基于软化拉-压杆模型的RC空间边节点抗剪承载力计算方法     

李振宝  郝娜  崔燕伟  宋坤 《震灾防御技术》2019,14(1):1-9

实际地震作用是多维的、随机的,框架节点在2个方向同时受力,其抗震能力相比于单向地震作用会降低。目前,对节点核心区在2个方向同时受力时抗剪承载力的研究尚未完善。在双向受力下,节点核心区2个方向传来的剪力形成合剪力作用面,在节点核心区内部形成不同于单向受力下的斜向斜压杆。本文基于软化拉-压杆模型,针对水平双向受力相同的空间边节点,在合剪力作用面内建立抗剪承载力计算模型,确定空间边节点核心区斜压杆以及钢筋拉杆的计算方法。利用有限元软件建立不同参数空间边节点模型,并收集部分空间节点试验数据,将剪力计算值与模拟值或试验值进行对比。结果表明,基于软化拉-压杆模型建立的双向受力下钢筋混凝土框架,其边节点抗剪承载力计算值与模拟值或试验值吻合良好。  相似文献   

Spatial distribution and temporal trends of rainfall and erosivity in the Eastern Africa region   总被引：1，自引：0，他引：1       下载免费PDF全文

Ayele Almaw Fenta  Hiroshi Yasuda  Katsuyuki Shimizu  Nigussie Haregeweyn  Takayuki Kawai  Dagnenet Sultan  Kindiye Ebabu  Ashebir Sewale Belay 《水文研究》2017,31(25):4555-4567

Soil erosion by water is one of the main environmental concerns in the drought‐prone Eastern Africa region. Understanding factors such as rainfall and erosivity is therefore of utmost importance for soil erosion risk assessment and soil and water conservation planning. In this study, we evaluated the spatial distribution and temporal trends of rainfall and erosivity for the Eastern Africa region during the period 1981–2016. The precipitation concentration index, seasonality index, and modified Fournier index have been analysed using 5 × 5‐km resolution multisource rainfall product (Climate Hazards Group InfraRed Precipitation with Stations). The mean annual rainfall of the region was 810 mm ranging from less than 300 mm in the lowland areas to over 1,200 mm in the highlands being influenced by orography of the Eastern Africa region. The precipitation concentration index and seasonality index revealed a spatial pattern of rainfall seasonality dependent on latitude, with a more pronounced seasonality as we go far from the equator. The modified Fournier index showed high spatial variability with about 55% of the region subject to high to very high rainfall erosivity. The mean annual R‐factor in the study region was calculated at 3,246 ± 1,895 MJ mm ha^?1 h^?1 yr^?1, implying a potentially high water erosion risk in the region. Moreover, both increasing and decreasing trends of annual rainfall and erosivity were observed but spatial variability of these trends was high. This study offers useful information for better soil erosion prediction as well as can support policy development to achieve sustainable regional environmental planning and management of soil and water resources.  相似文献   

地基抗液化能力评估方法讨论   总被引：1，自引：1，他引：0  

潘健  刘利艳 《地震工程与工程振动》2006,26(3):242-244

为了评估地基抵抗液化的能力及其影响因素,本文介绍了标准贯入试验、静力触探试验以及剪切波速试验三种评估地基抗液化能力方法的研究成果,分析了震级比例系数、覆盖压力与倾斜地面的修正系数、地震震级与峰值加速度的影响,并对地基抗液化能力的概率分析方法进行了讨论,得到的结论可为地基的抗液化能力评估提供参考。  相似文献   

邢台地震与我国地震预报的发展     

张国民  李志雄  杨林章 《华北地震科学》2006,24(2):16-23,45

详细叙述了自1966年邢台地震以来,我国地震预报研究与实践的主要进展:建设成了多学科的地震观测系统,为地震预报打下了良好基础;进行了大量震例研究,初步建立了地震预报的判据和指标体系;进行了地震预报理论的实验和研究,提出了多种地震孕育发生模型及前兆机理;通过20多年的5次地震预报攻关研究,形成了数十种地震预报方法;边研究,边预报,几十年来成功地预报了20多次破坏性地震,并取得了减灾实效,使我国地震预报的科学水平居于世界前列。本文还对地震预报尚需解决的科学难题进行探讨。  相似文献   

钢筋混凝土-砖组合砌体结构在抗震设防中的应用     

魏书华 《华北地震科学》2006,24(3):44-46

砌体结构是一种传统的结构形式,在抗震设防区,钢筋混凝土—砖组合砌体结构与同层数的框架房屋相比,其经济效益相当明显,对此本文论述了钢筋混凝土—砖组合砌体结构的定义及相关计算公式。  相似文献   

基于支持向量机的浙江汛期旱涝预测方法研究     

滕卫平  俞善贤  胡波 《气象科技》2008,36(2):139-144

利用浙江省38个测站的降水量资料,得到了能够反映全省旱涝状况的指标,将其作为预报量,通过对前期大气环流场、海温场的相关分析,提取高相关因子,然后运用逐步回归和支持向量机回归技术分别建立浙江省汛期早涝短期气候预测模型,并进行了对比分析.结果表明:支持向量机回归模型集中了众多预报因子的预报信息.有效地利用了支持向量机方法的非线性映射能力,无论在历史样本拟合的精度上还是模型实际预测的能力上都比逐步回归模型有一定提高,有良好的应用前景.  相似文献   

用多元门限回归模型作区域夏季旱涝预测     

徐家良 《气象科学》1996,16(4):391-395

考虑了气候系统中一些变量突变时对预测关系的改变作用，用多元门限回归模型的建模方法建立长江下游地区夏季旱涝趋势预测模型。拟合效果较理想，用１９９４－１９９５年的独立资料检验，预测结果与实况较为接近。  相似文献   

Spatio-temporal Distribution of Famine and Its Relationship with Climate,Disaster, Harvest in North China During 1736-1911     

Lingbo Xiao 《地球科学进展》2020,35(5):478-487

Based on records on famine kept in historical documents, 2950 famine events counted with “county time” in North China during 1736-1911 were collected, and annual famine index series in North China was reconstructed using weighted average method according to the severity of famine. Spatio-temporal distribution of famine and its relationship with climate, disaster and harvest was analyzed. The research shows that variation of temperature and precipitation has significant negative correlation with poor harvest and famine. The drought has a more significant correlation with harvest and famine than flood. In 1736-1795 when was at the peak of the Qing dynasty, the sensitivity of poor harvest and famine to drought was significantly lower than in 1796-1911 when was in decline, because effective social response to disaster could reduce the risk of poor harvest and famine. Using the kernel density estimation method, three main high risk areas of famine were indentified: Fen River Valley in south Shanxi Province, south-central He'nan Province, and the junction of Hebei, Shandong and He'nan Province. In general, there is significant corresponding relationship between the spatial distribution of drought, poor harvest and famine, however, abnormally high probability of famine in south-central He'nan Province might be related to local special socio-economic vulnerability. This study would enhance our understanding of the nature of interactions between climate change and socioeconomic system. Further research would focus on the mechanism by which famine originated in the past, and the pathway through which climatic impacts were delivered in human society.  相似文献   

Soil hydrological response under simulated rainfall in the Dehesa land system (Extremadura,SW Spain) under drought conditions     

Artemi Cerda  Susanne Schnabel  Antonio Ceballos  Dionisia Gomez-Amelia 《地球表面变化过程与地形》1998,23(3):195-209

Soil hydrology was investigated in the Guadelperalón experimental watershed in order to determine the influence of land use and vegetation cover on runoff and infiltration within the Dehesa land system. Five soil–vegetation units were selected: (1) tree cover, (2) sheep trials, (3) shrub cover, (4) hillslope grass and (5) bottom grass. The results of the simulated rainfall experiments performed at an intensity of 56·6 mm h⁻¹ during one hour on plots of 0·25 m², and the water drop penetration time test indicate the importance of water repellency in the Dehesa land system under drought conditions. Low infiltration rates (c. 9–44 mm h⁻¹) were found everywhere except at shrub sites and in areas with low grazing pressure. Soil water repellency greatly reduced infiltration, especially beneath Quercus ilex canopies, where fast ponding and greater runoff rates were observed. The low vegetation cover as a consequence of a prolonged drought and grazing pressure, in conjunction with the soil water repellency, induces high runoff rates (15–70 per cent). In spite of this, macropore fluxes were found in different locations, beneath trees, on shrub-covered surfaces, as well as at sites with a dominance of herbaceous cover. Discontinuity of the runoff fluxes due to variations in hydrophobicity causes preferential flows and as a consequence deeper infiltration, especially where macropores are developed. © 1998 John Wiley & Sons, Ltd.  相似文献   

双峰、界岭幅岩溶地下水开发利用与区划研究     

姚海鹏  阮岳军  李旭杰 《地下水》2020,(1):68-71,106

双峰、界岭幅位于湖南省中部邵阳凹陷盆地,地处西南岩溶丘陵区,总面积913 km^2,所涉行政区有:邵阳的新邵县、邵东县和娄底的双峰县、涟源市,特殊的地貌地质形态造就了湖南省著名的"衡邵干旱走廊"。根据调查统计,区内干旱面积64. 71 km^2,总缺水人口38 500人,占区内人口总数的11. 46%。本文意在探索区内的合理、高效、科学的地下水开发利用方式,提出了5种地下水开发利用区划方案,为区内解决干旱缺水困难问题提供理论依据。  相似文献