橡胶座非线性弹性界限特性和屈曲特性理论和试验研究

本文系统地研究分析了橡胶隔震支座(以下简称为橡胶座)的界限特性和屈曲特性,界限特性的研究包括橡胶座的界限压缩、界限拉伸、界限剪切等特性,屈曲特性研究包括橡胶座的屈曲应力与界限剪切应变的相关特性。基于橡胶座的压缩刚度因子和拉伸刚度因子,给出了计算橡胶座界限压缩和界限拉伸应力的实用计算理论,同时提出了屈曲应力和界限剪切应变的评价方法。针对橡胶座的界限特性和屈曲特性理论,采用天然橡胶和铅芯橡胶座原型试件进行了试验研究,结果表明本文提出的界限压缩、界限拉伸、屈曲应力等计算理论和评价方法是偏于安全的。文末汇总了本研究涵盖的橡胶座压缩、拉伸、回转、剪切和界限等相关特性的研究成果,初步形成了建筑用橡胶座的基础理论体系。     

土工格栅加筋橡胶砂强度特性试验研究

橡胶砂作为轻质、耗能填料在土木工程中有广泛的应用前景,但其强度往往会随橡胶含量的增大而降低。土工格栅常用于对散体材料的加筋补强,研究土工格栅对橡胶砂强度特性的加筋效应具有重要意义。基于三轴压缩试验,对3种不同格栅布置方式（1、2、3层）下的干燥橡胶砂强度特性展开研究,重点考察加筋层数对不同围压（50、100、200 kPa）下、不同配比（0%、10%、20%、30%、40%）橡胶砂的强度参数,如峰值强度、似黏聚力、内摩擦角的影响规律。结果表明：土工格栅加筋橡胶砂的强度参数,包括峰值强度、似黏聚力、内摩擦角,相对于未加筋橡胶砂均有明显提高,提高幅度随土工格栅加筋层数的增加而增大,随着围压的降低而增大;土工格栅对配比为20%橡胶砂的强度加筋效应最为明显;土工格栅加筋橡胶砂的强度参数恢复系数与加筋密度之间呈良好的线性关系;土工格栅加筋橡胶砂的强度特性可由试验所得的经验恢复函数较好地估计。     

含水率对大应变下橡胶砂动剪模量和阻尼比的影响

橡胶砂作为轻质耗能填料在工程中应用广泛,其含水状态随应用领域及外界因素变化而不同。研究含水率变化对橡胶砂动剪模量和阻尼比的影响,对于其合理应用具有重要意义。利用大型循环单剪试验装置对6种含水率的橡胶砂在3种竖向压力下进行了循环剪切试验,得到了动剪应变幅值在1%～3%范围时,橡胶砂动剪模量和阻尼比随含水率变化的试验现象。结果表明：橡胶颗粒的加入使得纯砂的动剪模量随含水率的衰减受到抑制,当橡胶颗粒含量达到30%时,橡胶砂动剪模量随含水率的增大反而表现出增大的趋势;随着橡胶颗粒含量的增大,橡胶砂阻尼比随含水率的增大表现出衰减的趋势;虽然离散性较大,但含水率对橡胶砂动力特性的影响不可忽略,橡胶砂动剪模量受含水率影响的平均最大变化幅值可达20%,阻尼比受含水率影响的平均绝对变化值接近0.025;在动力特性随含水率的稳定性方面,橡胶颗粒质量含量为20%的橡胶砂表现相对较好。     

Time domain identification of hybrid base isolation systems using free vibration tests

A procedure for the dynamic identification of the physical parameters of coupled base isolation systems is developed in the time domain. The isolation systems considered include high damping rubber bearings (HDRB) and low friction sliding bearings (LFSB). A bi‐linear hysteretic model is used alone or in parallel with a viscous damper to describe the behavior of the HDRB system, while a constant Coulomb friction device is used to model the LFSB system. After deriving the analytical dynamical solution for the coupled system under an imposed initial displacement, this is used in combination with the least‐squares method and an iterative procedure to identify the physical parameters of a given base isolation system belonging to the class described by the models considered. Performance and limitations of the proposed procedure are highlighted by numerical applications. The procedure is then applied to a real base isolation system using data from static and dynamic tests performed on a building at Solarino. The results of the proposed identification procedure have been compared to available laboratory data and the agreement is within ±10%. However, the need for improvement both in models and testing procedures also emerges from the numerical applications and results obtained. Copyright © 2010 John Wiley & Sons, Ltd.     

坝体岩基-橡胶粉改性混凝土现场抗剪（断）试验研究

坝体岩基与混凝土间的抗剪（断）参数关系着大坝的设计和运行安全。利用橡胶粉能够增大混凝土内部各质点的摩擦和能量耗散的特性,结合淌水崖水库,通过现场试验,比较了普通混凝土和橡胶改性混凝土与岩基的抗剪（断）性能。结果表明：橡胶改性混凝土与岩基的抗剪断和抗剪性能均优于普通混凝土。橡胶改性混凝土与岩基的抗剪断摩擦系数为1.344,普通混凝土与基岩的抗剪断摩擦系数为0.790,抗剪断摩擦系数提高了70.1%;橡胶混凝土与岩基的凝聚力与普通混凝土基本相当。就抗剪参数而言,橡胶改性混凝土与岩基的抗剪摩擦系数为1.108,普通混凝土与基岩的抗剪摩擦系数为0.683,抗剪摩擦系数提高了62.2%;橡胶混凝土与基岩的凝聚力几乎是普通混凝土的两倍,橡胶混凝土与岩基的凝聚力为0.138 MPa,而普通混凝土的凝聚力则为0.061 MPa。分析探讨了橡胶粉能够改善混凝土与坝体岩基抗剪和抗剪断性能的机制,为提高坝体岩基-混凝土的抗剪（断）参数提供了一种有效的技术措施。     

An improved rheology model for the description of the rate-dependent cyclic behavior of high damping rubber bearings

An improved rheology model, inspired from explicit experiments is conceived to represent rate-dependent cyclic shear behavior of high damping rubber bearings at subzero and room temperatures. Total stress has been decomposed into nonlinear rate independent elasto-plastic stress, nonlinear elastic stress and nonlinear visco-elasto-plastic overstress branches. To represent nonlinear viscosity behavior, ‘overstress branch’ has been generalized by putting linear elastic spring in parallel to nonlinear elasto-plastic model, placed in series with nonlinear dashpot. Constitutive relations for model elements have been designated for respective fundamental phenomenon observed in constant strain rate experiments. An optimum calculation approach is developed to determine a unique set of overstress parameters capable not only of representing constant strain rate cyclic tests but also sinusoidal tests with variable input strain rates. Essential abilities of the proposed model and adequacy of estimated parameters have been confirmed by comparing numerical simulation results with experiments conducted at −30 °C, −10 °C and 23 °C.     

用于阻尼器结构不锈钢丝金属橡胶元件力学性能试验研究

为研究金属橡胶材料用作土木工程结构消能减震阻尼器的力学性能,本文针对不同成型密度的金属橡胶阻尼元件,分别在静力、动力荷载作用下进行了压缩性能试验,测试加载幅值、循环加载次数、元件成型密度、动力加载频率等因素对金属橡胶元件阻尼耗能的影响规律。研究结果表明,金属橡胶材料有着良好的弹性和阻尼特性,其滞变耗能能力随着成型密度、加载幅值的增加而增大;加载频率和加载次数对金属橡胶滞变性能几乎没有影响。     

中国老挝跨境生物多样性保护区的林地变化(英文)

This paper analyzed forest land use change in Trans-Boundary Laos-China Biodiversity Conservation Area which is called Namha National Biodiversity Conservation Areas (Namha NBCAs), with 1992 and 2002 TM (ETM). Based on GIS and statistical methods, the intensity, state index of land use change and transfer matrix were used to study spatiotemporal land use change in the region. The results showed that the area of forest land decreased greatly, also the area of bamboo and grassland decreased. The other way round, the area of unstocked forest, slash and burn and rice paddy land increased. As a whole, the intensity of forest land change was higher, but others were lower. From the transfer matrix, most of the forest land changed into unstocked forest and urban area, some to slash and burn. The grassland and bamboo were mainly transferred to forest and unstocked forest. The unstocked forest land mostly came from forest land and grassland. It was showed there were three main causes of the land use change namely: opium poppy cultivation, rubber plantation and also ecotourism activities and finally some policies were developed in order to address the land use change in the study areas.     

橡胶座非线性弹性拉伸特性的理论和试验研究

本文系统地研究分析了橡胶隔震支座(简称橡胶座)拉伸相关的基础理论,提出了原点拉伸纵弹性模量、拉伸刚度因子、原点拉伸刚度、偏拉原点刚度等基本概念,还提出了计算橡胶座非线性段拉伸刚度的双刚度和原点拉伸刚度应力应变模型等理论。基于原点拉伸刚度和偏拉原点刚度,提出了预测橡胶座的拉伸变形量计算理论。针对新提出的基本概念和计算理论采用低弹性天然橡胶和铅芯橡胶座原型试件进行了试验研究工作,结果表明本文建立的计算理论能够较理想地定量分析橡胶座拉伸相关的刚度和变形特性。     

隔震橡胶垫极限性能足尺试验结果与评价

针对隔震建筑中使用的天然橡胶类叠层橡胶垫、高阻尼叠层橡胶垫和铅芯叠层橡胶垫,调查了日本叠层橡胶垫制造公司持有的极限性能足尺试验结果,并对这三类叠层橡胶垫进行了新的足尺极限性能试验.调查与试验结果表明,ISO标准采用的叠层橡胶垫极限性能预测公式是合理可行的.