基于丽攀模式的高速公路建设效益评价分析

文章结合丽攀高速公路攀枝花段工程项目建设实践,采用层次分析法,建立高速公路路地共建三层次效益评价指标体系,对高速公路建设效益进行多层次评价分析,指出了丽攀高速公路综合效益高的关键点,为今后的高速公路建设管理提供借鉴。     

外接平板型金属夹层结构连接构件极限强度分析

激光焊接钢质夹层结构在国外已用于实船,其连接形式是亟待解决的关键问题之一。基于有限元分析软件ANSYS,研究了面内载荷作用下,I型金属夹层结构外接平板型连接构件的失效模式和极限承载能力,以及5种典型初始缺陷的尺寸和连接构件的设计参数对极限载荷的影响规律。结果显示,连接构件较短时,结构失效的主导因素是焊接接头形成了塑性铰;连接构件较长时,主导因素是连接构件失稳。对于各种类型的初始缺陷,随初始缺陷尺寸的增大,极限载荷均降低;连接构件、以及靠近连接构件的夹层面板和夹层腹板的初始缺陷对极限载荷的影响较大。在控制重量的条件下,欲增大极限承载能力,最有效的途径是增大连接构件厚度,并选取合适的连接构件长度。     

Marginal and total exceedance probabilities of environmental contours

Various methods have been proposed for defining an environmental contour, based on different concepts of exceedance probability. In the inverse first-order reliability method (IFORM) and the direct sampling (DS) method, contours are defined in terms of exceedances within a region bounded by a hyperplane in either standard normal space or the original parameter space, corresponding to marginal exceedance probabilities under rotations of the coordinate system. In contrast, the more recent inverse second-order reliability method (ISORM) and highest density (HD) contours are defined in terms of an isodensity contour of the joint density function in either standard normal space or the original parameter space, where an exceedance is defined to be anywhere outside the contour. Contours defined in terms of the total probability outside the contour are significantly more conservative than contours defined in terms of marginal exceedance probabilities. In this work we study the relationship between the marginal exceedance probability of the maximum value of each variable along an environmental contour and the total probability outside the contour. The marginal exceedance probability of the contour maximum can be orders of magnitude lower than the total exceedance probability of the contour, with the differences increasing with the number of variables. For example, a 50-year ISORM contour for two variables at 3-h time steps, passes through points with marginal return periods of 635 years, and the marginal return periods increase to 10,950 years for contours of four variables. It is shown that the ratios of marginal to total exceedance probabilities for DS contours are similar to those for IFORM contours. However, the marginal exceedance probabilities of the maximum values of each variable along an HD contour are not in fixed relation to the contour exceedance probability, but depend on the shape of the joint density function. Examples are presented to illustrate the impact of the choice of contour on simple structural reliability problems for cases where the use of contours defined in terms of either marginal or total exceedance probabilities may be appropriate. The examples highlight that to choose an appropriate contour method, some understanding about the shape of a structure's failure surface is required.     

探析“联合采购法”在公路工程项目中的应用

根据公路工程项目的特点,针对传统采购模式的缺点,参照"联合采购法"在政府采购中的应用成果,提出"相邻合同段项目部联合采购法"、"公司内项目部联合采购法"、"公路工程施工企业联合采购法"以及"跨行业联合采购法"四种联合采购方法,通过改进采购方法、优化采购模式,能有效降低采购成本。     

一种考虑纵向连接间隙的带式浮桥变位计算方法

传统的带式浮桥变位的计算都是采用弹性地基梁的方法进行的,舟单元法中有类似算法。本文利用组成浮桥的多个舟体的平衡条件进行求解,并且在平衡方程中考虑了间隙闭合对浮桥变位的影响,编制了相应的求解程序,通过将文中算例与实测结果相比较,验证了该方法正确可行。     

国内外常用预防性养护措施介绍

对国内外采用的常见的预防性养护措施,如灌缝技术、雾封层、稀浆封层、微表处、石屑封层、超薄磨耗层等养护措施的技术特点、适用的病害类型、施工工艺等进行了论述.     

浅谈高速公路灌缝施工工艺

介绍了高速公路对沥青混凝土路面裂缝修补所采用的几种方法、施工组织,并对几种方法进行比较,并得出了采用开槽修补法最适合高速公路灌缝施工。     

Modelling users’ behaviour of a carsharing program: Application of a joint hazard and zero inflated dynamic ordered probability model

This paper presents an econometric model for the behaviour of carsharing users. The econometric model is developed to jointly forecast membership duration, the decision to become an active member in a particular month, and the frequency of monthly usage of active members. The model is estimated using the membership directory and monthly transaction data of a carsharing program, ‘Communauto Inc.’, based in Montréal, Canada. The model shows a high degree of fit to the observed dataset and provides many behavioural details of carsharing users. The results are instructive to carsharing planners in devising efficient policies.     

道岔工电结合部问题的差异化描述和技术标准分析

道岔是铁路工务、电务专业联系最频繁、结合最紧密的重要基础设备.道岔工电结合部是道岔设备问题和故障多发的薄弱环节,是工务、电务专业联合整治的重点.但由于工务、电务现场人员对结合部问题的理解和描述存在差异,有关专业技术标准也不完全一致,影响了双方的沟通甚至造成分歧.本文遵循现行技术规章,以普速铁路道岔设备为示例,从工务、电务2个专业分别对结合部问题展开描述,并进行技术标准分析,以求达成一致或找到最大公约数,同时给出整治建议.     

隧道围岩优势节理面统计及其块体稳定性分析

对于节理发育的破碎围岩隧道工程,根据开挖面的节理发育情况对围岩稳定性作出快速判断是至关重要的.文章以宁波象山港大桥接线段的茶园里隧道右线为例,通过对该隧道右线YK21+670～YK21+718段围岩节理发育特征的精细化描述和统计分析,确定了该段围岩的优势节理面,并在此基础上利用赤平投影解析法进行了围岩块体稳定性分析,得出了围岩块体滑移形式及块体的受力状态,并与数值计算结果相互验证,确定了可能发生失稳的块体,明确了加固区域,对有效保证隧道开挖施工安全有重要意义.