沥青混凝土路面渗水规律研究

通过国内外成果对比分析、现场渗水试验,对路面的孔隙渗水规律、接缝渗水规律、裂缝渗水规律和中央分隔带与土路肩渗水规律进行详细探讨。发现孔隙率在5%～8%时沥青混凝土路面就开始渗水,路面与路缘石或预制边沟的接缝具有相当的渗水能力。     

静力触探CPT在水力吹填砂土地基承载力评估中的应用

为了更好控制科威特LNGI工程水力吹填砂土地基质量,合理评估水力吹填砂土地基处理后的承载力,选取基于CPT的3种经验公式,计算满足设计承载力200 kPa作用下所需的最小锥尖阻力qc值。结果显示,Bowles(1996)法和BS EN1997-1:2004 Annex D推荐法计算的最小qc值与水力吹填质量等级有关,但两者结果较接近,而EslaamizaadRobertson(1996)法计算的结果较小,仅为3. 8 MPa。基于保守考虑,最终结果取前两种方法平均值中的最大值7. 5 MPa。同时基于现场实际,在地基处理后预先进行CPT检测,得到平均锥尖阻力远大于计算验收值,并由大型载荷板ZLT试验验证了满足长期沉降的设计承载力。可见,在地基处理后可预先采用CPT对处理后地基处理承载力进行评估并辅助少量大型ZLT试验进行验证,可有效对地基承载力进行验收。     

不同信息下的逐日路径选择行为实验与模型

为研究先进出行者信息系统(ATIS)对出行者逐日路径选择行为的影响,本文基于 Braess路网设计5组具有不同ATIS市场占有率(0、25%、50%、75%、100%)的行为实验.结果表明：3条路径的流量及新增路径保持选择的次数持续波动,随着ATIS市场占有率增大,路网平均行程时间趋于用户均衡,新增路径保持选择的次数呈现增长趋势,且被试对新增路径的选择性偏好增强,Braess悖论的效果也更明显.基于5组实验数据,分别建立普通Logit模型和基于面板数据的随机效应Logit模型刻画路径选择行为.结果表明：当ATIS市场占有率为0时,最佳模型为普通Logit模型;当ATIS市场占有率增大甚至达到100%时,最佳模型均为随机效应Logit模型;未配备ATIS的出行者的个体差异性比配备ATIS的小.     

网联通信时延下的混合队列控制特性分析

针对CACC协同自适应巡航控制技术,探究其在车联网通信时延影响下,与驾驶员驾驶汽车共存而构成的混合队列系统的性能。从微观跟车行为角度,基于频域传递函数,推导通信时延下的CACC队列稳定最小跟车时距的理论表达式,并通过数值验证指出CACC队列稳定最小跟车时距随通信时延增大而增大的特性。从交通激波特性角度,针对无时延CACC、有时延CACC和时延过大而退化后的ACC自适应巡航3种情形,给定相同的跟车时距,进行不同渗透率下的大规模交通仿真实验,实验结果表明,在无时延和1 s时延这2种情形下,CACC在20%及以上的渗透率时均能显著降低交通扰动,削弱激波,性能差别不明显; 相比而言,退化后的ACC性能明显恶化。     

Field implementation feasibility study of cumulative travel‐time responsive (CTR) traffic signal control algorithm

The cumulative travel‐time responsive (CTR) algorithm determines optimal green split for the next time interval by identifying the maximum cumulative travel time (CTT) estimated under the connected vehicle environment. This paper enhanced the CTR algorithm and evaluated its performance to verify a feasibility of field implementation in a near future. Standard Kalman filter (SKF) and adaptive Kalman filter (AKF) were applied to estimate CTT for each phase in the CTR algorithm. In addition, traffic demand, market penetration rate (MPR), and data availability were considered to evaluate the CTR algorithm's performance. An intersection in the Northern Virginia connected vehicle test bed is selected for a case study and evaluated within vissim and hardware in the loop simulations. As expected, the CTR algorithm's performance depends on MPR because the information collected from connected vehicle is a key enabling factor of the CTR algorithm. However, this paper found that the MPR requirement of the CTR algorithm could be addressed (i) when the data are collected from both connected vehicle and the infrastructure sensors and (ii) when the AKF is adopted. The minimum required MPRs to outperform the actuated traffic signal control were empirically found for each prediction technique (i.e., 30% for the SKF and 20% for the AKF) and data availability. Even without the infrastructure sensors, the CTR algorithm could be implemented at an intersection with high traffic demand and 50–60% MPR. The findings of this study are expected to contribute to the field implementation of the CTR algorithm to improve the traffic network performance. Copyright © 2017 John Wiley & Sons, Ltd.     

Deriving macroscopic fundamental diagrams from probe data: Issues and proposed solutions

Well-defined relationships between flow and density averaged spatially across urban traffic networks, more commonly known as Macroscopic Fundamental Diagrams (MFDs), have been recently verified to exist in reality. Researchers have proposed using MFDs to monitor the status of urban traffic networks and to inform the design of network-wide traffic control strategies. However, it is also well known that empirical MFDs are not easy to estimate in practice due to difficulties in obtaining the requisite data needed to construct them. Recent works have devised ways to estimate a network’s MFD using limited trajectory data that can be obtained from GPS-equipped mobile probe vehicles. These methods assume that the market penetration level of mobile probe vehicles is uniform across the entire set of OD pairs in the network; however, in reality the probe vehicle market penetration rate varies regionally within a network. When this variation is combined with the imbalance of probe trip lengths and travel times, the compound effects will further complicate the estimation of the MFD.To overcome this deficit, we propose a method to estimate a network’s MFD using mobile probe data when the market penetration rates are not necessarily the same across an entire network. This method relies on the determination of appropriate average probe penetration rates, which are weighted harmonic means using individual probe vehicle travel times and distances as the weights. The accuracy of this method is tested using synthetic data generated in the INTEGRATION micro-simulation environment by comparing the estimated MFDs to the ground truth MFD obtained using a 100% market penetration of probe vehicles. The results show that the weighted harmonic mean probe penetration rates outperform simple (arithmetic) average probe penetration rates, as expected. This especially holds true as the imbalance of demand and penetration level increases. Furthermore, as the probe penetration rates are generally not known, an algorithm to estimate the probe penetration rates of regional OD pairs is proposed. This algorithm links count data from sporadic fixed detectors in the network to information from probe vehicles that pass the detectors. The simulation results indicate that the proposed algorithm is very effective. Since the data needed to apply this algorithm are readily available and easy to collect, the proposed algorithm is practically feasible and offers a better approach for the estimation of the MFD using mobile probe data, which are becoming increasingly available in urban environments.     

关于某离岸式高桩码头引桥桩基承载力的讨论

某在建散货码头,引桥采用桩基础,预制混凝土桩沉至设计标高,贯入度仍有100 mm,现场高应变检测发现桩基实测承载力远小于设计承载力.本文通过分析地质钻孔资料、桩基设计承载力计算、桩基终锤贯入度、高应变检测结果和超静孔隙水压力消散过程,对本项目桩基的承载力进行讨论.本文对类似工程的勘察、设计和施工有借鉴意义.     

截锥形弹体穿甲薄板的数值计算研究

为了探讨薄板斜穿甲的破坏机理和弹体剩余速度,采用非线性动力学程序AUTODYN分析了截锥形弹体不同入射角度冲击下薄板的破坏模式,以及入射角度对靶板吸能和弹体剩余速度的影响,提出了靶板梨形孔的破坏模式．数值计算表明弹体斜穿甲时靶板吸收的能量与垂直穿甲时相差不大,斜穿甲时弹体在靶板上有滑移现象,并在高斜角低速撞击时弹体发生明显偏转,靶板也表现出不同的破坏模式。     

疏水化合孔栓物对高性能混凝土性能影响的试验及应用

研究疏水化合孔栓物对不同强度等级的高性能混凝土工作性、力学性能及耐久性的影响。结果表明:疏水化合孔栓物可改善新拌混凝土工作性、显著降低混凝土吸水率,混凝土吸水率普遍降低50%以上,同时可提高混凝土抗氯离子渗透性。疏水化合孔栓物降低混凝土早期强度,但对后期强度无明显影响。该内掺型疏水材料在范和港跨海大桥、东华大桥等工程中得到推广应用,显著提高了混凝土结构耐久性。     

超高分子量聚乙烯纤维增强层合厚板抗高速钝头弹侵彻的理论模型

结合超高分子量聚乙烯纤维增强塑料(UFRP)层合厚板抗高速侵彻的特点,将整个侵彻过程分为开坑镦粗、剪切压缩和拉伸变形3个阶段。通过改进开坑镦粗阶段的计算方法和拉伸变形阶段的计算过程,基于能量守恒原理建立UFRP层合厚板抗高速钝头弹侵彻的弹体侵彻深度和靶板弹道极限的计算模型,并给出相应的计算流程图。通过采用该模型计算相关文献试验工况下的弹体侵彻深度和层合厚板弹道极限,发现计算值与文献试验结果均吻合较好。改进后的模型考虑了弹丸初速度对开坑镦粗阶段侵彻深度的影响,能够对高速钝头弹侵彻UFRP层合厚板的弹体侵彻深度和层合厚板的弹道极限进行合理的预测,并可降低试验成本。