某工程大屋面结构施工关键技术质量控制

针对某地铁车辆段运用库工程预应力钢筋混凝土大屋面工程施工中涉及的高支模、大体积混凝土、预应力工程等施工关键技术 ,主要介绍大屋面结构质量形成过程中的施工措施和控制要点     

二个不等式的构造证明

本文介绍(Σfrom i=1 to n x_i y_i)~2≤(Σfrom i=1 to n x_i~2)'(Σfrom i≠1 to n x_i y_i)~2≥(Σfrom j≠1 to n x_i y_j)(Σfrom j≠1 to n x_i y_j)的二种构造证明。     

河口垂向二维悬沙输移数学模型

针对窄深的潮汐河口建立了沿宽度方向积分平均的垂向二维悬沙输移数学模型,潮流场的模拟采用三维MOHID模型,悬沙对流扩散方程采用Galerkin有限元法进行求解。利用该模型模拟了长江口北槽段潮流输沙过程,计算结果与实测资料较好吻合,表明了该模型能够模拟窄深的潮汐型河口地区悬沙输移过程。     

双线铁路箱梁施工阶段跨中截面应力的有限元分析

在双线高速铁路建设中，广泛采用整体箱型梁结构形式。本文采用弹性力学有限元方法。建立了8节点六面体等参数单元的三维应力分析有限元模型。结合双线铁路预应力混凝土简支箱梁的施工，利用SAP90通用结构有限元分析程序，建立了整体箱梁三维实体单元模型，通过梁单元施加预应力荷载效应。箱梁采用后张法施工工艺，分别以预应力初张拉阶段、预应力终张拉完成、二期恒载作用为分析荷载工况，计算了箱梁跨中截面应力，给出在施工过程中箱梁跨中截面的应力随预应力张拉的变化及分布情况。通过有限元分析结果与铁路桥涵设计规范的比较得出，该箱梁结构设计合理，施工方案可行。本文所采用的分析方法和结论对于双线铁路箱粱的设计与施工有一定的借鉴意义。     

连续纤维在工程结构加固中的应用

纤维聚合物(Fiberreinforcedpolymer,简称FRP)复合材料由于其质轻、高强、耐腐蚀等特点,已被广泛应用于土木工程中。为了更好地维修加固桥梁、延长构件的使用寿命,文中对普通粘贴FRP加固法、嵌入式加固法(NearSurfaceMounted,简称NSM)以及预应力FRP加固法在工程结构加固中的应用进行了概述。提出了粘贴FRP加固工程结构中,被加固构件的长期性,包括复合材料和粘贴固化后的老化性能、耐久性能,胶粘剂徐变收缩对梁体性能的影响以及疲劳可靠性、加固结构的整体性能等问题,这些问题都有待进一步研究解决,并拟将预应力加固技术应用于铁路桥加固工程中。     

张拉自动控制系统在箱梁预制中的应用

通过对箱梁预应力张拉自动控制系统在襄汾制梁场箱梁预制中的应用,阐述了系统原理及组成,总结了箱梁预应力张拉自动控制系统的施工工艺及特点,提出了系统改进的建议。     

Three-dimensional override analysis of crashed railway multiple units

Override simulations of two train units in frontal collision have been carried out using multi-body dynamics. The aim of this paper is to investigate the possible factors influencing the overriding behaviour throughout frontal collisions. In addition to the initial vertical offset defined in the standard EN 15227, the pitching motion of vehicles has a great effect on the overriding phenomenon. It depends on several factors, such as collision mass, pitching frequency, height of the centre of mass above the rail level. In this paper, it has been shown that the overriding phenomenon is more sensitive to variations in pitching frequency and height of the centre of mass, compared with the factor of the collision mass. Moreover, it has been demonstrated from simulation results that a 200-kN vertical force is required for the combined anti-climber devices (100 kN for each side anti-climber) to constrain the vertical relative motion between crashed train units.     

Community structure of mesopelagic copepods (>500 μm) in the Ligurian Sea (Western Mediterranean)

The distribution of mesopelagic copepods between 250 and 1000 m depth was studied along a transect off the coast of Villefranche-sur-Mer in June 1991 by means of a BIONESS multiple-net sampler. Among the most abundant species at all stations were Pleuromamma gracilis, Paraeuchaeta acuta and overwintering Calanus helgolandicus CV copepodites, each species inhabiting different depth layers with maximum abundances in the 250–350 m, 450–550 m and the 700–850 m layer, respectively. Cluster analysis of the vertical distribution of all species caught revealed three distinct strata (‘TOP', ‘INTERMEDIATE', ‘BOTTOM') consisting of characteristic species that occurred in the same stratum at all stations. Differences in total abundances of the species assemblage occupying each layer are discussed with regard to predation pressure by mesopelagic macroplanktonic crustaceans and fish. We show that each stratum is characterized by distinct trophic interactions and life strategies, which play an important role in the structuring of mesopelagic zooplankton communities.     

预应力技术在大桥高墩托架预压中的应用

结合杨家岭特大桥施工实例,介绍了在高墩连续刚构桥梁0号梁段施工时应用预应力技术,对高墩托架进行预压的方法,并与传统堆载的预压法进行了比较。     

平面交叉口智能化竖向设计

在比较国内外已有的平面交叉口竖向设计软件基础上，提出一种全新的交叉口数学模型——MESH—GRID模型。基于该模型的交叉口设计方法简捷、精确，适用于所有交叉口样式，能快速绘制等高线、标注板块高程，更能实时直观的查看、调整交叉口设计面三维模型。