45℃,自来水的温度必须要高于12℃;若洗浴废水入口温度达到35℃,即使自来水温度为6℃,热水出口温度也能达到45℃。     

波纹管对纳米复合相变材料蓄放热性能影响的试验研究

以纳米复合材料作为相变蓄热材料,加工制作了相变蓄热装置,并搭建了蓄热器热性能实验台,对传热元件分别为光管和波纹管的蓄热容器进行了相变蓄热实验,测量了相变材料的温度并通过数据采集仪进行数据采集,整理绘制了在不同条件下的温度时间曲线并进行了分析讨论。结果表明波纹管能够加快热媒体在波纹管中的流动,缩短蓄热所需时间,并且提高放热速率。