A. James Clark School of Engineering

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The collections in this community comprise faculty research works, as well as graduate theses and dissertations.

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Author: search.filters.author.Lu, Yang

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    Fatigue Assessment of Highway Bridges under Traffic Loading Using Microscopic Traffic Simulation
    (IntechOpen, 2018-11-13) Zhao, Gengwen; Fu, Chung C.; Lu, Yang; Saad, Timothy
    Fatigue is a common failure mode of steel bridges induced by truck traffic. Despite the deterioration caused by environmental factors, the increasing truck traffic volume and weight pose a premier threat to steel highway bridges. Given the uncertainties of the complicated traffic loading and the complexity of the bridge structure, fatigue evaluation based on field measurements under actual traffic flow is recommended. As the quality and the quantity of the available long-term traffic monitoring data and information have been improved, methodologies have been developed to obtain more realistic vehicular live load traffic. A case study of a steel interstate highway bridge using microscopic traffic simulation is presented herein. The knowledge of actual traffic loading may reduce the uncertainty involved in the evaluation of the load-carrying capacity, estimation of the rate of deterioration, and prediction of remaining fatigue life. This chapter demonstrates a systematic approach using traffic simulation and bridge health monitoring-based fatigue assessment.
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    INTEGRATED VARIABLE SPEED LIMIT AND RAMP METERING CONTROL FOR MANAGING RECURRENT FREEWAY CONGESTION
    (2017) Lu, Yang; Chang, Gang-Len; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Recurrent congestion due to highway bottlenecks is one major factor contributing to daily commuting delays in most traffic corridors. The resulting traffic queues often start from the bottleneck, and then spill back to further upstream segments to block their on-ramps and off-ramps. Consequently, the entire corridor -- freeways and their connected local arterials -- often suffers from severe gridlocks. To address such a critical issue, this research aims to develop an integrated control system, using both ramp metering and variable speed limits to improve the operational efficiency and to keep the traffic flows moving steadily near roadway capacity. The control system developed in this study includes a traffic state prediction model, a local bottleneck control module, and integrated corridor control strategies. The primary objective of the traffic state prediction model is to reliably predict the evolution of traffic conditions under the implemented control strategies, such as variable speed limit (VSL) and ramp metering. Based on the estimated compliance rate of drivers, the developed system with VSL is capable of capturing traffic flow dynamics – made up of VSL-complying and non-complying vehicles – and adjusting model parameters in real time, based on the on-line detected traffic data. The system’s predicted traffic dynamics will in turn serve as the basis for exercising a local and/or corridor integrated control. Grounded on the embedded mixed traffic flow model, the second component of this developed system is a local bottleneck control module, using both ramp metering and variable speed limits to tackle the recurrent congestion. This module is capable of selecting the activation time for each available control strategy – based on predicted traffic information – and determining the number of VSLs to be activated so as to ensure that the flow rate at the bottleneck segment will not exceed its capacity. The local control module can also activate the ramp metering in a timely manner to support the VSL operations within the target segment. The system under the local control state can also have the flexibility to select different control objectives based on the monitored traffic patterns. When traffic demand exhibits a sustained increase, the local bottleneck control alone may not be enough to prevent the freeway from breaking down. Hence, this study has further developed an integrated corridor control module, which can dynamically incorporate the upstream highway segments into control boundaries and exercise ramp metering controls to distribute excess volumes among different on-ramps. This will concurrently address both operational efficiency and equity concerns between freeway and ramp vehicles.
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    Study of real-time traffic state estimation and short-term prediction of signalized arterial network considering heterogeneous information sources
    (2013) Lu, Yang; Ali, Haghani; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Compared with a freeway network, real-time traffic state estimation and prediction of a signalized arterial network is a challenging yet under-studied field. Starting from discussing the arterial traffic flow dynamics, this study proposes a novel framework for real-time traffic state estimation and short-term prediction for signalized corridors. Particle filter techniques are used to integrate field measurements from different sources to improve the accuracy and robustness of the model. Several comprehensive numerical studies based on both real world and simulated datasets showed that the proposed model can generate reliable estimation and short-term prediction of different traffic states including queue length, flow density, speed and travel time with a high degree of accuracy. The proposed model can serve as the key component in both ATIS (Advanced Traveler's Information System) and proactive traffic control systems