浅海抗风浪网箱养鱼技术研究

浅海网箱养殖是现代海水养殖业发展的重要途径。由于我国东南沿海多台风和热带风暴 ,加上现有海水网箱结构大多属于小型简陋型 ,结构非规范化 ,抵御海洋自然灾害能力弱。而国外开发的抗风浪网箱养鱼技术投资成本很高 ,技术复杂 ,在我国推广有一定的难度。因此 ,开发适合我国国情的浅海抗风浪网箱养鱼技术就成为必要。有关浅海抗风浪网箱养鱼技术至今未见报道。本文将作者近年在这方面开展的研究所获成果报道如下。１材料与方法１．１材料分别选择浙江乐清湾中心水域的抛西海区、大坦海区和湾口外侧的南排山海区为试验区。水深１０ｍ ,底质为…     

水平循环荷载作用下单桩动力特性的数值模拟

采用修正的p-y曲线方法，分析了桩基础振动过程中桩土之间由于土体塑性变形导致的桩土脱开现象，给出了计算桩土脱开现象的数值模拟方法，并据此分析计算了中国渤海湾JZ20－2MUQ平台的桩基础动力特性，得到了桩基础振动过程中桩土脱开的区域，分析了桩土之间的脱开对桩基础动力响应的影响等问题。     

养护期介入电迁阻锈保障混凝土耐久性试验研究

沿海地区氯盐侵蚀会对混凝土结构造成严重的耐久性问题,混凝土设计使用寿命难以保障。对于新建工程,若在自由水含量较高混凝土养护期进行电迁阻锈处理,则有利于电迁移性阻锈剂在钢筋周围聚集以达到更佳的阻锈效果。为此,针对两种电迁移性阻锈剂对处于氯盐侵蚀环境中的混凝土适用性展开研究,并测试了干湿循环前后混凝土内钢筋电化学参数、氯离子扩散特征及钢筋周围电迁移性阻锈剂含量研究两种电迁移性阻锈剂对混凝土耐久性保障的作用。结果表明,试验中养护期介入电迁阻锈后试件阻锈效果良好,经过干湿循环后钢筋腐蚀电位正向高于-162.6 m V,同时,钢筋附近出现明显的阻锈剂聚集现象,能保持钢筋的钝化状态。     

波频和慢漂组合作用下钢悬链线立管疲劳损伤研究

为了有效地考虑浮体慢漂运动对钢悬链线立管疲劳损伤的影响,提出了波频和慢漂运动组合作用下钢悬链线立管疲劳损伤简化计算的位置组合叠加法。其核心是:基于浮体慢漂运动概率分布选取若干典型慢漂位置,进行波频运动作用下钢悬链线立管动力响应分析;根据钢悬链线立管运动位置变化特征,截取若干慢漂位置对应的波频应力时程叠加到慢漂应力时程上,得到波频和慢漂运动的组合应力时程;编写基于雨流计数法的MATLAB程序处理立管各节点应力,采用海水环境下Do E.E型S-N曲线和Palmgren-Miner累积损伤准则计算立管各节点疲劳损伤。应用位置组合叠加法对某海域500 m水深的立管进行了疲劳分析,并与全耦合法、权重组合叠加法以及波频和慢漂疲劳损伤简单相加法的结果进行了对比,结果表明该方法具有较高的精度和效率。此外,进行了区域设定系数、波浪高度、波浪周期和土壤表面剪切强度等参数对组合作用下立管疲劳损伤的敏感性分析。     

Reliability-Based Load and Resistance Factors Design for Offshore Jacket Platforms in the Bohai Bay: Calibration on Target Reliability Index

The target reliability index has been effectively used as the best solution to deal with the relationship between the structural safety and the optimal economy in any structural design. However, the target reliability index for off-shore jacket platforms based on different sea areas in China has never been calibrated. This paper presents an approach for its calibration, and suggests many kinds of associated load cases. The uncertainties of loads and structural resistance are mainly investigated. The target reliability index for structural components, tubular joints and piles of offshore jacket platforms are discussed respectively in detail. Finally, through the calibrated results from the offshore jacket platforms of QK18-1, JZ20-2, SZ36-1 and BZ28-1 in the Bohai Bay, it is proposed to adopt 2.8 as the target reliability index of offshore jacket platforms in the Bohai Bay for a 25-year design period. The results provide significant reference for the design of offshore jacket platforms.     

A Method for Analyzing System Reliability of Existing Jacket Platforms

Owing to the ageing of the existing structures worldwide and the lack of codes for the continued safely management of structures during their lifetime, it is very necessary to develop a tool to evaluate their system reliability over a time interval. In this paper, a method is proposed to analyze system reliability of existing jacket platforms. The influences of dint, crack and corrosion are considered. The mechanics characteristics of the existing jacket platforms to extreme loads are analyzed by use of the nonlinear mechanical analysis. The nonlinear interaction of pile-soil-structure is taken into consideration in the analysis. By use of FEM method and Monte Carlo simulation, the system reliability of the existing jacket platforul can be obtained. The method has been illustrated through application to BZ28-1 three jacket platforms which have operated for sixteen years. Advantages of the proposed method for analyzing the system reliability of the existing jacket platform is also highlighted.     

Hybrid Analysis Approach for Stochastic Response of Offshore Jacket Platforms

The dynamic response of offshore platforms is more serious in hostile sea environment than inshallow sea.In this paper,a hybrid solution combined with analytical and numerical method is proposedto compute the stochastic response of fixed offshore platforms to random waves,considering wave-struc-ture interaction and non-linear drag force.The simulation program includes two steps:the first step is theeigenanalysis aspects associated the structure and the second step is response estimation based on spectralequations.The eigenanalysis could be done through conventional finite element method conveniently andits natural frequency and mode shapes obtained.In the second part of the process,the solution of theoffshore structural response is obtained by iteration of a series of coupled spectral equations.Consideringthe third-order term in the drag force,the evaluation of the three-fold convolution should be demanded fornonlinear stochastic response analysis.To demonstrate this method,a numerical analysis is carrie     

分析初始地应力场的位移函数法

岩体初始地应力的确定是地下洞室、边坡等岩土工程设计和施工的必要条件。笔者从实用的角度出发,提出了一种将位移函数法和有限元法相结合来模拟初始地应力场的分析方法。实例应用的结果表明:该方法能很好地模拟岩体的初始地应力场,并能为后续开挖过程的有限元分析提供一种与初始地应力场等效且方便的加荷途径,具有良好的实用性。     

散货船及油船垂向波浪载荷短期预报经验公式

应用WALCS软件对6艘散货船及6艘油船进行了短期波浪载荷直接计算,依据计算结果分析了这两种船型在航速为0、迎浪、均匀满载及隔舱满载工况下的船舯垂向弯矩、L/4(L为船长)处垂向剪力、3L/4处垂向剪力的若干规律。根据这些规律,总结出了一套针对散货船及油船的垂向波浪载荷短期预报经验公式。依据此经验公式,在缺乏完备图纸资料的情况下,可以快速估计航行于海上的受损船舶的短期载荷情况,为评估其安全状态提供数值依据,为事故船东方做出安全可行的处理决策提供优质服务。