Fe_(2)O_(3)-MWNTs Composite with Reinforced Concrete Structure as High-performance Anode Material for Lithium-ion Batteries

A Fe_(2)O_(3)-MWNTs(multi-walled carbon nanotubes)composite with a reinforced concrete structure was fabricated employing a two-step method which involves a sol-gel process followed by high-temperature in situ sintering.This Fe_(2)O_(3)-MWNTs composite,intended to be used as an anode material for lithium-ion batteries,maintained a reversible capacity as high as 896.3 mA·h/g after 100 cycles at a current density of 100 mA/g and the initial coulombic efficiency reached 75.5%.The rate capabilities of the Fe_(2)O_(3)-MWNTs composite,evaluated using the ratios of capacity at 100,200,500,1000,2000 and 100 mA/g after every 10 cycles,were determined to be 904.7,852.1,759.0,653.8,566.8 and 866.3 mA·h/g,respectively.Such a superior electrochemical performance of the Fe_(2)O_(3)-MWNTs composite is mainly attributed to the reinforced concrete construction,in which the MWNTs function as the skeleton and conductive network.Such a structure contributes to shortening the transport pathways for both Li+and electrons,enhancing conductivity and accommodating volume expansion during prolonged cycling.This Fe_(2)O_(3)-MWNTs composite with the designed structure is a promising anode material for high-performance lithium-ion batteries.

3D fracture modelling and limit state analysis of prestressed composite concrete pipes

In this manuscript,we study fracture of prestressed cylindrical concrete pipes.Such concrete pipes play a major role in tunneling and underground engineering.The structure is modelled fully in 3D using three-dimensional continuum elements for the concrete structure which beam elements are employed to model the reinforcement.This allows the method to capture important phenomena compared to a pure shell model of concrete.A continuous approach to fracture is chosen when concrete is subjected to compressive loading while a combined continuous-discrete fracture method is employed in tension.The model is validated through comparisons with experimental data.

水工钢筋混凝土结构三维配筋CAD系统的方案及其实现

本文针对三峡工程中大量的钢筋混凝土结构的配筋设计问题，分析了配筋设计绘图的特点，提出了三维可视化配筋设计方案，研究了系统实现的部分技术问题．该方案的原型系统已基本完成，即将应用于实际配筋设计．最后结合系统的应用示例。

寒冷地区某渡槽裂缝成因及钢筋锈蚀对耐久性影响

北方寒冷地区某大型调水渡槽,采用大跨度三向预应力钢筋混凝土结构。在其施工建设期间,检查已建渡槽槽墙表面有竖向长裂缝、流白膏、碱蚀渗水的现象,敲击墙面内部有空鼓声音。为了研究上述问题,采用理论分析、数值计算方法,从预应力张拉、积水冻胀、环境温度等方面考虑,分析表明槽墙表面裂缝和内部空鼓缝是积水冻胀造成的。非线性有限元精细模型计算和钢筋锈蚀耐久性分析结果表明:(1)冻胀量达到0.4%时,管周边出现纵向拉裂缝,当冻胀量达到1%时,表面开始出现竖向裂缝,冻胀量达到3%时,表面形成长裂缝,内部空鼓缝贯通;(2)灌浆孔道有空气和积水恶劣工况下,预应力钢筋发生锈蚀,速率达到0.102 mm/a;空鼓缝深度8 cm且管内破裂进水,其锈蚀速率为0.024 mm/a,15 a后其重量损失率即可达6%;当空鼓缝深小于8 cm时,10 a后竖向普通钢筋的锈蚀将致槽墙生成新的锈胀裂缝。建议对渡槽进行二次灌浆并控制好灌浆质量及做好保温和防水措施,防范渡槽产生新裂缝。

大直径无梁三分岔管结构研究

本文采用解析法、三维有限元法和物理模型试验方法对某一无梁岔管进行了结构分析．分析结果表明，钢衬钢筋混凝土无梁岔管与无梁明钢岔管相比，具有受力条件好、钢衬较薄、施工方便、安全性高、造价低等优点，是一种新的岔管结构形式，具有广阔的应用前景．

型钢混凝土结构钢筋复杂密集节点设计优化与施工技术

以青岛市地铁运营控制中心项目为例,对型钢混凝土结构梁柱节点进行3D设计优化和施工技术改进,解决了许多复杂节点钢筋密集及交叉作业施工难题.实际应用中,该施工技术对主体结构施工过程中节约成本、加快进度、保证施工质量和提高效率起到了重要作用.对现场施工中的持续改进经验进行总结,可为相关工程施工提供参考.

钢筋混凝土三维多向固定裂缝本构模型

为了研究钢筋混凝土结构在复杂荷载作用下裂缝间存在的交互作用,用三维数值分析方法模拟了裂缝交叉特性。采用有限元中弥散裂缝概念,建立了三维多向固定裂缝模型。进行了本构关系检验和试验验证。结果表明:该模型能够分析钢筋混凝土结构多向裂缝问题。通过正六边形截面梁构件变换加载面和加载方式试验,研究分析了裂缝空间交叉的相互影响作用。将三维多向固定裂缝模型应用于上述试验的结果表明:该模型能够较好地分析钢筋混凝土结构三维多向开裂及裂缝交叉扩展过程。