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大跨径连续刚构桥的温度效应分析 总被引:4,自引:0,他引:4
以魏家洲特大桥为例,按照我国公路桥涵设计规范、英国BS5400规范、新西兰规范确定不同的计算模式,对大跨径连续刚构桥进行温度效应分析,得出:温度应力在大跨径连续刚构桥整个桥梁设计中占有很大的比重,且采用不同的温度梯度计算模式,所得到的梁内温度应力值相差较大,甚至出现异号的温度应力. 相似文献
73.
Emissions of GHG from the transport sector and how to reduce them are major challenges for policy makers. The purpose of this paper is to analyse the level of greenhouse gas (GHG) emissions from ships while in port based on annual data from Port of Gothenburg, Port of Long Beach, Port of Osaka and Sydney Ports. Port call statistics including IMO number, ship name, berth number and time spent at berth for each ship call, were provided by each participating port. The IMO numbers were used to match each port call to ship specifications from the IHS database Sea-web. All data were analysed with a model developed by the IVL Swedish Environmental Research Institute for the purpose of quantifying GHG emissions (as CO2-equivalent) from ships in the port area. Emissions from five operational modes are summed in order to account for ship operations in the different traffic areas. The model estimates total GHG emissions of 150,000, 240,000, 97,000, and 95,000 tonnes CO2 equivalents per year for Gothenburg, Long Beach, Osaka, and Sydney, respectively. Four important emission-reduction measures are discussed: reduced speed in fairway channels, on-shore power supply, reduced turnaround time at berth and alternative fuels. It is argued that the potential to reduce emissions in a port area depends on how often a ship revisits a port: there it in general is easier to implement measures for high-frequent liners. Ships that call 10 times or less contribute significantly to emissions in all ports. 相似文献
74.
In this paper, the procedure for flaw acceptability assessment is examined through a case study of a semi-elliptical surface crack in an offshore monopile as it grows till it forms a through thickness crack. Using the procedure prescribed in an industrial standard (BS 7910), the fracture ratio, Kr is shown to increase monotonically with increasing crack depth. The load ratio, Lr, is initially insensitive to the crack depth. However, there is a rapid increase in Lr when the crack depth to thickness ratio exceeds 80%. Lr values obtained from detailed 3D FE limit analysis using elastic-perfectly-plastic material behaviour do not exhibit the asymptotic behaviour predicted by BS 7910 as the flaw transitions from deep crack to through-thickness crack. Furthermore, Kr predicted by BS 7910 is shown to be an over-estimation for the typical dimensions of offshore monopiles. The findings suggest that a structure with a deep flaw may be identified as unacceptable based on BS 7910 when it may still possess a non-trivial amount of structural residual life. This is a concern for monopiles where crack growth as a large flaw forms a significant part of the total life. 相似文献
75.
Transfer functions are often used together with a wave spectrum for analysis of wave–ship interactions, where one application addresses the prediction of wave-induced motions or other types of global responses. This paper presents a simple and practical method which can be used to tune the transfer function of such responses to facilitate improved prediction capability. The input to the method consists of a measured response, i.e. time series sequences from a given sensor, the 2D wave spectrum characterising the seaway in which the measurements are taken, and an initial estimate of the transfer function for the response in study. The paper presents results obtained using data from an in-service container ship. The 2D wave spectra are taken from the ERA5 database, while the transfer function is computed by a simple closed-form expression. The paper shows that the application of the tuned transfer function leads to predictions which are significantly improved compared to using the transfer function without tuning. 相似文献
76.
为了研究内压作用下管道裂纹应力场分布规律,以含有表面裂纹的X80管道为研究对象,对不同形状、不同方向、不同内压、不同尺寸的含裂纹管道进行仿真分析和实验验证。结果表明:裂纹尖端处应力远大于裂纹中心应力。裂纹形状对应力影响作用较小,随着裂纹方向与管道轴向夹角增大,裂纹尖端应力先增大后减小,随着管道内压、裂纹深度、裂纹长度的增大,裂纹尖端处应力随之线性增大。其中,裂纹长度对裂纹尖端应力的影响小于管道内压和裂纹深度。 相似文献
77.
Stress concentration and residual stress have a significant influence on fatigue life of welded joints. In order to reduce the stress concentration of welded joints, a mathematical design method of tensile triangles (MTT) based on bionics was applied to weld shape design. Accordingly, the stress concentration of various weld beads in the corner boxing welded joint and the fillet welded T-joint was dissected using our in-house FEM software JWRIAN. It was found that there existed a large stress concentration in the conventional welded joints, whereas those welded joints with elongated weld bead were accompanied by a lower stress concentration, especially for elongated weld bead with MTT design. Furthermore, among the weld shapes of the corner boxing fillet welded joint, the rectangle shape of weld bead had the minimum stress concentration factor (1.05). For the fillet welded T-joint with MTT design, the stress concentration of weld toe decreased dramatically with the increase of the index of designed shape, but there was a minor difference of stress concentration at weld root between the weld beads with MTT design. In addition, application of low transformation temperature (LTT) weld metal utilizing martensitic transformation to the fillet welded T-joints can produce compressive residual stress at weld toe. 相似文献
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79.
文中探讨了一起国际航行船舶关于港口国船舶污染物接收设施问题报告的调查情况,介绍了此次船舶污染物接收设施问题报告的原因分析及采取的措施,并向接收设施的提供者和使用者给出了优化建议,明确了各有关部门在港口国船舶污染物接收设施履约工作上的重点。 相似文献
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