非均布轮载下钢桥面铺装力学响应分析

为了对非均布轮栽作用于不同钢桥面系的效应进行预估,在构造理想传力垫层建立三维有限元接触分析模型的基础上,计算了均匀分布、凸形分布、凹形分布3种荷栽分布下铺装层的力学响应。计算分析表明,构造传力垫层加栽的接触分析方法是分析正交异性桥面系作用复杂荷栽模式的一种有效方法,特别是当要考虑多种复杂荷栽模式、多个作用位置时。不同荷栽下铺装层力学响应的对比显示：3种荷栽模式下横向拉应变沿横断面的分布规律相当一致,但凸形分布的计算结果最大、均匀分布次之、凹形分布的计算结果最小;轴载一定时,高胎压轮胎服从凸形分布,所以高压轮胎对铺装层有更大的破坏作用。     

大跨径钢桥面铺装层动力响应研究

为了揭示钢桥梁桥面沥青混凝土铺装的实际受力特性,利用有限元方法对大跨径正交异性钢桥面铺装层的瞬态动力学响应进行了分析和计算。在不同层间接触条件时,对铺装层静力和动力响应计算结果分析的基础上,着重对完全光滑条件下不同加载周期、不同铺装层模量以及不同铺装层厚度等对铺装层动力响应的影响进行了探讨。结果表明,完全光滑和完全连续接触条件下铺装层的动力响应截然不同,完全光滑时铺装层的最大拉应力为完全连续时的近10倍;加载周期及铺装层模量对铺装层的动力响应影响不显著;铺装层厚度对铺装层动力响应影响较大,当铺装层与钢桥面板之间完全滑动时,6 cm左右的铺装层厚度是最不利的。与静力学计算结果相比,动力计算结果更加接近实际情况。     

一种基于Fourier-Bessel级数求解FRP筋粘结锚固径向反应的解析方法

根据FRP筋表面沿纵向呈周期的特性,提出了一种基于Fourier-Bessel级数求解FRP筋粘结锚固径向反应的实用解析方法。从轴对称问题的基本方程出发,利用标准化Fourier-Bessel级数三角函数等式,推导了修正贝塞尔方程,得到了各向同性材料和横观各向同性材料的解析解,最后针对FRP筋粘结式锚具的边界条件,得到了钢套筒约束的粘结介质以及FRP筋在径向应力作用下的位移和应力计算公式。解析解与有限元解基本一致,验证了基于Fourier-Bessel级数求解FRP筋粘结锚固的径向反应是一种可靠的、实用的解析方法。计算表明,在径向应力作用下,对于钢套筒约束的粘结介质和CFRP筋,轴向位移在粘结界面的径向应力中心位置处最大;钢套筒外壁的径向位移仅为粘结界面处的径向位移1/8;CFRP筋的径向位移在中心轴为零,并向筋材表面线性增加。     

动态分段技术在公交查询系统中的应用

针对空间二维坐标下存储城市公交系统数据存在的问题,文中提出了采用动态分段技术建立公交系统数据库的方法．并在该数据库的基础上实现了换乘次数最少的乘车方案。基于ArcGIS Engine组件和．Net开发平台．实现了基于动态分段技术的公交查询系统,表明动态分段技术在公交查询系统中的适用性。     

美国卡特彼勒HEUI共轨液压式喷油系统

美国卡特彼勒公司生产的共轨液压式（Hydraulic Electronic Unit Injection,HEUI）柴油喷射系统广泛应用于各种货车和客车上,结合其最新变型产品,重点分析和探讨其结构原理特点和使用性能以及在柴油发动机上的应用,同时介绍喷油器的结构和响应特性。     

Two- and three-dimensional hydroelastic modelling of a bulker in regular waves

The relatively high rates of bulk carrier casualties in recent years, as well as structural features such as large deck openings, make this vessel type a suitable example for investigating the influence of hydroelastic modelling on predicting wave-induced loads and responses. Two- and three-dimensional fluid–flexible structure interaction models, due to their different degree of complexity and associated data requirements, can be used at different stages of the design process when estimating wave-induced loads, namely preliminary and detailed design stages, respectively.

In this paper, therefore, two- and three-dimensional hydroelasticity theories are applied to predict and compare the dynamic behaviour of a bulk carrier hull, based on OBO MV Derbyshire, in waves. Both symmetric and antisymmetric motions and distortions are incorporated in these investigations. The three-dimensional structural model consists entirely of shell finite elements, representing all major external and internal structural components, whilst the two-dimensional model is generated using Timoshenko beam finite element and finite difference discretisations. Issues relevant to the structural modelling stage, for both idealisations, are discussed. The in vacuo dynamic characteristics are compared for all models, with particular emphasis on the influence of hatch openings, shear centre and warping on the antisymmetric dynamics of the structure. For the wet analysis the fluid–flexible structure interaction is carried out using two-dimensional (Timoshenko beam and strip theory) and three-dimensional (beam and shell finite element idealisations combined with potential flow analysis based on pulsating source distribution over the mean wetted surface) analyses. Comparisons are made between steady-state responses predicted by two- and three-dimensional models in bow quartering regular waves.

It is shown that whereas the predicted symmetric dynamic responses obtained from two- and three-dimensional models are in good agreement, differences are observed for the antisymmetric dynamic characteristics. It is thought that this may be due to inadequacies in the beam models employed when simulating the global dynamic behaviour of this highly non-prismatic hull girder whilst allowing for the effects of warping.     

重载铁路路基基床不同改良厚度的动力响应研究

重载列车荷载对路基基床的影响较为显著,为探究北方风沙地区选择水泥改良的粉细砂作为基床填料后路基体的变形及动力稳定性。通过动三轴试验对比分析了不同掺入率水泥改良土临界动应力大小及不同围压下回弹模量的变化规律,进一步结合FLAC3D建立三维动力仿真模型,重点探讨了列车激励荷载作用下路基基床换填不同厚度的5%水泥改良土时动应力、沉降变形、振动加速度的变化分布规律。结果表明:5%水泥改良土临界动应力、回弹模量较原状土提高幅度最大;路基体竖向动应力、位移、加速度峰值均随深度增加而逐渐减小;路基基床对动应力的扩散抑制作用较强,动荷载传递经基床后平均衰减约83.5%;路基沉降主要产生在中上部,且随基床底层改良厚度增加路基顶部最大竖向位移逐渐减小,最大减小约45.6%;此外,振动加速度传播经改良后的路基基床衰减幅度较明显,约为69.4%。     

两种减隔震支座性能对比研究

通过对摩擦摆支座及弹塑性钢阻尼支座两种不同类型的减隔震支座的抗震性能进行对比,选择适合项目要求的支座类型。对比结果表明:两种减隔震支座均能够有效延长桥梁结构自振周期,支座横向刚度较小的摩擦摆支座更有利于周期的延长,同时产生的墩顶剪力也较小;对于墩底截面及基顶截面的弯矩和剪力,在墩高较低时横向刚度小的摩擦摆支座减隔震性能较好,而墩高大于20 m时,横向刚度大的弹塑性钢阻尼支座更有优势。     

A Two-Stage Optimization Model for Staggered Work Hours

Traditional or standard work schedules refer to the requirement that workers must be at work the same days and during the same hours each day. This requirement constrains work-related trip arrivals, and generates morning and afternoon peak hours due to the concentration of work days and/or work hours. Alternative work schedules seek to reschedule work activities away from this traditional requirement. The aim is to flatten the peak hours by spreading the demand (i.e., assigning it to the shoulders of the peak hour), lowering the peak demand. This not only would reduce societal costs but also can help to minimize the physical requirements. In this article, a two-stage optimization model is presented to quantify the effects of staggered work hours under incentive policies. In the first stage, a variation of the generalized quadratic assignment problem is used to represent the firm’s assignment of workers to different work starting times. This is the input of a nonlinear complementarity problem that captures the behavior of the users of the transportation network who are seeking to overcome the constraints imposed by working schedules (arrival times). Two examples are provided to show how the model can be used to (a) quantify the effects and response of the firm to external incentives and (b) evaluate what type of arrangements in starting times are to be made in order to achieve a social optimum.     

模数式桥梁伸缩缝水平向动力学响应分析

运用有限元分析软件对模数式桥梁伸缩缝进行水平向动力学研究,建立了其水平向有限元动力学模型,研究了车轮对中梁的水平冲击以及车速、中梁弹性支承刚度及预压量、滑动摩擦系数和剪切弹簧刚度的变化对中梁水平位移的响应特性。研究表明,当车速高于100 km/h,中梁弹性支承刚度小于70 000 N/mm时,应考虑车轮对中梁的水平冲击,当车速低于120 km/h,中梁弹性支承刚度及预压量分别大于80 000 N/mm和0.3 mm,滑动摩擦系数大于0.03,剪切弹簧刚度大于400 N/mm时,此时中梁水平位移小于0.5 mm,且车轮对中梁的水平冲击也可不考虑。