鸭池河水电站压力钢管外压稳定性设计

采用解析法和半解析有限元法分别对鸭池河水电站埋藏式加劲压力钢管进行外压稳定性计算。在计算分析过程中,考虑了初始缺陷因素对埋藏式加劲压力钢管抗外压稳定性的影响,使得计算结果更加接近于工程实际;从而为埋藏式加劲压力钢管的外压稳定性计算提出了一种更加行之有效的方法。     

Temporal dynamics and drivers of lake ecosystem metabolism using high resolution observations in a shallow,tropical, eutrophic lake (Laguna Lake,Philippines)

The physical, chemical, and biological dynamics under changing atmospheric conditions of Laguna Lake, Philippines were analyzed from intensive observations. Diel measurements were conducted for 48 continuous hours for both dry and wet tropical seasons in addition to fine resolution long-term monitoring. Results revealed significant vertical and diel variations of lake variables in spite of a shallow water depth (2.5 m) caused by the intense surface heating from solar irradiance (~800 W m^?2) and accentuated by the lake's high turbidity (16–32 ftu). Late afternoon land-lake breeze (~5–7 m s^?1) regularly breaks daytime thermal stratification, and convective cooling at night maintains isothermal condition until dawn of the next day. The stratified condition demonstrated a wind-driven, density-induced 2-layer current pattern with a windward moving epilimnion (~4 folds faster) and a compensating hypolimnetic flow in the general lake circulation direction. Laguna Lake was observed to have a dominating diel cycle but also undergoes significant seasonal limnological variations brought primarily by climate, hydrology, and its interaction with the adjacent sea. Significantly correlated variations of pH, chlorophyll-a and DO in the dry season were indicative of the higher biological activity associated with the intrusion of polluted waters from Metro Manila. The non-occurrence of thermal over-turn was observed to be regularly followed by bottom hypoxic conditions (2–4 mg L^?1), indicative of the eutrophic condition of the lake and the importance of diel wind-induced mixing in the bottom supply of DO. Laguna Lake was found to be predominantly net heterotrophic (GPP:R < 1, NEP < 0).     

基于极限学习机的堤防工程多元风险指标评价方法

为提高堤防工程风险评价的准确性,提出了基于极限学习机的堤防工程多元风险指标评价方法。首先,综合考虑影响堤防风险的28个评价指标,利用层次分析法从预警系统、堤防工程系统、环境系统和社会经济系统这4个方面建立了堤防工程多元风险评价指标体系。接着,基于极限学习机算法对28个指标进行标准化处理及分级标准构建,以风险指标作为输入量,分级隶属度作为输出量,划分风险等级,量化评价指标,估计多元风险评价指标值和判断风险的严重程度。最后,依托鄱阳湖重点堤防——康山大堤,构建多元风险评价指标体系,运用极限学习机算法计算多元风险评价指标值。评价结果表明:康山大堤目前处于基本安全水平,符合康山大堤经过两次加固后的工程实际情况,并与其他方法进行对比,验证了提出方法的可靠性和有效性。该方法可拓展应用到其他重要水工结构工程风险评估中。     

Crack elongation and its width of large depth reinforced concrete beams

In order to meet the requirement of structural inspection,the crack spacing and crack width at various heights in the tensile zone of six large depth reinforced concrete beams were measured under several loading levels of serviceability state.The effects of the depth of normal section beams on the crack spacing and crack width were analyzed,and the modified model is proposed for calculating the average crack spacing by thinking about the depth of normal section,the reinforcement arrangement and the effective reinforcement ratio.The relationships of crack widths at any position in the tensile zone and at the reinforcement level on the side surface of beam were studied.By theoretical and statistical analysis,a method is proposed to calculate the ratios of crack widths between any position and the reinforcement level on the side surface of large depth reinforced concrete beams.     

型钢翼缘狗骨式削弱在型钢混凝土节点的作用

为了防止地震时型钢混凝土节点核心区发生剪切破坏以及梁柱连接焊缝发生脆性断裂,提出对型钢混凝土节点核心区附近梁端型钢的上、下翼缘采取狗骨式削弱,并系统研究翼缘削弱对提高型钢混凝土节点抗震性能的作用.研究表明,由于在梁端型钢翼缘采取狗骨式削弱,不仅能够将塑性铰控制在梁型钢削弱的位置,从而有效地降低了节点核心区所受的剪力以及梁柱连接焊缝的应力;而且能够改善节点塑性铰区的转动能力和抗剪性能,提高节点的延性和耗能能力.     

堤防工程标准化管理体系风险评估方法

为了完善堤防工程管理体系,依托鄱阳湖区重点堤防工程,将风险管理理论与堤防工程工作、技术、管理和考核标准化体系有机结合,建立了基于风险的堤防工程标准化管理体系,并且提出了标准化管理体系风险评估方法。首先,确定我国中部地区堤防工程生命、经济和社会与环境风险标准图;再借助风险矩阵法拟定生命、经济和社会与环境风险考核指标系数,估计综合考核指标系数,并将其融入标准化考核管理中得到基于风险的堤防工程标准化管理评分;最后,根据评分值来评价堤防工程标准化管理是否合格。结果表明:建立的堤防工程标准化管理体系不仅可为制定科学合理的堤防失事风险管理决策及措施提供理论和技术支持,而且可为其他堤防工程运行管理提供借鉴。     

TRIME-T3管式TDR土壤水分测定系统在宁夏泾源地区的标定研究

通过对比TDR(时域反射仪)法与烘干称重法测定土壤含水率,针对TDR在宁夏泾源县的土壤水分测定进行了标定及适用性研究.结果表明,TRIME-T3 TDR不适用于精确的表层土壤含水率的测定;在TDR标定过程中采用分段标定的方法能够取得相关性更好的标定方程.     

沙源区水库氮磷营养盐时空分布与相关性分析

为揭示典型沙源区水库水体氮磷等营养盐时空分布特征和相关性,以大河口水库为研究区,布置5个监测断面,对水库水质进行采样分析,结果表明:受风沙降尘、上游河流水质和库区底泥影响,在时间分布上,4月水体解冻至6月,各检测断面TN、TP等营养盐浓度总体呈明显持续升高趋势;在空间分布上,从入库口A-A断面和B-B断面至出库EE断面TN、TP浓度逐渐降低;在垂向分布上,水库表层水体和底层水体氮磷浓度高于中层水体;TN、TP在水库中的变化规律一致,呈一定比例存在于水库中;温度是影响TN、TP浓度变化的重要因子;藻类的生长对TN和TP起抑制作用;水库中TN、TP的变化与DO含量基本无关。     

淮北平原主要农作物涝渍灾害 损失评估研究

针对淮北平原除涝减灾综合治理与规划中缺乏主要农作物受涝损失调查与评估基础资料的实 际问题,于2010年9月初区域降雨成灾之际,对受涝区进行主要农作物受涝经济损失调查。依据实 地调研成果,通过综合统计分析推求了不同耕地类型不同暴雨强度下的受涝损失率,在此基础上实现 了对淮北平原受涝经济损失的合理评估。