苏通大桥外部变形监测内容的确定     

周家刚  岳东杰 《现代测绘》2011,34(3)

桥梁外部变形监测是运营期桥梁检查和检验的重要内容之一,可以与结构监测相互补充、相互验证,为确保桥梁的安全提供充足的技术支持。从讨论桥梁变形监测的重要性出发,分析了苏通大桥运营期变形监测的必要性。在综述桥梁外部变形监测内容的基础上,充分分析苏通大桥结构组成、桥型等现状,确定了变形监测部位与项目,以期为类似桥梁监测工程提供借鉴。  相似文献   

绕流对称性破缺诱发柔细结构振动研究——以Tacoma大桥风振致毁事故为例     

葛秀坤  赵庆贤  邵辉  陆钰 《地震学刊》2011,(4):430-435

绕流对称性破缺往往对柔细结构产生很大的作用效应,诱发结构振动,严重影响其可靠性和安全性。基于圆柱平面绕流模型,系统分析了实际流体圆柱绕流纵向对称性破缺以及各种情况的横向对称性破缺现象。为了更加深入地理解理论分析的结果,利用Fluent软件对圆柱绕流模型进行了计算机模拟,详细分析了雷诺数为10、20、40、100、200、2000、20000时的绕流情况,结果显示,当雷诺数为200时,流场开始出现横向对称性破缺。在此基础上,以Tacoma大桥风振致毁事故为例,分情况探讨了旋涡同步交替脱落导致的桥面起伏性振动,以及旋涡异步交替脱落导致的桥面扭振。分析结果表明,绕流对称性破缺是诱发大桥振动破坏的直接原因。  相似文献   

双层板桁钢梁应力分析     

焦常科  李爱群 《地震学刊》2011,(2):146-151

以跨度最大的双层斜拉桥闵浦大桥为背景,研究了双层板桁钢梁桥面板的受力特性,阐述了精细壳单元与梁单元结合的整体有限元模型,并分析了上、下桥面间腹杆的受力特性与桥面板的应力分布特性;采用桥面纵横梁间带U肋精细桥面模型,分析了桥面板和U肋在车辆荷载作用下的应力分布。研究表明,上、下层桥面横桥向应力小于纵桥向应力,并且横桥向应力的不均匀性明显大于纵桥向;车轮荷载作用下,正交异性桥面板应力分析时,荷载位置对纵横向应力峰值的影响很小,并且横桥向应力起控制作用,峰值均出现在U肋与顶板交接处。  相似文献   

Migratory Patterns and Settlement Experiences of African Australians of Refugee Background in Murray Bridge,South Australia     

L.V. Nayano Taylor-Neumann  Mohana Raj Balasingam 《The Australian geographer》2013,44(2):161-175

In the past decade Australian immigration policy has emphasised settlement of refugees/humanitarian entrants in rural and regional locations, in preference to metropolitan areas. The settlement outcomes of a case study of African humanitarian entrants of South Sudanese background in Murray Bridge, a regional centre in South Australia, are examined. These participants were self-settled secondary movers from metropolitan Adelaide. The factors which attracted them were centred on employment. Settlement outcomes for Murray Bridge respondents were better than their urban counterparts, in terms of both housing and employment outcomes. However, some later left Murray Bridge because of a lack of opportunities for tertiary education. The results highlight issues of sustainability of settlement and retention, in regional centres in Australia, and of the fluidity of attraction and retention factors and therefore settlement in regional centres.  相似文献   

苏通大桥形变的GPS动态监测     

吴杰  胡夏闽  苗恒亚 《测绘科学》2016,41(11):171-174

针对目前大桥监测的现状及各种监测方法的优缺点,该文结合苏通大桥运营情况,研究了GPS动态监测的原理、系统组成、坐标转换及监测注意事项,并对其进行了GPS动态监测试验。采集了桥面沿轴线方向、横向及竖向位移数据,对大桥在温度、风荷、车载等因素影响下的运营期大桥响应情况进行了分析。表明大桥轴线方向位移与温度正相关,1/4跨处相关系数为0.859;竖向位移与温度负相关,1/4跨处相关系数-0.817。并对数据进行了频谱分析,分析结果表明频谱没有明显变化;大桥各方向振幅在安全范围内,表明运营期的大桥十分健康;同时也表明GPS动态系统监测结果是可靠的。  相似文献   

Good practice policies to bridge the emissions gap in key countries     

《Global Environmental Change》2022

One key aspect of the Paris Agreement is the goal to limit the global average temperature increase to well below 2 °C by the end of the century. To achieve the Paris Agreement goals, countries need to submit, and periodically update, their Nationally Determined Contributions (NDCs). Recent studies show that NDCs and currently implemented national policies are not sufficient to cover the ambition level of the temperature limit agreed upon in the Paris Agreement, meaning that we need to collectively increase climate action to stabilize global warming at levels considered safe. This paper explores the generalization of previously adopted good practice policies (GPPs) to bridge the emissions gap between current policies, NDCs ambitions and a well below 2 °C world, facilitating the creation of a bridge trajectory in key major-emitting countries. These GPPs are implemented in eleven well-established national Integrated Assessment Models (IAMs) for Australia, Brazil, Canada, China, European Union (EU), India, Indonesia, Japan, Russia, South Korea, and the United States, that provide least-cost, low-carbon scenarios up to 2050. Results show that GPPs can play an important role in each region, with energy supply policies appearing as one of the biggest contributors to the reduction of carbon emissions. However, GPPs by themselves are not enough to close the emission gap, and as such more will be needed in these economies to collectively increase climate action to stabilize global warming at levels considered safe.  相似文献   

整体桥高性能混凝土桩−土相互作用试验研究     

黄福云  周志明  庄一舟  刘帆  刘名琦 《岩土力学》2022,43(3):591-601

高性能混凝土（高性能复合水泥基材料engineered cementitious composite,简称ECC与超高性能混凝土ultra-high performance concrete pile,简称UHPC）桩基具有良好的抗开裂性能和较高的承载能力,能较好地满足整体桥纵桥向变形。开展了砂土中高性能混凝土桩低周往复拟静力试验,得到了桩基的破坏特点、抗开裂能力以及极限承载力,分析了其桩身变形、桩侧土抗力以及桩身应变等分布规律,并与钢筋混凝土（RC）桩进行了比较。在此基础上,讨论了几种常用规范的适用性。试验结果表明,ECC、UHPC材料能有效减轻桩基的破坏程度、提高桩基的抗开裂能力以及水平承载力;相比RC桩基,高性能混凝土桩基的破坏位置更深,桩基的有效桩长更大,抗震性能更好;其中,ECC桩基的抗开裂能力最强,开裂荷载可达5.8 kN,开裂位移可达15 mm。试验结果还表明,高性能混凝土桩基的变形沿埋深方向不断的减小,埋深1.5 m以下位置基本为0;桩侧土抗力先增大后减小,桩底土抗力和变形量为0;桩身应变分布较为对称,且呈“橄榄”形,在埋深4D～6D（D为桩径）区间内桩身应变较大。分析计算表明,当桩顶位移在10 mm以内时,“m”法与API新规范法均能较好地计算高性能混凝土桩的桩身变形;当位移超过10 mm后,“m”法与实际数值相差较大。“m”法与API新规范法均不能较好地计算桩身弯矩,适用性不高;桩侧土抗力建议采用API新规范法。  相似文献   

Local scour around two side-by-side cylindrical bridge piers under ice-covered conditions     

Mohammad reza Namaee  Jueyi Sui 《国际泥沙研究》2019,34(4):355-367

In the current study, 108 flume experiments with non-uniform, cohesionless sediments have been done to investigate the local scour process around four pairs of side-by-side bridge piers under both open channel and ice-covered flow conditions. Similar to local scour around bridge piers under open channel conditions and a single bridge pier, it was observed in the experiments that the maximum scour depth always occurred at the upstream face of the pier under ice-covered conditions. Further, the smaller the pier size and the greater the spacing distance between the bridge piers, the weaker the horseshoe vortices around the bridge piers, and, thus, the shallower the scour holes around them. Finally, empirical equations were developed to estimate the maximum scour depth around two side-by-side bridge piers under both open channel and ice-covered flow conditions.  相似文献   

利用振动法测量预应力体外索的索力     

林友勤 《地震工程与工程振动》2007,27(3):64-69

为了能够利用振动法测量316国道洪塘大桥预应力体外索的索力,本文根据理想弦的振动方程以及梁的横向振动方程,建立起有灌浆预应力体外索索力的计算模型,该计算模型中含有两个权重系数λ1、λ2。利用该桥体外预应力索的模型实验数据,通过最小二乘法拟合出系数λ1、λ2并得到体外索索力的计算公式。误差分析表明该体外索索力计算公式误差小,可以用于洪塘大桥体外索索力计算以及该桥体外索长期健康监测。  相似文献   

胶州湾跨海大桥对海湾水体交换的影响   总被引：1，自引：0，他引：1  

陈妍宇  宋德海  鲍献文  严聿晗 《海洋与湖沼》2019,50(4):707-718

跨海大桥的建设有利于环湾经济的发展,但桥墩入水不可避免地会对海湾内水动力和水交换造成一定的影响。本文以胶州湾为例,利用无结构网格有限体积海洋模型,建立了能够描绘胶州湾跨海大桥入海桥墩的高精度网格,构造了胶州湾及邻近海域的三维水动力模型,模拟了胶州湾建桥前后的潮(余)流结构。在此基础上,通过污染物示踪对比了胶州湾内污染物在建桥前后的对流扩散过程。模拟结果表明,大桥的建设对胶州湾南部大部分区域的影响较小,包括潮(余)流、水交换等方面;但对大桥北侧以及南侧靠近大桥一定范围内的区域有显著影响。大桥北侧潮致余流整体减小约2cm/s,靠近桥南侧的余流则由向北转为沿桥向东流动。由于大桥的影响,污染物在大桥北侧堆积,重点集中于桥北的红岛以西(Ⅰ区)沿岸区域以及红岛以东(Ⅱ区)大部分区域。其中,Ⅰ区建桥后的半交换时间增加了2.00d,Ⅱ区增加了2.04d。在减缓污染物扩散速率的同时,大桥也同样阻碍了径流输出的淡水向胶州湾南部的输运,使得桥北水体的盐度降低,有可能是造成近年来胶州湾冬季冰情加剧的原因之一。  相似文献