为研究波形钢腹板PC组合箱梁抗火性能及抗火设计方法，采用ANSYS软件建立热-力耦合分析模型，分析了受火工况下组合箱梁的挠度、侧向位移、钢束张力以及抗弯承载能力的变化规律，并以组合箱梁的挠度和腹板侧向位移为判定指标，提出了一种关于波形钢腹板组合箱梁的抗火设计方法。结果表明：荷载比是影响组合箱梁挠度发展的关键因素；受火全过程中，钢束张力的变化对组合箱梁挠度、侧向位移以及承载能力的变化影响较大；组合箱梁受火初期挠度增长缓慢，在横隔板处形成塑性铰后，跨中挠度快速增大，然后在加载处形成塑性铰，随即组合箱梁因顶板被压碎而破坏；采用抗力准则判断组合箱梁的耐火极限偏于不安全；通过在组合箱梁的波形钢腹板转角处增设立柱，能够减缓组合箱梁挠度和腹板侧向位移的发展，有效提高该类组合箱梁的抗火性能，当无立柱组合箱梁达到耐火极限时，有立柱组合箱梁跨中挠度为无立柱组合箱梁跨中临界挠度的64.3%。研究成果可为该类型组合箱梁的抗火设计提供参考。
The relationship between railway alignment and passenger comfort under high-speed driving conditions is even closer, requiring alignment smoothness to a greater extent. However, vertical curve dynamic detection alarm is a chronic, difficult-to-resolve issue in operational high-speed railways. Therefore, a novel method combining alignment parameters and track geometry from the perspective of smoothness is proposed to optimize the curve radius by controlling elevation differences and to calculate track adjustments by improving the long wavelength irregularity. To validate the performance, the proposed method is adopted to develop vertical curve maintenance schemes for Beijing-Hong Kong high-speed railway, and the daily average number of level II warnings of vertical acceleration decreased by 95% after applying the schemes. The results demonstrate that the proposed method effectively improves alignment smoothness in the dynamic detection alarm section. The method still needs to be subsequently extended to improve its adaptability to different irregularity bands and complex line conditions.
A finite element model was established to study the long-term deformation coordination mechanism of a CRTS III slab ballastless track-prestressed concrete simply supported girder system (girder-track system). Considering the randomness of key parameters, the mean value of the creep coefficient with a 95% confidence interval was obtained using the Latin hypercube sampling method. Secondary development using Abaqus software was used to simulate concrete shrinkage, creep, and relaxation of the prestressed tendons. Subsequently, the uncertain long-term deformation of the girder-track system was analysed in detail. The results indicated that the CRTS III ballastless track significantly increased the mid-span creep camber of the girder (MCCOG). The long-term deformation of the girder causes a difference in vertical deformation between the layers of the girder-track system and induces voids between the base plate and the self-compacting concrete. Additionally, rail irregularities also appear. The deformation amplitude of the rail is exponentially related to time and proportional to the MCCOG with a scale factor of 1.02. Moreover, the small resistance fastener (SRF) can effectively weaken the girder-track interaction.
研究目的:黏土在间歇动载作用下的刚度软化是黏土重要的动力特性之一,同时土体在间歇期会发生内部结构的调整,从而对土体的力学性质产生影响.为探究间歇动载作用下黏土刚度的变化特性,采用共振柱试验系统,对南昌地区粉质黏土在间歇振动荷载作用下的模量软化及恢复进行研究.试验中详细地研究了荷载幅值、含水率、围压等因素对土体模量变化的影响,并引入土体模量演化模型,对土体软化和恢复的关键影响因素进行分析. 研究结论:(1)随施加动载幅值的逐渐增加,土体模量软化程度也显著增强;含水率对土体软化指数的影响与其对干密度影响相似;(2)增大围压能够提高土体的抗软化能力,有利于减小土体在间歇性动载下所产生的变形;(3)黏土在间歇动载作用下的软化和恢复可以统一由所引入的理论模型进行描述,证实了所引入的理论模型的适用性;(4)尽管本文是针对区域性土进行的研究,但是采用的分析方法、使用的模型及相应的结论可以推广至其他地区黏土相关性质的研究.
研究目的:环长株潭城市群作为长江中游城市群的重要组成部分,是中部崛起战略实施的重要载体和平台,对其技术创新效率的研究和探讨,有利于长江中游城市群经济整合与协同发展.本文就测度环长株潭城市群的技术创新效率及其时序发展特征展开研究,并研究其空间演化、区域差异、空间关联格局. 研究结论:(1)环长株潭城市群技术创新效率整体处于增长趋势,核心城市的技术创新效率领先于外围城市;(2)技术效率进步是技术创新全要素生产率变化的主要因素;(3)对各城市技术创新投入-产出-效率类型进行了划分,揭示了不同类型城市技术创新发展差异;(4)环长株潭城市群技术创新效率表现为"东南-中北-西南"递减的空间分异格局,各城市效率差距呈现出先缩小、后扩大的变化趋势,空间关联表现为"核心强、外围弱"的特征,存在"强者愈强"的空间关联现象;(5)本研究成果可从要素配置、创新协同、要素流动等方面为区域技术创新提供政策建议.
