桥上双块式无砟轨道结构参数影响分析

根据梁板有限元理论,针对桥上双块式无砟轨道结构的特点,建立了相应的梁板有限元模型,分析了轨道结构参数对桥上双块式无砟轨道受力的影响,为双块式无砟轨道结构的设计提供了依据。     

Wind loading effects on a catenary

The effects of wind loads on the static profile and force transmission efficiency of a tether tied to a kite-like aerodynamic body has been theoretically examined. Two important parameters which characterize the behavior of the tether have been obtained. These are the tether weight parameter, which is the ratio of tether weight to the tether tension, and the wind load parameter, which is the ratio of wind load to the tether weight. Results obtained from five different tether models (straight line, catenary, constant velocity, variable velocity and maximum stress) have been compared to determine regions of applicability of these models in terms of the above two parameters.     

三角高程测量在高铁特大桥无碴轨道施工测量中的应用

高速铁路轨道铺设在平面和高程上要求很高的位置精度。但在桥梁施工后,已很难用几何水准测量方法将地面上水准点的高程传递到桥面上。本文介绍了在高速铁路特大桥无碴轨道施工测量中,采用三角高程测量方法将地面水准点的高程传递到桥面临时水准点上,使CPⅢ精密水准测量能与地面二等水准点附合,以满足无碴轨道施工测量要求。     

Influence of the ballasted track on the dynamic properties of a truss railway bridge

This article presents numerical and experimental analyses of a steel truss railway bridge. The main feature of this work is that dynamic experiments have been performed before and after the ballasted track was placed on the bridge. Consequently, it has been possible to quantify the effect of the ballast and the rails on the dynamic properties of the bridge. For that, two finite element models, with and without the ballasted track, have been implemented and calibrated using the experimental results. It appears that the ballast gives an additional stiffness of about 25–30% for the lowest three eigenmodes. This additional stiffness can be only partly explained by the stiffness of the ballast. In fact, it seems that this additional stiffness is also due to a change in the support conditions.     

Suspension bridge response due to extreme vehicle loads

A 269 tonne trailer travelled across the Tamar Suspension Bridge in October 2010, and the authors monitored the response of the structure to the load. The following investigation documents the deflection of towers and the deck during the vehicle's passage, as well as the change in cable tensions. This was achieved by studying monitored data from the bridge collected by accelerometers and strain gauges attached to the stay cables, as well as two robotic total stations that measured the deflection of the mid-span and the sway of the tower saddle. These results were subsequently compared to the response predicted by a finite element (FE) model of the bridge, indicating an accurate match. The FE model was also used to simulate the variation of the dynamic response of the structure, which suggests that the natural frequencies vary depending on the vehicle's location to each mode shape's anti-nodes.     

某市双层钢结构特大桥消防设计研究

通过对某市双层钢结构特大桥过往运输车辆的分析,列举了该桥发生火灾的种类,同时结合规范要求,提出了两种设计方案并进行了比选,得出防火涂料加消火栓系统的方案为最佳方案,为类似工程提供了参考依据。     

浅谈双钢混凝土桥面铺装施工质量控制

根据大同绕城高速公路平旺高架桥双钢混凝土桥面铺装施工实践,从钢纤维混凝土原材料控制和桥面钢筋加工与安装控制以及钢纤维混凝土拌和、运输、摊铺机连续摊铺施工程序的控制等方面提出了具体控制措施和改进方法,以使双钢混凝土桥面铺装施工质量得到不断的提高.     

简支梁桥上板式无砟轨道伸缩力影响因素分析

为研究桥上板式无砟轨道无缝线路受力变形规律,基于有限元法建立了多跨双线简支梁桥上板式无砟轨道空间整体有限元模型,计算梁体温度荷载作用下的钢轨附加伸缩力与位移,并分析了桥梁跨数、墩顶固定支座纵向水平线刚度以及扣件纵向阻力等因素对钢轨伸缩受力与变形的影响规律。     

一座大跨径双曲拱桥的承载能力鉴定

对一座单孔跨径80 m的双曲拱桥拱波顶部存在的纵向裂缝进行了介绍,该裂缝整段贯通,且该桥一侧拱肋明显下沉,通过病害检查、材料强度测试、线形测量和结构检算,确认该桥承载能力已不能满足通行现有荷载等级的要求。     

某铁路大桥静载试验分析

针对三种不同的工况,对某一铁路桥的20 m跨梁和16 m跨梁分别进行了静载试验分析.梁的跨中最大变形计算值与实测变形值吻合良好.试验结果及相关的分析表明:20m与16m试验梁在试验过程中基本上处于弹性工作阶段;在试验荷载作用下,两试验跨预应力梁的变形能力和承载力均满足要求.     

沿竖向运动的水中截断圆柱体辐射波浪问题的解析解答

根据线性势波理论,分析了水中截断圆柱体作竖向简谐运动时结构周围的辐射波浪.利用分离变量法,分别得到了含有未知常数的3个流体子域速度势的简谐表达形式,并采用一个较为简单的匹配方法,使其在流体子域的共同边界上满足压力和法向速度的连续条件,于是求解得到速度势,进而可得到由等效附加质量和附加阻尼表示的柱体上、下表面的动水力.本文方法不仅能考虑自由表面波对动水压力的影响,也适用于位于任意水深处的截断圆柱体.算例结果证明了该方法的正确性.     

A new approach to estimate the wind speed probability distribution along a railway track based on international standards

The plan to establish a European market for railway services and equipment requires technical regulations for interoperability. One topic to be regulated is the safety of railway operation under crosswind conditions. For this a method is necessary for categorising high-speed tracks with respect to their wind exposure. This method has to be simple and robust, and it has to be applicable to all European countries. The method presented here is based on available and reviewed wind data and on procedures described in the Eurocode and other standards. The new approach is compared to the well-established German method which has been used in the past for all high-speed lines in Germany.     

Strengthening of a steel railway bridge and its impact on the dynamic response to passing trains

Two different strengthening methods for a through-girder steel railway bridge are investigated. The studied structure is the Söderström Bridge, located in the city of Stockholm, Sweden. Due to fatigue problems, it is in need of assessment and strengthening. In one of the methods, arches are added under the bridge modifying the structural system and lowering the stress ranges for all structural members. The other method consists of prestressing the floor beams. This increases their stiffness and transforms the mean stress in the lower flanges from tension to compression. A 3D finite element model is created and verified with measurements. The different strengthening methods are tested in the model by dynamic analysis with moving train loads. The strengthening methods show some positive effect concerning the fatigue life. Changes in vertical bridge deck acceleration for high speed traffic are also presented. A comparison between the European code and the Swedish code regarding vertical bridge deck acceleration levels for high speed traffic shows large differences for the bridge.     

某拟建跨江大桥桥位岸坡稳定性研究

在研究某拟建跨江大桥桥位区工程地质条件的基础上,采用Geo Studio软件分析了桥墩荷载施加及库水位变动情况下岸坡的稳定性,结果表明:桥墩荷载施加后,主桥墩处的应力及位移改变显著,斜坡稳定性情况较好;在库水位升降作用下,斜坡稳定性进一步变差,整体稳定性尚满足要求。     

浅谈PC桥梁的顶推施工技术

1 顶推法施工的技术原理和方法1.1 顶推法施工原理　　顶推法施工原理是沿桥纵轴线方向台后设置预制场,预制梁体,预应力张拉后,通过千斤顶水平施力,借助滑动装置,将梁逐段向前顶推,就位后落梁,更换正式支座。　　单点顶推的动力学原理可用下述数学表达式表示：　　当H＞Ri(fi+ai)时,梁体才能向前移动　　多点分散顶推的动力学原理可用下述数学表达式表示： 当Hi＞Ni（fi+ai）时,梁体才能向前移动式中：　　H 单点顶推力　　Hi第i桥墩（台）千斤顶所施的力　　Ri第i桥墩（台）滑道瞬间垂直支反力　　Ni第i桥墩（台）…     

强化路桥施工技术 控制路桥施工质量

结合实际路桥施工情况,对路桥施工技术的合理控制进行分析,进一步阐述路桥施工技术控制的主要策略,最后分析强化路桥施工技术的质量控制措施,以期促进路桥施工建设高效发展。     

Human-induced landslide on a high cut slope: a case of repeated failures due to multi-excavation

The paper attempts to represent a case of repeated failures on a high cut slope due to multi-excavation. The characteristics of each failure induced by excavation are analyzed through geological investigation, and then a geological model at different failure stages is proposed. The geological analysis shows that the excavation-induced repeated failures are related to the exposure of the weak bedding plane and the toe unloading of the cut slope. Numerical modeling is conducted based on a sequential method, taking into account the main failure stages of cut slope. The simulation results fairly coincide with the practical phenomena observed in field. It is shown that the decrease in normal stress of displaced mass on cut slope will induce the increase in shear stress in bedding planes and that at the toe of the cut slope. The released stress leads to repeated gravitational instabilities of cut slope due to the decrease in normal stress and the increase in shear stress along the bedding planes of mudstone.     

谈对桥梁工程施工成本控制的几点看法

论述了成本控制在企业生存和发展中的重要性,从计划成本的制定、实施过程中的控制、安全管理对施工成本的影响等方面探讨了桥梁工程施工成本控制的具体方法,指出施工企业只有抓好成本管理,才能创造好的效益。     

Development of a tram track degradation prediction model based on the acceleration data

Abstract

Although vibration is considered as one of the important factors in passenger ride comfort, yet it has not been applied for predicting tram track degradation in tram network. Rail track degradation prediction models form an essential part of the rail infrastructure maintenance management systems. Vibration can be measured by acceleration signals. The acceleration signal is derived from the movement of railway vehicles on rail structure. In this study, vehicle acceleration data along with other track structural parameters have been used to predict tram track degradation index which can be considered as a representative of tram track quality. The index used in this study has been developed based on a mixture of tram track geometry deviations of several years. Three types of machine learning models have been employed for creating the prediction models. In this study, Melbourne tram network data have been applied for developing as well as predicting the degradation index. Based on the evaluation results, the proposed random forest regression model made more accurate predictions on track degradation compared to other developed models. The results of this study can help tram track managers to deploy cost-effective maintenance strategies by applying vehicle acceleration data in their decision-making processes.     

Analysis of girder bridge pier subjected to barge collision considering the superstructure interactions: the case study of a multiple-pier bridge system

This paper aims to numerically evaluate the effects of girder bridge superstructure on the impact responses and load paths transferring the shear force of pier subjected to a moderate-energy barge collision in LS-DYNA. First, two multiple-pier systems of St. George Island Bridge in Florida which have different piers in terms of structural characteristics (such as mass and stiffness), geometry, and the height of impact location are considered as the cases of study. From the numerical barge collision simulations, different impact responses and load transferring paths from the impact location to farther zones are observed. In addition, the sensitivity of impact responses, and the impact load paths transferring shear force to the superstructure mass, stiffness, and damping are studied by developing four different models of pier-superstructure interaction and carrying out a parametric study. It is found that the increase in the value of superstructure parameters has positive effects on the impact forces and the internal stresses in the piers. However, the sensitivity of shear stresses generated at various zones of the pier extremely depends on the impact load paths transferring shear force in different piers with different relative characteristics rather than the superstructure.