Time filter

Source Type

Feng Y.,Alaska Department of Transportation and Public Facilities | Kowalsky M.J.,North Carolina State University | Nau J.M.,North Carolina State University
Journal of Structural Engineering (United States) | Year: 2015

This paper investigates the impact of seismic load history on longitudinal bar buckling in reinforced concrete (RC) bridge columns. Previous research has shown that reinforcing bars are prone to buckling upon reversal from tensile strain. To quantify this effect, a hybrid analysis method using both fiber and solid elements is developed and implemented to assess the impact of seismic load history on reinforcing bar buckling. Forty earthquake ground motions are utilized to conduct nonlinear time history analysis of bridge columns using a fiber-based model. The longitudinal bar strain history from the fiber-based model is then utilized as the input to the finite element model. A parametric study is conducted for the purpose of developing design equations that provide strain limits prior to the onset of bar buckling. Simple design approaches are proposed based on the design equations. © 2014 American Society of Civil Engineers.

Liu J.,University of Alaska Fairbanks | Saboundjian S.,Alaska Department of Transportation and Public Facilities | Li P.,University of Alaska Fairbanks | Connor B.,Alaska Department of Transportation and Public Facilities | Brunette B.,Alaska Department of Transportation and Public Facilities
Journal of Materials in Civil Engineering | Year: 2011

A number of completed or ongoing studies on different aspects of warm-mix asphalt (WMA) have being conducted in the United States, indicating pavement professionals' strong interest in exploring the application of this innovative technology. In the summer of 2008, a field trial project using Sasobit-modified WMA was established in the southeastern region of Alaska, which was Alaska's first experience with a WMA technology. In line with this field experimental feature project, this paper presents a systematic laboratory study of both Sasobit-modified WMA binders and mixes. Engineering properties of Sasobit-modified WMA binders and mixes were experimentally evaluated, and the effects of Sasobit addition on the WMA's performance in terms of low temperature behavior, rutting resistance, and moisture susceptibility were investigated. Research results identified a number of engineering benefits of Sasobit-modified WMAs over conventional HMA. Sasobit-modified WMAs reduced mixing and compaction temperatures, improved workability and rutting resistance, and had insignificant effect on moisture susceptibility. These effects indicated the suitability of this WMA technology for central and southeastern regions of the Alaska Department of Transportation and Public Facilities (AKDOT&PF). The indirect tension test results showed a decrease of WMAs tensile strength at low temperatures. Additional tests at lower temperatures, along with a more complete thermal cracking analysis need to be performed to obtain a more definitive answer regarding the low temperature performance of these mixes for the northern region of AKDOT&PF. © 2011 American Society of Civil Engineers.

Li P.,University of Alaska Fairbanks | Liu J.,University of Alaska Fairbanks | Saboundjian S.,Alaska Department of Transportation and Public Facilities
Journal of Materials in Civil Engineering | Year: 2011

Asphalt-treated bases (ATBs) are the most commonly used type of stabilized layer in Alaska because of locally available asphalt resources and its relatively lower cost. As an essential material input parameter for pavement design, resilient modulus (MR) of ATBs has been studied in laboratory evaluations, field investigations, and empirical and mechanistic modeling. However, most ATBs' MR values available in the database of the Alaska flexible pavement design software were obtained from in-service roadways through nondestructive testing and back calculation. Therefore, there was a need to characterize these stabilized materials by taking into account the main factors that influence their engineering behavior. In this study, the MR characterization of two types of ATBs was achieved through laboratory testing: hot asphalt-treated base (HATB) and foamed asphalt-treated base (FATB). The effects of loading amplitude, confining pressure, temperature, binder content, and aggregate source and properties on the resilient behaviors of HATB and FATB were investigated. Testing results were discussed and used to develop stress-dependent MR equations for both HATB and FATB that can be incorporated in current pavement design procedures. The effects of temperature and material variables were correlated to regression constants of the equations. © 2011 ASCE.

Stanley D.A.,Alaska Department of Transportation and Public Facilities | Pierson L.A.,Landslide Technology
Geotechnical Special Publication | Year: 2013

Development of Geotechnical Asset Management (GAM) is part of a national effort to implement Transportation Asset Management (TAM) and Performance Management (PM). Recent research is moving development of GAM beyond the initial steps of inventory and condition surveys towards condition forecasting, estimating service life, and setting levels of service and performance standards. Geotechnical assets such as rock and soil slopes, embankments, materials sites, retaining walls and other elements are complex and our understanding of their services lives is incomplete. Means to estimate the condition of these assets and monitor their condition over time are required for a fully functioning asset management program. These steps are necessary precursors to conducting credible life cycle cost analysis. When life cycle costs are determinable, critical geotechnical elements can be included as part of an asset management program. This paper includes discussion of: 1) problems and issues with estimating service life and condition forecasting for geotechnical assets; 2) development of a Geotechnical Asset Condition Index to represent the condition of rock and soil slopes and embankments; and 3) performance measures for rock and soil slopes and embankments. © 2013 American Society of Civil Engineers.

Metzger A.T.,University of Alaska Anchorage | Hutchinson J.,Alaska Department of Transportation and Public Facilities | Kwiatkowski J.,Reid Middleton Inc
Marine Structures | Year: 2014

Load demands on ferry berthing structures are not well understood due to lack of information about berthing parameters for ferry-class vessels. Therefore, a great deal of uncertainty exists when designing these structures. Engineers are often forced to make assumptions about the magnitude of vessel impact energy as well as forces imparted to the structures. In order to gain a better understanding of berthing demands on ferry landings, an automated monitoring system was devised and implemented at active ferry terminals. This manuscript discusses berthing parameters of interest when designing vessel berthing structures. It also presents previous work on the topic of measuring these parameters. With modern data acquisition systems, it is possible to collect a much more sophisticated representation of berthing parameters than in the past. This manuscript discusses how a state-of-the-art monitoring system was devised and implemented for the purpose of measuring vessel berthing parameters. This included nearly simultaneous measurement of vessel approach velocity, fender displacement and axial strain in structural components. With this system, vessel berthing parameters and structural response may be actively monitored. The output of the monitoring system is presented here and demonstrates the utility of the system. © 2014 Elsevier Ltd.

Fulmer S.J.,North Carolina State University | Nau J.M.,North Carolina State University | Kowalsky M.J.,North Carolina State University | Marx E.E.,Alaska Department of Transportation and Public Facilities
Journal of Constructional Steel Research | Year: 2016

Described in this paper is the evaluation of a series of design concepts which attempt to improve the inelastic cyclic response of steel bridge substructures. The bridge system under consideration consists of hollow circular steel piles welded to steel cap beams. Described first is the motivation for the use of this type of structure, followed by a discussion of the research methods which include large scale reversed cyclic testing supplemented by finite element analysis. Next, the performance of the current as-built system, the fillet welded connection, is evaluated. This connection is shown to perform poorly with little inelastic deformation capacity prior to failure. A variety of alternative connections are then proposed and evaluated. These alternative connections include modified weld detailing and plastic hinge relocation approaches. Alternative weld detailing focuses on the complete joint penetration weld with reinforcing fillet welds. The plastic hinge relocation alternatives include a gusseted connection, a reduced column section, and the recently proposed grouted shear stud (GSS) connection. Alternative weld details produce only slight improvement in performance. Of the plastic hinge relocation concepts, the grouted shear stud (GSS) connection offers the most promising approach to improve inelastic cyclic response. © 2015 Elsevier Ltd. All rights reserved.

Stickel J.,Alaska Department of Transportation and Public Facilities | Vandervalk A.,Cambridge Systematics Inc.
Transportation Research Record | Year: 2014

The Moving Ahead for Progress in the 21st Century Act (MAP-21) established a performance-and outcome-based transportation program for safety, infrastructure condition, congestion reduction, system reliability, freight movement, environment sustainability, and reduced project delivery delays. Transportation data are essential in addressing those challenges. Data are valued assets, but they carry a significant risk-bad data can lead to ineffective planning and ultimately to poor agency business decisions. An effective transportation data business plan coupled with institutional data governance can mitigate the risk by providing an approach for delivering comprehensive, quality data. Better data provide better information, which in turn results in informed decisions. A data business plan with an established data governance environment can lead to proactive rather than reactive decisions. Many state departments of transportation have embraced such concepts and best practices and are beginning to apply them in overall data governance. However, the terms and application are not mainstreamed and are not assimilated into the transportation agency culture. This paper provides the context for data management, data governance, and data stewardship; a business need for establishing data governance in a transportation agency; key features to be considered for a data business plan; approaches to developing a data governance program; and finally a process for evaluating data program governance.

Darrow M.M.,University of Alaska Fairbanks | Jensen D.D.,Alaska Department of Transportation and Public Facilities
Cold Regions Science and Technology | Year: 2016

Construction of roadway embankments over permafrost often results in settlement due to thawing of ice-rich foundation soils. The air convection embankment (ACE) is a relatively new design developed to reduce thaw settlement. In 2012 an ACE and an adjacent thermal berm were constructed as part of a realignment of the Taylor Highway near Lost Chicken Creek, Alaska. The Taylor Highway, a minor roadway with a gravel surface, is closed and not maintained during the winter months. To evaluate the thermal performance of the newly-constructed ACE and thermal berm, we performed field work and laboratory testing to determine foundation soil and embankment properties, measured temperatures at the base of the embankment, and developed two-dimensional finite element models to estimate long-term stability. Measurements indicated temperatures beneath the ACE were significantly colder than beneath the thermal berm. In the modeling, we simulated plowed (PC) and snow-covered (SC) conditions. Both models indicated that the ACE experienced density-driven air convection during the winter months. The PC scenario produced significantly colder temperatures within the ACE and underlying foundation soils. The SC model results more closely matched measured temperatures beneath the ACE, which is reasonable considering the lack of maintenance on the Taylor Highway during winter. The modeling indicates that ACE performance is improved through plowing of the surface, and that an ACE is more effective in maintaining frozen conditions in the foundation soils than the thermal berm; in fact, the modeling and measured temperatures indicate that the thermal berm actually raises the temperature in the foundation soils. Based on the results, we expect that thaw settlement will occur beneath the thermal berm until thermal equilibrium is reached, whereas the majority of the ACE will remain stable. © 2016 Elsevier B.V.

Feng Y.,Alaska Department of Transportation and Public Facilities | Kowalsky M.J.,North Carolina State University | Nau J.M.,North Carolina State University
Journal of Earthquake Engineering | Year: 2014

This article presents the application of fiber-based analysis to predict the nonlinear response of reinforced concrete bridge columns. Specifically considered are predictions of overall force-deformation hysteretic response and strain gradients in plastic hinge regions. This article discusses the relative merits of force-based and displacement-based fiber elements, and proposes a technique for prediction of nonlinear strain distribution based on the modified compression field theory. The models are compared with static and dynamic test data and recommendations are made for fiber-based modeling of RC bridge columns. © 2014 A. S. Elnashai.

Hendrikx J.,Montana State University | Murphy M.,Alaska Department of Transportation and Public Facilities | Onslow T.,Alaska Department of Transportation and Public Facilities
Cold Regions Science and Technology | Year: 2014

The Seward Highway is located in coastal Alaska and is subject to an extreme maritime climate, with strong winds, and large storms that can bring several meters of snow to the start zones and total snow in the start zones often exceeding 10. m per year. The highway extends for over 200. km through steep glacially carved valleys, from Seward to Anchorage, Alaska. Along its route, from mileposts 18 (29. km) to 107 (171. km), avalanche paths threaten the road and in many cases these avalanches flow down from their starting zones in excess of 1000. m above the road.Using a classification tree, we examined 28. years (1983-2011) of snowpack, weather and avalanche data. This suite of data contained more than 4500 individual avalanche events on over 100 paths, with 20 paths seeing regular activity. We used this wealth of data to train our classification tree model for days with significant avalanche activity. We tested trees with both equal and unequal misclassifications costs. The equal tree using only three parameters; the sum of 72. h of water, the 24. h high temperature, and the 72. h average high temperature, managed to obtain a probability of detection of 0.77 with 422 of the 545 avalanche days correctly predicted. The unequal tree using only two parameters; the sum of 72. h of water and 24. h high temperature, managed to obtain a probability of detection of 0.94 with 510 of the 545 avalanche days correctly predicted, but at the expense of a high false alarm rate. Testing these trees in a hindcast mode outside of their training period results in a drop in the model performance metrics considered. However when used in a forecasting mode in an operational setting no further reduction in model performance is observed. We conclude with a demonstration and test of a simple approach to use these trees in an operational avalanche forecasting program. We show how these trees have been used in a combined approach as a tool to assist avalanche forecasters with reasonable success. © 2013 Elsevier B.V.

Loading Alaska Department of Transportation and Public Facilities collaborators
Loading Alaska Department of Transportation and Public Facilities collaborators