Cyclic performance and simplified pushover analyses of precast segmental concrete bridge columns with circular section     

Zhanyu Bu  Jian Guo  Rongyue Zheng  Jianwei Song  George C. Lee 《地震工程与工程振动(英文版)》2016,15(2):297-312

In recent years, precast segmental concrete bridge columns became prevalent because of the benefits of accelerated construction, low environmental impact, high quality and low life cycle costs. The lack of a detailed configuration and appropriate design procedure to ensure a comparable performance with monolithic construction has impeded this structural system from being widely used in areas of high seismicity. In this study, precast segmental bridge column cyclic loading tests were conducted to investigate the performance of unbonded post-tensioned segmental bridge columns. One monolithic and two precast segmental columns were tested. The precast segmental column exhibited minor damage and small residual displacement after the maximum 7% cyclic drift; energy dissipation (ED) can be enhanced byadding ED bars. The experimental results were modeled by a simplified pushover method (SPOM), as well as a fiber model (FIBM) finite element method. Forty-five cases of columns with different aspect ratios, axial load ratios and ED bar ratios were analyzed with the SPOM and FIBM, respectively. Using these parametric results, a simplified design method was suggested by regressive analysis. Satisfactory correlation was found between the experimental results and the simplified design method for precast segmental columns with different design parameters.  相似文献   

西藏地区GPS水汽资料与降水量之间的对比分析   总被引：1，自引：0，他引：1  

罗布  杨秀海  央金 《高原山地气象研究》2010,30(1):54-57

利用2008年7月份西藏地区地基GPS遥感大气水汽总量的观测资料,研究了大气水汽总量与日平均温度、相对湿度和降水量的关系。研究结果表明:1海拔高度对站点上空水汽总量的影响比较明显,一般情况下海拔越高水汽总量越低;其次高原上某地的降水转化率高低与该地所处的长期天气背景有关2.水汽总量值与实际降水量的大小之间并不是一种简单的正比关系,水汽梯度值和水汽源源不断地输送对降水量的大小有重要影响。3.日平均温度和GPS大气可降水量跟相对湿度之间呈反相关;降水往往出现在高温高湿后面,这种现象可以用湿旋转效应解释;最低温度跟GPS大气可降水量之间有良好的正相关。   相似文献   

Grain size in sediments from Lake Sugan: a possible linkage to dust storm events at the northern margin of the Qinghai–Tibetan Plateau     

Mingrui Qiang  Fahu Chen  Jiawu Zhang  Ruiping Zu  Ming Jin  Aifeng Zhou  Shun Xiao 《Environmental Geology》2007,51(7):1229-1238

Samples of surface deposits in the Lake Sugan catchment, as well as surface lake sediments, eolian materials occulted in the lake ice cover, and airborne dust were collected for grain-size analysis. The results show that the coarse fraction of the lake sediments could be transported by ambient winds and to a lesser extent by river flow in the study area. Sediment cores were retrieved from Lake Sugan in December 2000, and ²¹⁰Pb and ¹³⁷Cs dating and grain-size analyses were performed on these samples. ²¹⁰Pb ages and the volume percentage of the fraction of lake sediments >63 μm were used to reconstruct the dust storm history from 1957 to 2000. Observational data for dust storm events collected at a local meteorological station largely agrees with the reconstructed trend for the past 44 years, suggesting that lake sediments can be employed to trace the dust storm history of the northern Qinghai–Tibetan Plateau.  相似文献   

中国古代军事地理研究     

王树连  卜毅博 《测绘科学与工程》2007,27(2):25-29

军事地理是军事谋划的基本要素。中国古代纷繁的战争实践促进了军事地理研究的不断深入。《孙子兵法》中有关军事地形的系统论述是先秦军事地理研究的丰硕成果。南宋开始出现军事地理专著。明清时期，边患日重，有关边防、海防地区的军事地理研究之风盛行，成果颇多。兵要地志、军用地图是军事地理研究的基本成果。实地考察与考证地理典籍是军事地理研究的基本方法。中国古代军事地理研究中对战略要地、古代战场与战例、御敌方略的记述与研判，对今天的国防筹划仍然具有借鉴意义。  相似文献   

Preparation and Certification of Biogeochemical Reference Materials     

Changyi Shi  Tiexin Gu  Wei Bu  Weidong Yan  Mei Liu  Mingcai Yan 《Geostandards and Geoanalytical Research》2008,32(3):337-345

The Institute of Geophysical and Geochemical Exploration in China recently prepared ten biogeochemical certified reference samples GSB1‐10 (CRMs). The samples are primary agricultural products such as rice, wheat, corn, soybean, cabbage, spinach, tea, powder, chicken and apple. Lyophilisation technology and a high‐alumina ball mill were used to process the samples. Fourteen laboratories and hundreds analysts in China participated in the certification analysis. Over ten reliable analytical methods, predominately ICP‐MS, ICP‐AES and INAA, were used for analysing the samples for fifty‐nine elements. A total of 22477 determinations led to 5136 average data sets. Certified values of fifty‐four elements were assigned.  相似文献   

杭州城市多级通风廊道体系构建初探     

俞布  贺晓冬  危良华  陈亮  周雯 《气象科学》2018,38(5):625-636

随着小城镇建设及城市总体规划修编的实施,基于城市通风廊道构建的生态环境效应成为当前城市生态规划研究的热点。以杭州为例,研究构建了集合城市气候观测、多尺度数值模拟、城市形态控制为一体的城市多级通风廊道系统,综合考虑能够表达或影响城市通风环境的多源评价指标,如分区风玫瑰、近地面风流场、城市风功能区及风流通潜力等。结论表明:杭州城市主导风空间差异明显,可划分为15个截然不同的风玫瑰分区。利用区域边界层模式(RBLM)耦合多层城市冠层模型提取多种地面风流场信息,并结合主导风观测综合划定杭州城市一级通风廊道。结合建筑覆盖率、迎风面系数和地表粗糙度综合评价城市风流通潜力,并将其作为杭州城市二、三级风道划定的辅助依据。同时,利用RNGκ-ε湍流模型验证风道对局部通风环境改善的有效性。最终,基于多源信息的空间叠置分析,综合构建了由6条一级风道、11条二级风道和12条三级城市绿廊构成的杭州城市多级通风廊道体系,为其他城市开展通风廊道研究提供了通用的技术方法,从而科学有效的服务于城市生态规划及管理。  相似文献   

Machine learning-based methods for sea surface rainfall detection from CYGNSS delay-doppler maps     

Bu  Jinwei  Yu  Kegen  Ni  Jun  Yan  Qingyun  Han  Shuai  Wang  Jin  Wang  Changyang 《GPS Solutions》2022,26(4):1-13

GPS Solutions - Accurate secular trend estimates and their uncertainties of GNSS coordinate time series is imperative for its geophysical applications. However, trend estimates would be...  相似文献   

黔东杨立掌——道坨南华纪“大塘坡”式含锰盆地地质分析及找矿预测          下载免费PDF全文

王佳武  洪万华  姚希财  安正泽 《地质找矿论丛》2017,32(1):1-7

根据杨立掌—道坨地区沉积锰的矿体厚度、品位数据资料,分析了含锰盆地展布及岩性组合特征,认为黔东杨立掌—道坨南华纪"大塘坡"式含锰盆地受古断层控制,沿65°方向展布,盆地延伸长15.0km,宽2~2.5km,规模巨大;含锰盆地由4个岩性带组成,从中心向外依次为:块状、气泡状菱锰矿夹碳质页岩带;碳质页岩夹块状、条带状菱锰矿带;碳质页岩夹条带状、层纹状菱锰矿带;碳质页岩、含锰碳质页岩、含锰白云岩带。根据含锰盆地岩性组合分带及其展布特征,预测含锰盆地中心中段高地一带具较好的找矿远景。  相似文献   

Research on the Energy Criterion for Rockbursts Induced by Broken Hard and Thick Rock Strata and Its Application     

Jun Wang  Jianguo Ning  Jinquan Jiang  Tengteng Bu  Xinshuai Shi 《Geotechnical and Geological Engineering》2017,35(2):731-746

In this study, the occurrence conditions of rockbursts induced by broken hard and thick rock strata (HTRS) in fully mechanized longwall face are investigated by dividing the surrounding rock of a roadway rib into three zones: burst-resistance zone (BRZ), burst-inoculation zone, and stable zone. On this basis, the process of impact vibration energy (released by the broken HTRS) transformation in these zones was analyzed, and theoretical equations are presented to calculate the strain energy, dissipated energy and shock vibration energy. In addition, an energy criterion associated with the critical broken length of the HTRS, the width of burst-resistance zone, and the burst proneness index was proposed to predict rockbursts induced by broken HTRS in fully mechanized longwall face. Moreover, to control these types of rockbursts effectively, a quantitative method was proposed for determining the limit broken length of the HTRS and the BRZ. The research results show that the energy criterion may forecast these typical rockbursts, and rockburst hazards can be eliminated using the proposed method.  相似文献   

钻井进尺测量电路的防振措施   总被引：1，自引：0，他引：1  

补家武  鄢泰宁  朱玉峰  周刚  龚元明 《地质科技情报》1999,(Z1)

针对钻机在钻井过程中产生强烈振动给一些参数的测量带来困难的问题,在介绍机电测量中常用的光电编码器的电路组成及其工作原理的基础上,分析了将编码器用于钻速及进尺测量时,在电路上所采取的防振措施,并给出了在实际使用中已取得很好效果的测量电路。  相似文献