Vertical Upheaval Buckling of Submarine Buried Heated Pipelines with Initial Imperfection

In this paper,a theoretical solution of vertical buckling is proposed with regard to the typical initial imperfection cases of submarine pipelines.Analytical tools are applied to predicting the occurrence and consequence of inservice buckling of a buried heated pipeline in Bohai Gulf.An evaluation is performed to ensure the pipeline structural integrity during operation under loading conditions.Different protection measures are proposed and their validities are analyzed.Analyses show that for the same magnitude of initial imperfection,the upheaval buckling of pipeline with isolated prop model is the most likely to occur.The empathetic model represents a special sub-case of continuous prop model,and the calculated buckle temperature is between the first stage and the second stage of post-upheaval buckling of continuous prop model.And the larger the initial imperfection,the less the axial force required for the upheaval buckling.Meanwhile,it can be seen that a peak point appears on the curves of temperature difference against buckling amplitude for small initial imperfection.Besides,trenching-burial is one kind of protection measures preventing the pipeline from thermal upheaval.The covered depth-to-diameter ratio depends on the design conditions and subsoil properties.For the given pipeline in this paper,the covered depth-to-diameter ratio is recommended to be 5.     

Prediction of Buckling of Plain Knitted Fabric Sheets Subjected to Simple Shear in Wale Direction

Knitted fabric is very different from woven fabric due to its more complicated knitting structures. The buckling of knitted fabric sheets subjected to simple shear in the wale direction is investigated analytically in consideration of the large deformation of fabric sheet in critical configuration. The theory on instability of finite deformation is applied to the analysis. All the stress boundary conditions of knitted fabric sheet are satisfied. An equation to determine the buckling direction angle is derived. It is shown that there are two possible buckling modes, flexural mode and barreling mode. The buckling condition equations for the flexural mode and barreling mode are also obtained respectively. Numerical illustrations reveal that only the flexural mode can actually occur and the barreling mode cannot, which agrees with the experimental observations. For a permitted buckling mode on margin boundaries, the critical value of shear amount and the buckling direction angle can be determined.     

Research progress of buckling propagation experiment of deep-water pipelines

In recent years, the extraction of fossil resources, especially oil and gas in deep and ultra-deep water areas has been playing a more important role and been paid more attention to. For this reason, the working depth of submarine pipelines, which are used for the transportation of oil and gas, has been increasing sharply. As the main failure pattern of deep-water pipelines, buckling and its propagation problem have drawn more attention of many research institutions and engineering units around the world. Based on the existing research, the summary of experiments and their outcomes of deep-water pipeline buckling failure is made in this paper. Research status and developing prospects of the experiments of buckling propagation and buckle arrestor are discussed in detail.     

Dynamic stiffness for thin-walled structures by power series

INTRODUCTION Thin-walled structures have considerable tech-nological importance in many situations of engi-neering practice. The rotary and warping inertia terms should be considered in the analyses of thin-walled structures (Alwis and Wang, 1996), although it is difficult to obtain the analytical solutions of govern-ing differential equations, especially of thin-walled frame and spatial twisted structure. The finite element method (FEM) is widely used for vibration and sta-bility analy…     

Numerical investigation and design of thin-walled complex section steel columns

A numerical investigation of thin-walled complex section steel columns with intermediate stiffeners was performed using finite element analysis. An accurate and reliable finite element model was developed and verified against test results. Verification indicates that the model could predict the ultimate strengths and failure modes of the tested columns with reasonable accuracy. Therefore, the developed model was used for the parametric study. In addition, the effect of geometric imperfection on column ultimate strength and the effect of boundary conditions on the elastic distortional buckling of complex section columns were investigated. An equation for the elastic distortional buckling load of fixed-ended columns having different column lengths was proposed. The elastic distortional buckling load obtained from the proposed equation was used in the direct strength method to calculate the column ultimate strength. Generally, it is shown that the proposed design equation conservatively predicted the ultimate strengths of complex section columns with different column lengths.     

年平均降雨入渗补给对滨海含水层系统水位波动影响的解析研究

降雨入渗补给是影响滨海含水层系统水位波动的主要因素之一.本文建立了一个较为一般的滨海含水层系统模型.模型中不仅考虑了年平均降雨入渗补给对含水层系统水位波动的影响,同时也考虑了潜水含水层中地下水的波动及其通过半透层对承压含水层的越流补给.利用解析法分析了降雨入渗补给对潜水水位、承压水头和地下水海底排泄量的影响.     

海底(子母)管道在波流作用下水动力载荷的实验研究

本文是在研究组对“波流作用下海底管道水动力系数 C_D、C_M、C_L 值的确定和选取”、“带压块海底管道上的水动力载荷实验研究”和“部分埋设海底管道渡流作用时的水动力效应实验研究”等项目研究成果的基础上,以 JZ20-2海底输气管道工程的为背景,对 JZ20-2的子-母管在波流作用下水动力载荷的确定进行的实验研究。同样,子-母管的水动力系数 C_D、C_M 与 KC 数明显相关,随KC 数的增大而减小;水动力系数 C_M 多在1—4之间变化。实验中对规则波加拖厢造流与不规则波自然加流的试验结果,二者比较—致。因而建议在工程设计中,可直接按规则波加拖厢造流的方法和设备,并偏于保守。     

一类具有偏差变元的高阶中立型微分方程周期解的存在性和唯一性

研究了一类具有偏差变元的高阶中立型微分方程周期解问题.利用重合度理论,获得了其周期解的存在性和唯一性的充分条件.     

Submarine Pipeline Routing Risk Quantitative Analysis

A new method for submarine pipeline routing risk quantitative analysis was provided, and the study was developed from qualitative analysis to quantitative analysis. The characteristics of the potential risk of the submarine pipeline system were considered, and grey-mode identification theory was used. The study process was composed of three parts: establishing the indexes system of routing risk quantitative analysis, establishing the model of grey-mode identification for routing risk quantitative analysis, and establishing the standard of mode identification result. It is shown that this model can directly and concisely reflect the hazard degree of the routing through computing example, and prepares the routing selection for the future.     

弹性有限长度杆在轴向应力波传播和反射过程中的屈曲

讨论弹性有限长度杆端部受冲击载荷作用，在轴向应为波传播和反射过程中的动态屈曲问题．利用扰动方程的解、端部支承条件和应力波反射前后波阵面相容条件得到了动态屈曲的分叉条件，临界载荷和屈曲模态．数值结果表明：临界载荷有多个分支且随时间增加而降低；由于应力波在端部的反射，使临界载荷进一步下降．这个结果就解释了实验中的一些现象．     

用于海底管线阴极保护的镯式铝基牺牲阳极制造技术

用于海底管线阴极保护的镯式铝基牺牲阳极,由于其必须适应海底这种高腐蚀性的服役条件,所以对它的制造技术含量要求是很高的。通过对海底管线的阴极保护腐蚀保护系统、镯式阳极的模具设计、浇注方法、质量控制、镯式阳极的安装技术等的论述,突显出镯式铝基牺牲阳极制造工艺技术的特点与新点,以实现海底管线有效防腐之目的。     

Free vibration of pre-tensioned nanobeams based on nonlocal stress theory

The transverse free vibration of nanobeams subjected to an initial axial tension based on nonlocal stress theory is presented. It considers the effects of nonlocal stress field on the natural frequencies and vibration modes. The effects of a small scale parameter at molecular level unavailable in classical macro-beams are investigated for three different types of boundary conditions： simple supports, clamped supports and elastically-constrained supports. Analytical solutions for transverse deforma- tion and vibration modes are derived. Through numerical examples, effects of the dimensionless nanoscale parameter and pre-tension on natural frequencies are presented and discussed.     

Nonlinear dynamic buckling of stiffened plates under in-plane impact load

This paper presents a simple solution of the dynamic buckling of stiffened plates under in-plane impact loading. Based on large deflection theory, a discretely stiffened plate model has been used. The tangential stresses of stiffeners and in-plane displacement are neglected. Appling the Hamilton's principle, the motion equations of stiffened plates are obtained. The deflection of the plate is taken as Fourier series, and using Galerkin method the discrete equations can be deduced, which can be solved easily by Runge-Kutta method. The dynamic buckling loads of the stiffened plates are obtained form Budiansky-Roth criterion.     

水工大体积混凝土温度裂缝施工控制

水工混凝土具有及其严格的抗冻、抗渗、防裂要求,而大体积混凝土由于内外温差较大,容易在混凝土表面产生最终向贯穿裂缝发展的裂缝。故水工大体积混凝土施工应采取不同于其它大体积混凝土的施工措施。本文将讨论水工大体积混凝土温度控制的施工措施。     

Buckling design of large steel silos with various slendernesses

Large steel silos are typical kinds of thin-walled structure which are widely used for storing huge quantities of granular solids in industry and agriculture. In the present analyses, the buckling design of large steel silos subject to Eurocode-specified solid pressure is demonstrated. The finite element model is established using the commercial general purpose computer package ANSYS. Six types of buckling analyses are carried out for the geometrically perfect and imperfect models with and without consideration of material plasticity. The load cases of concentric discharge, discharge patch load, large eccentricity discharge, and large eccentricity filling are considered. The buckling behavior of six example steel silos with capacities of 30 000–60 000 m³ is investigated. The silos’ slenderness ranges from 4.77 to 0.35, comprising very slender, slender, intermediate slender, squat, and retaining silos. The index called the ratio of capacity to steel consumption (RCS) is initially defined in the paper, which provides an effective measure for the economical design of steel silos. It is validated that the RCS index increases rapidly with the decrease of silo slenderness, and the storage efficiency of steel silo improved greatly as the slenderness changes from slender silo to retaining silo. The effects of patch load reveal that the buckling modes in the case of discharge patch load are very different from those of silos under concentric solid pressure, and the effect is unfavorable for buckling resistance of all levels of slenderness of the example silos, but contributes a small decrease to the RCS index (less than 10%). The buckling deformations from both the linear and nonlinear buckling analyses in large eccentric discharge are strongly asymmetrical arising from the circumferential and meridional non-uniform distribution of the solid pressures. The buckling is mainly governed by the non-uniform distribution of the solid pressure other than other influential factors such as the weld imperfection, geometrical and material nonlinearity, compared with the load case of concentric discharge. The RCS index of example silos under large eccentric discharge is reduced substantially, and is approximately half that of silos under concentric discharge. The linear and nonlinear buckling deformations in large eccentric filling are also asymmetrical, deviating from the center to the side where the most friction locates to the highest wall contact. The RCS index of example silos under large eccentric filling is also reduced substantially, and is approximately 70% that of silos under concentric discharge. This reveals that the large eccentricity both in discharging and filling could result in a strong decrease of storage efficiency of steel silos.     

一类高阶P—Laplacian方程周期解的存在性和唯一性

利用重合度理论,研究一类高阶P—Laplacian方程,获得其周期解存在性和唯一性新的充分条件,推广和改进了已有文献中的相关结论．     

一类高阶泛函微分方程多个周期解的存在性

利用重合度理论,研究一类高阶泛函微分方程周期解存在性的问题,获得了这类方程至少存在两个周期解的结果,并通过两个数值例子表明所获结果的有效性.     

In-plane creep buckling of concrete-filled steel tubular arches

The creep-induced deformation of the arch rib of concrete-filled steel tubular （CFST） arches under a sustained load can increase the bending moment, which may lead to earlier stability failure called creep buckling. To investigate the influences of concrete creep on the buckling strength of arches, a theoretical analysis for the creep buckling of CFST circular arches under distributed radial load is performed. The simplified Arutyunyan-Maslov （AM） creep law is used to model the creep behavior of concrete core, and the creep integral operator is introduced. The analytical solutions of the time-dependent buckling strength under the sustained load are achieved and compared with the existing formula based on the age-adjusted effective modulus method （AEMM）. Then the solutions are used to determine the influences of the steel ratio and the first loading age on the creep buckling of CFST arches. The results show that the analytical solutions are of good accuracy and applicability. For CFST arches, the steel ratio and the first loading age have significant influences on creep buckling. An approximate log-linear relationship between the decreased degrees of the creep buckling strength and the first loading age is found. For the commonly used parameters, the maximum loss of the buckling strength induced bv concrete creen is close to 40%     

海底管道水动力和在位稳定性研究的近代进展

海洋工程中海底管道为保证其正常运行和结构生存期的安全,直接与海底管道水动力和在位稳定性研究密切相关的。本文着重叙述了70年代、80年代国外对接近于海底、部分埋入海底和海底敞口浅沟内管道的水动力和在位稳定性方面的研究结果,并就进一步开展这方面研究进行讨论。     

化学分析课程中应用项目教学法探索

＂十一五＂期间项目教学法在高职核心专业课程教学中的实施得到了很好的教学效果。本文设计了在高职专业基础课程———化学分析课程中应用项目教学法的教学内容、教学实施和考评的整体方案,该整体方案的设计对＂十二五＂期间项目教学法的推广有实际意义。