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关于钢结构抗震存在的问题及建议 总被引：5，自引：4，他引：5
本文探讨了目前钢结构抗震设计中存在的两个主要问题:其一是钢结构的地震作用,由于多高层钢结构房屋被列入“建筑抗震设计规范”(GB50011-2001)中时没有考虑钢结构延性好和弹性阶段阻尼比较小的特点,使得钢结构地震作用偏大,用钢量偏高;其二是钢结构承载力抗震调整系数对梁和焊缝的规定与焊缝强度高于母材强度的实际情况不符,造成设计困难。本文对现行抗震规范、“建筑工程抗震性态设计通则”和美国UBC规范的地震作用进行了分析比较,提出按照耗能能力将钢结构体系分为四类,在此基础上引入结构体系调整系数,对每类结构的地震作用取值给出建议。针对梁柱刚性连接,从抗震设计原则出发,对7、8和9度区分别建议了适合采用的连接形式,并给出了小震和大震下的设计验算公式。 相似文献
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地震作用下钢筋混凝土（RC）桥墩容易损坏。为完善RC桥墩的抗震设计及验算方法,对比最新中国和欧洲规范中关于RC桥墩的延性抗震设计及验算方法的不同之处。基于Midas/Civil软件所建立的常规连续梁桥有限元模型,对比分析采用中欧规范开展的RC桥墩延性抗震设计及验算结果。结果表明:中欧规范中关于RC桥墩的延性抗震设计理念、抗剪和变形验算方法及延性构造细节均有区别。基于中欧规范设计的RC桥墩配筋情况存在差异。与中国规范相比,欧洲规范关于RC桥墩的横向钢筋配筋率和纵筋最小配筋率要求较高,有利于保证结构的抗剪强度和延性;箍筋最大间距要求较低,不利于防止纵筋压曲。 相似文献
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《地震工程与工程振动》2017,(2)
为研究钢筋混凝土(RC)框架结构在两次地震作用下的抗震能力,给出在设计中考虑两次地震作用的建议,本文以某典型3层RC框架结构为例,对其进行了两次地震作用下的弹塑性动力时程分析,并定义了一个考虑两次地震作用的设计调整系数。首先选取了100条同类场地地震动记录,将每条记录幅值调整到0.05 g、0.1 g、0.2 g、0.3 g、0.4 g、0.5 g,然后两两组合得到36种工况、相当于3 600条序列型地震动记录,利用这些记录作为输入,对结构进行动力时程分析,得到了其经历两次地震作用后的整体损伤指数,最后通过对整体损伤指数统计分析,得到了典型RC框架结构在两次地震作用下的抗震能力和损伤状态。结果表明:两次地震作用下,框架结构损伤累积效应明显,与单次地震作用相比,损伤水平提高较大,最大加重约41%。因此,仅考虑单次地震的设计理论与方法是不完备的。根据计算结果,建议按照目前规范抗震设防水平的1.26倍进行抗震设计,以考虑两次地震的影响。本文方法、结果与结论可供结构抗震设计、结构抗震分析等工作参考。 相似文献
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《地震工程与工程振动》2016,(1)
有研究表明,我国抗震规范中的钢筋混凝土抗震墙约束箍筋设计法无法将延性量化,使同一抗震等级下能达到的延性不平衡。为了克服规范中的不足,提出了基于钢筋拉断破坏和混凝土压溃破坏两种破坏下基于量化延性指标的约束箍筋设计法。利用评估结果将我国规范抗震等级一级(9度),一级(7、8度)和二、三级时的延性设计指标定量为5、3.5和2.5,并将我国规范修改成定量的延性设计法,结果表明修改后的方法量化了不同抗震等级的延性,且克服了现行规范同一抗震等级延性不平衡的不合理性。 相似文献
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《地震工程与工程振动》2017,(5)
钢筋混凝土柱端弯矩增大系数是减缓柱端在强地面运动下形成屈服区,改善结构性能的重要抗震措施。目前虽已见有对中国规范取值有效性的分析评价结果,但对影响其取值的主要因素与影响程度则未见有关文章发表。本文设计了不同抗震等级的3个典型空间框架结构,通过对其非弹性动力反应分析结果的逐时点量化识别以及梁端抗弯能力超强的考察,识别出"梁端抗弯能力超强"和"节点处柱端弯矩比例从多遇到罕遇地震作用的增长率"是决定ηc取值的两个主要因素,而柱轴力从多遇到罕遇地震作用的变化则对ηc取值无明显影响。在完成以上两个主要因素定量统计的基础上,对各抗震等级ηc的合理取值作了进一步评价。 相似文献
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《地震工程与工程振动》2015,(1)
分析了中国、美国、新西兰规范三种不同钢筋混凝土剪力墙约束箍筋设计方法的内在机理,讨论了三国规范存在的问题。结果表明,中国规范仅按照轴压比判断是否加约束箍筋的设计方法不合理,使同一抗震等级剪力墙的位移和延性指标不平衡。美国和新西兰规范是基于位移和延性的设计方法,但其没有考虑剪力墙钢筋拉断的受拉破坏,导致混凝土高度很小时高估了位移和延性能力,而实际位移和延性不能满足要求。提出了基于修正后的美新规范位移角和延性计算方法,评估了现行中国规范不同的抗震等级、烈度下剪力墙具有的位移和延性能力。按照中国规范设计剪跨比为4的剪力墙在抗震等级为一级(9度)、一级(6、7、8度)、二三级时,延性指标平均值分别能达到5.1、3.6和2.6,位移角指标能达到1/81、1/129和1/175。 相似文献
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为了研究地震时地面运动加速度作用下高层房屋建筑深基坑支护承压结构的局部抗震性能,针对高层房屋建筑深基坑支护承压结构进行局部抗震性试验分析.采用有限元软件对某高层房屋建筑深基坑工程进行分析,构建高层房屋建筑深基坑支护承压结构有限元计算模型.利用地震模拟振动台,分别输入0.4g、0.5g、0.6g的地震时地面运动加速度,测... 相似文献
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近断层地震动作用下钢筋混凝土桥墩的抗震性能 总被引：9，自引：2，他引：9
通过对满足规范延性要求的12根典型钢筋混凝土桥墩试件的线性和非线性地震反应分析，指出在近断层地震动作用下满足延性需求与延性能力比小于1.0的桥墩仍可能发生严重破坏和倒塌，若考虑桥墩的地震损伤性能，允许的延性需求与延性能力比不宜超过0.6-0.8。讨论了桥墩延性抗震设计中强度折减系数Rμ和设计基底剪力系数BSC取值问题。 相似文献
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M. N. French R. L. Bras W. F. Krajewski 《Stochastic Environmental Research and Risk Assessment (SERRA)》1992,6(1):27-45
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. 相似文献
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Gtz Schroth Luciana Ferreira Da Silva Marc‐Andree Wolf Wenceslau Geraldes Teixeira Wolfgang Zech 《水文研究》1999,13(10):1423-1436
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. 相似文献
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M. A. Kahn 《洁净——土壤、空气、水》2000,28(2):95-101
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. 相似文献