Rate Effects on the Stress-Strain Behaviour of Eps Geofoam

The rate-dependency of the stress-strain behavior of EPS (Expanded Polystyrene) geofoam with densities of 19.3 and 28.0 kg/m³ was investigated by performing unconventional unconfined compression tests. A set of monotonic loading (ML) tests were performed at different constant values of vertical (axial) strain rate, ε_v. The ε_v value was stepwise changed many times and several sustained loading (SL) tests were performed during otherwise ML at a constant ε_v in other tests. A number of SL tests were performed during global unload and reload cycles to infer the stress-strain relation when ε_v=0. The elastic properties were evaluated by applying minute unload/reload cycles during otherwise ML. The rate-dependent stress-strain behaviour observed in these tests was described by an elasto-viscoplastic model (i.e., a non-linear three-component model), for which the vertical (axial) stress, σ_v, consists of inviscid and viscous components, σ_v^f and σ_v^v, while ε_v consists of elastic and irreversible components, ε_v^e and ε_v^ir. It is shown that the viscous property of EPS geofoam is of Isotach type in that, under the loading conditions where ε_v^ir is always positive, the current σ_v^v value is a unique function of instantaneous ε_v^ir and ε_v^ir, therefore the strength increases with ε_v. This viscous property was quantified based on the test results and incorporated into the model. The rate-dependent stress-strain behaviour, including the creep behaviour, observed in the experiment is simulated very well by the proposed model. In particular, the fact that the creep strain becomes significant when the sustained σ_v value becomes larger than the inviscid yield vertical stress is well simulated.     

土工泡沫工程性质及其应用

综述了土工泡沫作为土工合成材料的主要工程性质 ,特别对其热绝缘性、轻质、高压缩性等传统土工合成材料产品所不具有的特点予以阐述 ,并介绍了其在岩土工程上的应用。作为热绝缘材料 ,可以防止基底及边墙受冻 ;利用轻质性能 ,作为路堤填料 ;利用高压缩性 ,产生土拱效应 ;也可用作减振材料     

论膨胀聚苯乙烯颗粒保温功能砂浆

如今为了大力发展循环经济,保障我国经济的可持续发展,降低能源和资源的耗费,建筑节能已成为国家的重要政策.由此衍生出来众多节能型建筑材料,膨胀聚苯乙烯颗粒保温功能砂浆就是其中一种性价比较好的节能型砂浆.膨胀聚苯颗粒保温功能砂浆主要由膨胀聚苯乙烯颗粒、合成纤雏、化学外加剂及水泥构成,每个原材料都有其相应的技术要求,各原材料通过合理的生产改性及配制工艺,检验合格后方可出厂并应用于实际工程,在施工过程中还应严格遵守相关施工注意事项,这样才能充分发挥膨胀聚苯乙烯颗粒保温功能砂浆的保温性能,达到节能的目的.     

Temperature Dependence of Stress-Strain Properties of Freshwater Ice

Soil Mechanics and Foundation Engineering - We present the results of experimental investigation of the temperature dependences of the stress-strain properties of freshwater ice and pykrete. It is...     

膨胀聚苯板薄抹灰外墙外保温系统防火构造研究

该研究采用大尺寸墙角火试验,对比研究了防火隔离带对聚苯板外墙外保温系统受到火源攻击时的防火性能及火焰传播性。试验结果证明:防火隔离带能够有效阻止火焰快速传播,延缓火灾进程,降低火苗高度,提高聚苯板外墙外保温系统的整体防火安全性。     

Use of Compressible Expanded Polystyrene Blocks and Geogrids for Retaining Wall Structures

The use of a compressible layer such as expanded polystyrene blocks behind a rigid retaining wall and geogrid layers embedded in a dense granular backfill is examined as a reinforcement technique for retaining wall structures. The mobile model retaining walls adjacent to reinforced model specimens are subjected to different surcharge pressures, and are caused to move laterally to measure the lateral earth pressure during the wall movement. The coefficients of earth pressure at rest and active earth pressure are carefully inferred from test results. Three series of tests are conducted; one test series with expanded polystyrene blocks installed behind the wall, another with geogrid layers embedded within model specimens, and the last series with expanded polystyrene blocks installed behind the wall and geogrid layers fixed between two adjacent expanded polystyrene blocks and embedded within model specimens. The reductions in the earth pressure at rest and the active earth pressure due to various patterns of reinforcement are interpreted in relation to the concept of controlled yielding of compressible expanded polystyrene blocks, tensile strains induced along geogrid layers, fixity between expanded polystyrene blocks and geogrid layers, and a facing unit consisting of expanded polystyrene blocks.     

EPS纤维轻质土导热系数测定

文章对新型填土材料EPS纤维轻质土,利用导热系数仪,对养护龄期28 d、不同配比条件下的轻质土的导热系数λ进行了试验探讨。试验结果表明：在其它条件相同的条件下,试样的导热系数λ随EPS含量的增加而减小;纤维含量的增加对导热系数λ没有大的影响。     

建筑工业行业产品标准《膨胀聚苯板薄抹灰外墙外保温系统》主要特点简介

随着我国各项节能技术的发展和对节能重视程度的不断提高,近年来,我国在建筑节能方面已取得了长足的进展,其中外墙外保温技术的发展尤为迅速。国内有关企业通过直接引进国外先进技术,或结合我国国情进行研制开发,涌现出多种外墙外保温技术,在许多省、市、地区的工程中取得了成功的应用。膨胀聚苯板薄抹灰外墙外保温系统(以下简称薄抹灰外保温系统)作为其中一种有代表性的类型,也得到了广泛的应用和推广,取得了十分可喜的成绩。目前,《膨胀聚苯板薄抹灰外墙外保温系统》产品行业标准(以下简称本标准)的编制工作已经完成,并由建设部正式批准为…     

EPS材料在桥头软基处理中的技术经济分析

采用EPS超轻质材料填筑路堤,通过与其他处理方式比较,结果表明,EPS材料在深厚软土地基低填方路堤中具有良好经济性和处理效果。     

EPS板外墙外保温+氟碳平面金属漆系统施工质量控制

文章概述了外墙外保温及氟碳平面金属漆系统的应用,着重介绍了外墙外保温及氟碳平面金属漆系统施工时的质量控制。     

聚苯乙烯轻质骨料掺量对混凝土砌块性能影响的试验研究

通过试验研究了聚苯乙烯轻质骨料掺量对混凝土材料强度、干表观密度和导热系数以及对混凝土砌块及其墙体性能的影响,探讨了聚苯乙烯骨料应用于凝土空心砌块以提高其保温隔热性能的可行性.     

聚合物对膨胀珍珠岩轻集料混凝土性能的影响

研究了聚合物胶乳和聚丙烯纤维(PP纤维)对膨胀珍珠岩轻集料混凝土力学性能的影响及微观结构.结果表明:在一定的范围内,聚合物胶乳和聚丙烯纤维可以显著提高膨胀珍珠岩轻集料混凝土的抗压强度和抗折强度,使膨胀珍珠岩轻集料混凝土的吸水率明显降低,抗冲击性能明显提高.通过SEM扫描电镜观察发现,掺入聚合物胶乳后,聚合物聚集在毛细孔中,形成聚合物网络,改善了硬化水泥浆体结构,使界面结合更加致密.     

石膏基聚苯颗粒砂浆及其墙板性能试验研究

以轻钢龙骨和钢板网为骨架,石膏基聚苯颗粒砂浆为填充材料制备两种构造形式的新型复合墙板,并对其抗弯承栽性能、隔声性能和耐火性能进行了研究.结果 表明:石膏基聚苯颗粒砂浆的干密度、导热系数和抗压强度均随着聚苯颗粒掺量的增加而降低,且聚苯颗粒的最佳掺量为0.8％;两种构造形式复合墙板的破坏荷栽与自重荷载的比值达到7.0以上;...     

Fire Performance of External Thermal Insulation Composite System (ETICS) Facades with Expanded Polystyrene (EPS) Insulation and Thin Rendering

External Thermal Insulation Composite System (ETICS) facades with expanded polystyrene (EPS) insulation and thin rendering are applied frequently in buildings. Considering high combustibility of EPS, with these facades concerns also arise regarding spread of a possible fire between neighbouring compartments of high-rise buildings. Fire tests of two large-scale facades were performed to study two parameters presumably influencing significantly the fires of such facades in real-life settings, i.e. incident heat flux upon the facade’s surface (IHFFS) and damage of the facade’s render (the latter being a consequence of poor or unfinished construction work, ageing or fire-induced thermal strain). The first facade was rendered fully and was exposed to moderately-fast increasing IHFFS. In the second (partially unrendered) facade case the IHFFS progressed faster. The facade flame body (temperatures and shape) was monitored by thermocouples, photo and video cameras. For detection of melting of EPS and internal burning, thermocameras were used within the facades areas outside the visible plume. In the plume zone, however, a group of thermocouples was embedded inside EPS and the shapes (plateaus and slopes) of the collected time-temperature graphs were observed for these purposes. The IHFFS imposed on the facades during fire testing were estimated by numerical calculations. In both cases the first pronounced render crack was evolved at the estimated average between-windows IHFFS of around 30 kW/m(^2) and was followed by internal burning of EPS. While the latter did not seem to spread across the facade for the fully-rendered facade, a fast fire spread was detected for the second specimen.     

结构性黄土应力应变特征分析

利用GDS三轴试验系统开展了饱和黄土等压/偏压固结不排水常规三轴压缩试验研究(应变控制式),获得了一组结构性黄土应力～应变关系曲线。此类曲线反映了饱和黄土应力～应变关系具有"暂稳态"特征,其后发生强烈应变软化。此外又开展了应力控制式三轴压缩试验研究,试验结果表明,应力增量式剪切能够最大程度地反映土体微观结构特征,应力失控的拐点即为土体结构强度。而应变增量控制的传统剪切模式,在应变速率精确控制的同时,削弱了其结构性。因此,研究在外界荷载作用下的黄土的力学性状,建议开展应力控制式三轴压缩试验,以获得更为合理的结果。     

结构轻骨料混凝土的应力-应变全曲线

测定了采用高强轻骨料配制的强度等级LC30～LC55的结构轻骨料混凝土(LWAC)的应力-应变全曲线。该强度范围的LWAC应力-应变全曲线的方程可采用与现行设计规范中普通混凝土相同的形式,但其中系数不同;实验与拟合结果吻合良好。LWAC应力-应变全曲线的峰值应力与峰值应变、收敛点应力和拐点应力都有良好的线性关系,峰值应变为(2 01～2 93)×103με。在同等峰值应力情况下,结构轻骨料混凝土的峰值应变比普通混凝土的约大600με。     

Forecasting Stress-Strain Behavior of a Thermally-Stabilized Base

Soil Mechanics and Foundation Engineering - The paper proposes an improved procedure for projecting thermal and stress-strain behavior of the base of an oil tank erected on permafrost soil by...     

玻化微珠保温砂浆保温性能改善及固化性能研究

以玻化微珠为轻骨料、引气剂为改性剂,配制玻化微珠保温砂浆,研究不同种类引气剂对保温砂浆导热系数、干湿表观密度、压折比、保水性、和易性、凝结时间、压剪粘结强度等性能的影响。实验结果表明,引气剂A掺量为0.2%～0.4%、引气剂B掺量为0.3%～0.4%时,随着引气剂掺量的增加,玻化微珠保温砂浆的水料比、干密度、导热系数、线收缩率逐渐降低,保水性、和易性逐渐提高,保温隔热性能显著改善。     

约束混凝土的应力-应变分析模型

众所周知,混凝土的强度和延性在很大程度上取决于侧向约束水平。约束的刚度和基本性能（弹性,弹塑性等）是影响混凝土性能的重要因素。本研究中,建立了一个新的简单的约束混凝土模型来描述三向受压状态下混凝土的轴向和侧向变形特性。定义约束混凝土的轴向应力-应变关系为非线性曲线的弹性区。采用常失效能量准则定义了应力-应变关系曲线的下降区域。     

Stress-Strain Relationship of Frozen Sand as a Composite Geomaterial

The present paper aims at developing a simplified model for a stress-strain relationship at small strains up to an initial yielding of homogeneous saturated frozen sand. The modelling of elastic moduli for an ice-sand mixture as a composite geomaterial is first introduced based on previous studies, where a saturated frozen sand is treated as the ice- sand mixture. The applicability of modelling the elastic moduli under constant temperature is then discussed from the theoretical and experimental points of view. In addition, the hyperbolic stress-strain modelling of saturated frozen sand at small strain is presented. The effect of the volume fraction of sand, stiffness of sand inclusion and temperature changes on the elastic moduli and the stress-strain behaviour up to about 1-2% axial strain, which is defined as an upper yield stress, are investigated through the model, whose applicability is verified in comparison with the experimental data.