CLOSE OVERLAY
Project Details
STATUS

In-Progress

START DATE

05/01/20

END DATE

04/30/22

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, BEC, CTRE
SPONSORS

Federal Highway Administration State Planning and Research Funding

Researchers
Principal Investigator
Brent Phares

Bridge Research Engineer, BEC

About the research

This project is a task order under the main Federal Highway Administration (FHWA)-sponsored project, “Infrastructure Research and Technology Deployment Program.”

The process of bridge load rating, posting, and overweight permitting is constantly evolving due to the regulatory requirements regarding frequency of inspections and relevant changes to the bridge that necessitates re-rating. These factors include changes to the dead load, strength of members, or any maintenance/rehabilitation work. The US has over 600,000 bridges, making the process of load rating and posting a significant effort that benefits greatly from improvements to efficiency. As such, states are very interested in modifying their procedures to implement technology and improved means and methods to reduce the time demand associated with load rating. However, there does remain some disparity in how quickly different states are to adopt new technologies and concepts. Being able to load rate bridges efficiently and accurately is a necessity, particularly in the use case of permit load routing. In many instances, the permit load processing units of bridge owner agencies must evaluate non-standard loadings potentially traversing complex structures in a matter of a few days to avoid negative impacts to commerce.

While many states are evolving individually, it is important to learn from one another and provide consistency across the nation. This proposed work will address this need via the development of best practices and model frameworks.

Project Details
STATUS

In-Progress

START DATE

08/20/19

END DATE

08/19/22

SPONSORS

Federal Highway Administration State Planning and Research Funding

Researchers
Principal Investigator
Anuj Sharma

Research Scientist and Leader, REACTOR

About the research

Computer vision algorithms have been improved significantly to provide accurate detection, tracking, and recognition of objects in general. Available public datasets are crucial for extracting key features thanks to ever developing machine learning and deep learning algorithms. Since cameras are becoming vastly available to be employed on vehicles to extract useful information for both autonomous driving and intelligent driver assistance, we are aiming to develop intelligent driver state estimation algorithms that are based on state-of-the-art detection and recognition using computer vision. One of the main drawbacks for naturalistic driving data is having low-resolution and noisy video data that limits the overall accuracy when we test with the models trained on clear images. The research team has proposed (1) a comprehensive AI platform for data management, modeling, and enhanced annotations; (2) video quality enhancement using deep models, (3) face detection at acute angles, and (4) recurring network-based driver state estimation.

Project Details
STATUS

Completed

PROJECT NUMBER

15-553

START DATE

07/15/15

END DATE

08/31/19

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, CP Tech Center
SPONSORS

Federal Highway Administration State Planning and Research Funding
Iowa Department of Transportation

Researchers
Principal Investigator
Franciszek Hasiuk
Student Researcher(s)
Joseph Orso IV

About the research

Coarse aggregate, depending on intended usage, constitutes roughly 20–45% of portland cement concrete as well as being a major component in the construction of granular surface roads and shoulders for paved roads. However, coarse aggregate quality greatly varies among sources based on its petrophysical properties. Therefore, it is important to understand how these properties emerge from the depositional and diagenetic history of a deposit in order to accurately predict pavement durability, which can be negatively impacted by oscillating freeze/thaw cycles. To derive more information about a coarse aggregate’s pore system, this study used a “third generation” Iowa Pore Index (IPI) device capable of measuring the volume of intruded water at various time intervals ranging from 0.1–2.0 seconds, as well as measuring intrusion at variable pressures up to 70 psi (480 kPa). Using this new device, 21 carbonate samples (10 dolostones and 11 limestones) were compared to “traditional” IPI measurements. The new method gave slightly higher primary loads.

Additionally, with cumulative volume plotted for the first five minutes of intrusion, dolostones and limestones with elevated primary loads stood apart from the remaining, less macroporous limestone sources. By decreasing apparatus chamber size, higher total intrusion was recorded and IPI values were more correlative with traditional measurements. However, by analyzing the effect of variable pressure intrusion (15, 35, and 60 psi), it was observed that the transition point between intrusion of macropores and micropores was sample-dependent based on lithological properties (i.e., porosity, connectivity of pores, and pore-throat sizes). Although prior methods utilized 60 seconds as this transition point, incremental intrusion data suggest most samples complete macropore intrusion within the first 12 seconds. Therefore, by assessing the incremental intrusion of each source, new primary and secondary loads were calculated, which may be more characteristic of individual lithologies. As a result, secondary load values increased as more intrusion was accounted to micropores than through utilization of the previous method.

With further study, this method could better predict the longevity and overall durability of coarse aggregate based on pore structure in a more individualized fashion than the previous IPI method.

Project Details
STATUS

Completed

PROJECT NUMBER

14-511, TR-680

START DATE

07/01/14

END DATE

02/28/19

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, BEC
SPONSORS

Federal Highway Administration State Planning and Research Funding
Iowa Department of Transportation
Iowa Highway Research Board

Researchers
Co-Principal Investigator
Brent Phares

Bridge Research Engineer, BEC

Co-Principal Investigator
Travis Hosteng

Co-Director, NCWTS

About the research

Buchanan County, Iowa, has been working with the National Center for Wood Transportation Structures and a timber fabricator to develop the next-generation timber bridge. The goal is to increase the structural efficiency of timber bridges and increase longevity by (1) creating a composite deck-girder system and (2) using an epoxy overlay. These design elements have the potential to increase viable bridge options for use not only on Iowa’s roadways, but nationally and internationally as well.

The bridge system developed for this research was a composite glue-laminated (glulam) girder-deck system utilizing epoxy for the connection and an epoxy overlay wearing surface on the deck. This design was investigated through small- and large-scale laboratory testing of the composite epoxy connection and a field demonstration bridge built utilizing this girder to deck connection detail and epoxy overlay.

The small-scale tests showed that the best overall joint connection is an epoxy and lag bolt connection. The joints with epoxy at least tripled the shear capacity of the lag bolt joint, and addition of mechanical fasteners to the epoxy connection marginally increased performance. The large-scale laboratory tests showed a small increase in the load capacity and movement of the neutral axis when the deck panels are affixed to the girders, both of which indicate potential composite action. Furthermore, the epoxied connection exhibited an improved composite connection over the lag bolt connection.

Three live load tests on the field demonstration bridge in 2015, 2016, and 2017 indicated that transverse load distribution for all load cases was adequate. The composite action observed was not likely substantial enough to be accounted for in design. The chip seal shows signs of cracking at the transverse deck panel joints, but because of the epoxy the joints remain sealed and show no signs of moisture intrusion on the underside of the deck. The epoxy wearing surface on the deck performed better as an impermeable joint filler than a wearing surface.

Project Details
STATUS

Completed

PROJECT NUMBER

17-624, 18-SPR0-008

START DATE

07/01/17

END DATE

11/25/19

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans
SPONSORS

Federal Highway Administration State Planning and Research Funding
Iowa Department of Transportation

Researchers
Principal Investigator
Franciszek Hasiuk

About the research

In cold climates, the modern method for making durable portland cement concrete (PCC) pavement has been to entrain air in the paste. This method enables the formation of an air void network that permits the drainage of liquid water and accommodates pressure increases during freezing conditions. The Iowa Department of Transportation (DOT) has required air entrainment since the mid-1950s, and yet some pavements constructed before this period show little to no deterioration and remain in service. It remains uncertain which properties have allowed these pavements to last so long and if these properties can be used to increase the durability or reduce the cost of modern pavement designs.

This project aimed to study the evolution of pore networks in pre-1950 and post-1950 Iowa PCC pavements and interpret the deterioration of pavement aggregates. For this study, helium pycnometry was used to examine the total connected porosity of the air void network. Computed tomography (CT) scanning was used to cross-validate the helium porosity results as well as to calculate pore and aggregate size distributions. Mercury porosimetry was used to identify pore-throat size distributions and cross-validate the CT-measured values. Samples were also thin sectioned to characterize the physical state of coarse aggregate particles, determine their lithology, and identify their modes of deterioration. Finally, a script was developed for the coding platform, MATLAB, to provide similar metrics to the RapidAir 457 Air Void Analyzer but for CT images (e.g., porosity, pore size distribution, grain size distribution).

The initial hypothesis motivating this study was that pores forming around and inside deteriorating coarse aggregate particles in some unusually durable pre-air-entrainment PCC pavements are connected through pore throats in the paste serving to create effective air void networks. It was instead found through this study that the porosity of pavements showed strong correlation between decreasing porosity and increasing age. These results indicate that PCC porosity can be predicted from pavement age, at least in Iowa. Petrographic data suggest that this phenomenon is due to a reduction of pore space in the paste, with the reduction in paste porosity having more impact than the increase in porosity due to coarse and fine aggregate deterioration.

Project Details
STATUS

Completed

PROJECT NUMBER

18-654, 18-SPR1-001

START DATE

05/01/18

END DATE

04/30/20

RESEARCH CENTERS InTrans, CTRE
SPONSORS

Federal Highway Administration State Planning and Research Funding
Iowa Department of Transportation

PARTNERS

Auburn University Highway Research Center

Researchers
Principal Investigator
Michael Perez
Co-Principal Investigator
Bora Cetin
Student Researcher(s)
Jaime Schussler

About the research

The National Pollutant Discharge Elimination System General Permit No. 2 requires the Iowa Department of Transportation (DOT) to develop a stormwater pollution prevention plan for all construction activities that are covered by the permit. The Stormwater Pollution Prevention Plan includes the design, installation, and maintenance of erosion and sediment control (E&SC) practices to minimize downstream impact from stormwater discharges. The Iowa DOT has specifications, standard drawings, and guidance for the design of E&SC practices, but these practices had not been formally evaluated for field performance.

This research aimed to understand the performance of current E&SC practices and enhance the design guidance available to the Iowa DOT. Silt fence ditch checks, wattle ditch protection, silt fence perimeter control, and temporary sediment control basins were monitored for performance on US 30 in Tama County, Iowa. Two modified silt fence ditch check installations had an average of 2.5 and 4 times as much sediment accumulation as a standard silt fence, the modified wattle ditch protection had 13.15 times the sediment retention of a standard wattle installation, and silt fence perimeter control modifications led to less T-post deflection and failures observed than with the standard installation.

A temporary sediment control basin was monitored as a single basin and as basins in series. In the single basin, turbidity increased by an average 92 nephelometric turbidity units (NTUs) after residence in the basin, whereas the basins in series provided a turbidity reduction of 215 NTUs in the first basin and 870 NTUs in the second basin. However, the system of basins provides negligible turbidity reduction.

In addition to field monitoring, laboratory flume testing was conducted to compare the hydraulic performance of wattles. Average depth and length ratios were calculated for each tested wattle in addition to the percent difference between the wattle and an impervious weir and were classified from Class 1–4 with Class 1 being the least effective and Class 4 being the most effective at reducing supercritical flows. From flume testing, straw wattles meet Class 2; coconut coir, wood chips, and synthetic fiber wattles fall into Class 3; and miscanthus fiber would qualify as Class 4.

This field study provided researchers insight on the performance of standard and several trial modified E&SC practices. Controlled testing should continue to verify results observed in the field.

Project Details
STATUS

Completed

START DATE

10/01/15

END DATE

08/31/18

SPONSORS

Federal Highway Administration State Planning and Research Funding
Iowa Department of Transportation
Midwest Transportation Center
USDOT/OST-R

Researchers
Principal Investigator
Anuj Sharma

Research Scientist and Leader, REACTOR

Co-Principal Investigator
Skylar Knickerbocker

Research Engineer, REACTOR

Co-Principal Investigator
Ravi Nath

MTC Lead, Creighton University

Co-Principal Investigator
Neal Hawkins

Associate Director, InTrans

About the research

Maintaining optimal mobility on high-volume arterial traffic corridors is important to transportation agencies and the public. Corridor performance often can be enhanced by updating traffic signal timing, but most agencies find it necessary to prioritize their retiming efforts based on resource constraints. To facilitate prioritization, a set of arterial corridor performance measures was developed using INRIX probe vehicle data. These commercially available data are derived from in-vehicle global positioning system (GPS) observations transmitted wirelessly, eliminating the need for supplemental traffic observation infrastructure to be installed in the field.

The main objective of this study was to present a methodology to compare arterial corridors in terms of mobility-based performance measures. This process can help agencies select the corridors that are in need of signal retiming and can help identify corridors suited for adaptive signal control implementation. The two-step methodology began by identifying the number of days in a year with abnormal traffic patterns and comparing the volume-normalized performance of the remaining segments to identify corridors that are problematic on normal days.

The proposed methodology was applied to 12 corridors in Des Moines, Iowa, and 1 in Omaha, Nebraska. Three corridors were found to have a high number of anomalous days. Among the remaining corridors, three were identified as under-performing on normal days. In addition, the impact of implementing an adaptive signal control system on one corridor (University Avenue) was evaluated, where small improvements in travel rate and daily variation were observed, but the overall variability increased.


Funding Sources:
Federal Highway Administration State Planning and Research Funding
Iowa Department of Transportation ($47,758.00)
Midwest Transportation Center
USDOT/OST-R ($46,040.00)
Total: $93,798.00

Contract Number: DTRT13-G-UTC37

Project Details
STATUS

Completed

PROJECT NUMBER

13-449, TR-652

START DATE

01/01/13

END DATE

04/30/18

FOCUS AREAS

Safety

RESEARCH CENTERS InTrans, CTRE, CWIMS
SPONSORS

Federal Highway Administration State Planning and Research Funding
Iowa Department of Transportation
Iowa Highway Research Board

Researchers
Principal Investigator
Neal Hawkins

Associate Director, InTrans

Principal Investigator
Omar Smadi

Director, CTRE

About the research

Maintaining effective pavement markings year-round is a challenge in Iowa, where winter maintenance causes so much damage due to the harsh winter exposure from snow plow blades, sand, and salt brine. Given these conditions, and a limited painting season, it is critical that agencies select the proper pavement marking materials for the roadways in their network.

The overarching objective of this work was to support the Iowa Department of Transportation (DOT) Pavement Marking Task Force (PMT) in achieving better pavement markings statewide.

While the initial scope of this project was to evaluate different durable markings and pavement grooving configurations in an effort to make better choices for year-round markings, limited funding, difficulty in finding a contractor for a small test site, and adverse weather conditions caused the project to be revised to omit the field evaluation.

Instead, the project focused on supporting PMT decision making in light of challenging financial conditions, and particularly supporting efforts to determine paint truck and material choices by looking at peer states, and also by looking at contracting options for installation on the state system.

Pavement markings play a critical role in guiding motorists and delineating roadways for safe travel. The identification and use of more durable pavement markings may be the key to improving visibility, operations, and—most importantly—safety.

Project Details
STATUS

Completed

PROJECT NUMBER

16-573, 16-574, TR-683

START DATE

04/26/16

END DATE

03/31/18

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, BEC
SPONSORS

Federal Highway Administration
Federal Highway Administration State Planning and Research Funding
Iowa Department of Transportation

Researchers
Principal Investigator
Sri Sritharan

Faculty Affiliate

About the research

A large number of bridges in the nation are rated as structurally deficient and require immediate retrofits or replacements that will impose a significant financial burden on bridge owners. A fast, cost-efficient, and reliable retrofit solution is needed to tackle this problem. Typical bridge deck deterioration starts with shrinkage cracks, and additional cracks may occur due to traffic loads and time-dependent effects, which are worsened by freeze-thaw cycles over time. These cracks then lead to water and chloride penetration into the concrete deck, causing rebar corrosion and further damage to the superstructure.

A potential solution, suggested in a previous study, is to apply a thin layer of ultra-high-performance concrete (UHPC) on top of normal concrete (NC) bridge decks. Because UHPC has a higher tensile strength and low permeability, cracking as well as water and chloride ingression can be minimized, which in turn will extend the lifespan of the bridge. Moreover, UHPC is also deemed to have a higher fatigue resistance than NC.

In this study, a new UHPC mix to accommodate surface crowning was developed by a material supplier and tested in the laboratory. Using this new mix, the thin UHPC overlay concept was successfully implemented on a county bridge in Iowa. The implementation involved state and county engineers, a local contractor, and a material supplier. The bridge overlay was periodically monitored, and thus far there have been no concerns regarding the performance of the UHPC overlay or the bond at the interface between the UHPC and NC layers. In addition to the field implementation, three concrete slabs with and without a UHPC overlay were tested in the laboratory.

The results showed that a UHPC overlay in the positive moment region increased the strength by 18% while showing a more ductile response. In the negative moment region, although wire mesh was used, its effectiveness was not significant due to its small steel area. The effectiveness of the wire mesh could be improved by increasing the amount of steel area within the overlay, but its impact on the UHPC-NC interface bond needs to be evaluated.

Project Details
STATUS

Completed

PROJECT NUMBER

16-564, SPR RB29-015

START DATE

04/01/16

END DATE

03/31/18

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, BEC
SPONSORS

Federal Highway Administration State Planning and Research Funding
Iowa Department of Transportation

Researchers
Principal Investigator
Brent Phares

Bridge Research Engineer, BEC

About the research

The Iowa Department of Transportation (DOT) rating engineer is sometimes asked by field personnel to make quick decisions regarding pile capacity and stability when scour is identified around bridge pile bents. A numerical evaluation program was developed and implemented to offer a user-friendly assessment tool that can be used to quickly evaluate pile strength.

The numerical program consists of finite element (FE) models established for steel H-piles with or without concrete encasement with consideration of linear and non-linear buckling and behavior. The research team validated the FE models against capacities calculated based on the provisions outlined in the American Institute of Steel Construction (AISC) Steel Construction Manual.

After validating the FE modeling techniques, the researchers performed parametric studies to understand the influence of concrete encasement on the pile buckling strength. The individually encased pile bents in the P10L standardwith five H-pile sections (HP10×42, HP10×57, HP12×53, HP14×73, and HP14×89) were utilized for the parametric studies. These studies took into account different combinations of the unbraced pile lengths and concrete encasement lengths. The relationships between buckling strength of the steel H-piles with concrete encasements under concentric and eccentric loading conditions were derived from the results of the parametric studies.

The stiffness contributions of concrete encasements are not taken into account using the AISC Steel Construction Manual and American Association of State Highway and Transportation Officials(AASHTO) load and resistance factor design (LRFD) specifications for estimating the buckling strength of steel H-piles. The pile assessment tool that the researchers developed to quickly calculate the buckling strength of steel H-piles with concrete encasements includes the relationships between the buckling strength of steel H-piles with concrete encasement lengths for five cross-sections and two loading conditions. For the user’s convenience, the researchers developed agraphical user interface for the tool, which requires the input of four parameters: loading eccentricity, H-pile section type, unbraced pile length, and concrete encasement length. This pile assessment tool can be utilized to quickly calculate the pile capacity and to assist state rating engineers in making rapid decisions regarding pile capacity.

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