输入界面对反应谱平台值的影响

为了研究输入界面对设计反应谱平台值(αmax)的影响,利用目前工程上广泛应用的场地地震反应的一维等效线性化波动方法,计算了4类场地在6种不同强度的地震动输入下的地表加速度反应谱。将计算得到的地表加速度反应谱拟合成建筑抗震设计规范规定的设计反应谱的形式,分析了输入界面的改变对反应谱平台值的影响。结果发现:Ⅱ类和Ⅲ类场地在较小强度地震动输入时,输入界面的改变对平台值影响较小,在大强度地震动输入时,对平台值的影响较大;对于Ⅰ类和Ⅳ类场地,输入界面的改变对平台值的影响较小。     

Multi-Fractal Analy is of Daily Air Temperature Time Series in Coastal Areas of China

In this article, the Multi-Fractal Detrended Fluctuation Analysis (MF-DFA) method is adopted to study the temperature, i. e., the maximum temperature (Tmax), mean temperature (Tavg) and minimum (Tmin) air temperature, multifractal characteristics and their formation mechanism, in the typical temperature zones in the coastal regions in Guangdong, Jiangsu and Liaoning Provinces. Following are some terms and concepts used in the present study. Multifractality is defined as a term that characterizes the complexity and self-similarity of objects, and fractal characteristics depict the distribution of probability over the whole set caused by different local conditions or different levels in the process of evolution. Fractality strength denotes the fluctuation range of the data set, and long-range correlation (LRC) measures the stability of the climate system and the trend of climate change in the future. In this research, it is found that the internal stability and feedback mechanism of climate systems in different regions show regional differences. Furthermore, the research also proves that the Tavg, Tmax and Tmin of the above three provinces are highly multifractal. The temperature series multifractality of each province decreases in the order of temperature series multifractality of Liaoning > temperature series multifractality of Guangdong > temperature series multifractality of Jiangsu, and the corresponding long-range correlations follow the same order. It reveals that the most stable temperature series is that of Liaoning, followed by the temperature series of Guangdong, and the most unstable one is that of Jiangsu. Liaoning has the most stable climate system, and it will thus be less responsive to the future climate warming. The stability of the climate system in Jiangsu is the weakest, and its temperature fluctuation will continue to increase in the future, which will probably result in the meteorological disasters of high temperature and heat wave there. Guangdong possesses the strongest degree of multifractal strength, which indicates that its internal temperature series fluctuation is the largest among the three regions. The Tmax multifractal strength of Jiangsu is stronger than that of Liaoning, while the Tavg and Tmin multifractal strength of Jiangsu is weaker than that of Liaoning, showing that Jiangsu has a larger internal Tmax fluctuation than Liaoning does, while it has a smaller fluctuation of Tavg and Tmin than Liaoning does. Guangdong and Liaoning both show the strongest Tmin multifractal strength, followed by Tavg multifractal strength, and the weakest Tmax multifractal strength. However, Jiangsu has the strongest Tmax, followed by Tavg, and the weakest Tmin. The research findings show that these phenomena are closely related to solar radiation, monsoon strength, topography and some other factors. In addition, the multifractality of the temperature time series results from the negative power-law distribution and long-range correlation, in which the long-range correlation influence of temperature series itself plays the dominant role. With the backdrop of global climate change, this research can provide a theoretical basis for the prediction of the spatial-temporal air temperature variation in the eastern coastal areas of China and help us understand its characteristics and causes, and thus the present study will be significant for the environmental protection of coastal areas.     

结构性吹填土压缩变形微观机理试验

吹填土是一种人造土,具有大孔隙比、压缩性强、低强度等特点,其微观结构对土的力学性质有很大的影响,是一种强结构性土。通过分析不同轴向应力下压缩土样的微观SEM照片,探讨了孔隙微结构参数与轴向应力之间的关系,得出在吹填土压缩变形过程中存在屈服应力。在所受应力大于和小于屈服应力时,吹填土的压缩性存在差异,其微观表现为微结构参数在压缩过程中产生了突变,其根源是在压缩变形过程中,吹填土的微观结构产生了破坏。简要分析了结构性吹填土压缩变形微观机理。结果表明,吹填土的压缩过程分为孔隙中气体的压缩与水份的运移、团粒的相对滑移和结构破坏与新结构形成3个阶段。     

北京城镇规划对气象条件影响的定量分析

针对北京地区城镇化快速发展带来的气象环境问题,选取夏季晴天典型个例,采用数值模拟的方法,研究了2004—2020年北京城市总体规划方案中新城建设、绿地增加和水体恢复的环境效应。结果表明:规划对夏季六环内高温、小风、低湿的气象环境有所改善。其中,城镇用地增长地区,气温增幅达1~2℃,夜晚最大;风速和比湿的降幅分别在0.2~1 m·s~(-1)、0.2~1 g·kg~(-1)之间,白天降幅最大;在城镇扩张周边地区,气温的受影响范围最大,白天可达城镇增长面积的3倍,增幅在0.2~1℃;风速和比湿的降幅影响范围都在城镇增长面积的0.3~0.5倍之间,且晚上风速影响范围广,比湿白天影响幅度和范围大。以亦庄为例,基于地理信息系统的精细分析表明,城镇用地增长率与气温增幅、风速降幅和比湿降幅都成线性正相关关系。当城镇用地增长率达到15%~30%时,气象要素的变化幅度会急剧加大。因此,初步建议在城镇规划中将建设用地的增长率控制在20%以内,将用地扩张对局地气象环境造成的不良影响降到最低。     

结构性吹填土剪切破坏的微结构效应

室内压缩试验、剪切试验和灵敏度试验分析表明吹填土的微观结构对其力学性质有很大的影响,是一种强结构性土。通过对剪切试验过程土样微观SEM照片进行微结构定量分析,探讨了孔隙和结构单元体微结构参数与轴向应变之间的关系。最后,对结构性吹填土剪切破坏的微结构效应进行了简要分析。结果表明,吹填土的剪切过程经历了孔隙气体压缩-水分运移、团粒散裂-颗粒滑移明显-结构破坏和新结构形成三个阶段。     

宜川—泰安剖面的密度结构、构造特征和地震活动

文中利用宜川—泰安重力剖面的相对联测和同址GNSS测量数据获得沿线的布格重力异常、剩余密度相关成像和地壳密度结构,可以看出：剖面的布格异常变化范围为-(161.7～5.5)×10^-5m/s²,自西向东总体呈上升趋势,在临汾盆地有明显“凹陷”,可能与上地壳存在低密度构造有关;剖面地壳密度分布具有明显的不均匀性,以太行山重力梯级带为界,西部密度较高,东部密度较低,中下地壳存在低密度体,可能是上地幔物质上涌岩石含部分高温流体和熔融岩体所致;不同构造块体的密度差异明显,在断裂带分布区域均存在密度差,说明密度分布与构造有一定关系;地壳介质的不均匀性和地震活动相关：鄂尔多斯断块的地壳介质相对均匀,不容易积累能量,地震活动水平低;山西断陷带和华北平原断块则相反,具有显著的不均匀性,地震活动频繁。