Riser-soil interaction model effects on the dynamic behavior of a steel catenary riser

A mathematical model employed to analyze the global dynamics of a Steel Catenary Riser (SCR) taking into account the interaction with the seafloor and the effect of the soil reaction forces is established. The choice of soil model plays an important role for the dynamic behavior of SCRs. The riser has been modeled using flexible beam with large curvature and elastic foundation beam to describe the riser-soil interaction by means of realistic nonlinear load-deflection (P–y) curves. The study is made to improve an existing finite element numerical code for dynamic analysis of mooring lines and risers, known as CABLE 3D, which is based on a slender rod assumption. Effects of nonlinear seabed model on the dynamic behavior of SCRs under vessel cyclic perturbation have further been investigated and discussed using a realistic P–y curve to simulate soil deformation and resistance forces. The interaction model depends on several factors, such as soil strength, penetration depth and riser characteristics. The dynamic responses of the riser Touchdown Point (TDP) excited by vessel periodic heave motion are studied and the results are compared with those from the linear spring model. SCR has been perturbed by 10 regular sinusoidal cycles and the responses calculated by improved code show a number of features such as suction force mobilization, gradual increasing penetration depth, and gradual reduction of soil resistance at maximum penetration. The riser behavior at the touchdown zone (TDZ) depends on the riser top motion amplitude, nonlinear soil stiffness and suction force. The impact of the riser-soil interaction model on the dynamic behavior in the TDZ has been thoroughly studied in this paper.     

膨胀土路基工程施工

主要介绍膨胀土在高速公路工程中的应用。     

中小城市交通生成预测模型研究

城市交通生成预测是城市交通规划的基础，如何客观、科学地进行交通生成预测，是当前我国城市交通规划中共同面临的课题。一般来说，不同的土地利用布局、不同的土地利用性质和不同的土地利用强度，对应着不同的交通生成。因此，建立土地利用与交通生成的相互关系模型，实现土地利用-出行生成相关因素-交通生成的三步式预测方法向土地利用-交通生成两步式预测方法的过渡，将在大大简化交通需求预测过程的同时提高预测结果的可靠性。     

地铁车站新预筑法施工中顶管间距的优化设计

基于土拱效应理论,建立新预筑法顶管施工中顶管土拱效应模型.根据模型中土拱轴线的受力,推导出土拱轴线支座约束反力与模型几何参数之间的关系式.将此关系式与拱顶和拱脚的强度控制条件方程联立,得到求解顶管间距的方程组.给出验算土拱能体稳定性的判别式,验证顶管间距计算值的合理性.以采用新预筑法施工的沈阳地铁新乐遗址站1号风道为例.采用上述方法计算得到的顶管间距为3.28 m;通过调整切管位置和钢管半径可以优化没计顶管间距,从而减少管材消耗,节省施_上时间,降低地表沉降.     

A Comparative Study of Three Multivariate Short-Term Freeway Traffic Flow Forecasting Methods With Missing Data

Short-term traffic flow forecasting is a critical function in advanced traffic management systems (ATMS) and advanced traveler information systems (ATIS). Accurate forecasting results are useful to indicate future traffic conditions and assist traffic managers in seeking solutions to congestion problems on urban freeways and surface streets. There is new research interest in short-term traffic flow forecasting due to recent developments in intelligent transportation systems (ITS) technologies. Previous research involves technologies in multiple areas, and a significant number of forecasting methods exist in the literature. However, most studies used univariate forecasting methods, and they have limited forecasting abilities when part of the data is missing or erroneous. While the historical average (HA) method is often applied to deal with this issue, the forecasting accuracy cannot be guaranteed. This article makes use of the spatial relationship of traffic flow at nearby locations and builds up two multivariate forecasting approaches: the vector autoregression (VAR) and the general regression neural network (GRNN) based forecasting models. Traffic data collected from U.S. Highway 290 in Houston, TX, were used to test the model performance. Comparison of performances of the three models (HA, VAR, and GRNN) in different missing ratios and forecasting time intervals indicates that the accuracy of the VAR model is more sensitive to the missing ratio, while on average the GRNN model gives more robust and accurate forecasting with missing data, particularly when the missing data ratio is high.     

泰州长江大桥巨型深水沉井施工技术

泰州长江大桥中塔沉井号称"世界第一巨型深水沉井",高76m,入土深度达55m,详细介绍了该沉井施工的整体工艺流程,其多项创新性施工工艺对类似沉井施工具有借鉴意义。     

高速公路弃渣场设计原则与思路研究

根据新水土保持法对建设项目弃渣场提出的严格要求,结合"沈四高速公路改扩建工程",对弃渣场选址、挡护措施、排水措施及植被恢复措施等设计要素进行探讨,供高速公路弃渣场设计参考。     

季冻区道路冻胀翻浆产生的原因及防治措施

季节性冻土地区(简称季冻区),路基随季节交替发生冻结和融化循环变化,产生的病害主要是冻胀和翻浆。本文结合抚顺市城市道路冻胀状况调查,分析道路冻胀翻浆产生的机理、影响因素,并提出具体的防治措施,为今后抚顺等季节性冻土地区的城市道路设计和养护提供参考。     

TSP超前地质预报在中天山隧道1#斜井雁行式断裂带探测中的应用

TSP超前地质预报系统是利用接收入工地震波来完成地下工程的超前探测。以发育在中天山隧道1#斜井的雁行式断裂带为研究对象,介绍了TSP超前地质预报系统的应用。重点介绍了解译过程中将前期地质工作和地质物探资料有机结合在一起,确定超前地质预报目标体的特征及其与中天山隧道的关系,从而使得TSP超前地质预报探测有了明确的目标,保证TSP超前地质预报的质量。     

V250双缸电喷发动机活塞烧蚀的研究(1)

在化油器摩托车改制电喷摩托车过程中发现,电喷发动机在使用中油门全开时,火花塞垫片温度及排气温度较化油器发动机要高,影响了电喷摩托车的骑乘舒适性,并且发动机的使用寿命、特别是活塞的使用寿命会降低。通过调整电喷发动机全油门状态下的点火角和空燃比,改善发动机缸头的散热条件,来达到降低发动机火花塞垫片温度、保护发动机、延长发动机使用寿命的目的。