大跨斜拉桥悬臂端钢箱梁上监测点高程测量新方法

在斜拉桥的主梁施工中,需要高精度测量悬臂端钢箱梁的高程。随着悬臂的增长,桥面的晃动越来越大,水准仪读数的难度也越来越大,甚至读不出数据;同时由于梁面上施工设备的影响,测量的难度很大,时间也很长。本文提出采用Leica TCA2003全站仪测量高差和水准仪测量工作基点高程相结合的方法,测量钢箱梁上监测点的高程,通过理论分析和对比实验证明了该方法的可行性。     

南京长江二桥南汊桥主塔基础钢围堰施工测量

对大型斜拉桥主塔基础钢围堰的制作、并装、定位及下沉的施工测量作了全面论述。包括大型双壁钢围堰的底节制作、拼装接高、基准面传递、精密定位着床、吸泥下沉至着岩、清基及竣工测量。旨在为大型斜拉桥建设提供可知后主塔基础钢围堰施测方法。     

厂房内重型冲床基础沉箱防护工程综合处理技术

在长春拖拉机厂重型冲床基础沉箱防护工程中,由于在沉箱过程中采用的地下降水措施不当,出现厂房墙体开裂、倒塌、墙体损害程度严重等问题。通过详细的分析与研究,制定出切实可行处理方案,采用降水、注水、托换和变形观测等综合手段,有效地控制了不均匀沉降,沉箱顺利完成。经过观测和综合评价,效果好,具有推广价值。介绍了该沉箱防护工程中的综合处理技术。     

Steel stocks and flows of global merchant fleets as material base of international trade from 1980 to 2050

Exploring the dynamic changes of steel from the ships is critical for developing sustainable strategies for waste management of shipping industry. However, the information of stocks and flows of ships and related steel is currently unavailable, hindering the sustainable development of shipping industry. By collecting dispersed information on production, use, material composition, and end-of-life management of five types ships, we first estimated the historical steel stocks and flows respect to global ships from 1980 to 2019, and further projected the amount of steel scraps from shipbreaking by 2050. The steel stocks of ships increased by 2.6 times from 208.4 Mt in 1980 to 542.9 Mt in 2019. The top 2 regional contributors, Asia and Latin America & the Caribbean, were together responsible for about half of the total increase. A transition from oil tankers to container ships and bulk carriers reduced the in-use steel stock due to the lower steel intensity of the latter. The rapid increase of ship stocks after year 1980 led to significant increase of steel scrap in the 2010 s, reaching 10.1 Mt/year in 2019. Our projections showed that the steel from scrapped ships worldwide will increase by around 4-fold to 40.4–47.3 Mt/year by 2050, which imposed a great challenge on coordination of recycling ship-related steel and require long-term planning on ship recycling facility development. By identifying the stocks and flows of ships and related steel, this study provides insights for the steel waste and recycling management of end-of-life ships worldwide.     

不锈钢内衬技术在江阴市供水管网改造中的应用

本文结合不锈钢内衬技术在江阴市玻璃钢供水管道改造中的应用,介绍了不锈钢内衬玻璃钢管施工工艺流程和施工技术措施,分析了不锈钢内衬施工效果和优势。展望了不锈钢内衬技术在城市供水管网改造中的应用前景。     

Undrained Bearing Capacity of Suction Caissons for Offshore Wind Turbine Foundations by Numerical Limit Analysis

Determining the ultimate capacity of suction caissons in response to combined vertical, horizontal, and moment loading is essential for their design as foundations for offshore wind turbines. However, the method implemented for stability analysis is quite limited. Numerical limit analysis has an advantage over traditional limit equilibrium methods and nonlinear finite element methods in this case because upper and lower bounds can be achieved to ensure that the exact ultimate capacity of the caisson falls within the appropriate range. This article presents theories related to numerical limit analysis. Simulations are conducted for centrifuge model tests, the findings of which reveal the ability of numerical limit analysis to deal with the inclined pullout capacity of suction caissons. Finally, this article proposes an estimation of the ultimate capacity of a 3.5 MW offshore wind turbine foundation on normally consolidated clay based on the typical environmental parameters of Bothkennar, Scotland. Undrained failure envelopes and safety factors are obtained for suction caissons with different embedment ratios. Failure mechanisms, plastic zones, clay stress distributions, and the influence of the skin friction coefficients of caissons are discussed in detail.     

砂土中吸力式沉箱基础的最佳荷载作用点位置模型试验研究

通过一系列模型试验研究了倾斜荷载作用下吸力式沉箱基础的最佳作用点位置,试验中考虑了荷载作用点、荷载作用角度和长径比3个重要因素。基于模型试验得到的荷载-位移曲线,采用合适的破坏标准确定了各工况下吸力式沉箱基础的抗拔承载力,根据承载力的变化规律分析确定了吸力式沉箱基础的最佳作用点位置。结果表明,荷载作用角度对吸力式沉箱基础承载力的影响显著,当荷载水平作用于基础时,其承载力最大。荷载作用点位置对吸力式沉箱基础承载力的影响取决于荷载作用角度的大小,当荷载作用角度较小时,荷载作用点位置的影响显著,且最佳作用点位置位于沉箱高度的2/3～3/4处;当荷载作用角度较大时,荷载作用点位置的影响很小,可以忽略。结合荷载与吸力式沉箱基础的转角关系,分析了荷载水平作用于最佳作用点下吸力式沉箱基础的破坏模式。     

明基床上开孔沉箱总力矩试验研究

通过二维水槽内规则波以及不规则波作用下开孔沉箱的受力试验研究,分析研究了明基床上开孔沉箱所受的总力矩与相对基床高度、消浪室相对宽度、相对水深、波陡以及开孔率等影响因素间的相关关系,并利用最小二乘法给出总力矩比值(开孔沉箱/实体沉箱)与其影响因素间的拟合公式,同时将计算值与试验值对比,二者吻合较好,所得经验关系式可供工程设计参考。     

水平荷载作用下裙式吸力基础承载性能研究

传统吸力基础是一个单桶结构,被广泛作为海洋平台、漂浮结构的基础,近年来也被推广到海上风电塔架。作为风电塔架基础,要充分提高其水平承载能力。为此,提出一种改进的基础形式—裙式吸力基础。采用Z_SOIL有限元软件,针对砂土地基,从水平单调加载和循环加载两个方面,对传统单桶吸力基础和裙式吸力基础进行了承载性能对比研究,得到了相应的荷载-位移曲线。研究结果表明,裙式吸力基础由于设置了"裙"结构,显著提高了其抵抗水平静载和循环水平动力荷载的能力,并能有效控制基础的水平位移,是值得推广应用的一种新型海洋工程基础形式。     

Theoretical studies on penetration resistance of suction caissons in clay

ABSTRACT

The suction caisson is commonly a top-closed cylindrical steel structure with large diameter, short length and much thinner skirt wall thickness. The resistance to penetrating is calculated as the sum of the tip bearing capacity and the adhesion on the both sides of the skirt wall. Since the thickness of the skirt wall is very small, the downward adhesion produced by the skirt wall will cause the additional vertical stress and shear stress in the soil at the skirt tip level, increasing the skirt tip resistance. However, the increase in skirt tip resistance caused by the additional vertical stress rather than shear stress in soil at the skirt tip level was only considered, this may lead to an inaccurate estimation for the tip bearing capacity and the suction required. Thus, a modified slip-line field is put forward in this study to estimate the tip resistance. The expression of obtaining the minimum suction to install the suction caisson in clay is derived in terms of the force equilibrium. Results from calculations of the minimum suction have been proved to be in a good agreement with the measured data.