Cyclic bending performance of joint on precast composite hollow RC for submerged floating tunnels

In case of a submerged floating tunnel (SFT), which is difficult to cast in-site underwater construction, it is modularized on land and then assembled them in the field. Therefore, it is influential to investigate the structural performance of the joints between the modules. A concept of the steel-concrete composite hollow in the SFT, which stably maintains the joints, has been proposed by applying prestressing method to resist various external loads. In this study, the bending behavior of module joints was experimentally analyzed to evaluate the safety for the bending deformation that is dominant in SFT. Test results show that there is a difference at the module joint portion in the performance depending on whether or not the inner steel tube is connected. The bending stiffness of the module joints in the SFT was very similar but there was a difference in strength. The maximum strength was increased from 700 kN to 1200 kN when the inner tube was connected, and the residual displacement was increased from 15 mm to 40 mm. As a result, in the design of the module joint, depending on the purpose of SFT, it is possible to consider both methods which is allowing the ductility behavior of internal tube and controlling the tight connection. Moreover, the failure criterion of the bending behavior of the module joint can be selected as the maximum load or deformation limit.     

轴法兰螺栓安装失效机理分析

某船在安装过程中发现轴法兰螺栓联接副存在不同程度的咬合。通过现场检查和计算分析,确认螺栓安装失效机理在于加工孔时刀具装夹不正,造成轴法兰沉孔的平面度超差,在对螺栓施加拧紧力矩时,螺栓联接副接触应力超过轴材料屈服强度,从而形成咬合。本文以经典计算和有限元计算作为支撑,揭示了形位公差对螺栓联接的影响,通过控制螺栓联接副的形位公差,同时建议采取适当的防咬合措施,可避免螺栓在安装时发生失效。     

固定式近岸风机导管架结构完全重叠节点的极限强度研究（英文）

This paper presents an innovative eccentric jacket substructure for offshore wind turbines to better withstand intense environmental forces and to replace conventional X-braced jackets in seismically active areas. The proposed eccentric jacket comprises of completely overlapped joint at every joint connection. The joint consists of a chord and two braces in a single plane. The two braces are fully overlapped with a short segment of the diagonal brace welded directly onto the chord. The characteristic feature of this joint configuration is that the short segment member can be designed to absorb and dissipate energy under cyclic load excitation. The experimental and numerical study revealed that the completely overlapped joint performed better in terms of strength resistance, stiffness, ductility, and energy absorption capacity than the conventional gap joints commonly found in typical X-braced jacket framings. The eccentric jacket could also be designed to becoming less stiff, with an inelastic yielding and local buckling of short segment member, so as to better resist the cyclic load generated from intense environmental forces and earthquake. From the design economics, the eccentric jacket provided a more straightforward fabrication with reduced number of welded joints and shorter thicker wall cans than the conventional X-braced jacket. It can therefore be concluded based on the results presented in the study that by designing the short segment member in accordance with strength and ductility requirement,the eccentric jacket substructure supporting the wind turbine could be made to remain stable under gravity loads and to sustain a significantly large amount of motion in the event of rare and intense earthquake or environmental forces, without collapsing.     

A study of fatigue crack propagation at a web stiffener on a longitudinal stiffener

Predicting fatigue crack growth after its detection during in-service inspection is necessary to prevent a loss of serviceability, such as the oil and/or water tightness of critical compartments. This paper focuses on the most typical fatigue cracks that start at the weld joint between a flat bar stiffener on a transverse web frame and the flange of a longitudinal stiffener on a bottom plate or inner bottom plate. An experiment is carried out to observe the fatigue crack propagation for two kinds of flat bars at the abovementioned connection. The experimental results, especially the surface crack growth on the flange (which dominates during the total fatigue life of the longitudinal stiffener), are compared with crack growth curves predicted using a few existing formulas. Based on the comparative study, a formula that shows the best agreement with the experiment results is selected. Weld toe magnification factors for the web stiffener are computed from the crack propagation rates measured in the experiment, and two equations for the magnification factors versus crack depth are developed for two types of web stiffeners. The selected existing formula and the proposed equations are applied to two connections at the inner bottom and side longitudinal bulkhead of an LNG carrier. The equivalent stress approach based on a long-term distribution is employed to avoid the complexity involved in dealing with the actual stress history. Using this prediction, the remaining service life until an oil or water leakage occurs at a tank boundary can be estimated when a fatigue crack at the connection is detected.     

Capacity and failure mechanism of monopile-wheel hybrid foundation in clay-overlaying-sand deposits under combined V–H-M loadings

Innovative monopile-wheel hybrid foundations are proposed to enhance the lateral load and moment capacities of monopile for offshore wind systems. This paper presents a comprehensive numerical study on the bearing capacities of this hybrid foundation in clay-overlaying-sand soil conditions under combined V–H-M (vertical-horizontal-moment) loadings. Numerical models are generated and validated by comparing with laboratory experiment results and available centrifuge testing data on similar foundation systems. Parametric analysis is then carried out to quantify the effects of potential influencing factors on the failure mechanisms and bearing capacities of hybrid foundations, including the hybrid foundation geometry, soil properties, upper clay thickness, height of the lateral loading and pre-vertical load. It is found that in clay-overlaying-sand deposits, the hybrid system manifests totally different failure mechanism compared with that in uniform soil deposits. The thickness of the upper clay layer (T_c/L), within the practical range of T_c/L = 0.1–0.7, has a significant influence on the failure patterns and the bearing capacities of the hybrid system, and the proportion of bearing capacity provided by the pile and wheel is determined by the ratios of D_w/L and L/D_p. In addition, the failure envelopes in the V–H-M space manifests that the failure envelopes are shrank with the increase of the normalized vertical resistance, V/V_ult, which is highly related to the clay layer thickness (T_c/L).     

Laser-welded web-core sandwich plates under patch loading

This paper presents an approach to the structural analysis of patch-loaded, laser-welded web-core sandwich plates. This approach is especially suitable for the concept design phase of ship structures. The method consists of two parts; the global bending response is evaluated using sandwich plate theory and the local response of the patch-loaded face plate is determined with the help of basic plate theory. Both analyses utilise analytical and numerical methods and include the effect of the rotation stiffness of the laser-welded T-joint between the face and web plate. Combining the results of these two analyses gives the total response of the web-core sandwich plate. The results of the proposed approach are compared to those given by 3D solid and shell element FE analyses and the agreement of deflections and normal stresses is found to be good. The sensitivity of the response to patch-load size, T-joint rotation stiffness, and plate aspect ratio is studied. The main benefits of the proposed approach are its short analysis time and the good accuracy of deflections and stresses. This considered advantageous when applied to the design of large ship structures such as hoistable car decks.     

邮轮高腹板梁开孔应力分析

针对邮轮的甲板纵桁和横梁的腹板布置大量开孔,开孔削弱腹板截面尺寸,并且次弯距的影响显著,引起开孔边缘出现应力集中的问题,结合船级社规范开孔规则要求,采用有限元法分析开孔尺寸、开孔位置和补强方式对孔周切向正应力的影响,结果表明,孔周切向正应力对于开孔高度变化的敏感度大于开孔长度变化;当开孔的垂向位置越偏向面板时,孔周切向...     

平面框架结构中变截面杆件的刚度计算

矩形截面抛物线楔形梁作为一种变截面杆件在平面框架结构中经常使用。本文通过求矩形截面抛物线楔形梁的单元柔度系数、刚度系数,提出了平面框架结构中矩形截面抛物线楔形梁的单元刚度矩阵。     

弹性地基梁弯矩系数的影响因素

针对文克尔地基上的两种不同断面(矩形和倒梯形)的弹性地基梁,分析了地基反力系数、外加荷载、混凝土强度等级以及梁的长高比、宽高比等因素对弯矩系数的影响规律。结果表明:弯矩系数随着地基反力系数的增加而减小,随着混凝土强度等级的增加而增加,随着梁长高比的增加而减小,随着外加荷载和梁的宽高比的增加不变;同等条件下,倒梯形断面形式的地基梁在受力方面优于矩形断面形式梁。     

门机臂架纵筋失效对其局部稳定性和动刚度的影响

定量分析箱型结构起重臂下翼缘纵向加劲杆失效对其局部稳定性和动刚度的影响 ,揭示港口门机普遍存在的起重臂受压翼缘板波浪度增大及振动加剧这 2种现象之间的内在联系 ,指出提高其振动基频的有效方法。     

玄武岩纤维布加固连续梁弯矩重分布特征分析

对4根玄武岩纤维布加固的混凝土 T 形截面连续梁和1根对比梁进行抗弯试验,分析了试验梁的破坏模式和各控制截面的弯矩调幅系数.试验结果表明：加固梁跨中截面纵筋屈服前,加固梁和对比梁各控制截面荷载-挠度曲线基本重合;跨中截面纵筋屈服后,加固梁发生了明显的弯矩重分布,跨中截面弯矩调幅系数为0.09~0.22,中支座截面弯矩调幅系数为0.15~0.38;1~3层纤维布加固梁荷载-挠度曲线具有屈服平台,表现出明显的延性破坏特征.     

Static and dynamic loading behavior of a hybrid foundation for offshore wind turbines

Considering the deficiencies of the traditional monopile foundation for offshore wind turbines (OWTs) in severe marine environments, an innovative hybrid foundation is developed in the present study. The hybrid foundation consists of a traditional monopile and a wide–shallow bucket. A series of numerical analyses are conducted to investigate its behavior under the static and dynamic loading, considering various loading eccentricities. A traditional monopile with the same steel volume is used as a benchmark. Although the monopile outperforms the hybrid foundation in terms of the ultimate moment capacity under each loading eccentricity, the latter can achieve superior or the same performance with nearly half of the pile length in the design loading range. Moreover, the horizontal load and moment are mainly resisted by the bucket and the single pile in the hybrid foundation respectively. The failure mechanism of both the hybrid foundation and the monopile is excessive rotation. In the rotation angle of 0.05 rad, the rotation center is located at the depth of approximately 0.6–0.75 times and 0.65–0.75 times the pile length for the hybrid foundation and the monopile respectively. The increasing loading eccentricities can lead to increasing moment bearing capacity, increasing initial stiffness and upward movement of the rotation center of the two foundations, while decreasing load sharing ratio of the single pile in the hybrid foundation. Three scenarios are considered in investigating the dynamic loading behavior of the hybrid foundation. Dynamic response results reveal that addition of the bucket to the foundation can restrain the rotation and lateral displacement effectively. The superiority of the hybrid foundation is more obvious under the combined wave and current loading.     

外接平板型金属夹层结构连接构件极限强度分析

激光焊接钢质夹层结构在国外已用于实船,其连接形式是亟待解决的关键问题之一。基于有限元分析软件ANSYS,研究了面内载荷作用下,I型金属夹层结构外接平板型连接构件的失效模式和极限承载能力,以及5种典型初始缺陷的尺寸和连接构件的设计参数对极限载荷的影响规律。结果显示,连接构件较短时,结构失效的主导因素是焊接接头形成了塑性铰;连接构件较长时,主导因素是连接构件失稳。对于各种类型的初始缺陷,随初始缺陷尺寸的增大,极限载荷均降低;连接构件、以及靠近连接构件的夹层面板和夹层腹板的初始缺陷对极限载荷的影响较大。在控制重量的条件下,欲增大极限承载能力,最有效的途径是增大连接构件厚度,并选取合适的连接构件长度。     

中美规范港区水泥混凝土面板接缝设计对比

针对国内外规范关于港区水泥混凝土面板接缝设计存在较大差异的问题,对比中、美规范在接缝形式、间距和荷载传递机制的异同点,并通过调研和有限元计算分析温度、地基刚度和荷载对接缝的影响,提出采用限制板长和相对刚度半径比与板块应力分析相结合的方法确定接缝间距。结果表明,水泥混凝土面板应少设或不设胀缝,且接缝应带有传力杆,以便更好地传递荷载。     

预应力混凝土曲线梁桥几个问题研究

曲线梁桥是弯扭耦合作用下的空间受力结构,现行桥梁规范所包括的内容滞后于桥梁的发展,平面分析的方法已不适用。文中对曲线梁桥的弯扭耦合效应、内外梁体受力不均以及恒载作用下结构产生较大的转矩等受力特点进行了分析。分析结果表明：曲线梁桥中间支承方式的设定不能改变支座的反力,外侧腹板弯矩内力均大于内侧腹板的弯矩内力,曲线半径越小,变化幅度越大。     

设备典型接合面的刚度线性化处理方法研究

舰艇设备结构复杂,存在大量的接合面,冲击载荷通过接合面来传递,因此接合面的动力学特性模拟是冲击情况下舰艇设备动响应计算的关键技术。文章选取一舰艇设备进行有限元模拟,利用刚度等效与动力等效的方法对设备典型接合面间的刚度进行线性化处理。利用试验获得的设备基础冲击环境数据作为输入载荷,采用动力设计分析方法对设备进行动响应计算,并与试验结果进行对比,结果表明文中给出的接合面刚度线性化处理方法满足工程需要。     

浮式平台上部模块非管节点SCF控制方法

应力集中系数（Stress Concentration Factor，SCF）是评估节点疲劳损伤的重要参数。针对浮式平台上部模块非管节点的SCF控制，设计5种加强形式，采用Ansys软件对非管节点进行SCF分析。结果表明：筋板加强可有效改善面外弯矩作用下的应力集中；扣管加强对轴向力、面内弯矩和面外弯矩均具有较好的改善效果。     

Local joint flexibility of tubular T/Y-joints retrofitted with GFRP under in-plane bending moment

In the present paper, the Local Joint Flexibility (LJF) of tubular T/Y-joints retrofitted with Glass Fiber Reinforced Polymer (GFRP) under IPB moment is studied and discussed. For this aim, a finite element (FE) model was generated and verified with the results of available experimental data and parametric formulas. Afterward, a set of 158 finite element (FE) models was created to evaluate the efficacy of the FRP sheets (number, length, and orientation), the brace inclination angle (θ), and the non-dimensional parameters (β, τ, and γ) on the LJF coefficient (f_LJF) and the f_LJF ratio of the retrofitted to the associated un-retrofitted joint. In the FE models, the efficacy of the weld profile and the contact between the FRP and the steel members (chord, weld, and brace) was considered. Also, analysis of variance (ANOVA) is used to identify the most dominant parameters which affect the f_LJF ratios. Results showed that in the retrofitted joints, the increment of the FRP sheet number results in the notable drop of the f_LJF. But, the efficacy of the FRP sheet orientation on the f_LJF can be ignored. Despite the considerable efficacy of the FRP sheets on the behavior of the tubular joints, there was not any study on the LJF in the joints retrofitted with FRP. Hence, after an extensive parametric study, the results were used to derive a parametric equation for determining the f_LJF of T/Y-joints retrofitted with FRP. Moreover, the derived equation was checked according to the UK DoE acceptance criteria.     

砂性地基自动化集装箱堆场ARMG基础分段长度

弹性地基梁具有施工速度快、经济效益高、结构刚度大等优点,是目前自动化集装箱堆场ARMG基础的优选方案。依托某境外砂性地基上的自动化集装箱堆场工程,利用有限元软件建立不同分段长度的ARMG基础模型,分析了弹性地基梁对分段长度、地基不均匀沉降和温度的敏感性。结果表明,在ARMG轮压作用下,弹性地基梁的弯矩和接缝剪力随梁长增大而增大,梁长超过10 m后,梁内弯矩和接缝剪力趋于稳定;当地基发生不均匀沉降时,梁长越大ARMG基础对不均匀沉降的适应性越强,梁长超过10 m后,梁内弯矩和接缝剪力趋于稳定;温度对梁内力影响较小,温度引起的弯矩随梁长增大而增大,当梁长大于25 m,温度引起的弯矩趋于稳定。     

Hinge joint damage identification method of soft yoke mooring system based on multibody dynamic modeling and structural monitoring data

Soft yoke mooring system (SYMs) is a single-point mooring system used in shallow water oil and gas development. In general, SYMs consists of mooring framework support, mooring legs, yoke, and single-point turret and it forms a multibody dynamic system with 13 hinge joint structures such as universal joints and thrust bearings. The hinge joint is one of the key components of SYMs; therefore, it is necessary to accurately evaluate the operating behavior of the hinge joints. In this study, real-time damage identification is conducted based on the multibody dynamic features of the SYMs. First, a long-term monitoring strategy for the prototype application is developed based on the multibody governing equations of the SYMs. The motion behaviors and stress state of the hinge joints and bodies are calculated using prototype monitoring data. A hinge joint damage identification based on the virtual moment is proposed by considering the changes in the friction coefficient in the damage state. The virtual moment method is used to transform the damage identification problem of the SYMs into a problem of seeking the optimal solution to the dynamics identification function. Genetic algorithm (GA) is implemented to seek the optimal solution of the friction coefficient of each hinge joint. A large-scale model testing system of the SYMs is established to perform the damage identification of the bottom hinge joints of the SYMs. The results show that the proposed method can effectively identify the damage degree and position of the hinge joints of the SYMs and provide a real-time warning system for the in-service operation of the SYMs.