海上风电吸力式筒型基础应用研究

  [目的]  筒型基础是一种极具潜力的环境友好型海上风电基础,如何有效的实现筒型基础顺利下沉到设计深度和下沉过程结构垂直度的精准控制,避免筒内土塞隆起或筒裙及分舱板变形甚至屈曲带来的安装风险是筒型基础应用层面的关键问题。  [方法]  通过总结吸力式筒型基础在国内外风电工程中的应用,分析了筒型基础施工过程中下沉和调平两个关键问题涉及的相关机理和方法。  [结果]  研究表明:准确预测复杂土质条件下筒型基础施工过程下沉阻力及施工临界吸力和施工过程可能发生的结构变形等不稳定性态分析将有效规避单筒型、多筒型和单筒多舱复合型筒型基础吸力下沉调平过程中的施工风险。  [结论]  海上风电吸力式筒型基础应用总结分析,可以为实际工程提供筒型基础下沉和调平施工方案的相关参考。     

单筒多舱筒型基础临界吸力与需要吸力计算方法研究

针对单筒多舱筒型基础中舱压力小于边舱工况，研究其沉放过程渗流场特性；分析舱压比和中舱相对尺寸对临界吸力的影响，建立可考虑舱压比和中舱尺寸的临界吸力计算方法；分析舱压比对减小摩阻力与端阻力的影响规律，并基于有效应力原理建立可考虑舱压比的沉放需要吸力的计算方法。     

筒型基础预应力过渡段结构传力特性研究

复合筒型基础是目前应用于海上风电工程中的一种新型基础型式,过渡段结构作为一种连接筒基和塔筒的结构形式在整个基础结构的传力体系中起到关键作用。基于大型有限元软件ABAQUS,建立2种典型的过渡段结构型式,具体分析不同过渡段结构在单调荷载及复合荷载作用下过渡段结构的应力响应及传力特性。计算结果表明:单调水平或竖向荷载作用下,带分舱板的钢筒直线型过渡段模型受力均匀,过渡段结构表现出更好的综合传力特性;单调弯矩荷载作用下,带分舱板的钢筒弧线型过渡段模型受力均匀,过渡段结构表现出更好的综合传力特性;复合荷载作用下,带分舱板的钢筒弧线型过渡段模型受力性能最好,过渡段结构的传力性能最优。     

砂土中宽浅式复合筒型基础刚度退化试验研究

针对有分舱宽浅式复合筒型基础和无分舱宽浅式复合筒型基础,对2种不同结构形式的基础首先在干砂和饱和砂中进行单向水平加载试验,然后对其进行双向循环加载试验,研究2种不同结构形式的基础的动态承载能力和刚度退化现象。结果表明,分舱板的作用增强了宽浅式复合筒型基础的动态承载能力,提高了复合筒型基础的耗能能力,可延缓筒型基础的刚度退化。     

砂土中宽浅式复合筒型基础三维包络面研究

采用有限元软件ABAQUS对砂土中海上风力发电新型宽浅式复合筒型基础的承载能力进行数值模拟分析,并将有限元结果与试验结果进行对比,验证有限元模型的准确性。水平与弯矩作用下,复合筒型基础产生转动位移,旋转中心随荷载的增大从模型中轴线附近沿加载方向移动至分舱板底部;竖向荷载作用下,可将筒内土体和筒型基础当作一个受力整体计算。在二维荷载平面中水平和弯矩荷载呈线性关系,先施加一定的竖向荷载对砂土中复合筒型基础抵抗水平力和弯矩有利,水平与弯矩的极限承载能力均能得到较大提高。结合二维破坏包络线进行大量计算后得出三维包络面,进一步明确复合筒型基础在三维荷载作用下的承载能力与承载特性。     

单侧冲刷对海上风电筒型基础稳定性影响研究

海上风电筒型基础在位工作期间长期受到海流的冲刷,基础的稳定性受到一定影响.通过模型试验和数值方法研究粉土地基中,单侧冲刷工况单筒多舱筒型基础的水平向和抗倾覆极限承载力与冲刷率之间的关系,以及冲刷对基础水平向-倾覆荷载(H-M)复合承载特性的影响.研究结果表明,筒型基础的水平向和抗倾覆承载力主要由筒外前侧和筒内土体提供,...     

粉质黏土中厚壁筒型基础沉放及受力分析

筒型基础具有海上施工效率高、建造成本低等优点,已成功应用于实际工程。为了进一步降低筒型基础结构的制造成本,避免建造、运输、安装过程中钢制筒裙的屈曲,文章研究并优化了混凝土筒壁和钢质内分舱板的组合式筒型基础结构。首先,针对厚壁筒型基础沉放安装难度增加问题,开展了室内试验,研究了粉质黏土中厚壁沉放阻力计算方法;然后,利用三维有限元模型对该组合式筒型基础在位状态下的结构受力进行了分析。研究结果表明：考虑形状和深度系数的端阻力计算公式可以用于该新型风电基础;混凝土筒壁+钢质内分舱板组合式筒型基础倾斜率、结构强度和自振频率满足设计要求,且在造价上更为经济。     

考虑缺陷的大型风力机塔筒屈曲分析与稳定性设计

介绍了风力机塔筒在多荷载联合作用下临界屈曲荷载的工程算法与有限元分析方法,并以某5 MW风力机塔筒为研究对象,对比分析不同方法得到的临界屈曲荷载。计算结果表明,线性屈曲分析由于未考虑非线性因素的影响,得到的临界屈曲荷载偏大,而非线性屈曲分析与工程算法得到的计算结果相近。根据计算结果得出,相关标准提出的工程算法存在一定的局限性,在实际验算中需采用有限元方法进行辅助分析,同时提出一种考虑初始缺陷的非线性屈曲分析方法。     

复合筒型基础在粉土中的抗扭承载特性研究

复合筒型基础作为一种新型海上风电基础结构,在承受自重及风浪流产生的竖向荷载V,水平荷载H,弯矩荷载M以外,还会承受机头带来的扭矩荷载T。该文利用有限元软件Abaqus,分析了粉土地基中复合筒型基础的扭矩承载特性。结果显示,复合筒的分舱板可提高扭矩承载力,高径比越大,复合筒的扭矩承载力越大,同时结合抗扭承载失效模式提出一个简化的抗扭承载力公式,与数模吻合较好。此外还计算了复合筒在复合加载下的承载力特性,发现H和T存在耦合效应,V在一定程度上可提高H和T的承载力。     

筒形结构抗屈曲加劲肋优化设计

针对风电塔筒极易发生屈曲破坏的问题,以筒形结构抗屈曲加劲肋设计为例,提出了一套集成化风电塔筒抗屈曲加劲肋设计方法。采用APDL语言进行建模和加载,自动提取屈曲计算结果作为参数,建立优化的状态变量和目标函数,采用零阶函数对数目众多且离散的变量进行优化,并可提供多组可行数据供用户比对分析。算例分析表明,该方法有效可行。     

A new approach to instability testing of shells

In this paper, a new experimental technique for the buckling test of shells under external pressure is presented. This technique is simple and determines buckling load very efficiently. It has already been used extensively in the investigation of buckling load of electroformed sphericaltip conical shells under uniform external pressure. In this method, instead of the conventional monitoring of load and linear displacement of points on a shell, load and change in internal volume of the shell are recorded. Internal volumetric change of a shell is found to be a better indicator of its instability compared to the change in displacements of points on its surface. Volumetric change, a function of all the displacements and rotations contributing to the total change in its configuration, is observed to be a highly magnified indicator of shell deformation encompassing the whole shell, primarily the buckling zones and imperfection locations.     

吸力式桶形基础负压安装的渗流侵蚀过程研究

针对吸力式桶形基础负压安装渗流侵蚀效应,建立轴对称坐标下吸力桶在砂性土中负压沉贯的数值模型,应用包含土骨架、流体和液化土颗粒的三相耦合模型描述海床土体,计算负压作用下海床的渗流场分布,并模拟负压引起的渗流侵蚀过程.渗流侵蚀可改变不同区域土体的渗透率,进而引起水力梯度从内侧向外侧转移.基于孔隙水压力场的重新分布,揭示出负...     

Buckling of stiffened plates and design of stiffeners

This paper presents a closed-form solution of critical instability stresses for simply supported rectangular plates with an arbitrary number of stiffeners in longitudinal and/or transverse directions. It is shown that there are only two buckling modes that are coupled to each other for single direction stiffened plates and four for double direction stiffened plates. The coupling of buckling modes represents the feature of interactions of global and local buckling modes. It is also shown that stiffeners have twofold effects on the critical instability stress, one is by enhancing the “stiffness”, the other is by changing the buckling mode. Because of the twofold effects it becomes difficult to apply the conventional optimum method to design the stiffeners and the optimum design of stiffeners still remains a difficult problem. This paper discusses the way by which the stiffeners can effectively enhance the buckling resistance of plates.     

Thermal buckling analysis of FGM sandwich truncated conical shells reinforced by FGM stiffeners resting on elastic foundations using FSDT

This work presents an analytical approach to investigate the mechanical and thermal buckling of functionally graded materials sandwich truncated conical shells resting on Pasternak elastic foundations, subjected to thermal load and axial compressive load. Shells are reinforced by closely spaced stringers and rings, in which the material properties of shells and stiffeners are graded in the thickness direction following a general sigmoid law distribution and a general power law distribution. Four models of coated shell-stiffener arrangements are investigated. The change of spacing between stringers in the meridional direction also is taken into account. Two cases on uniform temperature rise and linear temperature distribution through the thickness of shell are considered. Using the first-order shear deformation theory, Lekhnitskii smeared stiffener technique and the adjacent equilibrium criterion, the linearization stability equations have been established. Approximate solution satisfies simply supported boundary conditions and Galerkin method is applied to obtain closed-form expression for determining the critical compression buckling load and thermal buckling load in cases uniform temperature rise and linear temperature distribution across the shell thickness. The effects of temperature, foundation, core layer, coating layer, stiffeners, material properties, dimensional parameters and semi-vertex angle on buckling behaviors of shell are shown.     

超大功率风力发电机组塔筒屈曲分析

以某型8 MW风力发电机组塔筒为对象,采用有限元方法开展超大功率风力发电机组塔筒屈曲特性分析.建立塔筒门洞段有限元模型,研究门框对塔筒屈曲稳定性的影响,结果表明:门洞加框能提高塔筒屈曲稳定性.为进一步提高塔筒屈曲稳定性,提出塔筒内壁设置加强筋的强化设计方法,研究加筋数目、加筋尺寸与塔筒屈曲稳定性的作用规律,结果表明:环...     

不同海况下近海超大型风力机动力学响应及结构损伤分析

以超大型DTU 10 MW单桩式近海风力机为研究对象,通过p-y曲线和非线性弹簧建立桩-土耦合模型,选取Kaimal风谱模型建立湍流风场,基于P-M谱定义不同频率波浪分布,并利用辐射/绕射理论计算波浪载荷,采用有限元方法对不同海况下单桩式风力机进行动力学响应、疲劳及屈曲分析。结果表明：不同海况波浪载荷作用下塔顶位移响应及等效应力峰值远小于风及风浪联合作用,其中风浪联合作用下风力机塔顶位移响应及等效应力略小于风载荷;波浪载荷对风载荷引起的单桩式风力机动力学响应具有一定抑制作用,此外相较于波浪载荷,风载荷为控制载荷;风载荷与风浪联合作用下风力机等效应力峰值位于塔顶与机舱连接处,波浪载荷风力机等效应力峰值位于支撑结构与桩基连接处;仅以风载荷预估风力机塔架疲劳寿命将导致预估不足;随着波浪载荷的增大,风力机失稳风险加大,波浪载荷不可忽略;不同海况下,风浪联合作用局部屈曲区域位于塔架中下端,在风力机抗风浪设计时,应重点关注此处;变桨效应可大幅降低风力机动力学响应、疲劳损伤及发生屈曲的风险。     

Buckling behaviour of imperfect ring-stiffened cone–cylinder intersections under internal pressure

Cone–cylinder intersections are used commonly in pressure vessels and piping. In the case of a cone large end-to-cylinder intersection under internal pressure, the intersection is subject to a large circumferential compressive force. While both the cone and the cylinder may be locally thickened to strengthen the intersection, it is often desirable and convenient to provide an annular plate ring at the cone-to-cylinder joint to supplement local thickening or as an alternative strengthening measure, leading to a ring-stiffened cone–cylinder intersection. Only limited work has been carried out specifically on ring-stiffened cone–cylinder intersections under internal pressure. This paper presents the first experimental study on such intersections. In addition to the presentation of test results including geometric imperfections, failure behaviour and the determination of buckling mode and load based on displacement measurements, results from nonlinear bifurcation analysis using the perfect shape and nonlinear analysis using the measured imperfect shape are presented and compared with the experimental results.     

Design by analysis of deep-sea type III pressure vessel

This paper explores the potential of hydrogen as an energy carrier for deep-sea applications. Finite element analysis of a type III pressurised cylinder to the intended working pressures of 300 bar internal and up to 600 bar external were carried out for different designs and safety factors. Design parameters such as helical angle, liner, helical, and hoop thicknesses were studied and optimised. A buckling analysis was carried out for the optimised designs and recommendations to increase the maximum allowable external pressure are given.     

利用特制传感器预警输电塔失稳的试验研究

针对输电线路中铁塔地基不均匀沉降造成的倒塔事故,基于传感器的受力特性,提出了利用应变式传感器传输铁塔主材的受力情况,并通过室内压力和拉力试验建立了传感器输出值与所加外荷载的关系式,以此来判断铁塔的失稳临界状态。结果表明,该方法及时、准确,可有效避免倒塔事故的发生。