Dave E.V.,University of New Hampshire |
Hoplin C.,University of Minnesota |
Helmer B.,University of Minnesota |
Dailey J.,University of Minnesota |
And 4 more authors.
Transportation Research Record | Year: 2016
Asphalt pavements in colder climates encounter significantly shortened service lives because of excessive transverse cracking. This paper presents the results for 26 pavement sections in Minnesota that were studied to evaluate the effects of asphalt mix designs on pavement cracking performance. The field performance is presented with various cracking measures and compared with mix design aspects such as amount of asphalt binder, binder grade, and amount of recycling. The disk-shaped compact tension (DCT) fracture energies measured on the field cored samples are also compared with cracking performance. In this study, asphalt pavement sections from several locations were evaluated to encompass various types of asphalt mixtures and asphalt construction types that were commonly used in Minnesota. The amount of transverse cracking for each section was converted into a newly proposed cracking performance measure that accounted for the amount, rate, and timing of cracking. The comparisons between asphalt mixture attributes and cracking performance measures showed that the amounts of total asphalt binder and recycled asphalt binder may not be sufficient. Performance testing, in addition to currently used controls (mix volumetrics and constituent properties), is recommended to ensure good cracking performance. The DCT fracture energy results for companion sections show that mixtures with higher fracture energies exhibit lower amounts of transverse cracking. © 2016, National Research Council. All rights reserved.
Crumly W.,L. Raymond and Assoc. |
Doxtad E.,L. Raymond and Assoc. |
Dearborn M.,L. Raymond and Assoc. |
Raymond L.,L. Raymond and Assoc. |
And 5 more authors.
Bridge Structures | Year: 2015
After tensioning high-strength steel rods installed on the lower housing of Shear Key S1 and Shear Key S2 at Pier E2 of the San Francisco-Oakland Bay Bridge, 32 of 96 threaded rods failed. The rods were tensioned to 0.7 Fu and the failures were delayed failure, from 3 days to 14 days after tensioning. Failure analysis found that failure was due to Hydrogen Embrittlement. A six part test program performed to evaluate safety of additional rods in the field. This paper reports on Test V and Test VI - Small Threaded Specimen Testing. Small (Charpy-sized) threaded specimens were used to predict the threshold Load for the onset of hydrogen induced stress corrosion cracking of large A354BD Rods. The procedure used was to measure the hydrogen embrittlement threshold load for a small specimen and use a validated model to calculate the corresponding threshold stress intensity factor from the threshold load. With this threshold stress intensity factor, a model was used to calculate threshold load of the full size rod. Three independent methods were used to validate the accuracy of using small specimens to predict full-size failures. 1) Use finite element analysis to relate the local conditions at the thread root for a sub-size specimen to the thread root for a full-size threaded rod. 2) Correlate stress intensity factor between sub-size specimens to full-size threaded rods. 3) Mechanical testing of full-size rods in tension. It was found that the analysis methods agreed with each other, thus validating the use of data from sub-size specimens to predict the failure performance of full-size threaded rods. The data generated from Test V has the additional advantage of being able to quantitatively determine the effects of variations in the applied potential from compositional differences in the galvanizing and the variation in the hardness of the rods on the threshold stress. © 2015 - IOS Press and the authors. All rights reserved.
Danielsen F.,Nordisk Fond for Miljo og Udvikling |
Skutsch M.,National Autonomous University of Mexico |
Skutsch M.,Sustainable Development Technology |
Burgess N.D.,Universitetsparken 15 |
And 17 more authors.
Conservation Letters | Year: 2011
Reduced Emissions from Deforestation and Forest Degradation in Developing Countries (REDD+) is a policy mechanism now agreed under the United Nations Framework Convention on Climate Change (UNFCCC). It aims to reduce carbon dioxide emissions from developing countries through the sustainable management of forests, while providing co-benefits of biodiversity conservation and livelihood support. Implementation challenges include linking remote sensing and national forest inventories of carbon stocks, to local implementation and measuring carbon loss from forest degradation. Community-based forest monitoring can help overcome some of these challenges. We show that local people can collect forest condition data of comparable quality to trained scientists, at half the cost. We draw on our experience to propose how and where local REDD+ monitoring can be established. Empowering communities to own and monitor carbon stocks could provide a rapid and cost-effective way of absorbing carbon dioxide emissions, while potentially contributing to local livelihoods and forest biodiversity conservation. © 2011 Wiley Periodicals, Inc.
Hadi M.,Florida International University |
Shen L.,Florida Transportation Engineering Inc. |
Li J.,Florida International University |
Xiao Y.,Florida International University |
Transportation Research Record | Year: 2010
Freeway service patrol (FSP) programs constitute one of the most popular elements of intelligent transportation systems and have been increasingly implemented around the United States. Despite the successes and the benefits of these programs, however, recent budget cuts have increased the need to demonstrate the benefits of the programs, to show the differences in the benefits of different operation schedules, and to select the parameters of the operations to make the best use of available resources. This paper reports on an effort to develop a tool (a) to assess the performance of FSPs under different operation parameters and the impacts of FSP performance on transportation network measures and (b) to select operation parameters. The tool was developed by means of a general purpose simulation modeling environment. The output from the simulation is fed into a spreadsheet that allows assessment of changes in incident durations on transportation network performance in terms of delays, fuel consumption, emission, safety, and dollar values. The applications of the tool indicate that it can be used to assess FSP operation parameters and the systemwide and economic impacts of changing these parameters.
Saha D.,Florida International University |
Gan A.,Florida International University |
Haleem K.,Florida International University |
53rd Annual Transportation Research Forum, TRF 2012 | Year: 2012
Traditionally, static signs are used to convey messages to the road users. The need to quickly communicate up-to-date messages to the road users has given rise to the use of dynamic message signs (DMS). A typical DMS includes only dynamic messages. An alternative to DMS is hybrid signs, which display both static and dynamic messages on a single sign. A hybrid sign consists of a conventional retro-reflective static sign that is embedded with one or more relatively small, dynamic, usually light emitting diode (LED) message panels. Potential advantages of hybrid signs over DMS include better legibility, shorter reading time, smaller size, and lower installation, operations, and maintenance costs. This paper provides the first state-of-the-practice review on the use, design, and performance of hybrid signs. It covers hybrid sign applications in different parts of the world, including the U.S., Europe, Australia, and Asia. The application areas reviewed included variable speed limits, lane control, managed lane operations, dynamic rerouting, travel time display, and graphical route information display. Multiple examples of each application, many of which were considered innovative and can potentially be adopted for use in the U.S., were given. Issues related to the applications were discussed and lessons learned were provided. © (2012) by the Transportation Research Forum. All rights reserved.
Page K.S.,Inland Fisheries Research Unit |
Zweifel R.D.,Inland Fisheries Research Unit |
Carter G.,District |
Radabaugh N.,District |
And 4 more authors.
North American Journal of Fisheries Management | Year: 2012
Angler surveys are reliant on the ability of anglers to accurately report various aspects of their fishing trips. Misidentification of sport fishes has been postulated as a source of error among angler surveys but has received little attention. We evaluated the overall ability of anglers to identify sport fishes common to Ohio and the potential impacts on catch estimates derived from angler surveys. During angler surveys conducted on lakes and reservoirs (2007, n = 34) and Ohio River tailwaters (2010, n = 3), anglers were presented with artist-rendered images of 18 different sport fishes common to these waters. Anglers (lake and reservoir, n = 2,442; Ohio River, n = 458) were asked to identify sport fish by their common name. On average, anglers correctly identified sport fishes 42% of the time, but accuracy varied widely among species (lake and reservoir, range = 4.4-85.1%; Ohio River, range = 9.4-71.8%), with greater accuracy exhibited for the most common species (e.g., largemouth bass Micropterus salmoides). However, by grouping angler responses into species groups (e.g., black bass Micropterus spp., sunfish Lepomis spp.) angler identification of sport fishes was more reliable (lake and reservoir, mean = 83.4%; Ohio River, mean = 83.8%). Using these estimates of angler accuracy, we simulated the potential error in sport fish catch estimates using data from an angler survey conducted at one Ohio reservoir. These results suggested that misidentification error may result in a substantial error in catch estimates. A survey of North American fisheries management agencies regarding angler surveys and angler sport fish identification revealed that the majority of agencies group similar species for analysis and cited species misidentification by anglers as the primary reason for doing so. © American Fisheries Society 2012.
Engeman R.M.,National Wildlife Research Center |
Duffiney A.,2820 East University Ave |
Braem S.,District |
Olsen C.,District |
And 5 more authors.
Journal of Experimental Marine Biology and Ecology | Year: 2010
Predation critically threatens reproductive success of sea turtles and shorebirds at many of Florida's beaches. We examined the biological and bioeconomic results of predator management on two adjacent barrier islands, Cayo Costa and North Captiva, along Florida's west coast. Both islands suffered severe nesting losses due to predation and disturbance due to raccoons, while Cayo Costa also was impacted by a large population of feral swine. In 2006, our initial year of study, neither island received predator management and no least tern production occurred on either island, and sea turtle nest predation was 74% and 60%, respectively, for Cayo Costa and North Captiva. Predators were managed in 2007 on Cayo Costa while North Captiva served as an untreated reference island. North Captiva again had no least tern production and sea turtle nest predation was 84%. In contrast, Cayo Costa produced 31 least terns and sea turtle nest predation plummeted to 16%. Both islands received predator management in 2008 when Cayo Costa and North Captiva respectively produced 20 and 55 least terns and had 15% and 0% sea turtle nest predation. The entire costs for predator management by experts over the course of the study was $USD 39,636, while the returns in additional production of least tern young and hatchling sea turtles was valued over $USD 1.1. million for a resulting benefit-cost ratio of 27.8. © 2010.