预应力混凝土枕枕中截面静载试验方法分析

根据预应力混凝土枕的枕中截面静载试验时轨枕放置方向的不同,以及我国现有轨枕静载试验机加载方式的不同,分析并换算出各种加载方式的实际荷载检验值,从而确保枕中截面静载试验负弯矩检验值的准确与合理。     

SG型轨道式水泥混凝土摊铺机组的主要机构设计

简单介绍了SG型轨道式水泥混凝土摊铺机组中布料机、振实机的升降机构设计构思,对该机构在静止、起升、下降状态进行了受力分析与计算,并详尽地给出了其计算程序,进一步对运算结果进行具体分析。     

Load-leveling suspension system with a magnetorheological damper

In this paper, a load-leveling suspension system with a magnetorheological (MR) damper is investigated. In this suspension system, the MR damper is connected to a spring to form a load-leveling suspension system. The system effective stiffness and damping can be adjusted by controlling the MR damper. The characteristics of a load-leveling suspension system are studied first. When the linear damper is replaced with an MR damper, the averaging method is adopted to obtain the steady-state response of the nonlinear system. A comparison demonstrates that the results of the averaging method are in good agreement with those obtained by numerical simulations. The analytical results are then verified experimentally. The load-leveling suspension system studied here is able to adjust both suspension stiffness and damping and, hence, it may provide more effective vibration control in a wider frequency range, when the damper is controlled.     

时速350 km/h铁路客运专线桥梁设计中应注意的几个方面

高速列车对桥梁结构的动力作用远大于普通铁路桥梁,桥梁出现较大的挠度会直接影响桥上轨道的平顺性,造成结构物承受很大的冲击力,并且会影响到列车的运行安全,其中设计活载图式的选择,离心力以及结构的变形变位,梁体的自振频率都会对桥梁的安全存在影响,因此,这些方面都是在设计中应该注意的。     

27t轴重通用货车应用下调车场连挂区调速控制研究

27 t轴重通用货车的应用给调车场连挂区调速控制提出了新问题。分析27 t轴重通用货车单位基本阻力更小、溜放动能更大等特点,减速顶对27 t轴重通用货车制动功的减小、临界制动速度的上浮等特性,以及与既有货车混合应用后超速连挂风险的增加、调速控制复杂性的增大等问题。通过模型建立、参数标定及仿真计算,得到减速顶对27 t轴重通用货车制动功的减幅及临界制动速度的漂移量。为解决27 t轴重与既有货车混合应用下调车场连挂区调速控制问题,提出3种调速控制方案,仿真计算显示,在满足27 t轴重通用货车调速控制、难行车不利溜放、最短溜放距离等约束下,增加布顶与调整坡度相结合的方案最优。     

基于虚拟支撑力的隧道合理支护时机探讨分析

以连云港北固山隧道为工程背景,利用有限元分析软件,分析了隧道开挖后在不同荷载释放系数下施加支护的作用效果；同时,结合超前注浆加固机理,对施作超前支护与不施作超前支护两种工况在不同支护时机下施作初期支护的围岩及支护结构的力学特征进行了对比分析,并根据两种工况下支护时机对隧道开挖后围岩及支护结构力学特征的影响,初步确定了较理想的初期支护时机.     

含大量块石、碎石回填土强夯地基加固效果检测

通过某一工程实例来说明采用载荷试验、动力触探试验、瑞利波试验检测含大量块石、碎石回填土强夯地基加固效果。     

Efficient estimation of extreme long-term stresses by considering a combination of longitudinal bending stresses

Longitudinal stresses due to combined horizontal and vertical bending moments in ships, corresponding to a return period of 20 years, are estimated by linear response analysis. In principle, the stress should be obtained by combining the stress in all sea states that can occur over a long-term period. A method to determine the desired long-term extreme stress by considering only a few short-term sea states is presented. The sea states have a certain probability of occurrence, and are each identified by a contour line in the (H _s, T _p)-plane. This approach makes it possible to estimate the extreme loads on the vessel in a practical and accurate manner. Moreover, it is shown that the long-term stress can be estimated by combining the individual long-term extreme stresses due to vertical and horizontal bending moments by using the sum-of-squares approach and accounting for the correlation between stresses. It was found that the correlation coefficient can be taken as the largest of the ones calculated along the contour line. It is shown that this correlation coefficient can even be approximated by the normalized phase angle at the wave length where the dominant response has its peak value. A comparison with the results obtained using well-known combination rules is presented. While linear analysis has been used here, it is believed that the approach can be generalized to stresses with nonlinear behavior, and hence represent a significant improvement in calculation efficiency. Received: September 18, 2001 / Accepted: December 18, 2001     

沥青加热技术中的热负荷计算

介绍了常见的沥青拌和厂（站）和沥表储库中供热系统设计和热源设备造型的关键－系统的热负荷计算方法。     

辽宁交通数据交换平台建设

数据交换是系统之间、部门之间进行数据共享的重要手段之一。本文针对辽宁交通数据交换平台建设，介绍了数据交换的原理，数据中心架构和具体功能，以及建设过程中应该注意的事项。