轨道交通曲线连续 钢—混组合梁抗剪分析

论述在钢混组合梁计算中,规范中按实体梁横向弯曲剪应力计算,没有扭转剪应力计算的规定。曲线组合梁的扭矩较大,讨论是否需要考虑扭转剪应力的影响。结合工程实例,计算分析自由扭转剪应力,按闭口薄壁构件和实体梁分别计算弯曲剪应力,并对计算结果进行对比分析,提出合理的计算方法。     

朔准黄河桥极限承载力分析

研究目的:大跨度钢管混凝土拱桥以其特有的自重轻、强度大、抗变形能力强、施工方便和外形美观等优点,被大量地的用于桥梁结构中。本文以一座在建360 m钢管混凝土拱桥为例,采用通用程序ANSYS建立该桥的空间有限元计算模型,分别对该桥进行裸拱状态和考虑拱上建筑共同作用状态下的特征值屈曲稳定性分析、考虑几何和材料双重非线性的极限承载力分析,并对计算结果进行比较分析,给出拱桥极限桥承载力计算的一般性方法。研究结论:(1)考虑拱上结构的特征值屈曲分析结果最小值为13.477,裸拱的特征值屈曲分析结果最小值为6.673,均大于规范要求的4～5,拱肋截面满足面内和面外的稳定性要求;(2)拱桥极限承载力计算结果最小值为2.252,表明在双重非线性及结构初始缺陷的影响下,主力工况下,全桥结构的安全系数为2.252,满足考虑结构的非线性影响弹塑性稳定安全系数不得小于2的要求,结构设计合理;(3)拱上墩柱等拱上结构对全桥的计算刚度有较大的贡献,但对全桥的极限承载力影响较小;(4)特征值屈曲分析结果是非保守的计算结果,在实际结构设计过程中,必须考虑双重非线性及初始缺陷等对结构极限承载力的影响。     

A simple formulation for predicting the ultimate strength of ships

The aim of this study is to derive a simple analytical formula for predicting the ultimate collapse strength of a single- and double-hull ship under a vertical bending moment, and also to characterize the accuracy and applicability for earlier approximate formulations. It is known that a ship hull will reach the overall collapse state if both collapse of the compression flange and yielding of the tension flange occur. Side shells in the vicinity of the compression and the tension flanges will often fail also, but the material around the final neutral axis will remain in the elastic state. Based on this observation, a credible distribution of longitudinal stresses around the hull section at the overall collapse state is assumed, and an explicit analytical equation for calculating the hull ultimate strength is obtained. A comparison between the derived formula and existing expressions is made for largescale box girder models, a one-third-scale frigate hull model, and full-scale ship hulls.List of symbols A _B total sectional area of outer bottom - A _B total sectional area of inner bottom - A _D total sectional area of deck - A _S half-sectional area of all sides (including longitudinal bulkheads and inner sides) - a _s sectional area of a longitudinal stiffener with effective plating - b breadth of plate between longitudinal stiffeners - D hull depth - D _B height of double bottom - E Young's modulus - g neutral axis position above the base line in the sagging condition or below the deck in the hogging condition - H depth of hull section in linear elastic state - I _s moment of inertia of a longitudinal stiffener with effective plating - l length of a longitudinal stiffener between transverse beams - M _E elastic bending moment - M _p fully plastic bending moment of hull section - M _u ultimate bending moment capacity of hull section - M _uh ,M _us ultimate bending moment in hogging or sagging conditions - r radius of gyration of a longitudinal stiffener with effective plating [=(I _s /a _s )^1/2] - t plate thickness - Z elastic section modulus at the compression flange - Z _B ,Z _D elastic section modulus at bottom or deck - slenderness ratio of plate between stiffeners [= (b/t)(_y/E)^1/2] - slenderness ratio of a longitudinal stiffener with effective plating [=(l/r)(_y/E)^1/2] - _y yield strength of the material - _yB , _yB , _yD yield strength of outer bottom, inner bottom - _yS deck, or side - _u ultimate buckling strength of the compression flange - _uB , _uB , _uD ultimate buckling strength of outer bottom - _uS inner bottom, deck, or side     

Mode jumping in the lateral buckling of subsea pipelines

Unburied subsea pipelines under high-temperature conditions tend to relieve their axial compressive stress by forming localised lateral buckles. This phenomenon is traditionally studied under the assumption of a specific lateral deflection profile (mode) consisting of a fixed number of lobes. We study lateral thermal buckling as a genuinely localised buckling phenomenon by applying homoclinic (‘flat’) boundary conditions. By not having to assume a particular buckling mode we are in a position to study transitions between these traditional modes in typical loading sequences. For the lateral resistance we take a realistic nonlinear pipe-soil interaction model for partially embedded pipelines. We find that for soils with appreciable breakout resistance, i.e., nonmonotonicity of the lateral resistance characteristic, sudden jumps between modes may occur. We consider both symmetric and antisymmetric solutions. The latter turn out to require much higher temperature differences between pipe and environment for the jumps to be induced. We carry out a parameter study on the effect of various pipe-soil interaction parameters on this mode jumping. Away from the jumps post-buckling solutions are reasonably well described by the traditional modes whose analytical expressions may be used during preliminary design.     

肋骨侧向稳定性特征屈曲有限元分析

环肋圆柱壳通常在周向布置肋骨来提高其稳定性,在深水压力作用下,肋骨发生侧向失稳的可能性加大,进而影响环肋圆柱壳的整体稳定性。在理论分析的基础上,采用有限元法对环肋圆柱壳进行在静水压力和轴向压力作用下的特征屈曲分析,研究肋骨侧向失稳的屈曲特征,得到肋骨侧向失稳的判别方法,为工程设计提供参考。     

冰区航行船舶电力推进轴系机电耦合的扭振分析

通过螺旋桨桨叶与冰块的相互作用过程,建立单冰块对螺旋桨扭转振动的激励函数;同时建立机电耦合振动数学模型,推导得到机电耦联动力学方程,研究电机电磁激励力对扭转振动的影响。以3500吨科考船电力推进轴系为研究对象,基于冰载荷激励力和电磁激励力对轴系扭转振动进行分析,为复杂的船舶电力推进轴系在冰区航行时的振动研究奠定了基础。     

卷管铺设过程的时域动力分析

卷管法是海底管道铺设中的一种重要方法,由于其铺设过程涉及很多装备,因而管道的受力过程复杂。管道的上卷过程会使管道发生塑性变形并引起残余曲率,上卷过程造成的变形需要在退卷过程中进行校直,这个过程中的缠绕和校直引起的塑性变形,对管线造成的损伤不可忽视。首先介绍卷管式铺管法的铺设原理,然后利用有限元分析软件ABAQUS模拟管道上卷和退卷的动态过程,最后研究卷管铺设上卷和退卷过程中管道的轴向应变历史和应力应变关系以及管道弯曲曲率、截面椭圆率变化历史。结果表明,管道在经过卷筒、校准器、校直器时产生很大的弯曲曲率和截面椭圆率。     

基于大型打桩船桩架的三维力学特性分析

应用国际广泛使用的大型通用结构有限元分析程序ALGOR对110m大型打桩船桩架进行了三维力学分析,该装备是国内最高并在海上施工的桩架,因此对各工况进行了详细的分析研究,并给出了合理的设计建议。对从事该领域设计施工者有一定指导作用。     

船用低速柴油机曲轴轴向振动研究

以船用大功率低速柴油机柔性体曲轴为对象,在考虑气体力、运动部件惯性力、扭纵耦合效应等因素的情况下,建立曲轴、连杆、活塞的刚柔混合动力学模型。通过数值仿真,分别对连杆推力、连杆法向力和切向力对曲轴轴向振动的影响进行分析。分析结果表明：法向力是曲轴轴向振动的直接激励源,切向力是曲轴轴向振动的间接激励源-切向力引起曲轴扭振,进而引起曲轴纵振;同时法向力和切向力对曲轴轴向振动的影响非常相近;而连杆推力(法向力和切向力合力)引起的曲轴轴向振动是扭纵耦合振动的结果,并非两种分力作用结果的简单叠加。     

复杂载荷作用下船体板格屈曲强度计算公式研究

分析复杂载荷作用下船体板格结构屈曲强度的影响因素,基于ANSYS软件APDL模块参数化建模,对这些因素进行相关性分析,排除无关参数,保留有关参数,得到屈曲强度的定性表达式。然后变更有关参数,得到不同的有限元模型,通过计算得到不同模型下的屈曲强度,分析大量数据,最终得到屈曲强度的定量表达式。该公式可以在工程上用于复杂载荷作用下船体板格结构的屈曲评估,具有重要的实用价值。