BOTDR传感技术在桥梁移动荷载识别中的应用

文章针对我国桥梁移动荷载识别的测试技术还不能实现有效识别的现状,对应用BOTDR技术的可行性进行分析,表明BOT-DR技术用于桥梁移动荷载的识别具有广阔的前景。     

破碎波对直立堤作用的实验研究(英文)

Breaking waves can have tremendous destructive impact on vertical walls,yet they are poorly understood.By using particle imaging velocimetry(PIV) technology and high-precision pressure transducers,actual breaking wave loads on vertical walls were studied.By simultaneously comparing the flow field structure and wave pressure,the mechanisms of breaking wave pressure could be analyzed.The probability distribution of the peak value of the first impact of a breaking wave was investigated.The results showed that the impact pressure p is mainly distributed in the range of 0.25-2.75 ρν 2,with the greatest possible probability at p/ρ v2= 0.75.     

海上自升式平台动力分析方法研究(英文)

A jack-up platform,with its particular structure,showed obvious dynamic characteristics under complex environmental loads in extreme conditions.In this paper,taking a simplified 3-D finite element dynamic model in extreme storm conditions as research object,a transient dynamic analysis method was proposed,which was under both regular and irregular wave loads.The steps of dynamic analysis under extreme conditions were illustrated with an applied case,and the dynamic amplification factor(DAF) was calculated for each response parameter of base shear,overturning moment and hull sway.Finally,the structural response results of dynamic and static were compared and analyzed.The results indicated that the static strength analysis of the Jack-up Platforms was not enough under the dynamic loads including wave and current,further dynamic response analysis considering both computational efficiency and accuracy was necessary.     

Long-term correlation structure of wave loads using simulation

This paper proposes a new method for combining the lifetime wave-induced sectional forces and moments that are acting on the ship structure. The method is based on load simulation and can be used to determine the exceedance probabilities of any linear and nonlinear long-term load combination. It can also be used to determine the long-term correlation structure between these loads in the form of the long-term correlation coefficients. They are essential part of the load combination procedures in design and strength evaluations as well as in the fatigue and reliability analysis of ship structures.The simulation method treats the non-stationary wave elevations during the ship’s entire life (long-term) as a sequence of different stationary Gaussian stochastic processes. It uses the rejection sampling technique for the sea state generation, depending on the ship’s current position and the season. Ship’s operational profile is then determined conditional on the current sea state and the ship’s position along its route. The sampling technique significantly reduces the number of sea state-operational profile combinations required for achieving the convergence of the long-term statistical properties of the loads. This technique can even be used in combination with the existing long-term methods in order to reduce the number of required weightings of the short-term CDFs. The simulation method does, however, rely on the assumption that the ship is a linear system, but no assumptions are needed regarding the short-term CDF of the load peaks.The load time series are simulated from the load spectra in each sea state, taking into account the effects of loading condition, heading, speed, seasonality, voluntary as well as involuntary speed reduction in severe sea states and the short-crested nature of the ocean waves. During the simulation procedure, special care has been given to maintaining the correct phase relation between all the loads. Therefore, time series of various load combinations, including the nonlinear ones, can be obtained and their correlation structure examined. The simulation time can be significantly reduced (to the order of minutes rather than hours and days) by introducing the seasonal variations of the ocean waves into a single voyage simulation. The estimate of the long-term correlation coefficient, obtained by simulating only a single voyage with the correct representation of seasonality, approaches the true correlation coefficient in probability. This method can be applied to any ship and any route, or multiple routes as long as the percentage of the ship’s total lifetime spent in each of them is known.A study has been conducted to investigate the effects of ship type, route and the longitudinal position of the loads on the values of the correlation coefficients between six different sectional loads; vertical, horizontal and twisting moments, as well as shear, horizontal and axial forces. Three ocean-going ship types have been considered; bulk carrier, containership and tanker, all navigating on one of the three busy ship routes; North America-Europe, Asia-North America and Asia-Europe. Finally, the correlation coefficient estimates have been calculated for five different positions along the ship’s length to investigate the longitudinal variation of the correlation coefficient.     

平板在组合载荷作用下的极限强度预报的一种简化解析法

船体平板强度在船舶结构极限强度分析中起到十分重要的作用。最近几年，一些作者提出了计算平板极限强度的一种简化解析方法。但绝大部分的研究只考虑了平板纵向受压这一种简单载荷的情况。在我们成功地解决了三向组合载荷(纵、横压缩和垂向均布压力)的基础上，在本文中，我们又进一步将此方法推广到包含面内剪力在内的所有组合载荷分量均存在的一般情况。通过与一些规范公式的比较表明，本文所推导的公式是可以比较精确地预报平板在一般组合载荷作用下的极限强度。这一工作一方面可以为规范中的一些经验公式提供理论依据，另一方面也许可以提供比经验公式更好的外插能力。为了简化使用本文的方法，本文也在大量参数系列计算的基础上给出了一个回归的经验公式。     

自由面和岸壁对限制航道中船舶操纵性水动力的影响

本文在二阶抛物面离散后的船体表面单元上布置强度呈线性分布的Rankine源，在离散后的岸壁单元上和用贴体网格法离散船体附近自由面的单元上布置均匀Rankine源，在船体中纵面上布置强度在水深方向呈阶梯变化的附着涡线．计算了考虑自由而影响下船舶平行于岸壁航行时的水动力，还着重讨论了自由面和岸壁对限制航道中船舶水动力的影响．     

浮体剖面载荷的几种计算方法

水中浮体的剖面载荷计算对于总体强度分析起着至关重要的作用。利用三维势流水动力软件预报浮体的运动及受力响应,以此结果为前提条件,采用三种不同的方法（压力积分法、多体法和广义模态法）。计算浮体的剖面载荷：最后以一个半潜平台结构为算例,并得到三种方法的相互验证。     

破损船体剩余强度衡准研究

本文研究了船体破损非对称淹水和刚度损失引起的船体外载荷变化,并利用破损船体非对称弯曲极限强度计算方法详细分析碰撞、搁浅和爆炸破损对船体极限强度的影响.然后基于破损船体极值载荷和极限强度,给出破损船体剩余强度衡准,并对破损船体临界海况进行预报.     

浮式生产储油船锚泊定位性能计算

应用计算锚链的悬链线方程和计算船舶运动的格林函数方法的耦合数值方法，对一锚泊的浮式生产储油船进行了定位性能计算，给出了自由状态与锚泊状态系统的运动响应特性的对比、不同状态与工况的锚泊浮体的运动性能参数以及锚链承受的张力等计算结果。研究成果可以为浮式生产储油船锚泊系统设计、校核计算和锚泊系统形式与参数优化提供初步计算结果以及用于设计方案的比较。     

在非线性波浪载荷作用下计及多种应力组合时船体总纵弯曲累积损伤计算

在时域内计算计及非线性时的船体总纵弯曲应力,与船体局部弯曲应力迭加后,可得纵向构件中合成应力的时历.对该应力时历进行雨流计数,经统计分析获得应力范围的长期分布,进而算出船体总纵弯曲时纵向构件在多种应力成份组合下的疲劳损伤.为方便此时的计算,本文提出了基于等效规则波概念的简化方法.数例表明按严格方法与按简化方法所得的结果比较接近.