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压弯构件在主余震作用下的累积损伤试验研究 总被引：1，自引：2，他引：1
本文对相似比为１：４的三组钢筋混凝土压弯构件模型先后进行了振动台主余震模拟试验和周期性震静力试验，通过试验研究了钢筋混凝土压弯构件在主余震作用下反应与损伤特性，并首次探讨了有损伤压弯构件恢复力模型的特点，在此基础上给出了建立前损伤压弯构件恢复力骨架曲线的一般方法，从而为结构在主余震作用下的随机地震反应分析和有损伤结构的抗震加固奠定了基础。 相似文献
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本文简要评述了现有钢筋混凝土结构地震损伤分析的途径、方法及其合理应用。根据构件的滞回恢复力骨架曲线及卸载刚度退化规律,本文构造一个与构件地震损伤相关的能量参数,并据此提出一种构件地震损伤模型,该模型不显含组合系数α及β,计算较为简便。最后,根据Park and Ang模型导出构件滞回恢复力模型中反向加载曲线的超前指向距离,使构件的滞回恢复力变化描述与构件的地震损伤演化描述具有一致性。 相似文献
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恢复力模型研究现状及存在问题 总被引：7，自引：0，他引：7
恢复力模型是根据大量从试验中获得的恢复力与变形的关系曲线经适当抽象和简化而得到的实用数学模型，是结构构件的抗震性能在结构弹塑性地震反应分析中的具体体现。对迄今为止国内外关于钢筋、混凝土和钢筋混凝土结构构件的恢复力模型的研究成果进行了汇总和简要评述，分析了现有恢复力模型存在的主要问题，在此基础上提出恢复力模型今后的研究建议。 相似文献
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钢筋混凝土框架结构在地震冲击后,其刚体退化特性复杂,存在模拟时结果失真明显的问题。为此,在考虑刚度退化规律的基础上进行分析模拟,研究地震冲击下钢筋混凝土框架结构的恢复性。提取地震作用下钢筋混凝土框架结构滞回曲线,通过有限元分析获取不同的特征点,形成恢复力模型的骨架曲线;依据恢复力模型骨架曲线和刚度退化规律,构建滞回曲线,模拟地震作用后钢筋混凝土框架结构恢复过程。在模拟的钢筋混凝土框架结构恢复实验中,层间位移结果低于5 mm、层间绝对加速度和柱底抬升结果的误差均低于0.1 mm;模拟得到结构的弯矩缝隙都能够实现闭合,钢筋混凝土结构未出现屈服现象,说明模拟的结果较好。 相似文献
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对3种不同厚度的钢材标准试件进行酸性大气环境气雾加速腐蚀试验,并对锈蚀后的试件进行单向拉伸试验,得到钢材力学性能随失重率的衰变规律。同时考虑构件截面削弱与材料力学性能降低,建立不同锈蚀程度下的钢框架有限元分析模型,利用非线性静力推覆分析得到锈蚀钢框架结构的整体初始刚度随锈蚀程度增大的退化规律,以表征结构因锈蚀造成的损伤。提出同时反映最大变形效应和累积耗能效应的双参数结构整体地震损伤模型,并在此损伤模型的基础上集合钢材材性试验结果及有限元分析结果,提出适用于锈蚀钢结构的"时变"损伤模型。对比分析以层间位移角及时变损伤模型为性能指标建立的不同龄期钢框架结构的地震易损性曲线,结果表明:随着锈蚀程度的增加,在相同地震动强度下结构超越某一极限状态的失效概率均增大。 相似文献
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为实现地震作用下锈蚀钢筋混凝土柱精细化数值模拟分析,基于已有研究成果建立往复荷载作用下锈蚀钢筋与混凝土间的黏结滑移本构模型:结合课题组前期试验结果,采用ABAQUS有限元分析软件对建立的黏结滑移本构模型进行有效性验证,通过对数值计算结果与试验结果之间误差分析,进一步对黏结滑移模型中的摩擦黏结应力系数和退化系数进行修正,最终建立更为合理的锈蚀钢筋与混凝土间黏结滑移本构模型。通过数值计算结果与试验结果的再次比较,验证修正后黏结滑移本构模型的有效性。结果表明:修正后的锈蚀钢筋与混凝土间黏结滑移模型可更好地反映往复荷载作用下锈蚀钢筋混凝土柱的滞回性能。该成果可为地震作用下锈蚀钢筋混凝土结构的数值分析计算提供理论参考。 相似文献
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为研究地震作用下钢筋锈蚀对试件性能退化影响的规律,对6个锈蚀钢筋混凝土受弯构件进行低周反复荷载试验,得到不同锈蚀程度试件的滞回曲线及骨架曲线,分析了钢筋锈蚀对试件强度和刚度的影响。试验发现,随着钢筋锈蚀程度的增大,各试件强度退化基本呈增大趋势;低锈蚀率试件由于锈胀内力的存在,强度退化相对比未锈蚀试件和高锈蚀试件大;随着锈蚀率的增大,试件加载和卸载刚度总体上逐渐减小,且随着位移的增大而持续减小。此外,还分析了锈蚀钢筋混凝土结构刚度退化机理。成果可供锈蚀钢筋混凝土结构抗震性能研究参考。 相似文献
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钢筋混凝土结构基于地震损伤性能的设计 总被引：58，自引：14，他引：44
本文结合我国地震设防水准,在国内外有关地震损在量研究结果的基础上,提出钢筋混凝土结构地震损伤的“三水准”性能目标;其次,对于剪切型钢筋混凝土结构,提出了结构层间柱－压弯构件三线性恢复力模型参数确定和地震损伤计算方法;第三,提出了地震损伤直接验算和将地震损伤验算归结为变形验算的钢筋混凝土结构地震损伤性能设计方法;最后,通过设计例题说明了本文方法应用的可行性。 相似文献
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火灾后钢筋混凝土压弯构件的抗震性能研究 总被引：6，自引：0，他引：6
本文在火灾后钢筋与混凝土应力－应变关系试验结果的基础上，通过大量数值计算，给出了火灾后钢筋混凝土压弯构件恢复力架曲线特征参数的统计公式，从而为火灾后剪切型钢筋混凝土结构的地震反应分析及其抗震加固奠定了基础。 相似文献
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改进的钢筋混凝土结构双参数地震破坏模型 总被引：34，自引：4，他引：34
本文在分析现有结构地震破坏模型的基础下，提出了一种改进掇参数地震破坏模型。文中采用三线退化型恢复力模型对实际钢筋混凝土结构在实际地震作用下的变形与累积耗能，极限变形与极限滞回耗能进行了分析，通过模型计算的破损结果与实际在结果的对比，研究了模型参数，从而建立了钢筋混凝土结构的双参数地震破坏模型。 相似文献
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《国际泥沙研究》2014,(4)
正Director:Shangfu Kuang,China Vice-directors:Chunhong Hu,China Duihu Ning,China Guangquan Liu,China The International Research and Training Center on Erosion and Sedimentation(IRTCES)was jointly set up by the Government of China and UNESCO on July 21,1984.It aims at the promotion of international exchange of knowledge and cooperation in the studies of erosion and 相似文献
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《中国科学:地球科学(英文版)》2014,(3)
正SCIENCE CHINA Earth Sciences,an academic journal cosponsored by the Chinese Academy of Sciences and the National Natural Science Foundation of China,and published by Science China Press and Springer,is committed to publishing high-quality,original results in both basic and applied research. 相似文献
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Richard D. Hey 《地球表面变化过程与地形》1979,4(1):59-72
Feedback mechanisms, which operate upstream through drawdown and backwater effects and downstream through sediment discharge are responsible for channel evolution. By combining these mechanisms with channel processes it euables a dynamic process-response model to be developed to simulate the initial evolution of straight gravel-bed channels. When erosion commences on a land surface, sediment entrained in the headwater reach by hydraulic action is selectively transported, deposited and reworked. This produces a damped oscillation between degradation and aggradation as the channel and valley respond to spatial and temporal variations in sediment calibre and hydraulic conditions. The initial cut and fill phases are responsible for valley incision and floodplain development while secondary and subsequent activity can produce river terraces. Eventually sediment entrainment in the headwaters declines as slopes are reduced. Subsequent channel evolution is relatively insignificant because it is dependent on local weathering activity producing material that can be transported on declining slopes. Therefore landforms produced during the initial phase of development, when local weathering was non-limiting, dominate the landscape. 相似文献
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Based on relocating the Jiujiang-Ruichang earthquake sequence which occurred on November 26, 2005 in Jiangxi Province with the double-difference （DD） algorithm and master event technique, the paper discusses the focal mechanism of the main shock （MsS.7） and the probable seismo-tectonics. The precise relocation results indicate that the average horizontal error is 0.31kin in a EW direction and 0.40kin in a NS direction, and the average depth error is 0.48kin. The focal depths vary from 8kin to 14kin, with the predominant distribution at 10kin - 12kin. The epicenter of the main shock is relocated to be 29.69^oN, 115.74^oE and the focal depth is about 10.Skin. Combining the predominant distribution of the earthquake sequence, the focal mechanism of the main shock and the tectonic conditions of N-E- and NW-strike faults growth in the seismic region, we infer that the main shock of the earthquake sequence was caused by a NW striking buried fault in the Rnichang basin. The nature of seismic faults needs to be further explored. 相似文献
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《水文科学杂志》2013,58(6)
Abstract The western reservoirs represent the principal groundwater system in Morocco. Demographic, industrial and agricultural developments during the last decade have markedly altered groundwater quality. The Mamora coastal aquifer system is among the Atlantic systems which are most heavily threatened by pollution. Agricultural and industrial activities, and rapid urban growth contribute to the pollution of the groundwater. Contamination transport is facilitated by a high permeability of the aquifer formations. In order to assess the actual groundwater quality of the Mamora aquifer and to understand the influence of the factors generating the pollution, an extensive multidisciplinary research programme is in progress, with hydrochemistry and microbiology playing essential roles. The present paper concerns the spatial distribution of physico-chemical parameters in the groundwater, subjected to domestic, industrial and agricultural pollution. Fifty-seven samples were analysed for several parameters (Ca2+, Mg2+, Na+, K+, Cl?, SO4 2?, HCO3 ?, NO3 ?, pH, electrical conductivity and temperature). The microbiological analysis of 143 samples reveals the presence of four kinds of indicator bacteria in the groundwater resources: faecal Streptococci, faecal coliform, Escherichia coli and Clostridium. The physico-chemical results and bacteriological monitoring show that the nitrate and bacteria concentrations exceed the maximum admissible levels, notably around pumping stations in the sectors of Sidi Taibi, Sidi Ahmed Taleb and Aïn Sbaâ. Contamination is generated by uncontrolled anthropogenic activities and accentuated by the high intrinsic vulnerability of the aquifer system. Several parameters appeared to exceed admissibility standards. Measures are recommended to prevent groundwater pollution in the region. 相似文献
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K.-G. Malle 《洁净——土壤、空气、水》1992,20(4):196-204
Zinc in the Environment. In 1990 the world production of zinc ammounted to 7 Mio. metric tons. The main areas of application were: galvanization, alloys like brass and zinc metal. The content in the earth crust varies between 10–300 ppm zinc with a mean of 70 ppm. Uncontaminated surface waters contain less than 10 mg/m3 zinc. Apart from civilization air contains 1–10 ng zinc per m3. These background concentrations are exceeded by orders of magnitude in zinc deposit areas and where anthropogenic influences predominate. Accumulation can occur in sediments and sewage sludge. Molluscs and Algae also accumulate zinc. Zinc is essential for live. With normal food the zinc supply of man is just sufficient. Bioaccumulation of zinc towards man or chronic oversupply of man is not known. Zinc has no teratogenic or mutagenic effects, a suspicion on a carcinogenic effect proved wrong. In stockbreeding and plant cultivation a minimum supply of zinc is necessary. Plants are relatively less sensitive against higher soil contents of zinc. Considering the toxicological and ecotoxicological effects of zinc in the environment, the critical organismens are marine invertebratae like tubifex, daphnia, gammarus and algae. But normally only a minor part of the total zinc contest is biologically available, depending on salt content and pH of the waters. 相似文献