Composite Panels from the Combination of Rice Husk and Wood Chips with a Natural Resin Based on Tannins Reinforced with Sugar Cane Molasses Intended for Building Insulation: Physico-Mechanical and Thermal Properties

The objective of this work is to develop new biosourced insulating composites from rice husks and wood chips that can be used in the building sector. It appears from the properties of the precursors that rice chips and husks are materials which can have good thermal conductivity and therefore the combination of these precursors could make it possible to obtain panels with good insulating properties. With regard to environmental and climatic constraints, the composite panels formulated at various rates were tested and the physico-mechanical and thermal properties showed that it was essential to add a crosslinker in order to increase certain solicitation. an incorporation rate of 12% to 30% made it possible to obtain panels with low thermal conductivity, a low surface water absorption capacity and which gives the composite good thermal insulation and will find many applications in the construction and real estate sector. Finally, new solutions to improve the fire reaction of the insulation panels are tested which allows to identify suitable solutions for the developed composites. In view of the flame tests, the panels obtained are good and can effectively combat fire safety in public buildings.

The automobile steel of the third generation in B-pillar reinforced panel

The fundamental research and industry, trials of the third generation automobile steel QP980 were introduced in this paper, including chemical ingredient, mechanical properties, microstructure, forming limit and basic perform- ance parameters. The application of QP steel of the B-pillar was researched, and the QP980, DP600 and hot forming steel were compared in the aspect of formability, safety and cost. The resuhs showed that the QP980 replacing DP600 steel single piece carl reduce the weight by 2.4 kg. The security and performance is basically the same as that of hot forming steel using 22MnB5, and the cost is reduced by 30 %.

Stress and buckling analysis of a thick-walled micro sandwich panel with a flexible foam core and carbon nanotube reinforced composite (CNTRC) face sheets

In this paper,the stresses and buckling behaviors of a thick-walled mi-cro sandwich panel with a flexible foam core and carbon nanotube reinforced composite(CNTRC)face sheets are considered based on the high-order shear deformation theory(HSDT)and the modified couple stress theory(MCST).The governing equations of equi-librium are obtained based on the total potential energy principle.The effects of various parameters such as the aspect ratio,elastic foundation,temperature changes,and volume fraction of the canbon nanotubes(CNTs)on the critical buckling loads,normal stress,shear stress,and deflection of the thick-walled micro cylindrical sandwich panel consider-ing different distributions of CNTs are examined.The results are compared and validated with other studies,and showing an excellent compatibility.CNTs have become very use-ful and common candidates in sandwich structures,and they have been extensively used in many applications including nanotechnology,aerospace,and micro-structures.This paper also extends further applications of reinforced sandwich panels by providing the modified equations and formulae.

Acoustic Properties of Micro-Perforated Panels Made from Oil Palm Empty Fruit Bunch Fiber Reinforced Polylactic Acid

This paper presents the development and performance of micro-perforated panels(MPP)from natural fiber reinforced composites.The MPP is made of Polylactic Acid(PLA)reinforced with Oil Palm Empty Fruit Bunch Fiber(OPEFBF).The investigation was made by varying the fiber density,air gap,and perforation ratio to observe the effect on the Sound Absorption Coefficient(SAC)through the experiment in an impedance tube.It is found that the peak level of SAC is not affected,but the peak frequency shifts to lower frequency when the fiber density is increased.This phenomenon might be due to the presence of porosity in the inner wall of the holes.Increasing or decreasing the air gap and perforation ratio shifts the peaks of acoustic absorption either way.

Shear reinforcement effect of reinforced concrete tie-columns on the lateral resistance of confined masonry walls

Tie-columns improve significantly the lateral resistance of masonry bearing walls against persistent, transient and accidental loads. The research work described herein has been carried out to assess the lateral resistance of confined masonry walls, where contribution of the masonry panel is evaluated according to material mechanics and tie-columns effect is estimated by a proposed analytical formulation based on a model reported on previously. This approach takes into account the effect of dowel support on the reaction of its adjacent shear reinforcement： the conditions for the various contributions of transverse reinforcements are better defined following a clear evaluation of the participation ratio of these reinforcements. Lateral resistances of confined masonry walls measured in full-scale tests and gleaned from the literature are compared and checked with resistances calculated using the present approach.

装配式桥梁板玻璃纤维混凝土-U形钢筋湿接缝受力与变形分析

为解决装配式桥梁板体系湿接缝处力学性能不稳定、易变形的问题,提出采用玻璃纤维混凝土-U形钢筋加强方案优化湿接缝性能,以雄安新区荣乌高速荣乌主线桥为背景进行研究。选取主线桥2个试验段(试验段A湿接缝采用普通混凝土-U形钢筋方案,钢筋点焊;试验段B湿接缝采用玻璃纤维混凝土-U形钢筋加强方案,钢筋满焊)进行梁板体系湿接缝性能试验,监测湿接缝处搭接钢筋力学响应及混凝土接触面变形特征,同时对长期运载及强降雨影响下的钢筋受力与混凝土变形进行监测。结果表明:长期运载下,试验段B横筋受力约为试验段A的一半,其中部纵筋承受外力远大于试验段A,边缘纵筋承受外力较少,试验段B稳定性更优;试验段B较试验段A在湿接缝部位变形量小,其稳定性及耐久性更优;强降雨阶段,试验段B较试验段A变形及力学响应波动程度更低,其抗渗能力、耐久性更优。由此可知基于玻璃纤维混凝土-U形钢筋加强方案的湿接缝构造在外力传导、抵抗变形方面具有较强稳定性,不易受恶劣环境影响。

围缘扁钢加强的开圆孔无限平板应力解析算法

为了研究围缘扁钢加强的开圆孔无限平板应力解析计算方法,近似认为围缘扁钢区域的平均应力处于广义平面应力状态。运用复变函数论的方法,将应力函数表示为两个待定的解析函数;列出围缘扁钢的边界条件、围缘扁钢与平板之间的应力连接条件和位移连接条件,求出应力函数,根据求出的应力函数便可求出应力。为了描述围缘扁钢减缓孔口应力集中的效果,提出围缘扁钢加强系数的定义。算例计算表明:本文提出的解析算法计算结果与有限元法计算结果吻合良好,围缘扁钢加强的开圆孔无限平板应力普遍小于开圆孔无限平板应力,围缘扁钢加强效果明显;相同体积的加强构件,围缘扁钢的加强效果优于环形加厚板。

基于断裂力学的横隔板弧形切口CFRP加固参数研究

横隔板弧形切口疲劳开裂为正交异性钢桥面板的主要疲劳病害之一。为研究该部位的疲劳性能,分析碳纤维增强复合材料(carbon fiber reinforced polymer,CFRP)参数对加固效果的影响,首先,建立钢梁节段模型,在弧形切口应力幅最大处引入初始裂纹,基于断裂力学理论得到疲劳荷载作用下横隔板弧形切口处的开裂模式及疲劳寿命;然后,建立CFRP板加固模型,改变各加固参数,对比不同初始裂纹条件下裂纹扩展过程中的应力强度因子变化规律,探究CFRP板长度、宽度、厚度、弹性模量以及胶层剪切模量等参数对加固效果的影响;最后,给出推荐加固参数组合。研究结果表明:横隔板弧形切口处疲劳裂纹为I型裂纹,疲劳寿命约为576.42万次;CFRP板加固能有效降低裂纹尖端应力强度因子幅值,但是CFRP板长度与宽度存在加固的临界尺寸,当尺寸大于这一临界值时,其对加固效果影响极小;CFRP板厚度、胶层剪切模量对加固效果的影响随参数增大而逐渐减弱;采用长×宽×厚为45.0 mm×30.0 mm×2.0 mm、弹性模量为460 GPa的CFRP板进行加固后,裂纹将不再扩展,疲劳寿命显著提高。

多级加筋面板受力行为分析及优化

采用三点弯曲实验和有限元仿真方法,对多级加筋面板的变形和破坏进行分析.引入正六边形和内凹六边形两种加筋模式,将具有不同横纵向加筋肋壁厚、圆弧倒角优化的直角边界及二级加筋结构的加筋面板作为研究对象,分析在给定加筋面板几何参数的情况下,横纵向加筋肋壁厚、圆弧倒角优化处理、二级加筋结构对加筋面板结构强度和力学行为的影响.研究表明,加筋面板结构强度随着横纵向加筋肋壁厚的增加而增加,纵向加筋肋壁厚对加筋面板结构影响较大;内凹六边形加筋模式较正六边形加筋模式的加筋面板承载力高;圆弧倒角优化后可以明显改善边角处的应力集中现象、提升加筋面板的结构强度;二级加筋面板的承载能力得到明显提升,且次级加筋层胞元为内凹六边形时提升效果最明显.

高层钢筋混凝土框架结构楼板裂缝成因研究

以建筑项目为例,结合现场监测、检测以及仿真等手段分析钢筋混凝土框架结构楼板裂缝的产生机理,并提出了一定的针对性建议。结果表明:楼面板裂缝的产生机理是配筋率、温差以及楼板自身变形综合作用的结果;楼面自身变形比温差对楼面板力学响应的影响作用更加剧烈;裂缝主要出现在楼面板四角的位置以及外墙转角处,且均呈现45°斜向放射状分布。

Experimental investigation of engineered geopolymer composite for structural strengthening against blast loads

The recent increase in blast/bombing incidents all over the world has pushed the development of effective strengthening approaches to enhance the blast resistance of existing civil infrastructures.Engineered geopolymer composite(EGC)is a promising material featured by eco-friendly,fast-setting and strain-hardening characteristics for emergent strengthening and construction.However,the fiber optimization for preparing EGC and its protective effect on structural elements under blast scenarios are uncertain.In this study,laboratory tests were firstly conducted to evaluate the effects of fiber types on the properties of EGC in terms of workability,dry shrinkage,and mechanical properties in compression,tension and flexure.The experimental results showed that EGC containing PE fiber exhibited suitable workability,acceptable dry shrinkage and superior mechanical properties compared with other types of fibers.After that,a series of field tests were carried out to evaluate the effectiveness of EGC retrofitting layer on the enhancement of blast performance of typical elements.The tests include autoclaved aerated concrete(AAC)masonry walls subjected to vented gas explosion,reinforced AAC panels subjected to TNT explosion and plain concrete slabs subjected to contact explosion.It was found that EGC could effectively enhance the blast resistance of structural elements in different scenarios.For AAC masonry walls and panels,with the existence of EGC,the integrity of specimens could be maintained,and their deflections and damage were significantly reduced.For plain concrete slabs,the EGC overlay could reduce the diameter and depth of the crater and spallation of specimens.

整体现浇面板包裹式加筋土挡墙力学特性研究

为探究整体现浇面板包裹式加筋土挡墙在交通荷载作用下的受力变形特性,以成昆铁路峨米段整体现浇面板包裹式加筋土挡墙为工程背景,利用现场监测数据并运用大型岩土有限元软件midas GTS对整体现浇面板包裹式加筋土挡墙进行了系统研究,实际工程中应适当增加挡墙中部筋带数量,减少加筋间距,增大加筋长度,采用短筋和长筋交替布置的方案,充分发挥筋材的加筋作用,加强挡墙整体稳定性。

加筋土挡土墙施工方法在埃塞俄比亚公路建设项目中的应用及推广

文章在国内加筋土挡土墙的基础上,研究简易式加筋土挡土墙的施工使用材料、施工方法及施工中的注意事项。其目的是降低非洲国家公路建设造价,研究成果应用在埃塞俄比亚南方州莫卡-格恰-琴恰公路施工项目K39+740~K40+468段。该简易式加筋土挡土墙既满足了公路设计年限的使用需求,又达到了降低成本的效果,具有一定的参考价值。

预制+现浇组合式面板加筋土挡墙力学特性研究

为了分析预制与现浇组合式面板加筋土挡墙在交通荷载下的力学行为和变形特性,研究依托成昆铁路复线挡墙工程,以成昆铁路某段复合式加筋挡土墙结构为研究对象,通过现场实测和数值模拟结合的方式,对加筋土挡墙的力学特性进行了研究,重点分析了面板变形、墙后土压力、基底及墙顶沉降等分布规律。分析结果表明,实际工程中应适当增加挡墙中部筋带数量,减少加筋间距,增大加筋长度,采用短筋和长筋交替布置的方式,可充分发挥筋材的加筋作用,以加强挡墙整体稳定性。

考虑Ⅲ型断裂的复合材料加筋壁板界面损伤扩展

复合材料加筋壁板筋条-蒙皮界面损伤研究中Ⅲ型断裂能的作用往往被忽略,本文结合物理试验和数值方法对复合材料开剖面工形加筋壁板和闭剖面Ω形加筋壁板开展了后屈曲筋条-蒙皮界面损伤扩展研究。利用考虑法向压缩抑制界面剪切失效机制的新形界面损伤起始准则和考虑Ⅲ型断裂的Reeder界面损伤扩展准则对两种构形加筋壁板后屈曲历程进行数值模拟分析,对比两种构形壁板的屈曲模式、破坏形式以及筋条-蒙皮界面损伤扩展时的各形能量释放率的分布情况。得出闭剖面Ω形加筋壁板筋条-蒙皮界面主要在面外剥离力的作用下损伤扩展,I型断裂能在界面的损伤起始和扩展中起主要作用;开剖面工形加筋壁板界面主要在剪力的作用下损伤扩展,Ⅲ型断裂能在损伤横向扩展中起主导作用。上述研究阐述了各形断裂能在复合材料加筋壁板界面损伤扩展过程中的作用机理,为复合材料加筋壁板后屈曲数值模拟分析方法研究奠定基础。

模块化建筑研究应用现状及未来发展趋势

模块化建筑是一种高度集成的预制装配体系,具有建造周期短、品质易控、绿色环保、对劳动力依赖小等突出优势,符合中国人口密度大、住宅相对短缺,而制造业水平非常高的基本国情,是建筑工业化未来发展的重要方向,近年来在全国范围内得到了广泛关注和快速发展。然而,随着模块化建筑的持续推进,其存在的一系列问题逐渐暴露出来。在系统梳理模块化建筑国内外研究和应用现状的基础上,总结了模块化建筑在当前发展过程中面临的几个关键问题,并结合新型绿色建筑材料的发展,为其未来发展方向提出了建议,旨在促进模块化建筑的高质量发展。

分馏塔在不移位情况下对底部筒体更换

某公司重油裂解装置分馏塔在试压过程中出现塔体下部筒体立焊缝出现破裂并带动上下两块壁板受损现象,裂缝位置在塔底上方约10m处,对裂纹周边塔体母材经过力学性能试验未发现异常,符合要求。考虑施工成本与周期,决定对在分离塔不移位的情况下对开裂的3层筒体进行更换。对塔体破损部分进行结构加固,防止塔体在维修过程中垮塌,通过载荷计算,在最恶劣的载荷工况下,采取12根钢管立柱的加固方案,计算的强度和稳定性为116MPa,能满足筒体91.1MPa的需求。在加固措施安装完成后,按照一定顺序对壁板逐块更换,并按设计要求对焊缝进行100%无损检测,立式水压试验0.483MPa合格,保证设备能安全运行。

复合材料帽形加筋壁板加捻区质量问题研究

帽形加筋壁板结构的复合材料制件具有比强度高、比刚度高、可设计性良好等优点,在航空航天等工程领域得到了广泛的应用,而加筋结构的三角空隙必须使用捻条进行填充。采用“湿长桁+湿蒙皮”共固化工艺制造帽形加筋壁板复合材料制件时,发现捻条的外形会显著影响制件的成型质量。为了提高帽形加筋壁板制件的成型质量,研究了不同材质的长桁芯模、捻条制备方法、捻条填充量对加捻区长桁及蒙皮质量的影响。结果表明:由专用的加捻模具制备并在(60±5)℃的温度下预压实后,捻条预成型体的外形更精确,与其他结构配合更好;当捻条的填充量修正系数为1.1时,可有效避免蒙皮和长桁出现纤维褶皱;所选用的硅橡胶芯模固化成型后加捻区质量控制更好。

高低温循环作用下纤维增强面板混凝土力学性能研究

防止抽水蓄能电站堆石坝面板混凝土的开裂是电站长期安全运行的重要保障,在电站运行过程中,温差循环对面板混凝土耐久性的影响通常容易被忽视。在面板混凝土中掺入聚丙烯纤维,采用环境试验箱模拟5~85℃高低温循环作用,研究该高低温循环作用对纤维增强面板混凝土力学性能的影响。结果表明:450次高低温循环作用后,普通混凝土和聚丙烯纤维增强混凝土抗压强度较90次高低温循环时分别下降了29.1%、26.3%,极限拉伸应力分别下降了43.1%、32.5%;聚丙烯纤维的掺入可以明显降低混凝土的力学性能损失,且对混凝土拉伸性能的改善程度是抗压强度的5倍左右;聚丙烯纤维在抵抗大温差循环作用下混凝土的拉伸破坏中起到了良好的阻裂和桥架作用,纤维增强混凝土表现为延性破坏特征。

纤维增强树脂基复合材料加筋壁板研究概述

纤维增强树脂基复合材料作为航空航天领域重要的轻质高强材料,已广泛应用于各类壁板零部件中。其中,加筋壁板成型工艺是当前研究的热门方向。基于此,本文概述了国内复合材料加筋壁板成型工艺,并对未来复合材料加筋壁板研究方向作出展望,以期为科研和生产人员提供理论和实践参考。