Numerical evaluation method of lightning rod protection probability北大核心CSCD

［Objectives］Aiming at the current situation in which it is difficult to efficiently evaluate protection probability through traditional lightning rod evaluation methods, an efficient numerical evaluation algorithm is developed on the basis of an electrogeometric model (EGM) and attractive volume to realize the efficient calculation of lightning protection probability at any point in space.［Methods］This method first determines the attractive volume boundary of the lightning rod and protection object according to the interception process of the upward and downward leaders. The collection surface and exposure arc of the lightning stroke distance are then calculated, enabling the attractive risk and interception effect of the lightning rod to be quantified. Finally, the attraction and interception characteristics of the lightning rod are integrated to establish a numerical evaluation model of protection probability. To verify the accuracy of this method, the general rule of lightning rod protection probability is analyzed and the results compared with the existing analysis method.［Result］The evaluation results of this method show good agreement with those of classical leader progression model (LPM) theory.［Conclusions］ The method proposed herein has a high degree of quantification and can realize the efficient calculation of lightning protection probability at any point in space, which can provide useful references for lightning protection design work. © 2023 Authors. All rights reserved.     

Numerical investigations into the influence of geometric configurations on hydrodynamic characteristics of torpedo anchors

Torpedo anchors are an innovative and cost-effective technology in marine foundation engineering; however, there is a lack of systematic and comprehensive studies on the influence of torpedo anchor geometry on its hydrodynamic characteristics, especially the effect of anchor fin configuration on the hydrodynamic characteristics is rarely reported in the existing literature. Therefore, this study investigates the influence of geometric characteristics of both finless and finned torpedo anchors on their terminal velocity, drag coefficient and installation directional stability in water through CFD numerical analysis in a systematical manner. The considered geometric characteristics include the center of gravity position, shape and angle of anchor tip, shaft and fin aspect ratio, fin number, fin thickness, fin shape, fin position and fin area. Based on the obtained numerical results, some practical design recommendations and impact weighting charts of different anchor geometric factors are provided, which enables a quick qualitative and quantitative assessment of torpedo anchors. In addition, a simple weight-based approach for estimation of terminal velocity and drag coefficient of torpedo anchors considering multiple geometric configuration factors is proposed, which may provide some reference and scientific guidance for experimental and engineering design of torpedo anchors.     

大体积混凝土止浆垫块及拉杆装置在龙溪口航电枢纽中的应用

在船闸工程大体积混凝土施工过程中，常使用高大模板，为保证模板的稳固，增加其安全性，现场施工中往往采用斜拉杆对模板加固，并使用发泡剂或者缠绕胶带等进行止浆，然而这种传统的方法往往存在工序复杂、止浆效果不佳、拆模后混凝土外观质量差等缺点。为解决该问题，采用一种基于大体积混凝土高大模板施工的弹性材质止浆垫块，并辅以端头带螺纹的拉杆装置，可有效防止混凝土浆液渗漏，还可为拉杆预留保护层以防止锈蚀。该止浆垫块在现场施工的应用取得了较好成效，在提升施工质量及效率的同时，较大程度改善了混凝土表面外观，可为类似工程的大体积混凝土施工止浆提供参考。     

桥梁单锥孔夹片式预应力锚具握裹力分析

反拉法以测试曲线的拐点来判断锚下有效预应力，是当前最为广泛的锚下有效预应力检测手段。近年，众多学者发现测试曲线拐点处存在荷载骤降的情况。因此，针对反拉法测试曲线的突变段成因进行了探讨，提出了反拉荷载在夹片拉脱过程中需克服锚具握裹力从而导致突变段产生的观点。其中，锚具握裹力主要由锚圈与夹片的摩阻力和锚圈与夹片的机械咬合力构成。同时，为了得到握裹力的影响因素，建立了单锥孔夹片式锚具握裹力分析的有限元模型，设计并阐述了有限元模型的握裹力提取方法。通过有限元模型得到了影响锚具握裹力的3项影响因素——控制张拉力、摩擦系数、锥孔数量，并拟合了控制张拉力、摩擦系数与握裹力的关系曲线，得出了控制张拉力、摩擦系数与握裹力正相关的结论。     

锚链多体系统最优化求解方法及其对比分析

为了在不添加额外方程或判断条件的情况下，求解锚链多体系统悬链和卧链共存的状态，提出利用最优化原理描述静态锚链多体系统的状态方程，即最小势能方程，并与传统的悬链线方程和多体系统一般力学方程进行对比分析。结果表明，该方法不需要进行复杂的受力分析，形式简单且物理意义明确。数值计算结果与传统方法在计算悬链时是一致的，且可在统一的框架下计算悬链和卧链同时存在的状态。     

棒磨机挥发性气体排污特性分析

基于棒磨机挥发性气体逸出造成操作人员职业健康受损的问题，对棒磨机挥发性气体排污特性进行分析。建立棒磨机排污计算模型，分析流场、空气龄和挥发性气体的分布特征与排污效率。结果表明：缝隙可降低棒磨机氨气的体积分数、提升排污效率，但在压差小于15 Pa时挥发性气体会从缝隙中逸出，需要密切关注压差以保证棒磨机缝隙不发生外逸；在相同工况条件下，优化方案的平均排污效率分别提高约68.7%及71.8%，排污效率显著提升；综合考虑氨气的体积分数、外逸的潜在风险性及排污效率，选取60 Pa压差作为最优方案较为合理。     

自锚式悬索桥锚固段合理总体布置研究

锚固段是自锚式悬索桥的关键受力部位。结合某336 m跨径自锚式悬索桥的锚固段总体布置设计，对自锚式悬索桥的锚跨设置、散索鞍/套设置、锚固段重心调整等问题进行分析研究，建议主梁竖向刚度不控制设计时取消锚跨，边跨主缆入射角适中时优先采用散索套，提出了锚固段合理重心的调整思路。上述结论可为今后同类型结构的设计提供参考。     

基于预应力锚栓技术的悬挂式单轨钢柱脚设计

随着中国城市化进程的深化,全国轨道交通建设形势如火如荼.悬挂式单轨交通桥墩采用预制拼装钢立柱,施工速度快,占地少,可有效减少轨道交通建设对现状交通的影响.现以宁波杭州湾新区城市全域旅游配套基础设施工程为背景,对钢立柱柱脚常见构造形式进行回顾和比较,提出了一种基于预应力锚栓的节点连接形式.该节点连接形式施工方便,整体性好,节点刚度大,抗疲劳性能优越.