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71.
Ship-to-ship collision events can have severe consequences such as loss of life and environmental degradation. For this reason, modern ship designs are required to incorporate a double-hulled structure to prevent inner-hull damage from such events. Using the experimental or numerical method to analyze the crashworthiness of double-hulled ship structures entails much effort, for which reason neither method is easy to adopt at the early design stage. In this paper, an existing simplified method called Ito's method is improved by a new buckling-and-contact-based expansion method. This method can be applied to double-hulled-structure or outer-hull-local-rupture failure mode. The perpendicular bow-to-side collision scenario is assumed for a conservative estimation of damage to a double-hulled structure. The method was verified in the present study by numerical ship collision simulations of several cases. The results for the buckling-and-contact-based expansion method and numerical simulation were similar for a blunt shape of striking body but different for a sharp shape. 相似文献
72.
This study explores the use of localized necking for failure modeling in maritime crash analysis, using large shell elements. The assumption that the failure of a large shell element occurs simultaneously with the onset of localized necking is revisited. This study particularly investigates the numerical implementation of the localized necking condition and its implications on the results of ship collision analysis involving not only plate rupture but also various failure mechanisms such as the crushing and tearing of web girders, stringers, and their intersections. Through a series of large-scale collision simulations, the effects of bending deformation on the initiation of necking, non-proportional loading paths, and ductile fractures not preceded by localized necking, are investigated. It is demonstrated that a localized necking-based fracture model provides a reasonable, relatively mesh-insensitive estimate of the onset of fracture in the outer hull panels; however, fracture propagation is very sensitive to the numerical implementation of the necking and fracture model, especially for the cases involving the crushing of web frames and stringers. 相似文献
73.
悬索跨越形式是油气管道跨越工程中被广泛使用的结构,针对它的结构安全性检测及评价体系的研究具有重要意义,目前我国在本领域仍处于一个起步探索的阶段。从索力检测、外观检查、混凝土无损检测、钢结构无损检测、涂层劣化评价和线形观测6个方面归纳了悬索式跨越结构安全性的检测评价体系,并以9座悬索式跨越工程为例,在规范基础上提出了采用动态权重方法综合评价跨越工程的技术安全状况评级,使之更符合工程实际并为下一步养护维修提供依据,成果可供油气管道悬索式跨越工程结构安全性检测参考。 相似文献
74.
Samples of PM2.5 and PM10 at four types of roadside location (major road, secondary road, branch road, and expressway) in Tianjin were collected and analyzed in 2015. The average annual roadside PM2.5 and PM10 concentrations were higher than the national ambient air quality standard (NAAQS: GB3095-2012). The chromium (Cr), manganese (Mn), nickel (Ni), zinc (Zn), arsenic (As), and cadmium (Cd) concentrations in both PM2.5 and PM10 over four seasons displayed significant differences (p < 0.05). An enrichment factor (EF) analysis revealed that Cd, copper (Cu), Zn, As, Ni, and Pb in PM2.5 and PM10 mainly originated from anthropogenic sources. A factor analysis (FA) and correlation analysis (CA) revealed that vehicle emissions (exhaust and non-exhaust), soil dust, coal combustion, and industrial emissions were the main sources of roadside PM2.5 and PM10 in Tianjin. Both the total hazard quotients (total HQ) and the total carcinogenic risk (total CR) for selected elements in PM2.5 and PM10 were within acceptable limits. The HQ of Pb was higher than for other metals, and it should therefore be given special attention. The CR for traffic policemen was highest for Cr exposure (1.01 × 10−5 for PM2.5 and 1.52 × 10−5 for PM10), followed by As and Ni. A sensitivity analysis showed that the total contributions of the metal concentrations, exposure time (ET), and exposure frequency (EF) accounted for over 50% of the risk for Cr, As, and Ni, suggesting that these metals had the greatest impact on the uncertainty of health risk assessments. 相似文献
75.
张蕊 《郑州铁路职业技术学院学报》2021,(1):101-103
在国家对大学生创新创业政策的支持下,大学生群体中迅速掀起创新创业浪潮。应从强化大学生创新创业法律教育、完善大学生创业法律保护制度、加大政府政策引导支持力度和健全法律救助机制等四个方面加强大学生创业法律风险防控。 相似文献
76.
近年来,我国北京、上海、广州、成都、重庆等大城市已经将市域铁路规划和建设提上日程,其他诸多大城市也颇为关注。国务院同意国家发改委等单位《关于推动都市圈市域(郊)铁路加快发展的意见》,为市域铁路建设提供遵循,更加刺激市域铁路建设和发展。建设市域铁路地下段工程难度相较地铁更大,原因是市域铁路地下段线路埋深更深、车站规模更大、基坑挖深更深,城市穿越条件更复杂,所承受地下水土风险更加巨大。文章具体分析市域铁路地下段建设与运营可能存在的水土风险,从风险管控模式、监控技术及管控平台3方面提出应对建设期水土风险的控制对策,从巡查管理、立体感知和数据平台3方面提出应对运营期水土风险的控制对策,以期为市域铁路地下段建设与运营安全提供切实有效的保障与支撑。 相似文献
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79.
该文通过简要介绍黄岛辖区概况以及面临的监管压力,全面分析目前选船标准的现状及存在的3方面问题,并提出了3方面改进建议,最终以青岛黄岛海事处为例探索建立了以部海事局选船标准为基础,同时将货物、环境、码头3方面纳入其中,符合辖区监管特点的选船机制。 相似文献
80.
碰撞事故是基于事故极限状态设计重点考虑的对象,在设计中越来越受到重视。文章以某大型浮式结构物为研究对象,总结分析ISO、API、HSE、DNV、ABS、BV、LR等标准及规范对碰撞场景的相关规定,提出碰撞分析场景及设计衡准;基于简化分析技术建立碰撞力学模型,利用动态非线性结构分析软件ABAQUS进行仿真分析,通过分析塑性应变、塑性变形、吸能、碰撞力及运动等,校核评估舷侧结构的耐撞性能;分析不同碰撞位置、撞击船型式等对碰撞性能的影响。研究表明:目标大型浮式结构物舷侧结构碰撞事故极限强度满足规范要求,首柱撞击相对比较危险,可作为计算分析控制工况。 相似文献