Institute for Transportation

About the research

The objective of this project is to conduct an independent evaluation of the impact of biodiesel on fuel economy and carbon reduction in the Iowa Department of Transportation (DOT) snowplow fleet. This includes an evaluation of fuel economy, maintenance, and driver/maintenance personnel concerns.

The team will coordinate with the Iowa DOT and monitor snowplow operations. Fuel use and snowplow maintenance using varying levels of both biodiesel and regular diesel will be monitored.

About the research

A project recently completed for the Iowa Department of Transportation investigated the contributions of concrete encasements of steel H-piles used for bridges, which have historically not been considered in the design process. The initial reason for the project was to determine the remaining capacity of a pile when subjected to scour, leaving bare the uncased portion of a pile. A tool was developed to calculate capacity and a subsequent laboratory investigation was completed to validate the pile capacity assessment tool. The study concluded the pile capacity is greater than what has been otherwise calculated. As a secondary result, consideration has been given to revising the capacity calculations of new piles especially in fully-encased pile bents. This project aims to identify the unbraced height limits of steel H-piles when fully-encased.

About the research

Fiber-reinforced concrete (FRC) has become more widely used in thin concrete overlays in recent years. It is well known that synthetic macro-fibers increase the fracture toughness and residual strength of concrete, which mitigates cracking and improves the fatigue life of concrete overlays. Some of the other benefits of fiber-reinforcement could further benefit the performance and service life of concrete overlays by improving joint behavior, load transfer, and pavement smoothness. However, the performance benefits of these mechanisms are not well-quantified and are not considered in current concrete overlay design procedures. This study will take comprehensive performance measurements at a number of FRC overlay test sections that have been built in Iowa in recent years. The analysis will provide more insight into the full benefits of fiber-reinforcement and how they impact design choices and overlay service life. With a more complete understanding of the performance benefits of using fibers in concrete overlays, agencies would be able to optimize their FRC overlay designs, better predict long-term performance, and use resources more efficiently for maintaining Iowa’s roadway network.

About the research

With slide-in bridge construction (SIBC), the bridge superstructure is constructed off the final alignment and then slid laterally from the temporary worksite onto the in-place substructure. Once the sliding is complete, closure joints between the bridge super- and sub-structure are cast to establish continuity. The cementitious materials and reinforcement design used to complete the closure joints affect when the bridge can be opened to traffic or construction loading.

The goal of this research was to investigate the performance of closure joints using ultra-high performance concrete (UHPC) and noncontact lap-spliced reinforcing steel bar, with a specific focus on determining when a noncontact lap-splice has sufficient strength to either open a bridge or expose it to additional construction loading.

The research was also conducted to explore an alternative material to UHPC—hybrid composite synthetic concrete (HCSC)—which may be able to provide sufficient early-age capacity when used in the same way.

A series of laboratory tests were performed on 96 samples including four noncontact lap-splice connection designs with different rebar development lengths and joint filling materials. A time-dependent pull-out test was performed on each design with a focus on the performance at the material early age. Each sample was loaded with a pull-out force until failure. The ultimate capacity of each sample was captured and analyzed.

Based on the test results, recommendations for the selection of UHPC/HCSC closure joints reinforced with lap-spliced rebars were developed.

About the research

The objectives of this project were to correlate international roughness index (IRI) data (which are widely collected and directly related to bridge deck roughness) to impact factors and develop a process for determining the impact factor to use for all bridges in Iowa.To achieve the project objectives, a sample of 20 bridges was selected for bridge monitoring to collect dynamic strain data.

To estimate the static strain data, the locally weighted scatterplot smoothing (LOWESS) function was used to smooth the dynamic strain time history. The dynamic impact factor (DIF) value was then calculated using maximum dynamic and static strain data. IRI data were extracted from PathWeb, a web-based application provided by the Iowa Department of Transportation (DOT) for all bridges considered in the field test program. Once the bridge was identified in PathWeb, the IRI data from four locations near each bridge deck approach were extracted and used to study the relationship between the IRI and DIF. Based on the results from this research, these were the key findings:

• The DIF value decreases as the bridge skew angle increases. Based on linear regression, the DIF value decreases about 0.037 to 0.043 per 10-degree increment of bridge skew.
• The DIF value decreases as the bridge deck condition index increases, meaning that the dynamic response is lower when the bridge deck condition is better.
• For bridges with zero skew, the DIF value increased by 0.006 per 100 in/mile increment of the IRI value.

According to the research findings, an equation was developed for the prediction of DIF on existing bridges with consideration of the bridge skew and the maximum IRI value near the bridge deck approach. Although the proposed equation was validated uing data from 13 bridges, the researchers recommend using the equation with the limitation that the actual bridge dynamic response could deviate ±10% from the equation predicted value.

About the research

Each year a city public works focus group is convened the day before the spring conference of the Iowa Chapter of the American Public Works Association (APWA). Approximately five years ago, an idea was proposed at this focus group that responded to an identified need for more useful guidance related to the overall and elemental conversion of four-lane undivided roadway to three lanes (i.e., one lane in each direction and a two-way left-turn lane [TWLTL]). A literature review by the Iowa Department of Transportation (DOT) showed that a significant amount of material has been created on this subject. In fact, there has been so much documentation that it can be a challenge to practitioners. It was concluded by the project development team there was a need to combine this information in a more useful manner. The tasks in this project were designed to respond to this continuing need.

About the research

Connected and automated vehicle (CAV) technology is progressing rapidly. Numerous research and deployment initiatives are underway as the transportation industry continues to examine how roadway assets such as traffic control signs, markings, signals, guardrail, computing systems, communications infrastructure and systems, and other permanent and temporary ancillary devices can be designed or enhanced to facilitate CAV operations. Road Weather Information Systems (RWIS) are relied on across the US to help predict and manage the impacts of weather on transportation safety and mobility. RWIS data are used heavily by road authorities as well as across the public and private spectrum of weather service providers. The integration of mobile observational data from connected vehicle (CV) and probe-based data are providing agencies with new options for vehicle centric operational and weather-related data. In some situations, CAVs may benefit from direct data exchanges with the RWIS, thus creating a huge potential for road weather information and other operations functions to be complemented by field devices, which can be collected from the communications of passing CAVs.

About the research

With the adoption of Aurigo Masterworks software by the Iowa Department of Transportation (DOT), there is benefit to revising Section 1110 Progress Scheduling of the Iowa DOT Standard Specifications for Highway and Bridge Construction and other scheduling specifications and requirements. The Masterworks Project Management software has been implemented, and the Iowa DOT has enough licenses to distribute the program to contractors and county engineers. Section 1110 of the Standard Specification for Highway and Bridge Construction describes the Progress Scheduling requirements for the contractor. Currently, the specification is written prescriptively to favor high-end project enterprise software such as Primvera P6 by Oracle. This is problematic because most contractors and the Iowa DOT do not have expertise in Primavera nor do they have site licenses. As a result, contractors often must hire scheduling consultants with expertise and access to expensive scheduling software programs and the Iowa DOT has to hire consultants to review and comment on the CPM schedules submitted by the contractor. The existing Progress Scheduling specification results in a system where most contractors and the DOT cannot even open the schedules because they don’t have licenses for the software used to create them.

In addition to revising Section 1110, other Iowa DOT specifications and requirements need to investigated and revised to support the use of the Aurigo Masterworks software on projects of different sizes and scope, not just the very large projects. All projects may benefit from some level of additional schedule detail to support management and control of the project. However, not all projects warrant the level of detail of the larger projects.

About the research

The Central Iowa Expo facility is located in Boone, Iowa. The Iowa DOT initiated a research project (IHRB Project TR-671) to implement foundation stabilization technologies (Phase I), construction of the pavement layers using intelligent compaction technology (Phase II), and non-destructive evaluation of pavement systems right after construction (Phase III).

Falling Weight Deflectometer (FWD) tests were performed on the pavement layer and ground penetrating radar tests were performed to evaluate thickness of the asphalt layer and moisture conditions of the base layer. This project includes an assessment of those tests.

About the research

Traffic signal structures are an integral part of the transportation infrastructure system, ensuring the safety of motorists and pedestrians. These structures, however, have been found to perform poorly due to fatigue-related issues in their connections. This mostly originates from the large-amplitude vibrations caused under galloping, vortex shedding, and natural wind and truck-induced gusts. The inherent dynamic properties of these structures, especially their low mechanical damping (0.1%-0.4%), is proven to be a key contributing factor, further exacerbating the fatigue-related issues. While most of investigations performed to date have been focused on the development of vibration mitigation strategies or the design of fatigue-rated connections, much less attention has been given to a more fundamental solution, stemming from the modification of the aerodynamic characteristics of this category of structures, addressing the issues at their roots.Considering the large number of traffic signal structures used for traffic control, their cost of repair and reinstallation can add up fast, while their potential failure can pose an immediate risk to the traveling public. This has led to a growing need to develop more cost-effective solutions to mitigate the large-amplitude vibrations of both new and existing traffic signal structures.