An Application of Homogeneous Matrix Method of Multi-body System to the Dynamic Response of Floating Bridge

浮桥在快速移动重载作用下,荷载移动速度有可能接近甚至超过浮桥位移波的传播速度,这样就会造成移动荷载前方浮桥位移波的堆积效应.文中简要介绍了多体系统齐次矩阵方法,包括6个4×4阶动力学和运动学矩阵和它们之间的关系,并基于齐次矩阵方法对浮桥进行建模和求解.通过数值模拟和已有的模型试验都表明:当荷载的移动速度较大时,浮桥多体系统的运动呈现明显的波动现象,速度越大位移波的堆积越明显.     

波流联合作用下通载浮桥动力特性研究

为了研究波流环境中浮桥通载时的动力特性,探讨通载速度及波流联合作用对浮桥动力响应的影响,本文采用势流理论对浮桥所处流场的速度势进行分析,采用莫力森公式计算浮桥受到的水阻力,同时考虑多轴移动荷载的影响,建立系泊浮桥的时域运动方程;并对不同工况下浮桥的运动响应及系泊力进行了计算,在计算中考虑了瞬时湿表面变化对浮桥浮力及水阻力的非线性影响,通过计算得到了不同行驶速度、不同波况下浮桥各桥节的运动响应及系泊力时程曲线.结果表明:车辆行驶速度对浮桥桥节垂荡、纵摇响应及系泊力均具有明显影响,桥节垂荡、纵摇及上游系泊缆张力峰值随行驶速度增大而增大;通载浮桥中部桥节的系泊缆张力最大值小于两侧桥节系泊力最大值;波浪作用下桥节的运动响应及系泊力与车辆荷载引起的运动响应及系泊力具有一定程度的叠加效应,特别是垂荡响应的叠加效应更为明显;当波高较大时系泊力将由波浪作用控制.     

运动海床对近海风机单桩基础的影响

以东海大桥海上风电场为研究背景,首先基于Biot固结理论求解了不同波况下多层非均质土体的位移、超孔压的分布,讨论了波浪荷载对海床运动的影响。而后基于土体位移计算结果,应用支座位移加载法与p-y曲线法相结合的方法,求解了运动海床作用下近海风机单桩基础的内力和变形,并将其结果与不考虑运动海床作用的结果进行了对比。对比结果显示:运动海床对桩身的变形影响显著,设计中有必要进行运动海床作用下的变形校核。     

间隙对拼组式浮桥静态响应的影响分析

为了减小浮桥在通载状态下的结构内力及浮桥拼组拆卸的方便,拼组式浮桥通常在设计的时候就在舟节之间留有一定的连接间隙.在以往的分析中大多忽略了这种间隙对浮桥变形和受力的影响,而简单地将浮桥简化为连续或者铰接梁体系进行数值或者解析求解,这种方法并不能准确地给出桥节之间连接间隙的存在及其大小对浮桥静态响应的影响.本文以拼组式浮桥的连接间隙为研究对象,建立全桥分析的三维有限元模型,并用非线性单元的组合对浮桥连接件的力学特性进行有限元模拟,通过计算与试验结果的比较,表明了本文方法的正确性;在此基础上本文研究了浮桥在静载荷作用下的位移响应及不同位置的连接件内力与连接件间隙之间的关系,为此类浮桥的设计提供了必要的参考,并为其后续的动力分析提供了必要的理论依据.     

破碎波作用下直立堤的运动及其稳定性

分别建立了直立式防波堤与破碎波相互作用、防波堤的弹性振动、滑移运动和遥摆运动分析模型，对破碎波冲击作用下防波堤的弹性振动-滑移运动-摇摆运动过程进行了数值模拟，研究了各种运动对破碎波冲击力及其作用效应-防波堤的位移、转角、滑移力和倾覆力矩的影响。     

波浪作用下局部冲刷群桩动力特性试验研究

利用模型试验对深水桥墩群桩基础进行研究。用摇摆式造波装置施加波浪荷载,基于典型的冲刷坑形态,通过开挖桩周土体模拟不同的冲刷深度,探讨不同冲刷深度下桩基在波浪荷载作用下的动力反应。作为对比,同样进行了同参数下的单桩平行试验。研究结果表明:随着冲刷深度的增加,桩基础的自振频率逐渐降低,桩顶加速度和位移幅值呈增大趋势。桩基动力响应同时受水深的影响——随着水深的增大,位移和加速度也有所增加。在实际工程设计中,应该考虑桩基冲刷受损程度和水文条件的综合影响。     

波浪作用下考虑桩土相互作用的桩柱响应*

以一离岸深水桩柱为例,依据JTJ 2132—1998《海港水文规范》的环境条件和环境荷载规范,对桩柱进行有限元离散。在海洋深水环境条件下考虑流固耦合效应,计算了在海洋极端规则波以及不规则波条件下桩柱的运动响应;为了进一步研究分析泥面以下土体对桩柱运动响应的影响,对比分析了在考虑桩土耦合相互作用下桩柱的响应与基岩面固结解下的响应;考虑到海洋地基为两相饱和土介质,对比了在不同简化阻抗处理下的运动响应结果。结果表明,桩土耦合相互作用对于波浪尤其是不规则波作用下的桩柱响应有很大影响,简化阻抗下的运动响应相比两相饱和地基阻抗处理论误差在10%左右,考虑桩土耦合效应对于工程设计具有指导意义和实用价值。     

预加轴力下加强冷弯T型方钢管节点抗冲击试验研究

为深入研究加强方式对T型方钢管节点的抗冲击性能的影响,文章进行了预加轴力下加强冷弯T型方钢管节点抗冲击性能试验研究,研究了主管内部加劲肋和主管上翼缘垫板加强对节点试件冲击力、支管顶部及主管底部变形发展等受力性能指标的影响.通过试验得到管节点在冲击荷载作用下的破坏模态、冲击力和位移时程曲线以及荷载-位移关系曲线,获得加强后节点在冲击荷载作用下的抗冲击工作机理,为管结构抗冲击设计和加固维护提供参考.     

风浪联合作用下海上TLP浮式风机动态响应分析

为分析风浪联合作用下海上TLP浮式风机动态特性,采用叶素动量理论,建立了考虑平台运动的风荷载计算程序,并用FAST进行验证。通过AQWA二次开发实时调用耦合平台运动的风荷载计算程序进行海上TLP浮式风机全耦合动态响应分析,研究了风、浪作用下TLP浮式风机平台及张力筋腱响应特性。结果表明,平台运动致使风荷载波动幅度增大,风荷载幅值在波频处出现峰值,分析中需考虑平台运动与风速之间的耦合效应;正常工况下风荷载使得TLP浮式风机运动响应幅值在低频处的数量级明显增大,整体分析中需详细计算风荷载的影响。     

岛礁地形影响下多体浮桥的水动力性能研究

基于AQWA软件,对岛礁地形下带系泊系统的多浮箱浮式栈桥进行了运动响应的数值模拟,并与带岛礁地形模型试验的响应幅值算子(RAO)进行了对比分析,为浮式栈桥在实际海洋环境中的施工和运营安全等作准确预报.研究结果表明,基于AQWA软件,文中数值方法可有效模拟岛礁对多浮体的绕射和辐射等干扰;由于海底地形变化的影响,波浪将发生折射、绕射、反射等一系列的复杂变化,同时海底倾斜会对系泊缆绳张力造成影响,从而会影响浮桥的运动响应.数值模拟岛礁地形影响下多体浮桥的运动响应结果与水池试验得到的数值对比吻合良好.     

Inhomogeneous wave load effects on a long,straight and side-anchored floating pontoon bridge

In this paper, we present a numerical study on the hydroelastic response of a 4.6 km long fjord crossing floating bridge subjected to wave loads. The bridge is straight in design and supported by 35 pontoons along its full length. To limit the response to horizontal loads, four clusters of deep water mooring lines are engaged to increase the transverse stiffness of the bridge. Owing to the very large span across the fjord, inhomogeneity in the wave field exists. This study examines the various effects of inhomogeneous wave loads on the dynamic responses of the floating bridge. These include the spatial variations of the wave direction, significant wave height and peak period as well as the coherence and correlation of waves along the entire length of the floating bridge. For the purpose of comparison, the dynamic bridge responses under homogeneous wave load cases are also studied. In addition, the effects of wave load components and short-crestedness are presented and discussed.     

Hydroelastic analysis of a nonlinearly connected floating bridge subjected to moving loads

In this paper, the motion equations for the nonlinearly connected floating bridge, considering the nonlinear properties of connectors and vehicles’ inertia effects, are proposed. The super-element method is used to condense the whole calculation scale, and the direct integration and Newton–Raphson iteration method are applied to solve the reduced equations. Based on the modal and static analyses, the dynamic displacement and connection forces characteristics of a floating bridge with nonlinear connectors subjected to moving loads are investigated. It is found that nonlinearity and initial gap of the connectors are important for the hydroelastic response of a nonlinearly connected floating bridge.     

Design and construction of a floating swing bridge in Osaka

The world’s first swing and floating bridge is under construction in the Port of Osaka. It will be completed in the year 2000 to connect two reclaimed islands. The bridge rests on two hollow steel pontoons and is supported horizontally by rubber fenders and dolphins. Many important engineering issues such as the dynamic response to the wave, wind, earthquake and vehicle loads are investigated herein. The bridge can be regarded as a high-tech bridge on the advanced technology opening vistas onto 21st century.     

Experimental and numerical study on dynamic responses of floating bridge under the shielding effect of a floating platform

A floating bridge and a floating platform can serve as a transport channel between land and sea. They will interact with each other in the wave environment. In this paper, the dynamic response characteristics of a floating bridge under irregular waves and regular waves are studied by means of model tests and numerical calculations. The results of model test and numerical calculation based on potential flow theory are basically consistent and can be mutually verified. By comparing and analyzing the dynamic response results of the floating bridge under the condition of “with floating platform” and “without floating platform”, some conclusions are drawn. The floating platform will have a shielding effect on waves coming from the sea. Due to the shielding effect of the floating platform, the motions in heave, surge and pitch of the floating bridge are evidently diminished. Among them, the motion response of the pontoon near the floating platform decreases most obviously. The floating platform provides a relatively stable marine environment for the floating bridge, thereby improving the survival state of the floating bridge.     

Hydroelasticity based fatigue assessment of the connector for a ribbon bridge subjected to a moving load

In this paper, the prediction of the hydroelastic response of the floating bridge and the fatigue behavior of the connectors is presented. And based on the hydroelastic response analysis of the ribbon bridge, the dynamic alternating load of the connector can be obtained, in that the fatigue behavior analysis of the connector simulated by the solid elements can be conducted by employing the local stress–strain approach. It is revealed that the sequence of the dynamic loads acting on the connectors, the value of various fatigue parameters and the ultimate tensile strength should be sufficiently considered, especially the passing speed of a moving load, so that it can significantly reduce the fatigue damage of the connectors.     

张力腿式浮式风机平台的水动力和空气动力耦合响应分析

文章采用了空气动力、水动力、控制与弹性完全耦合的时域模拟方法研究了张力腿式浮式风机平台的动力响应.水动力载荷的计算采用了三维势流理论与Morison公式.空气动力载荷的计算采用了叶素动量理论和广义动态尾流理论.利用FAST软件得到了张力腿式浮式风机平台响应的时域结果,并分析了其动力响应特性.建立了描述平台纵荡运动的非线性微分方程,并采用了摄动方法求得其近似解,解释了纵荡运动中由非线性粘性效应引起的高频响应.对数值模拟结果的分析表明高频的响应分量对平台的动力性能有显著的影响.     

Methodology for global structural load effect analysis of the semi-submersible hull of floating wind turbines under still water,wind, and wave loads

In designing the support structures of floating wind turbines (FWTs), a key challenge is to determine the load effects (at the cross-sectional load and stress level). This is because FWTs are subjected to complex global, local, static, and dynamic loads in stochastic environmental conditions. Up to now, most of the studies of FWTs have focused on the dynamic motion characteristics of FWTs, while minimal research has touched upon the internal load effects of the support structure. However, a good understanding of the structural load effects is essential since it is the basis for achieving a good design. Motivated by the situation, this study deals with the global load effect analysis for FWT support structures. A semi-submersible hull of a 10-MW FWT is used in the case study. A novel analysis method is employed to obtain the time-domain internal load effects of the floater, which account for the static and dynamic global loads under the still water, wind, and wave loads and associated motions. The investigation of the internal stresses resulting from various global loads under operational and parked conditions and the dynamic behavior of the structural load effects in various environmental conditions are made. The dominating load components for structural responses of the semi-submersible floater and the significant dynamic characteristics under different wind and wave conditions are identified. The dynamic load effects of the floating support structure are investigated by considering the influence of the second-order wave loads, viscous drag loads induced global motions, and wind and wave misalignments. The main results are discussed, and the main findings are summarized. The insights gained provide a basis for improving the design and analysis of FWT support structures.     

车辆荷载作用下连续梁桥动力响应仿真分析

为研究桥梁在移动车辆荷载作用下的动力特性和承载能力,以某连续梁桥为计算实例,采用大型通用有限元软件ANSYS建立了质量-弹簧的车辆模型和桥梁结构的有限元模型,用时程分析法分析了车辆荷载作用下连续梁桥的动力响应特征,着重探讨了车辆刚度、车辆质量、行车速度等车辆荷载因素对连续梁桥动力响应的影响规律,并提出相应结论。     

Numerical simulation of the spreading dynamic responses of the multibody system with a floating base

To simulate the dynamic responses of the multibody system with a floating base when the upper parts spread with a certain sequence and relative speed, the homogeneous matrix method is employed to model and simulate a four-body system with a floating base and the motions are analyzed when the upper parts are spread sequentially or synchronously. The rolling, swaying and heaving temporal variations are obtained when the multibody system is under the conditions of the static water along with the wave loads and the mean wind loads or the single pulse wind loads, respectively. The moment variations of each joint under the single pulse wind load are also gained. The numerical results showed that the swaying of the floating base is almost not influenced by the spreading time or form when the upper parts spread sequentially or synchronously, while the rolling and the heaving mainly depend on the spreading time and forms. The swaying and heaving motions are influenced significantly by the mean wind loads. The single pulse wind load also has influences on the dynamic responses. The torque of joint 3 and joint 4 in the single pulse wind environment may be twice that in the windless environment when the system spreads with 60 s duration.     

浮基多体系统展开动力响应的数值模拟（英文）

To simulate the dynamic responses of the multibody system with a floating base when the upper parts spread with a certain sequence and relative speed, the homogeneous matrix method is employed to model and simulate a four-body system with a floating base and the motions are analyzed when the upper parts are spread sequentially or synchronously. The rolling, swaying and heaving temporal variations are obtained when the multibody system is under the conditions of the static water along with the wave loads and the mean wind loads or the single pulse wind loads, respectively. The moment variations of each joint under the single pulse wind load are also gained. The numerical results showed that the swaying of the floating base is almost not influenced by the spreading time or form when the upper parts spread sequentially or synchronously, while the rolling and the heaving mainly depend on the spreading time and forms. The swaying and heaving motions are influenced significantly by the mean wind loads. The single pulse wind load also has influences on the dynamic responses. The torque of joint 3 and joint 4 in the single pulse wind environment may be twice that in the windless environment when the system spreads with 60 s duration.