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Tallahassee, FL, United States

Ping W.,Florida State University | Sheng B.,Florida State University | Ling C.-C.,Florida State University | Dietrich B.,05 Suwannee Street | Horhota D.,007 Northeast 39th Avenue
Transportation Research Record | Year: 2010

The resilient modulus of pavement subgrade materials is an essential parameter for mechanistically based flexible pavement design procedures. "Base clearance" is defined as the clearance between the groundwater level and the pavement base layer within a pavement system. A high pavement moisture content, which is strongly influenced by the base clearance, causes detrimental effects on the resilient modulus of pavement subgrades. The determination of a pavement base clearance is one of the most important steps toward setting up grade lines in a roadway design. This paper presents an experimental study to evaluate the effects of base clearance on the resilient modulus of pavement subgrades. Full-scale dynamic pavement tests were conducted in test pits to simulate vehicle dynamic impact on field pavements. The level of base clearance was adjusted by raising or lowering the water level within the pavement layer in the pit. Ten types of Florida subgrade material were tested at different base clearances for this study. The dynamic plate load test results were compared with the resilient modulus obtained from the laboratory triaxial test by using layer theory. The differences between the resilient modulus from the laboratory test and the plate load test were typically about 20%. Resilient modulus measured from the laboratory triaxial test could be used to predict the resilient deformation of the pavement subgrade layers. The experimental results showed that, at lower base clearances, the high pavement moisture content caused a significant reduction of the resilient modulus of pavement subgrade layers. The resilient modulus of subgrade materials decreases with the decrease of base clearance.

Sobanjo J.,Florida State University | Thompson P.,17035 Northeast 28th Place | Kerr R.,05 Suwannee Street
Transportation Research Record | Year: 2013

The state of Florida is developing a risk-based decision support model, specifically for its state-maintained bridges, to handle the occurrence of natural hazards, such as hurricanes, tornadoes, floods, landslides, and wildfires. Many bridges in Florida are vulnerable to damage caused by these hazards. With a focus on hurricanes, this paper develops prediction models (estimates of likelihoods) based on historical data of hazard events in Florida, as well as on existing national models. The Poisson process was assumed for the occurrence of natural events; predictions were estimated for the annual probability of occurrence. It was observed that, on average, the probability of hurricane occurrence at bridge locations decreased with the hurricane intensity (category number). In comparison, wildfires, another common hazard, had the highest likelihood estimates of the natural hazards. With a focus on physical damage to bridges, the consequences of hurricanes were also estimated on the basis of historical data within Florida. The damaged bridge components and elements were identified, and the levels of damage and the associated repair costs were assessed.

Thompson P.,17035 Northeast 28th Place | Sobanjo J.,Florida State University | Kerr R.,05 Suwannee Street
Transportation Research Record | Year: 2013

The Florida Department of Transportation (DOT) has developed a set of risk models for its bridge management system; the models are built into its existing Excel-based project-level and network-level decision support tools and are intended for eventual use in AASHTO's Pontis 5.2. One of these new models is an analysis of the risk associated with advanced deterioration. This model extends the reach of Florida's existing deterioration models to estimate the likelihood of service disruption if a badly deteriorated element should be unrepaired. The Florida DOT maintains data about demolished and replaced bridges as inactive records in its Pontis database. The condition and characteristics of the removed bridges were statistically analyzed to explore the reasons for the end of each bridge's life. On the basis of the available data, including information on load posting and reconstruction, the likelihood of service disruption was reasonably quantified. The best models developed in the research used a combination of linear and lognormal forms and reflected the buildup of risk caused by repeated Markovian deterioration as well as the typical delay that occurred between the observation of the deteriorated conditions and the resulting action to replace or reconstruct the bridge. As a by-product of the research, a linear failure probability model was developed; the model is suitable for Pontis releases up to 4.5. This model will be helpful to bridge owners who do not have their own source of estimates for the probability of bridge element failure.

Theiss L.,Texas A&M University | Pratt M.R.,Texas A&M University | Ullman G.L.,Texas A&M University | Maxwell S.D.,05 Suwannee Street
Transportation Research Record | Year: 2014

The 2009 Manual on Uniform Traffic Control Devices recognizes the potential safety benefit of providing enhanced delineation on temporary traffic control devices and allows for warning light enhancements on channelizing devices and temporary barrier walls. The argument for using warning lights in work zones is that they provide an incremental benefit to safety. Ideally, the additional costs of using warning lights should be offset by that safety benefit; in other words, the reduction in crash costs should equal or exceed the costs of the devices. In this study, the researchers collected and analyzed data on the cost of steady-burn warning lights, computed the increases in crash costs that could be expected to occur in two types of work zones, and computed the reductions in crash costs (i.e., safety benefits) that would have to occur from the use of the steady-burn warning lights to justify their use on a benefit- cost basis. On the basis of the results of this cost-effectiveness evaluation, the researchers recommend that the use of steady-bum warning lights in work zones be discontinued.

Theiss L.,Texas A&M University | Miles J.D.,Texas A&M University | Ullman G.L.,Texas A&M University | Maxwell S.D.,05 Suwannee Street
Transportation Research Record | Year: 2014

This report documents the efforts and results of several photometric evaluations performed by researchers at the Texas A&M Transportation Institute to assess the performance of steady-hum warning lights in temporary traffic control devices used to delineate the correct travel path in work zones. The research included an assessment of the potential incremental Increase in luminance (and benefit of that increase to drivers) during vulnerable driving conditions. These conditions included periods of heavy fog, periods when dirt and grime had accumulated on the channelizing device, and misalignment of warning lights. The researchers found that fog adversely affected the apparent luminance (and thus the visibility distance) of both retroreflective sheeting and warning lights. However, retroreflective sheeting was still likely to be visible at distances needed for purposes of path guidance and delineation, and the use of warning lights was unlikely to provide much additional value to motorists. The researchers also found that the accumulation of dirt and grime on the retroreflective sheeting of drums in Florida work zones did have an impact on device luminance. Although the use of warning lights did increase the overall luminance of channelizing drums, a greater increase in luminance was noted when the drums were clean. Finally, misalignment of lights significantly reduced their photometric value.

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