混凝土T梁桥拓宽的长期效应分析

为了分析拓宽后桥梁的时间效应,研究了每一时段内由混凝土收缩引起的应力的连续变化和混凝土的弹性模量变化,根据能量原理推导了混凝土收缩徐变的位移法基本方程,按增量法分析了徐变应变的变化,编制了相应的计算程序。为验证理论计算的正确性,与小试件的试验结果作了比较。在拼接缝处的受拉区,应变计算值与实测值的相对误差为10%,计算精度比代数法高。在新梁混凝土的收缩应力和新梁自重应力的徐变作用下,3 a后新梁翼板的拉应力为2.67 MPa,可能会引起混凝土开裂。为减少收缩徐变对新旧梁受力的影响,建议新梁脱模后至少放置6个月后再进行拼接处理。     

Multilane first-order traffic flow model with endogenous representation of lane-flow equilibrium

In this study, we develop a multilane first-order traffic flow model for freeway networks. In the model, lane changing is considered as a stochastic behavior that can decrease an individual driver’s disutility or cost, and is represented as dynamics toward the equilibrium of lane-flow distribution along with longitudinal traffic dynamics. The proposed method can be differentiated from those in previous studies because in this study, the motivation of lane changing is explicitly considered and it is treated as a utility defined by the current macroscopic traffic state. In addition, the entire process of lane changing is computed macroscopically by an extension of the kinematic wave theory employing IT principle; moreover, in the model framework, the lane-flow equilibrium curve is endogenously generated because of self-motivated lane changes. Furthermore, the parsimonious representation enables parameter calibration using the data collected from conventional loop detectors. The calibration of the data collected at four different sites, including a sag bottleneck, on the Chugoku expressway in Japan reveals that the proposed method can represent the lane-flow distribution of any observation site with high accuracy, and that the estimated parameters can reasonably explain the multilane traffic dynamics and the bottleneck phenomena uphill of sag sections.     

On macroscopic freeway merge behavior: Estimation of merge ratios using asymmetric lane flow distribution

Data from several freeway merges reveal that, contrary to some previous findings, merge ratio can vary within a site with respect to the merge outflow and that the existing merge ratio estimates based on lane counts are not able to predict this within-site variation. Furthermore, the merge ratios estimated based on two well-known merging principles, “fair-share” and “zipper,” are found to be inaccurate for merges where merging streams compete directly due to a lane drop. In light of these findings, we estimate merge ratios using lane flow distribution (LFD) to better predict between and within site variations of merge ratio. In addition, we propose a merging principle specific for merges with a single lane-drop. The model was developed to better represent observed non-uniform redistribution of merging flow not captured by the current merge ratio estimation methods and merging principles. Empirical observations show that the proposed methods are able to improve merge ratio estimates, reproduce within-site variations of merge ratio, and represent more accurately non-uniform redistribution of merging flow dependent on the merge geometry.     

小缸径低速柴油机加装EcoEGR系统设计与布置

某型火车滚装船布置2台小缸径低速柴油机加装经济型废气再循环（Economical Exhaust Gas Recirculation，EcoEGR）系统，以满足Tier Ⅲ排放要求。以该船为依托，对该类型主机及相应船舶管路与控制系统的原理设计、实船布置等进行介绍和深入分析，为后续或类似船舶的小缸径低速柴油机加装EcoEGR系统及设备设计与建造提供有价值的参考。     

无缝线路轨道稳定性简便计算方法

无缝线路稳定性分析是无缝线路的理论基础和关键技术。本文在考虑轨道原始弯曲和非线性横向道床阻力的前提下,在轨道变形曲线假设为半波正弦曲线的情况下,应用内外力矩平衡法,进行无缝线路轨道稳定性分析,推导钢轨温度力计算公式。应用多元函数条件极值理论推导最不利的轨道弯曲波长,从而建立简便实用的无缝线路稳定性计算公式。将此模型的计算结果与《铁路线路设备大修规则》中铺设无缝线路允许温差表的要求进行了对比,两者计算结果较为接近。     

高速公路双台面秤体计重收费防作弊原理分析

简要介绍了高速公路计重收费系统中常见的几种非正常行车的逃费方式,同时对这些方式进行了仔细的研究与对策,并着重对采用双台面秤体计重收费装置防作弊的原理进行详细的分析与比较。     

车用减速型起动机原理及常见故障分析

通过对车用减速型起动机组成结构及工作原理的阐述,详细分析减速型起动机的测试方法及常见故障,并提出了故障的诊断排除流程,为使用者了解其结构原理、掌握其故障排除程序提供有益的帮助。     

灌浆法在公路桥梁隧道施工中的应用

公路桥梁隧道施工中常出现裂缝、砌石松动、砌浆唯落等问题,利用灌浆法对公路桥梁隧道基础进行加固能够有效改善上述问题,并显著提升墩台基础的承载能力.结合公路桥梁隧道工程实例,对灌浆法的加固原理,设计标准进行阐述,并提出具体的施工方法.     

The underground sewer drainage design analysis of highway subgrade under evaporation

According to the water balance principle, the expression of the phreatic table is established by considering evaporation and considering evaporation & drainage respectively. The law of phreatic table variation under the combined effects of considering evaporation & drainage is obtained. Based on Newton-Raphson itera-tive method, calculation and analysis programs are done to solve the first order implicit differential equation of the sewer drainage calculation considering phreatic evaporation. The calculation results show: after considering phreatic evaporation, in the need of reducing the same height of phreatic, the sewer spacing is appropriately larger than the case which didn’t consider the affection of phreatic evaporation; the phreatic drop speed in both effects of evaporation and drainage is faster than the case of just considering the drainage effect. Phreatic evaporation has a great influence to the subgrade sewer distance, phreatic evaporation needs to be considered in the subgrade drainage design.