改进框架支撑模型对剪力墙结构抗震性能的模拟

通过改变基本单元的数量m,本文提出的改进框架支撑模型不仅适用于不同层高宽比和材料的剪力墙结构,而且适用于框支、开洞等不同形式的剪力墙结构。通过对框支配筋砌块砌体剪力墙KZW-2子结构拟动力试验的模拟结果表明,改进框架支撑模型能有效地模拟剪力墙结构在地震作用下的弹塑性变形性能。     

三层单排配筋剪力墙结构抗震性能试验研究

为了对双排配筋剪力墙和单排配筋剪力墙的抗震性能进行对比研究,本文设计了1个1／3缩尺的三层混凝土剪力墙结构模型,模型的一侧墙体为双向双排配筋,另一侧墙体为双向单排配筋。对其进行了低周反复荷载下的抗震性能试验研究,分析了其承载力、延性、刚度及其退化过程、滞回特性、耗能能力和破坏特征。研究表明：在墙体的配筋率相同情况下,由于单排配筋墙体钢筋的间距相对于双排配筋墙体钢筋间距小,其首先约束混凝土裂缝的几率更大,其平面内的抗震性能优于双排配筋剪力墙;由于剪力墙的翼缘和腹板共同工作,单排配筋剪力墙平面外的性能也可满足多层剪力墙结构设计的要求。     

带窗洞配筋砌块砌体剪力墙抗震性能试验研究

通过2个带窗洞配筋砌块砌体剪力墙试件的拟静力试验,研究带窗洞配筋砌块砌体剪力墙的破坏形态、承载能力、变形能力等抗震性能以及墙体两端构造柱的影响。试验结果表明:试件为洞口两侧墙肢剪切破坏,洞口以下墙体有斜裂缝,但裂缝宽度不大;相对于无构造柱的试件,墙体两端设置构造柱的试件的水平力-位移滞回曲线略为饱满,名义屈服水平力和峰值水平力分别提高了约30%和20%,刚度退化较为缓慢;2个试件的极限位移角相同,均为1/90,满足大震作用下剪力墙结构的变形能力要求。     

隔震技术在高烈度区剪力墙结构中的应用研究

对于近断层处高烈度区高层剪力墙结构，传统设计难以解决墙体太厚、配筋太大等难题。为研究在考虑近断层影响下高烈度区剪力墙住宅采用隔震设计的技术可行性，采用隔震设计对某剪力墙结构工程进行全面分析。对比分析常规剪力墙结构方案及增设橡胶隔震支座的隔震方案，分析结果表明，隔震方案较常规方案前3阶结构自振周期延长约3倍，从而有效减小了上部结构的地震作用；在设防烈度地震作用下，结构水平向减震系数为0.281，上部结构所受水平地震作用和抗震措施可按降低一度进行设计；罕遇地震作用下隔震支座性能稳定，上部结构基本处于弹性工作状态。研究结论可为隔震支座设计和进一步研究提供参考。     

配筋砌体结构墙体出平面反应试验研究

为研究配筋砌体结构出平面反应,将配筋砌块未注芯的孔灌注了高密度铁砂,以提高缩尺模型材料的等效密度,更真实地模拟墙体出平面惯性效应.利用推导的模型与原型的相似关系,设计并实施了振动台试验.结果表明,模型结构主要以压弯变形为主,在现行规范规定的构造措施下,足以抵抗设防地震造成的墙体出平面破坏.通过敲击试验得到墙体出平面振动频率,该频率相对较高,远离地震动卓越频率.相邻楼层出平面频率不完全相同,振动的相位可能时而同相,时而反相.     

框架—剪力墙型结构的非线性随机地震反应和可靠性分析

框架-剪力墙结构在地震载荷作用下的非线性特性及其描述以及非线性随机反应分析是很复杂的。本文对剪力墙建议了一个能反映其主要弯曲和剪切非线性特性的简化模型,据此模型提出了框架-剪力墙结构非线性随机地震反应分析的等效线性化方法和以变形极限状态概率表示的地震可靠性分析方法,该方法比较简便实用,可用于剪力墙和框架-剪力墙型结构体系的非线性随机地震反应分析和可靠性分析。     

单排配筋剪力墙结构抗震性能及设计研究

以往剪力墙结构主要用于高层建筑并采用双排配筋剪力墙.笔者提出了单排配筋剪力墙多层住宅结构,为了研究其抗震性能,进行了较系统的单排配筋剪力墙结构及构件的抗震试验研究.文中简要介绍了单排配筋剪力墙抗震性能研究概况,将其与传统的砖墙进行了抗震性能比较,给出了其适用范围,提供了其抗震构造措施.研究表明,这种单排配筋剪力墙可以用于多层住宅结构的抗震设计.     

带斜筋单排配筋Z形截面剪力墙翼缘方向抗震性能

为了了解带斜筋单排配筋Z形截面剪力墙的翼缘方向的抗震性能,进行了2个Z形截面剪力墙的低周反复荷载试验,其中1个为普通双向单排配筋剪力墙,1个为带斜筋的双向单排配筋剪力墙。在试验的基础上,对比分析了2个剪力墙在翼缘方向的承载力、刚度、延性、滞回特性、耗能能力及破坏特征,并建立了其极限承载力的简化计算模型。研究结果表明,带斜筋单排配筋Z形截面剪力墙在翼缘方向的抗震性能明显优于普通双向单排配筋剪力墙,可以更好地满足多层住宅结构的抗震设计要求。     

新型钢板剪力墙钢框架结构的地震响应分析

本文在单片带缝钢板剪力墙理论研究的基础上,提出带缝钢板剪力墙的等效计算模型,对钢板剪力墙钢框架结构工程实例结构进行自振特性分析、常遇地震作用下的动力响应分析以及结构在罕遇地震作用下的三维非线性时程响应分析,得到一些有意义的结果和结论。     

双向单排配筋中高剪力墙抗震性能试验研究

双向单排配筋剪力墙结构适用于多层住宅结构。本文进行了1个普通双向双排配筋混凝土中高剪力墙、2个双向单排配筋混凝土中高剪力墙和1个带暗支撑双向单排配筋混凝土中高剪力墙的低周反复荷载试验,以研究双向单排配筋混凝土中高剪力墙的抗震性能及暗支撑对这种新型墙体结构的作用。较系统地分析了其承载力、刚度及其退化过程、延性、耗能、破坏机制和破坏特征等。试验表明,经过合理设计,这种双向单排配筋混凝土中高剪力墙可以满足多层住宅结构抗震要求。     

SCIENCE CHINA Earth Sciences SUBJECT INDEX TO VOLUME 57(2014)

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Distribution of throughfall and stemflow in multi‐strata agroforestry,perennial monoculture,fallow and primary forest in central Amazonia,Brazil

The partitioning of rain water into throughfall, stemflow and interception loss when passing through plant canopies depends on properties of the respective plant species, such as leaf area and branch angles. In heterogeneous vegetation, such as tropical forest or polycultural systems, the presence of different plant species may consequently result in a mosaic of situations with respect to quantity and quality of water inputs into the soil. As these processes influence not only the water availability for the plants, but also water infiltration and nutrient leaching, the understanding of plant effects on the repartitioning of rain water may help in the optimization of land use systems and management practices. We measured throughfall and stemflow in a perennial polyculture (multi‐strata agroforestry), monocultures of peach palm (Bactris gasipaes) for fruit and for palmito, a monoculture of cupuaçu (Theobroma grandiflorum), spontaneous fallow and primary forest during one year in central Amazonia, Brazil. The effect on rain water partitioning was measured separately for four useful tree species in the polyculture and for two tree species in the primary forest. Throughfall at two stem distances, and stemflow, differed significantly between tree species, resulting in pronounced spatial patterns of water input into the soil in the polyculture system. For two tree species, peach palm for fruit (Bactris gasipaes) and Brazil nut trees (Bertholletia excelsa), the water input into the soil near the stem was significantly higher than the open‐area rainfall. This could lead to increased nutrient leaching when fertilizer is applied close to the stem of these trees. In the primary forest, such spatial patterns could also be detected, with significantly higher water input near a palm (Oenocarpus bacaba) than near a dicotyledonous tree species (Eschweilera sp.). Interception losses were 6·4% in the polyculture, 13·9 and 12·3% in the peach palm monocultures for fruit and for palmito, respectively, 0·5% in the cupuaçu monoculture and 3·1% in the fallow. With more than 20% of the open‐area rainfall, the highest stemflow contributions to the water input into the soil were measured in the palm monocultures and in the fallow. Copyright © 1999 John Wiley & Sons, Ltd.     

A Monte Carlo study of rainfall forecasting with a stochastic model

A procedure for short-term rainfall forecasting in real-time is developed and a study of the role of sampling on forecast ability is conducted. Ground level rainfall fields are forecasted using a stochastic space-time rainfall model in state-space form. Updating of the rainfall field in real-time is accomplished using a distributed parameter Kalman filter to optimally combine measurement information and forecast model estimates. The influence of sampling density on forecast accuracy is evaluated using a series of a simulated rainfall events generated with the same stochastic rainfall model. Sampling was conducted at five different network spatial densities. The results quantify the influence of sampling network density on real-time rainfall field forecasting. Statistical analyses of the rainfall field residuals illustrate improvement in one hour lead time forecasts at higher measurement densities.     

Anthropogenic Eutrophication and Red Tide Outbreak in Lacustrine Systems of the Kashmir Himalaya

Red tide, a recurrent phenomenon has become conspicuous in several Kashmir lake ecosystems since 1991. The responsible organism (Euglena pedunculata), a rare flagellate rediscovered in the Kashmir Himalaya (Khan 1993) caused first and unprecedented red tide outbreak, constituting a maximum of 96% of resident numerical phytoplankton density in Dal Lake. At present, conflicting hypotheses exist on the generation of causal assemblage(s) imparting redness to waters: Jeeji Bai (1991) linked its origin to acid precipitation – a fallout of burning oil‐fields during the Gulf War – whilst Khan (1993) holds local factor(s) responsible. Field/experimental studies support the latter contention that the influx of untreated sewage, in unison with warm temperatures, high levels of PhAR, iron and interruption to hydrological flow‐pattern together with absence/or reduction in grazing activity created conducive environmental milieu for red tide outbreak. Dal Lake “red tide” drifted the bloom‐inoculum to other waters, including Lake Wular, where additional ecological niches were carved out, threatening the aesthetic value and biological diversity of Kashmir lakes. Ecological monitoring indicates frequent seasonal red tide occurrence in Dal Lake (including summer‐autumn event of 1998) which testifies its unabated eutrophication status. Further studies are needed on ecological adaptability and biogeographic distribution of this rare and unique red tide‐causing flagellate.