秦岭马白山隧道新型紧急救援站结构型式研究北大核心CSCD

针对艰险山区高速铁路隧道的防灾救援难题,文章依托秦岭马白山隧道,提出了适合该隧道的新型紧急救援站结构型式,并利用FDS软件模拟隧道内纵向通风时列车着火后的烟气扩散,确定了规范中尚未给出的紧急救援站隔离区长度参数。结果表明:(1)秦岭马白山隧道新型紧急救援站结构型式应包括疏散区、隔离区以及待避救援区;(2)利用FDS数值模拟时,在不考虑纵向通风下,烟气沿下坡方向的扩散长度为295 m;考虑沿下坡方向通风时烟气最远扩散长度为980 m,建议隔离区长度设置为1000 m。     

带自由液面有限长圆柱绕流数值模拟

[目的]为了探究自由液面及自由端对典型钝体绕流问题的影响,对带自由液面的有限长圆柱绕流进行研究。[方法]基于延时分离涡模拟(DDES)技术和分段线性界面重构(PLIC)方法,利用自主开发的naoe-FOAM-SJTU求解器开展数值模拟。[结果]结果显示,自由液面和自由端的存在增大了局部位置的升、阻力,推迟了圆柱表面流动分离的发生;相较于深吃水位置,自由液面附近流向的速度"恢复"延缓,横向的速度呈向外运动的趋势;自由液面的变形产生了大量细碎的漩涡,自由端的卷拧状漩涡在一定程度上抑制了卡门涡街的发展。[结论]研究表明,目前采用的数值方法能够准确捕捉复杂流场,同时,自由液面和自由端的存在将显著改变流场沿吃水方向的分布。     

全预制盾构隧道边箱涵精细化施工分析

依托京张高铁清华园隧道工程,介绍清华园隧道工程及其隧道内边箱涵施工工法,并详细讨论边箱涵预制化施工的优缺点。盾构隧道采用全预制轨下结构有5大优点:降低施工现场环境污染,有效改善施工现场工人作业环境,有助于提高工程整体施工效率,降低施工作业风险水平,保障钢筋混凝土构件的质量水平。但依然存在以下缺点:提升构件制造及运输维护费用,构件现场吊装精度要求较高。针对清华园隧道边箱涵吊装施工精细化施工问题进行有限元分析,发现由于边箱涵重心两侧吊装孔距不同,会导致边箱涵近重心侧产生应力集中现象,同时将随着吊装误差的提高应力集中现象显著提升。为保证边箱涵的精细化施工,边箱涵吊装误差不得超过60 mm,两侧边箱涵左右交错拼装施工,建议未来类似工程中异形构件吊装孔设计应考虑吊装误差产生的影响。     

Analysis of structural crashworthiness of double-hull ships in collision and grounding

A conceptual design framework for collision and grounding analysis is proposed to evaluate the crashworthiness of double-hull structures. This work attempts to simplify the input parameters needed for the analysis, which can be considered as a step towards a design-oriented procedure against collision and grounding. Four typical collision and grounding scenarios are considered: (1) side structure struck by a bulbous bow, (2) side structure struck by a straight bow, (3) bottom raking, (4) bottom stranding. The analyses of these scenarios are based on statistical data of striking ship dimensions, velocities, collision angles and locations, as well as seabed shapes and sizes, grounding depth and location. The evaluation of the damage extent considers the 50- and 90-percentile values from the statistics of collision and grounding accidents. The external dynamics and internal mechanics are combined to analyse systematically the ship structural damage and energy absorption under accidental loadings.     

Collision course? The North Airfield Safety Study at Los Angeles International Airport (LAX)

The LAX North Airfield Safety Study was undertaken by an Academic Panel consisting of the present authors, and was based in large part on a simulation that was conducted at FutureFlight Central at NASA Ames Research Center. The primary aim of the study was “to estimate as specifically as possible the level of future safety associated with several geometrical configurations of the LAX North Airfield.” This paper describes the study, and how it combined information from human-in-the-loop simulations at NASA with historical data from LAX and other US airports about runway incursions and collisions. The analysis indicated that, even under its existing physical layout, LAX North would experience very low risk of runway collisions at traffic levels projected for 2020. That risk could be reduced by about half if the North Airfield runways were reconfigured, and some reconfigurations would also add appreciably to the operational efficiency of the airport. But because the “baseline” level of risk is so low, the Study concluded that “it would be difficult to construct a compelling case on safety grounds alone for reconfiguring the North Airfield.”     

聚氨酯夹层板舱口盖振动特性研究

聚氨酯夹层板(SPS)因其出色的力学性能、减振降噪特性等在船舶建造领域得到了广泛应用。以船舶轻量化、高性能设计为目标,以64000DWT散货船钢制舱口盖为替代目标,采用聚氨酯夹层板设计新型舱口盖结构,基于有限元软件Ansys Workbench开展SPS舱口盖结构振动特性分析,研究其模态振型、谐响应和随机振动。通过与钢制舱口盖振动特性的对比研究,论证了聚氨酯夹层板在船舶减重和结构减振方面的优势与前景。研究结果表明:SPS舱口盖设计方案,在实现整体减重12%的情况下,使谐响应振幅降低75%;在1σ区域内,使随机振动的位移、应力响应分别降低了63.4%和76.1%。研究结果可以为船舶结构轻量化设计、舒适性改善等提供参考。     

基于交错并联的Ⅱ型五电平逆变器电路的仿真研究

研究了一种基于交错并联的Ⅱ型五电平逆变器电路。该拓扑是双BUCK电路的一种变形,可以视为双BUCK拓扑和交错并联技术结合的产物。这种拓扑减少了开关器件,降低了系统复杂度,而且提高了输出频率,大幅度减小了用于滤波的无源器件的体积。介绍了该拓扑存在的7种状态和4种模态。介绍了Ⅱ型五电平的单向仿真,详细阐述了其正弦脉宽调制.仿真结果符合之前的理论研究,说明该拓扑在大功率变换场合有其前景。     

Simplified buckling-and-contact-based expansion method for assessment of crashworthiness of double-hulled ship structure

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.     

与铁路同台驳接地铁站台排烟方案探讨

针对地铁、国铁同台驳接入铁路枢纽的地铁车站,地铁地面站台位于交通枢纽内部的特殊形式,站台层的排烟方案需根据建筑形式进行特殊考虑。对站台层的排烟方案进行对比分析,通过火灾烟气模拟,对烟气自然扩散、自然排烟和机械排烟3种排烟方案进行对比分析。烟气自然蔓延条件下,能见度无法保证人员安全疏散。由于建筑形式的特殊,无法满足自然排烟条件。为保证安全,设置了机械排烟系统。对与国铁站房结合的综合枢纽中地铁车站排烟方式,应将自然排烟的可行性纳入其初期建筑方案中优先考虑。     

基于ADAMS的舰载补给起重机摇摆仿真及减摇措施分析

舰载补给起重机吊运柱状箱体时,箱体会由于各种外界影响发生摇摆。针对舰载补给起重机起吊的柱状箱体在舰船摇荡、起重机启停、风载的影响下发生的摇摆进行了ADAMS动力学仿真,得到了这3种因素对柱状箱体摇摆的影响情况,以及柱状箱体在预设工况下的运动规律。改变钢丝绳数量和布置形式进行仿真,得到了不同钢丝绳数量和布置下柱状箱体的运动情况以及相对单根钢丝绳的减摇效果,为进行动基座起重机减摇、防摇研究提供了依据。