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Project Details
STATUS

Completed

PROJECT NUMBER

16-579, TR-710

START DATE

07/01/16

END DATE

03/29/24

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, BEC, CTRE
SPONSORS

Iowa Department of Transportation
Iowa Highway Research Board

Researchers
Principal Investigator
Brent Phares

Bridge Research Engineer, BEC

Co-Principal Investigator
Alice Alipour

Structure and Infrastructure Engineer, BEC

About the research

The Iowa secondary road system has a large number of scour-susceptible bridges or bridges with unknown foundation conditions. These structures are commonly required to have a plan of action (POA) to close them during flood events, or have countermeasures installed to keep them open. In the case of unknown foundations, countermeasures must be installed.

Among the many different countermeasures available is a potentially viable technique known as a partially grouted revetment. Partially grouted revetment construction involves the placement of rock, stone, and/or recycled concrete on a filter layer that is compatible with the subsoil. The voids of the matrix are then partially filled with a portland cement-based grout material.

Partially grouted revetment appear to achieve a desirable balance between full and no grouting of revetment. Specifically, partial grouting increases the stability of the system without eliminating the flexibility of a looser matrix. In addition, a partially grouted revetment system allows for the use of smaller (and less expensive) rock, stone, and/or recycled concrete, which also results in decreased layer thickness. The ideal system adheres adjoining pieces together while leaving relatively large voids between the stones.

The final project report presents background information on countermeasure types and their frequency of use, including a field review of existing countermeasures to determine quality of performance. These efforts were followed by several pilot installation sites on county infrastructure in Iowa using partially grouted riprap. These pilot installations are described and their performance documented after years of service.

Project Details
STATUS

Completed

PROJECT NUMBER

20-733, TPF-5(438)

START DATE

01/01/21

END DATE

03/08/24

FOCUS AREAS

Safety

RESEARCH CENTERS InTrans, SWZDI
SPONSORS

Iowa Department of Transportation
Smart Work Zone Deployment Initiative

Researchers
Principal Investigator
Timothy Gates
Co-Principal Investigator
Peter Savolainen
Co-Principal Investigator
Praveen Edara
Co-Principal Investigator
Henry Brown

About the research

This study investigated methods for improving the effectiveness of speed feedback trailers (SFTs) when used as a speed management strategy in highway work zones. The research included a literature review, a state department of transportation (DOT) survey, and field evaluations conducted at several freeway work zones. The findings were synthesized to provide recommendations on methods for optimizing the deployment of SFT in freeway work zones. The state DOT survey revealed that SFTs are widely implemented in work zones across the United States, most commonly for lane closures and traffic shifts. Their use varies across states, ranging from optional to mandatory under specific conditions. SFTs are most commonly positioned near the work area or in advance of the lane closure taper and are often relocated as the work progresses. From there, a series of field studies were conducted within freeway work zones in Michigan and Missouri to evaluate the effectiveness of various SFT deployment strategies towards reducing work zone speeds and improving speed compliance. These evaluations, conducted in multiple phases and at five freeway work zone locations, sought to yield insights and recommendations for optimizing SFT deployment and introducing measures to improve their overall effectiveness. The evaluations specifically assessed the impact of strategically placing SFTs at various locations within the work zones, including near the start of a lane closure, approaching a work area, approaching a lane shift, and within a freeway crossover. Additionally, the effectiveness of SFTs were also assessed when combined with other strategies, like digital speed limits (DSLs) signs and police vehicle presence within the work zone. Although SFTs were generally effective at reducing work zone speeds regardless of the deployment characteristics, they tended to be more effective when positioned closer to the work area, including ingress/egress locations, where speeds were up to 3.6 mph lower when the SFT was present and active. SFTs were also effective at lowering work zone speeds when positioned within 1,000 beyond the end of the lane closure taper, within 1,000 ft in advance of the start of the taper, and within freeway crossovers. The speed reduction effects were generally sustained for at least one-half mile beyond the SFT. SFTs were also found to improve speed reductions measured near a police vehicle positioned within the lane closure by an additional 1.4 mph. Additionally, when paired with DSL signs on the same trailer assembly, the speed feedback display reduced speeds near the work area by an additional 1.8 mph. It is recommended that if only a single SFT is to be used, it should be positioned near the work area, approximately 200 ft in advance of the active work. If additional SFTs are available, then it is recommended that one be positioned within 1,000 ft upstream of the lane closure, shift, or crossover. Additionally, an SFT should be placed shortly beyond the end (e.g., within 1,000 ft) of any lane closure taper, preferably adjacent to the initial speed limit sign.

Project Details
STATUS

In-Progress

PROJECT NUMBER

24-873, TR-831

START DATE

01/01/24

END DATE

12/31/26

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, BEC
SPONSORS

Iowa Department of Transportation
Iowa Highway Research Board

Researchers
Principal Investigator
Zhengyu Liu

Research Engineer, BEC

Co-Principal Investigator
Brent Phares

Bridge Research Engineer, BEC

About the research

State and federal legislators regularly request increases to the axle or gross weight limits for commercial vehicles. The question that is always asked is, “What is the impact on the life expectancy of a bridge when heavier loads are allowed on some vehicles?” There is no past or present method to determine how heavier loads affect the life of Iowa highway bridges. Bridge owners need a method of quantifying the effects of heavier loads or any load on a bridge’s life expectancy. The objective of this research is to qualify the relationship between increased legal loads and reduced bridge service life for Iowa bridges. To achieve the proposed objective, a 36-month research plan was developed, which includes conducting a comprehensive literature review, collecting Iowa-specific data, estimating bridge costs and life reduction due to truck weight limitation increases, and performing the laboratory test for the validation of bridge life reduction prediction. The result of this project will help the bridge owner make reasonable assumptions on the life of a bridge when subjected to increased truck loads.

Project Details
STATUS

In-Progress

PROJECT NUMBER

24-871, TR-829

START DATE

01/01/24

END DATE

12/31/27

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, CP Tech Center, PROSPER
SPONSORS

Iowa Department of Transportation
Iowa Highway Research Board

Researchers
Principal Investigator
Halil Ceylan

Director, PROSPER

Co-Principal Investigator
Sunghwan Kim

Associate Director, PROSPER

Co-Principal Investigator
Peter Taylor

Director, CP Tech Center

Co-Principal Investigator
Dan King

Research Engineer, CP Tech Center

About the research

Roller-compacted concrete (RCC) is a no-slump concrete having same basic ingredients as ordinary Portland cement concrete (PCC). While RCC has been used in commercial areas and for local streets and highways, its use for paving shoulders has not been studied in Iowa. The primary objective of this project is to develop mix design, construction, and maintenance/preservation specifications for using RCC in Iowa pavement applications. This will be achieved through execution of the following primary tasks: (1) literature review; (2) comprehensive laboratory assessment; (3) field demonstration construction and evaluation; (4) life-cycle cost analysis (LCCA) for quantifying cost effectiveness of various shoulder options; (5) facilitation of three workshops on RCC maintenance and preservation, life expectancy, recycling, and potential Iowa transportation infrastructure application types; and (6) Iowa RCC specification development. The successful outcomes of this research will be of great benefit when providing justification on the proper use of RCC as an alternative durable and strengthened material for the paving of shoulders and other applicable areas in Iowa transportation systems.

Project Details
STATUS

Completed

PROJECT NUMBER

18-665, TR-753

START DATE

07/01/18

END DATE

12/13/23

RESEARCH CENTERS InTrans, CMAT, PROSPER
SPONSORS

Iowa Department of Transportation
Iowa Highway Research Board

Researchers
Principal Investigator
Halil Ceylan

Director, PROSPER

Co-Principal Investigator
Sunghwan Kim

Associate Director, PROSPER

Co-Principal Investigator
Charles Jahren

About the research

Iowa has over 110,000 miles of roads, and they frequently support local residential vehicles as well as heavy trucks. Traditional bituminous surface treatments (BST) could be employed to maintain these roads properly, but these treatments typically require high-quality materials and standard construction equipment. Otta seal is a relatively new BST that allows for the use of more economical local aggregates and commonly available equipment. To evaluate the feasibility of Otta seal implementation, a Phase I study was launched to design and construct Iowa’s first Otta seal-surfaced road in Cherokee County in 2017. The successful construction of the first Otta seal road in Iowa provided valuable experience and knowledge for local public agencies, and a follow-up Phase II study was initiated in 2018. The Phase II study described in this report aimed to establish the recommended specifications through comprehensive laboratory evaluation and characterization and additional field implementation projects. In the Phase II study, more than 50 Otta seal sites constructed since 2017 were evaluated. These sites had various local aggregate and binder types, as well as various application rates. Five consecutive years of field measurements were executed in this Phase II study, including lightweight deflectometer-derived elastic modulus, International Roughness Index, dust generation, and skid resistance. The field evaluation in 2023 indicated that all Phase II Otta seal sites still exhibit satisfactory performance. A detailed laboratory investigation was conducted to establish a rational methodology for designing Otta seal road surfaces utilizing locally available materials. Four distinct aggregate types were considered in this study: limestone, recycled concrete aggregate (RCA), slag, and river aggregates. The McLeod method was modified to determine optimal rates for aggregate and binder application. The laboratory study primarily assessed Otta seal performance through a sweep test exploring the impact of material type, aggregate gradation, binder type, and application rate on aggregate loss. Key findings include the significance of aggregate gradation in reduced aggregate loss, the comparable performance of HFMS-2s and MC 3000 binders, the suitability of recycled materials (especially slag), and the effectiveness of the modified McLeod method. A life-cycle cost analysis revealed that the lowest cost was associated with Otta seal designed using the modified McLeod method. These findings contribute to a more efficient Otta seal design, enhancing road surface longevity while utilizing locally sourced materials.

Project Details
STATUS

Completed

PROJECT NUMBER

19-705, TR-777

START DATE

06/01/19

END DATE

12/13/23

SPONSORS

Iowa Department of Transportation
Iowa Highway Research Board

Researchers
Principal Investigator
Halil Ceylan

Director, PROSPER

Co-Principal Investigator
Sunghwan Kim

Associate Director, PROSPER

Co-Principal Investigator
Wensheng Zhang

About the research

Pavement roughness serves as a critical indicator of the overall ride quality of road surfaces. Elevated levels of pavement roughness can give rise to concerns regarding driving safety, fuel consumption, and exhaust gas emissions. The International Roughness Index (IRI) stands as the globally accepted standard for quantifying road surface roughness. Although one of the primary responsibilities of local public agencies (LPAs) involves monitoring and maintaining appropriate IRI levels for the local road system, existing techniques used to collect IRI data, such as using high-speed and walking profilometers, typically entail high annual costs for network-level inspection. Consequently, LPAs are in need of a cost-effective IRI data collection system that enables them to gather pavement performance data annually. Smartphones come equipped with an array of sensors, including multi-axis accelerometers and global positioning systems (GPS), that present an efficient and economical approach for collecting vehicle suspension data, specifically vertical acceleration. These data can then be harnessed to estimate pavement profiles and roughness. This study endeavored to develop a low-cost, smartphone-based, nonproprietary data collection system designed for use by LPAs to gather pavement roughness data on an annual basis. This adaptable system can be implemented on Android phones, iPhones, or custom-developed smart boxes that incorporate accelerometers and GPS units. All data gathered in this way can be seamlessly transferred to a cloud-based server and subsequently processed using a Python-based algorithm to compute the IRI. The accuracy of such a system was assessed using four distinct smartphones, one custom-developed smart box, and a Class 1 high-speed profilometer that was used to establish reference IRI values. The field data collection program encompassed 24 Story County sites selected to validate the accuracy of IRI measurements. The results demonstrate that the smartphone-based and smart box systems developed offer a dependable, low-cost, and user-friendly solution for LPAs to use in assessing local road roughness. A prototype smartphone application for detecting road surface distress through captured videos and images was also developed and evaluated.

Project Details
STATUS

In-Progress

PROJECT NUMBER

23-872, TR-830

START DATE

12/01/23

END DATE

11/30/25

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, CP Tech Center, PROSPER
SPONSORS

Iowa Department of Transportation
Iowa Highway Research Board

Researchers
Principal Investigator
Dan King

Research Engineer, CP Tech Center

Co-Principal Investigator
Halil Ceylan

Director, PROSPER

Co-Principal Investigator
Sunghwan Kim

Associate Director, PROSPER

Co-Principal Investigator
Peter Taylor

Director, CP Tech Center

About the research

Joint sawing is a critical part of concrete pavement construction, as the jointing system plays an important role in concrete pavement performance and service life. To ensure successful construction, it is important to understand the basic principles of the joint sawing process. These principles include proper timing, depth, and spacing of saw cuts, as well as the many factors related to materials, climate, and equipment that affect the sawing window. Understanding the fundamentals of joint sawing is even more important today thanks to the changing construction workforce and ongoing changes to mixtures and materials used in concrete pavements. The objectives of this research are to perform a comprehensive literature review on joint sawing of concrete pavements; to conduct a survey of agencies, contractors, and equipment providers to establish today’s typical practices and the most common problems related to joint sawing in Iowa; and to perform a field investigation that diagnoses these problems and tests out potential solutions on Iowa pavement construction projects. The results of each of these components will be combined and summarized in a guide culminating the best practices for joint sawing concrete pavements.

Project Details
STATUS

In-Progress

PROJECT NUMBER

23-869

START DATE

10/01/23

END DATE

08/31/25

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, CP Tech Center
SPONSORS

Iowa Department of Transportation

Researchers
Principal Investigator
Leif Wathne

Associate Director, CP Tech Center

Co-Principal Investigator
Peter Taylor

Director, CP Tech Center

About the research

Given that an ever-increasing number of state Departments of Transportation (DOTs) across the nation are exploring the use of Environmental Product Declarations (EPDs) as a means to quantify the embodied environmental impacts and emissions of their pavements (either as a result of “buy-clean” legislative mandates or executive policy), the Iowa DOT would benefit from better understanding what is involved with requiring contractors to produce EPDs associated with a concrete paving project, and how that information can be best used to inform improved decision-making in the sustainability and carbon emissions context. Additionally, the Iowa DOT aims to better understand how the embodied-impacts-only analysis (reflected through EPDs) compares to a whole life-cycle analysis (established via a full life cycle assessment, or LCA).

To meet these objectives, the Iowa DOT proposes to identify a concrete paving project (2023/24 construction season) where materials, production, and construction activities can be carefully monitored in order to collect the necessary information and data to develop EPDs consistent with current product category rules (PCRs). It is anticipated that adjustments in the prescribed process required by the relevant PCR will be necessary as the current PCR for concrete is tailored to ready-mixed concrete, and not concrete produced at a portable plant. This research will help establish what type of adjustments will be necessary to adequately capture portable plants as well. All information will be gathered in accordance with requirements consistent with a Type III EPD as defined by the International Standards Organization (ISO). The goal in collecting this information and developing the relevant EPDs is to enable Iowa DOT and in turn the Iowa paving industry to better understand the level of effort required (by both agency and industry) to generate EPDs for paving concrete, and identify areas where improvements in data collection, education and training are needed to facilitate possible routine EPD generation in the future.

This information will also inform a benchmarking analysis of current Iowa DOT concrete paving operations. In addition, Iowa DOT proposes to conduct additional analysis of lifecycle greenhouse gas (GHG) emissions (using LCA), including such use-phase impacts as pavement-vehicle interaction, albedo and carbonation, and suggestions on how to further reduce pavement related lifecycle GHGs emissions. The objectives of these additional analyses are to enhance the Iowa DOT’s understanding of the complete life cycle impacts associated with pavement assets, and inform improved decision-making in the pavement arena to lower the GHG emissions associated with Iowa’s pavement assets.

Project Details
STATUS

Completed

PROJECT NUMBER

17-605 TR-722

START DATE

04/01/17

END DATE

10/31/23

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, BEC
SPONSORS

Iowa Department of Transportation
Iowa Highway Research Board

Researchers
Principal Investigator
Behrouz Shafei

Structural Engineer, BEC

Co-Principal Investigator
Brent Phares

Bridge Research Engineer, BEC

About the research

Integral and semi-integral abutment bridges have become increasingly popular in Iowa and across the country because they eliminate joints at the bridge ends. Expansion joints in bridge decks allow water to seep in and corrode bearings along with other structural elements in conventional bridge construction. An integral abutment connects the bridge deck and girders with the substructure in one piece to reduce maintenance and increase service life. The abutment moves with the rest of the bridge, and this movement introduces new issues with water drainage, soil settlement, soil erosion, and concrete cracking. The objective of this research was to evaluate improved bridge end details to increase service life and investigate limitations placed on the use of semi-integral abutment bridges. Research methods include a literature review, visual inspections, field monitoring, and finite element simulations.

The extensive literature review identified research relevant to improving the performance of bridge ends. Abutments, approach slabs, geotechnical aspects, drainage, and expansion joints were evaluated in detail. It was found that innovative bridge abutments allow for the elimination of conventional bearings and attempt to reduce issues associated with integral construction. Semi-integral abutment bridges and those with approach slabs attached to the abutment were inspected across the state of Iowa to assess the performance of current design methods. The condition and performance of tied joints was found to be unsatisfactory in some instances, with measured openings much larger than those built during initial construction. Joints between wingwalls and approach slabs were also found to be in poor condition. Four bridges were outfitted with a multitude of sensors, including strain gauges and displacement transducers, to measure concrete expansion and bridge displacement. Finite element models were also created to investigate the movement of approach slabs on the soil below. Simulated bridge expansion provided insights into approach slab behavior and tie bar stresses due to friction. Parametric studies were completed on various approach slab properties, including friction with soil, soil stiffness, tie bar style, and bridge skew.

Project Details
STATUS

Completed

PROJECT NUMBER

21-783, TR-800

START DATE

11/01/21

END DATE

10/30/23

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, BEC
SPONSORS

ABC-UTC
Iowa Department of Transportation
Iowa Highway Research Board

Researchers
Principal Investigator
Justin Dahlberg

Director, BEC

Co-Principal Investigator
Brent Phares

Bridge Research Engineer, BEC

About the research

This project investigated helical pile foundation implementation for bridges, resulting in a design and construction guide. The simplicity and speed of helical pile installation, along with the ability to work within areas of limited size with smaller, more maneuverable equipment, can accelerate the construction of bridge structure foundations.

The guide provides bridge engineers and designers with direction and specifications for this substructure foundation option, which can be advantageous on any bridge project, but particularly for low-volume roads where budgetary considerations tend to be a specific priority.

The guide includes many useful design specification reference tables and also useful construction and installation documentation tools as examples and as table forms that can be used for helical pile bridge foundations.

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