风机基础分层事故的检测鉴定及加固处理

某工程7座风机基础在浇筑过程中,施工缝处理不当,基础存在分层。通过钻芯、地质雷达探测等方法对混凝土密实度进行了检测;并考虑风机基础结构和荷载的特殊性,分析分层面对基础承载能力的影响;综合检测和分析结果评价了各基础的安全性;对于安全性不满足要求的基础,提出压力注浆和在分层面增设抗剪键的加固方案,取得良好加固效果,现基础已安全运行2年;此外,对风机基础分层问题的防治提出了可行建议。     

Resonance Phenomena in Foundations Supporting Turbine-Driven Sets and Their Consideration in Dynamic Structure Analysis

Characteristic features of the dynamic performance of foundations supporting turbine-driven sets in thermoelectric power plants, which have been revealed in various experimental and theoretical research, including our own, are generalized. Among them, the vibration modes of the foundation components and their interrelation with the parameters of the effective dynamic loads are of determining significance. A new approach to dynamic analysis of turbine foundations, which takes these factors into account, is proposed. The proposed analysis is confirmed for a foundation segment in the form of a four-pedestal spatial frame.     

大型风电机组群桩基础受荷特性及长期累积沉降控制

大型风电机组基础顶部的巨大倾覆弯矩是其承受的主要荷载,该倾覆弯矩将转化为单桩顶部的竖向作用力。由于风的周期性,作用在风电机组群桩基础顶部的荷载具有明显的循环特性。循环荷载作用下风电机组基础将产生不均匀沉降并倾斜,因而累积沉降控制是风电机组基础设计中的关键问题之一。分析了风电机组及其群桩基础的受荷特点,计算了典型风电机组的桩顶循环荷载谱。通过桩基循环模型试验发现桩顶循环荷载比小于临界值λmin时,桩顶无累积沉降发生,因而保证风电机组循环荷载比小于该临界值则可较好地控制风电机组基础的长期不均匀沉降。根据试验结果建立了偏压条件下桩基累积沉降与循环次数的关系,用于预测风电机组基础的长期附加不均匀沉降。     

海上风机部分埋入群桩水平-摇摆振动与结构共振分析

对于海上风机部分埋入群桩基础,风机结构的高度将导致基础承受较大的倾覆力矩,因而在风机振动分析中需要考虑到基础的摇摆特性。为避免发生共振,风机结构第一阶自振频率应避开风轮转动频率（1P频率）和叶片通过频率（3P或2P频率）。目前关于风机结构动力特性的研究常常以底部刚性固定为假定,忽略了地基基础的影响,因而可能带来误差。结合既有研究成果,推导简化解析方法研究了部分埋入群桩基础的水平-摇摆耦合振动特性以及基础阻抗对风机结构共振特性的影响。首先,推导了采用动力Winkler地基模型的部分埋入群桩基础水平-摇摆动力阻抗,与精确解进行对比,验证了方法的正确性;其次,考虑基础阻抗的作用,推导了风机结构水平-摇摆振动方程;最后,通过简化方法和频域有限元方法对不同地基条件下某风机结构的共振特性及基础阻抗进行了计算和对比,研究了基础阻抗对结构共振特性的影响,并验证了简化方法的正确性。     

风浪联合作用下的钢格构式基础海上浮式风机耦合动力响应分析

结合半潜式和单立柱式海上风机浮式基础的特点,提出了一种用于海上风机的新型钢格构式基础.首先,根据美国可再生能源实验室(National Renewable Energy Laboratory,NREL)提供的5 MW海上风机样机对提出的新型浮式基础进行了结构设计.然后,采用水动力-空气动力-控制系统-系泊系统耦合方法对...     

水平受荷大直径单桩的桩土作用分析

大直径单桩现广泛应用于近海风电基础中。为抵抗水平推力,采用在桩侧设置翼缘的办法。通过建立大直径薄壁钢管桩三维有限差分模型,对水平推力作用下的大直径单桩的桩-土作用进行分析,并考虑桩侧翼缘对桩-土相互作用规律的影响。最后对翼缘进行参数分析,得出一些对工程实际有益的结果。     

Vertical dynamic impedance of suction caissons

Nowadays, suction caissons are being increasingly deployed as foundations to support offshore wind turbines (OWTs). Due to the overturning moment induced by waves and wind, vertical forces are the dominating ones acting on these foundations. In this study the dynamic stiffness and damping coefficients of suction caissons embedded in a viscoelastic soil layer over bedrock, subjected to vertical dynamic load were investigated. Numerical analyses of representative 3D finite element models were performed, while the numerical modelling was validated against existing analytical solutions for end bearing piles. The vertical dynamic response of suction caissons was evaluated by considering the effects of the foundation’s geometry, i.e. the slenderness ratio, and the stiffness of the soil layer on the vertical dynamic impedance of suction caissons. Results showed that the overall dynamic response is profoundly affected by the skirt length and by the variation of soil stiffness with depth.Mathematical expressions of the dynamic stiffness and damping coefficients were derived pertaining to foundations with various slenderness ratios and embedded in different soil profiles. The proposed expressions can be implemented in structural models used for the dynamic analysis of the support structure of a wind turbine, taking thus into consideration the effects of soil-structure-interaction.     

Complex dynamic investigations of foundations for low-speed turbine units at nuclear power plants

Conclusions 1. Dynamic tests indicated that the dynamic flexibility of both types of foundations diminishes on the whole as the equipment is assembled.2. During the startup and output adjustment of a turbine unit on both a foundation with lateral condensors and a foundation with basement condensors, the TFB system will itself be at relative rest. Acute resonance peaks are not observed and the vibration levels of the foundations do not exceed allowable values.Dniepropetrovsk Civil Engineering Institute. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 4, pp. 11–14, July–August, 1985.     

Cone-shaped hollow flexible reinforced concrete foundation (CHFRF) – Innovative for mountain wind turbines

This paper presents an innovative type of mountain wind turbine foundation, namely, the cone-shaped hollow flexible reinforced concrete foundation (CHFRF). It consists of a top plate, a base plate and a side wall that are made of reinforced concrete. The cavity of the CHFRF is filled with rubble and soil directly from the excavation for the CHFRF, which means that it can absorb the spoil. A rubber layer is placed beneath the CHFRF to increase the foundation flexibility to resist cyclic and dynamic loadings and to increase the bearing capacity. The great advantages of the CHFRF are the reduction in the usage of concrete and steel and the protection of the vegetation around the wind turbine, compared with conventional mountain wind turbine foundations that are solid structures. It is verified through model tests and a numerical simulation that the CHFRF can provide higher lateral bearing capacity in comparison to the regular circular gravity-based foundation under the same foundation diameter and height, and that the bearing capacity is increased by approximately 33.5% accordingly. It is also found that the rubber layer can effectively reduce the accumulated rotation of the CHFRF under cyclic loading. The accumulated rotation of the CHFRF with a rubber layer having a thickness of 4 mm is decreased by about 50% compared to that of the CHFRF with a rubber layer having a thickness of 2 mm. In addition, the volume of concrete used for the CHFRF is only one-fifth of that used for the circular gravity-based foundation. Therefore, the CHFRF outperforms regular mountain wind turbine foundations.     

Improved design of tubular wind tower foundations using steel micropiles

The constant increase in the wind power production leads to the need of higher wind towers, which brings up some questions regarding the effectiveness of tubular towers and respective foundations. This work focuses on the comparative structural design, life cycle behaviour and costs of onshore concrete shallow foundations for tubular wind towers (WT) when steel micropiles are used to improve resistance of the soil–structure interface (hybrid foundation). Typical wind loading for Turbine Class II and moderate seismicity (.25 g peak ground acceleration) is used to design and analyse 18 WT foundation case studies. This allows the comparison between shallow and hybrid foundations designed for three different hub heights and respective turbine rated power (80 m/2 MW, 100 m/3.6 MW and 150 m/5 MW) and for three different tubular tower solutions (steel, concrete and hybrid steel–concrete). The possible benefits of the solution using steel grouted micropiles are discussed in terms of potential environmental and economic impacts using life cycle analysis. The use of micropiles reveals to be an interesting solution to improve common shallow WT foundations since it allows the reduction of the dimensions of the foundation leading to significant environmental and cost benefits.     

高转速压缩机基础设计的几个问题

简捷全面地概述了n>3000r/min的高转速透平压缩机基础的设计与计算历程、振动实例,单自由度、多自由度简化计算以及不作动力计算的论据,对基础构造设计提出若干实用性的建议,为读者提供了修订《动规》(GBJ40-79)第六章透平压缩机基础的背景材料.     

Full-scale investigations of the static deformations of foundations below 1000-MW turbine units at nuclear power plants under construction

Conclusions 1. Systematic geodesic observations of static deformations should be organized in constructing foundations for turbine units at high-capacity nuclear power plants; the results of these observations will ensure attainment of the required operational control data during construction and operation.2. During the design of these foundations, it is necessary to consider the installation of special surficial and deep marks for the organization of observations on bed settlement, beginning from the moment when the lower concrete slab is poured.3. In placing distributive cushions for the foundations, it is necessary to provide for a high quality of compaction within the bounds of the entire lower surface of the foundation and for careful geotechnical control.4. In designing foundations for turbine units on inhomogeneous beds, we should consider the difference in the rheological properties of the soils, the character and sequence of bed loading, and the variations in its hydrogeologic regime in order to exclude nonuniform settlements during equipment assembly and operation of the machinery.Dniepropetrovsk Civil Engineering Institute. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 4, pp. 8–10, July–August, 1985.     

Bearing Capacity and Failure Mechanism of Different Types of Foundations on Sand

Performance-based design has slowly been adopted for the use in geotechnical design. In the future, various types of foundations suitable for a variety of soils and applications should be accepted as an alternative to conventional flat foundations for the increase of bearing capacity and the savings of materials. The concept of shells is not new in foundation design, considering the construction with inverted brick arch foundation. Shell foundations are economic alternatives to conventional flat foundations where heavy superstructural or lateral loads are to be transmitted to weaker soils. Various types of foundations with different geometrical shapes have been extensively investigated in the structural design. However, the corresponding studies on the geotechnical design in terms of bearing capacity and deformation are scare. As such the advantages of various types of foundations have not yet been clarified in terms of the geotechnical design. The objective of this paper is to examine the overall geotechnical performance of various types of foundations on sand using model loading tests and the numerical limit analysis. The general superiority of various types of foundations has been revealed by comparing the loading tests with the analytical results.     

土动力学与岩土地震工程

近年来,随着交通和能源基础设施建设的快速发展,循环动载引起的工程问题使得土动力学与岩土地震工程的研究面临许多新的课题。文章简要评述土动力学与岩土地震工程在国内外的研究现状,着重讨论土的剪切模量、高速铁路路基动力响应及累积沉降、土体地震液化、地下结构地震响应及其抗震设计、跨海桥梁与海上风电基础的动力学问题等方面的最新进展,并进一步阐述今后研究的方向。     

Structural monitoring of an onshore wind turbine foundation using strain sensors

To date, the vast majority of onshore wind turbines are cast integrally with the foundations through embedded rings. Local damage around the bottom flange of the embedded ring was observed in a large number of existing foundations. Wind turbine foundations lack structural redundancy. The tower-foundation interface is the weak point and the deterioration of the interface will reduce the foundation’s effectiveness. This study is focused on structural health monitoring of a 1.5-MW onshore wind turbine foundation with embedded ring, on the basis of strain signals acquired continuously from the turbine foundation. A strain sensor monitoring system was installed in field to monitor the concrete status by measuring strain patterns and subsequently alerting any abnormal state of concrete in long term. It was integrated with a dynamic strain acquisition system to develop a real time relationship between the behaviour of local concrete deformation and the characteristics of loads exerted on the foundation. The performance of the foundation was simulated through numerical calculations. The results obtained from the sensors, numerical model and environmental operating data showed that the wind speed and direction dominated the loads exerted on foundation and local concrete deformation inside the foundation. The concrete deformation varied around the circumference of the embedded ring resulting from changes of wind direction and rotor position. The overall distribution pattern correlated roughly with peaks and troughs of calculated forces as well as the mean wind speed. Moreover, cracks were detected to occur in both sides of the bottom flange of the embedded ring and those cracks outside the flange were observed to fluctuate correlated to the change of wind speed. The field test demonstrates that the long-term monitoring of the local concrete deformation is necessary to ensure the safety of the foundation.     

Comparison of the dynamic responses of monopiles and gravity base foundations for offshore wind turbines in sand using centrifuge modelling

Monopiles and gravity base foundations (GBF) are two of the most commonly used foundations for offshore wind turbines. As resonance can cause damage and even failure of wind turbines, understanding the difference between the dynamic responses of monopiles and GBFs under free vibration is important. However there is little experimental data regarding their natural frequency, especially from model tests carried out at correct stress levels. This paper presents the results of novel monopile and GBF tests using a centrifuge to directly determine the natural frequency (f_n) of the foundation-soil system. The natural frequencies of wind turbine monopiles and GBFs in centrifuge models were measured during harmonic loading using a piezo-actuator, with the results confirming that soil-structure interaction must be considered to obtain the system’s natural frequency as this frequency reduces substantially from fixed-base values. These results will contribute in preventing resonance induced damage in wind-turbines.     

毗邻旧厂房的多层钢结构厂房基础的设计与分析

在旧厂房改扩建中,由于工艺要求新建建筑物基础毗邻,而旧厂房的基础又不能承受新的荷载,这对新厂房基础的设计提出新的要求。依据工程实例介绍采用转换梁设计和施工方法,可供同类工程借鉴。     

水平-竖向-扭转荷载下吸力沉箱基础承载特性数值研究

海上风机吸力沉箱基础承受结构自重及环境因素引起的竖向、水平、扭转荷载,处于复合加载状态。以位于饱和黏土地基上长径比为0.25～1.0的单桶沉箱基础为对象,ABAQUS为计算工具,研究沉箱基础的承载特性,并考虑沉箱与地基土的摩擦接触作用。首先分析沉箱基础在单一的竖向荷载、水平荷载及扭转荷载作用下的极限承载力,并给出沉箱基础在这些荷载组合下的破坏包络面,其中倾覆力矩通过施加偏心水平荷载实现。结果表明,沉箱基础的竖向承载力可用改进的经典承载力公式计算,而水平承载力系数在给定的接触条件下随沉箱长径比增加而减少,扭转承载力与理论预测结果非常吻合;扭转荷载对沉箱的竖向承载力影响较大,但对水平承载力影响较小;不同扭转荷载下的V-H包络面可用椭圆曲线拟合。     

具有双重抗摇摆机制的浮式风机基础水动力性能研究

结合Spar基础和半潜式基础的浮态稳性特点,提出了一种具有双重抗摇摆机制的浮式风机基础.采用DTU-10 MW风机机组参数,对提出的新型浮式风机基础进行了方案设计.基于Morison方程和势流理论,分析了其在不同波浪入射角以及波浪周期下的水动力响应参数,包括运动响应幅值算子和波频力(矩)传递函数等.结果表明提出的浮式风...     

风电塔筒基础的设计研究

风电塔筒与基础连接一般采用地脚螺栓,因个别螺栓拧紧时断裂,处理较困难,有的工程改为埋入式基础.即在基础内埋置一段钢筒,与上部塔筒采用高强螺栓法兰盘连接,螺栓即使拧断,也可轻易更换.但这种基础受力较差,国内外均有整体拔出时出现倒塌事故的案例,且造价也较高.对风电塔筒基础设计进行研究,采用合理的地脚螺栓连接形式,可避免预埋...