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51.
海底管道是海洋石油主要的运输方式,但海底管道在外部静水压力作用下很可能发生局部屈曲压溃,造成灾难性后果。安装止屈器可有效阻止屈曲传播,保证管道安全,整体式止屈器在实际中应用最为广泛。整体式止屈器存在通过减小止屈器体积以节约成本进行优化的可能性,因此,在保证止屈器止屈效果的前提下,可通过减小止屈器的体积,以达到减轻重量、节约成本、减少安装难度等多种目的。研究过程中使用ABAQUS进行模型的仿真模拟,比较了广义弧长法的优缺点,决定选用更方便的静水流体单元法,计算得到不同止屈器的穿越压力以及相应的体积,对比各止屈器的穿越压力变化和体积变化,实现结构优化的目标。基于以上研究,可以得出减少止屈器体积的结构优化方案具有可行性的结论。 相似文献
52.
耐压舱设计是水下机器人的核心技术之一,其极限承载力研究是核心中的核心。针对球壳封盖加柱形壳体耐压舱,现行标准对于初始导入缺陷数值的确定往往过于保守,对于耐压舱体数量较多的无人潜水器来说,过大的设计质量是总体设计所无法接受的。首先采用装配体整体建模策略,建立复合屈曲的受力模型,将三大非线性影响因素同时引入到极限承载力研究中,提升了计算精度。然后分别针对确定性缺陷和非确定性缺陷结构开展极限承载力研究。最后,提出以0.23%的初始缺陷导入尺度作为球壳封盖加圆柱壳体的耐压壳体缺陷导入参数,给出了导入尺度的计算方法,并借助水压试验对上述参数的准确性进行验证。 相似文献
53.
基于ABAQUS的海底管道静水压溃压力的敏感性分析 总被引:1,自引:0,他引:1
局部屈曲压溃是海底管道发生稳定性破坏的一种形式,随着管道的刚度相对越来越柔,厚度相对越来越薄,管道发生屈曲压溃的问题也越来越突出。运用ABAQUS有限元分析软件进行管道的非线性屈曲分析,确定不同径厚比、初始椭圆度、轴向拉力和弯矩作用下的管道静水压溃压力,以分析静水压溃压力对这些因素的敏感性。 相似文献
54.
将海冰作为浮在海水上的半无限大的平板,将海水的浮力作为弹性地基,把海冰与桩柱的作用力看作为集中力,海冰的破坏看作为集中力作用下的平板失稳问题,给出了冰排在集中力作用下的压曲微分方程,数值计算结果给出了海冰在桩柱作用下的临界载荷的表达式,为海洋结构的设计提供了依据. 相似文献
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Over the last two decades, the probabilistic assessment of reinforced concrete (RC) structures under seismic hazard has been developed rapidly. However, little attention has been devoted to the assessment of the seismic reliability of corroded structures. For the life‐cycle assessment of RC structures in a marine environment and earthquake‐prone regions, the effect of corrosion due to airborne chlorides on the seismic capacity needs to be taken into consideration. Also, the effect of the type of corrosive environment on the seismic capacity of RC structures has to be quantified. In this paper, the evaluation of the displacement ductility capacity based on the buckling model of longitudinal rebars in corroded RC bridge piers is established, and a novel computational procedure to integrate the probabilistic hazard associated with airborne chlorides into life‐cycle seismic reliability assessment of these piers is proposed. The seismic demand depends on the results of seismic hazard assessment, whereas the deterioration of seismic capacity depends on the hazard associated with airborne chlorides. In an illustrative example, an RC bridge pier was modeled as single degree of freedom (SDOF). The longitudinal rebars buckling of this pier was considered as the sole limit state when estimating its failure probability. The findings show that the life‐cycle reliability of RC bridge piers depends on both the seismic and airborne chloride hazards, and that the cumulative‐time failure probabilities of RC bridge piers located in seismic zones can be dramatically affected by the effect of airborne chlorides. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
58.
International Maritime Organization (IMO) adopted a new regulation to request permanent means of access (PMA) for a regular inspection of ship structure. Horizontal platforms for an inspector to walk on should be provided at specified locations. The platform is attached perpendicular to longitudinal bulkheads or side shell like a common longitudinal stiffener. Since the platform is much wider than ordinary stiffeners, a mid-flat-bar is welded in the middle of the platform. The wide platform (i.e. the tall web plate) makes PMA structure prone to lateral torsional buckling prior to overall flexural Euler buckling subjected to axial compression. This study employs the Rayleigh-Ritz method to treat the elastic lateral-torsional buckling of the PMA structure. The deformation of the cross-section can be expressed using six independant parameters. Compared to the previous research for an ordinary stiffened plate (Hughes and Ma, 1996a), two additional parameters are employed to model the deformation of the mid flat bar. This study also proposes a new strain distribution of lateral bending introducing two respective neutral axes for the flange and the mid-flat-bar. Two mathematical models are developed for two cases; one without associated plating, and the other with both the plating and its rotational restraint. In the former, the coupling between the lateral torsional buckling (“tripping”) and the Euler buckling is investigated. In the latter, a plate rotational spring constant is suggested based on extended deformed shape of the plating. For each model, the validity of the proposed method is verified by a comparison with a number of linear buckling analyses carried out using the NASTRAN finite-element program. 相似文献
59.
Esra Mete Güneyisi 《地震工程与结构动力学》2012,41(5):853-874
The present paper investigates the seismic reliability of the application of buckling restrained braces (BRBs) for seismic retrofitting of steel moment resisting framed buildings through fragility analysis. Samples of regular three‐storey and eight‐storey steel moment resisting frames were designed with lateral stiffness insufficient to comply with the code drift limitations imposed for steel moment resisting frame systems in earthquake‐prone regions. The frames were then retrofitted with concentrically chevron conventional braces and BRBs. To obtain robust estimators of the seismic reliability, a database including a wide range of natural earthquake ground motion records with markedly different characteristics was used in the fragility analysis. Nonlinear time history analyses were utilized to analyze the structures subjected to these earthquake records. The improvement of seismic reliability achieved through the use of conventional braces and BRBs was evaluated by comparing the fragility curves of the three‐storey and eight‐storey model frames before and after retrofits, considering the probabilities of four distinct damage states. Moreover, the feasibility of mitigating the seismic response of moment resisting steel structures by using conventional braces and BRBs was determined through seismic risk analysis. The results obtained indicate that both conventional braces and especially BRBs improve significantly the seismic behavior of the original building by increasing the median values of the structural fragility curves and reducing the probabilities of exceedance of each damage state. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
60.
火灾高温作用下波纹腹板钢梁剪切屈曲系数研究 总被引:1,自引:0,他引:1
波纹腹板钢梁具有优良的抗剪切性能,在常温条件下,它的剪切屈曲模式通常有3种:局部剪切屈曲、总体剪切屈曲和相关剪切屈曲。根据火灾燃烧不同时刻波纹腹板钢梁的温度变化,考虑火灾高温对结构钢材料性能的影响,研究了波纹腹板钢梁在火灾高温作用下的3种剪切屈服模式,给出了高温下波纹腹板钢梁临界剪切屈曲应力和剪切屈曲系数的计算表达式,分析了其随火灾温度的变化趋势,提出在进行火灾高温作用下的波纹腹板钢梁的力学性能分析时,应首先根据钢梁剪切屈曲系数的变化,准确判断其在火灾燃烧不同阶段所处的受力状态,从而使火灾高温下波纹腹板钢梁的受力分析更加精确合理。 相似文献