深埋式混凝土桥头搭板结构计算分析

传统的浅埋式桥头搭板在使用过程中常会出现板底脱空甚至断裂的问题。以深埋式桥头搭板处治结构为主要研究对象,通过有限单元法分别建立深埋式、浅埋式桥头搭板力学模型,并运用Winkler弹性地基梁理论对两种搭板结构进行对比验算。结果表明:相对于浅埋式桥头搭板结构,采用深埋式桥头搭板处治结构可以有效减小台背地基沉降、搭板挠曲变形和板底应力,增强地基刚度,从而缓解桥头跳车和桥头搭板断裂问题。     

Long-term approach for assessment of sloshing loads in LNG carrier,part II: Grouping method

Assessing the sloshing loads has been a significant issue in designing the cargo containment system (CCS) of a liquefied natural gas carrier (LNGC). The sloshing problem contains numerous physical and technical uncertainties. The long-term approach has been suggested to reduce the possible uncertainties, but it has not been a feasible option owing to the incalculable number of experimental cases. Daewoo Shipbuilding and Marine Engineering Co., Ltd., Hyundai Heavy Industry Co., Ltd., Samsung Heavy Industry Co., Ltd., Korean Register, and Seoul National University conducted extensive sloshing model tests for the 174 K S-LNGC. To consider the long-term approach, Part I describes the differences between short- and long-term approaches based on the guidelines of different classification societies. To address the significant number of experimental conditions required for the long-term approach, a grouping method is investigated (Part II). Although this grouping method is typically used in practical design, it has not been validated, and its applicability is yet to be determined. In Part II, the sea states are classified using 16 different grouping methods. The long-term exceedance probabilities and pressures are obtained individually and then compared with the results obtained from fully considering all sea states. After performing the general sloshing model test of the shipbuilding industry, the sloshing impact pressure of a liquefied natural gas cargo model is measured via 6DoF irregular simulations, where the upper section of the cargo hold structure is considered. Long-term pressures are locally and globally investigated and compared among 16 different sea states and all the sea states. Based on the results, the best grouping method is suggested for the long-term approach.     

临涣船闸下游引航道优化设计

临涣船闸位于临涣节制闸南侧，上距省界李口集约30.0 km,下距南坪闸31.5 km,下游引航道连接段位于转弯河段，弯道转角约75°。受此地形影响，河道主流贴右岸凸嘴进入下游主河槽，使引航道连接段与凹岸之间形成逆时针回流，对引航道水流有压迫作用，局部主流宽度显著束窄。通过物模试验可知，河道主流对引航道口门区内水流形成较为明显的剪切，导致口门区内形成较大范围的回流，长度近350 m。由于回流区较长，形成多个复杂的异向回流组合流态，水流条件十分复杂，因此需提出相应的工程措施加以改善。通过河槽疏浚、增加隔流潜堤，有效地解决了下游引航道水流流态不佳、横向流速超标较大、口门区回流强度较大、回流流速无法满足规范要求的问题。     

Ultimate strength analysis of composite stiffened panels based on multi-scale approach北大核心CSCD

［Objectives］As composite materials have varied internal structures, an in-depth analysis of the damage mechanisms of their component materials can provide a research foundation for the ultimate strength analysis of composite stiffened panels. ［Methods］The microscopic, mesoscopic and macroscopic mechanical analyses of marine glass fiber reinforced plastic (GFRP) composite stiffened panels are carried out using a multi-scale approach. Microscopic and mesoscopic representative volume element (RVE) models of chopped strand mat (CSM) and woven roving (WR) materials are established, and the macroscopic equivalent stiffness is obtained by homogenizing the RVE models. The ABAQUS VUMAT subroutine is used to code the progressive damage evolution model of the composite materials to derive the damage evolution mechanism of the microscopic and mesoscopic models respectively. The equivalent strength of macroscopic laminates is also obtained. ［Results］The multi-scale approach can be used to accurately evaluate the macroscopic mechanical properties of composite materials, and the ultimate strength of composite stiffened panels is mainly determined by fiber bundle failure. ［Conclusions］The obtained macroscopic material parameters can be used to calculate the ultimate strength of composite stiffened panels, while the parametric study of the mesomechanics of composite materials can provide an analysis tool for investigating the influence of material processing technology. © 2023 Chinese Journal of Ship Research. All rights reserved.     

Long-term approach for assessment of sloshing loads in LNG carrier,Part I: Comparison of Short- and Long-term approaches

To assess the long-term sloshing loads of a liquefied natural gas carrier, Daewoo Shipbuilding and Marine Engineering Co., Ltd., Hyundai Heavy Industry Co., Ltd, Samsung Heavy Industry Co., Ltd. (SHI), Korean Register, and Seoul National University conducted a series of joint industrial experiments using a six-degree-of-freedom irregular sloshing model test. SHI provides a 174 K S-LNGC and its cargo hold information. To consider the numerous test conditions of the long-term approach, the present study focuses on the upper regions of the cargo hold structure, and feasible operating scenarios are assumed. A total of 3870 h at a real scale are simulated based on 387 sailing conditions. Extensive experimental results of sloshing loads are analyzed based on different guidelines suggested by different maritime classification societies. Part I of this study provides an assessment of sloshing loads based on a comparison of short- and long-term approaches distinguished by the guidelines, and the possible reference values are presented. A practical solution for the long-term approach will be discussed in Part II.