铁路超细粉煤灰预应力混凝土梁疲劳性能试验

通过9组32m铁路预应力混凝土标准梁的缩尺模型,对掺用超细粉煤灰的预应力混凝土梁在重复荷载作用下的力学性能进行研究,探讨粉煤灰掺量,混凝土等级以及养护条件等因素对铁路桥梁粉煤灰预应力混凝土梁力学性能的影响.试验结果表明:经200万次重复加载后,模型梁静力及动力特性与加载前相比基本不变,超细粉煤灰的合理掺用对梁体疲劳性能没有不利影响,为铁路桥梁粉煤灰预应力混凝土设计参数的选取及应用提供技术支持.     

半刚性基层沥青路面横向裂缝的演变规律

为了研究沥青路面横向裂缝的演变规律,依托江苏省高速公路历年的检测数据,选取部分路段进行精细化跟踪观测,考虑了环境和材料等因素的影响,分析了横向裂缝密度随路龄的演变规律,建立了演变模型,进行了预测分析。结果表明,横向裂缝受低温的影响较大;与AK-13或PAC-13相比,上面层材料采用SMA-13时裂缝密度较小;横向裂缝的宏观演变规律呈现出初步发展、稳步发展、快速发展的三阶段特征,可以使用结构行为方程表征;当路面养护及时时,裂缝发展较慢,方程参数β值较小。     

加筋挡墙加筋机理及其力学行为的分析

随着加筋挡土结构在我国公路建设中被广泛研究和应用,加筋挡墙的加筋机理及其力学响应分析越来越引起重视。在研究加筋挡墙的加筋机理及复合土体强度特性的基础上,运用AN SY S分析软件对加筋挡墙的受力机制及力学行为特点进行模拟计算分析,得出了一些有益的结论,对加筋挡土工程具有指导和借鉴作用。     

Travel to work and household responsibility: new evidence

A persistent empirical finding in the research on travel patterns is that women tend to engage in shorter work commutes than men. Research evaluating the degree to which this gender differential in commuting may be explained by the division of labor in the household has produced decidedly mixed findings. This paper presents a critical review of the methods and results of recent research on the gender differential in commuting along with the associated implications for the household responsibility hypothesis (HRH). While all of the articles reviewed are informative and unique, not all conclusions are well supported. The paper then tests the HRH using the 1990 NPTS travel data. The new evidence confirms that women continue to exhibit shorter commute times and distances than men and provides support for the HRH. The paper concludes with a summary of findings and recommendations for further research.     

A study of the bi-directional pedestrian flow characteristics at Hong Kong signalized crosswalk facilities

This paper investigates the bi-directional flow characteristics at signalized crosswalk facilities in Hong Kong. Pedestrian flow measurements were conducted at selected signalized crosswalks in Hong Kong urban area with and without the Light Rail Transit (LRT) railway tracks in the median of the carriageway. The pedestrian speed-flow functions for these crosswalk facilities were calibrated. The relationships between the walking speed at capacity and directional distribution of pedestrian flow (or flow ratio) are determined. The effects of different flow ratio on the effective capacity are also investigated. The bi-directional pedestrian flow effects on signalized crosswalk facilities with LRT tracks are found more significant than those without LRT tracks. The result could be used as a basis to improve the assessment of the crosswalk's capacity and to determine the design walking speeds under different flow ratios at signalized crosswalks in Hong Kong and in other Asian cities with similar environments.     

杭州湾大桥抗风性能试验研究

杭州湾大桥为目前世界最长的跨海公路大桥,包括南航道和北航道两座大跨度桥梁。对杭州湾大桥北航道桥成桥状态、最大双悬臂状态及最长单悬臂状态进行了动力特性分析,介绍了节段模型风洞试验的主要内容、试验结果, 据此分析评估了该桥的抗风性能,并得出了一些有益的结论。     

14MnNbq焊接件全范围疲劳裂纹扩展性能研究

由试验获得桥梁用钢14MnNbq焊接件的疲劳裂纹扩展da/dN、ΔK数据点及其疲劳门槛值ΔKth,断裂韧性Kc近似采用相同厚度母材试样得到的结果。采用四参数Forman公式利用多元线性回归法拟合试验数据,给出了14MnNbq焊接件的全范围疲劳裂纹扩展的表达式。在应力比R=0.05,0.25,0.50条件下Forman公式拟合曲线与试验数据吻合较好;相对于母材而言,在疲劳开裂和稳定扩展初期焊接件疲劳裂纹扩展速率较高。     

钢纤维增强聚合物改性混凝土的冲击性能

采用改进的SHPB装置对普通混凝土(PC)、钢纤维混凝土(SFRC)和钢纤维增强聚合物改性混凝土(SFRPMC)做了在不同冲击速度(10.9、20.8、27.4 m.s-1)下的冲击试验。试验结果表明:3种材料的抗冲击性能依次为普通混凝土差,钢纤维混凝土中,钢纤维增强聚合物改性混凝土良。进一步的分析说明钢纤维混凝土具有以刚克刚的性能特征;钢纤维增强聚合物改性混凝土具有以柔克刚的性能特征,是一种刚柔相济的复合材料,且具有良好的抗冲击性能,是理想的桥面铺装材料。     

对建设监理制度的探讨

本文结合我国推行建设监理制的现状,分析了当前我国建设监理工作面临的主要问题,进而提出解决这些问题的若干对策.     

A FEATURE SELECTION ALGORITHM DESIGN AND ITS IMPLEMENTATION IN INTRUSION DETECTION SYSTEM

Innetworkintrusiondetection ,on linebehav iorpatternsareestablishedaccordingtocollectedda ta ,thenintrusiondetectionrulesaregeneratedbasedonthesepatterns[1 ] .Accordingtotheserules,wecandeterminewhichbehaviorisinvasion .Thecor rectdecisionreliesontheaccuratedatausedforthedetermination .Becausethedatagatheredbythecol lectorarehugeinquantityandhavemanydescrip tionfeatures,someofthemareredundantwhichwillincreasethecostofpatternsmining ,evensomearethemainsourcesofnoisewhichwillmisleadus .Selecting…