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Project Details
STATUS

Completed

PROJECT NUMBER

22-818, TR-818

START DATE

10/01/22

END DATE

10/28/24

FOCUS AREAS

Safety

RESEARCH CENTERS InTrans, CTRE, Iowa LTAP
SPONSORS

Iowa Department of Transportation
Iowa Highway Research Board

Researchers
Principal Investigator
Keith Knapp

Director, Iowa LTAP

Co-Principal Investigator
David Veneziano

Safety Circuit Rider, LTAP

About the research

The project described in the report was developed in response to a documented need for more readily available guidance related to decision-making about roadway cross section reconfigurations. More specifically, there was a need for information that might help during the decision-making process involved in converting four-lane undivided roadway cross sections to three lanes (four- to three-lane conversion) with one through lane in each direction and a two-way left-turn lane.

In response to this need, this project, through consultation with practitioners, identified and developed summary responses to 14 commonly asked questions related to the planning, design, operation, and/or implementation of four- to three-lane conversions. Some of the responses to these questions may also be relevant to the process implemented for other types of conversions and roadway improvements. The summary responses to the questions identified were purposefully kept short and are contained in Appendix A of the report as well as separate standalone documents. References for each summary response, if needed by the user of this guidance, are provided in Appendix B of the report.

Conclusions and recommendations are summarized in the report based on the tasks completed as part of this project. The conclusions are related to the amount and relevancy of material available on four- to three-lane conversions and how the approach to roadway design and operational analysis is changing overall. Recommendations are made about the potential to answer more questions as they are identified, the development of materials specifically for elected officials, and a possible update of the Iowa guidelines for four- to three-lane conversions as an addendum to the national guidelines.

Project Details
STATUS

Completed

PROJECT NUMBER

21-781, TR-798, SPR-RE22(009)-8H-00

START DATE

11/01/21

END DATE

10/28/24

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, BEC
SPONSORS

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

Live load field tests of bridges were carried out using certain implements of husbandry (IoH) to observe the transverse load distribution and the dynamic impacts. A finite element (FE) analysis of the field-tested bridges was performed. The strain data from the FE analysis were validated with the field test data to establish an FE analysis method for a parametric study. This parametric study was performed to observe the influence of various bridge parameters on the load distribution factors. Observation of the load distribution factors from the parametric study shows that the load distribution factor equations prescribed in the AASHTO LRFD (2020) capture the distribution for these IoH loads. Live load factors for this load type for prestressed concrete (PC) bridges and steel girder bridges were found through a calibration process using reliability theory, which involves the selection of a target safety index. The live load factor for each bridge type was calculated for the Strength I and II limit states. An Iowa-specific legally loaded vehicle (Terragator Max) was established using a conservative axle configuration and axle loads of 25 kips. Calibration of the live load factors yielded the following key findings:

  • An update to the AASHTO load and resistance factors (LRFs) is not needed for existing terragator loads as long as the axle loads comply with the legal load limit of 25 kips.
  • When a target safety index of 3.5 is considered, the current live load factor of 1.75 for Strength I should be increased to 1.90 if husbandry vehicles of a configuration similar to that of Terragator Max are manufactured.
  • When a target safety index of 2.0 is considered, the same case does not suggest an update to the AASHTO live load factor.
  • An update to the AASHTO Strength II LRFs is not required.
  • The dead load factors were found to be lower than the current AASHTO-prescribed values. Therefore an update to the AASHTO LRFs is not required.
Project Details
STATUS

Completed

PROJECT NUMBER

19-684, TR-763

START DATE

01/01/19

END DATE

09/30/24

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, BEC
SPONSORS

Federal Highway Administration
Iowa Department of Transportation
Iowa Highway Research Board

Researchers
Principal Investigator
Sri Sritharan

Faculty Affiliate, BEC

Co-Principal Investigator
Jeramy Ashlock

Faculty Affiliate, InTrans

About the research

The design of drilled shafts in Iowa currently relies on the American Association of State Highway and Transportation Officials (AASHTO) LRFD Bridge Design Specifications. To improve design efficiency at the state level, a series of research projects was conducted to develop the Drilled SHAft Foundation Testing (DSHAFT) database, a regional database facilitating the collection, storage, and efficient access of load test data from Iowa and other states, and to utilize the collected data to establish regional resistance factors that are reflective of the uncertainties associated with predicting drilled shaft capacity under Iowa’s specific geological conditions and construction practices. Resistance factors established in a 2019 study for various resistance prediction methods generally showed improvements over those recommended by AASHTO.

The present research aimed to validate the proposed resistance factors and formulate design recommendations for implementation. To this end, the DSHAFT database was further expanded with additional test data. Additionally, regression analyses were conducted on test data from Iowa to develop local resistance predictions that may provide more accurate estimates of drilled shaft capacity locally. Results from the analysis indicated that a linear correlation between soil parameters and measured unit side resistance was the best fit for most soil types. Moreover, settlement data were collected at several production shafts that were part of a few Iowa DOT bridge replacement projects to evaluate the field performance of drilled shafts designed under the current Iowa DOT guidelines. Various challenges were encountered during the data collection process. Some of the data indicated unexpected negative settlements, and further investigation is needed to develop appropriate conclusions. Design recommendations were formulated based on all findings, and design examples were developed to illustrate the application of the design recommendations.

Project Details
STATUS

In-Progress

PROJECT NUMBER

24-910, TR-834

START DATE

07/01/24

END DATE

07/31/26

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, CTRE
SPONSORS

Iowa Department of Transportation
Iowa Highway Research Board

PARTNERS

Michigan State University
Iowa Army National Guard

Researchers
Principal Investigator
Jeramy Ashlock

Faculty Affiliate, InTrans

Principal Investigator
Bora Cetin

About the research

The goal of this project is to study the effectiveness of stabilization of granular-surfaced (“gravel”) roads using wicking and non-wicking geosynthetics. The project will continue a newly established cooperative partnership with the Iowa Army National Guard that enables long-term research on granular-surfaced roads at the Camp Dodge base in Johnston, Iowa. The Camp Dodge facility contains several miles of granular-surfaced roads that routinely exhibit various types of damage and distress including rutting, potholes, washboarding, frost boils, insufficient drainage, and other moisture related damage.

Project Details
STATUS

Completed

PROJECT NUMBER

19-726, TR-781

START DATE

11/01/19

END DATE

09/27/24

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, CTRE, 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
In-Ho Cho

About the research

Superheavy loading vehicles, commonly referred to as superloads, exhibit non-standardized loading configurations along with high gross vehicle weights and axle loadings, all of which may cause unexpected distresses on Iowa road infrastructure systems compared to those caused by conventional vehicle class types categorized by the Federal Highway Administration. Superloads encompass various types of vehicles, including implements of husbandry and superheavy loads, prevalent in the Midwestern region of the United States. The determination of critical load factors affecting road damage due to superloads is intricate due to their non-standardized loading configurations and high loading capacities.

This study developed methodologies to quantify superloads and evaluate their impact on Iowa’s road infrastructure, encompassing jointed plain concrete pavements, flexible pavements, and granular roads. It employed extensive mechanistic-based numerical analysis, life-cycle cost analysis, artificial intelligence (AI)-based predictive modeling, forensic investigations, field data analysis, and prototype tool development, with the research aimed at comprehensively evaluating superload impacts on various road types and structures.

Through extensive numerical analyses, incorporating both mechanistic and empirical methodologies, critical findings regarding the effects of different superload types on pavement and granular road distress, associated treatment cost, and service life reduction emerged. Moreover, the Road Infrastructure-Superload Analysis Tool (RISAT) developed in this study has the potential to provide a user-friendly platform for engineers and planners to evaluate structural damages and associated treatment costs induced by superload traffic. The integration of AI-based predictive models into the RISAT enables users to input pavement and superload properties to obtain highly accurate predictions of pavement damages, treatment costs, and service life reductions. Incorporating field data into the RISAT also enhanced its reliability and applicability to pavement management practices, providing engineers and planners with valuable insights for informed decision-making regarding pavement design, maintenance, and rehabilitation strategies.

Project Details
STATUS

In-Progress

START DATE

09/01/23

END DATE

02/28/26

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, AMPP
SPONSORS

Iowa Department of Transportation
Iowa Highway Research Board

PARTNERS

University of Iowa

Researchers
Principal Investigator
Hosin "David" Lee
Principal Investigator
Chris Williams

Director, AMPP

About the research

The main purpose of this research is to develop a comprehensive asphalt recycling strategy for high RAM mix up to 50% in consultation with surrounding state departments of transportation (DOTs), along with cities and counties, by performing the following tasks:

  • Evaluate existing and new high RAP projects and test sections
  • Select a cracking test procedure as a performance test
  • Conduct performance tests of high RAP mixtures up to 50%
  • Develop an approval process for rejuvenators
  • Evaluate warm mix asphalt (WMA) with a high RAM content
  • Develop a comprehensive asphalt pavement recycling strategy
Project Details
STATUS

Completed

PROJECT NUMBER

TR-770

START DATE

01/01/19

END DATE

03/31/22

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, AMPP
SPONSORS

Iowa Department of Transportation
Iowa Highway Research Board

Researchers
Principal Investigator
Hosin "David" Lee
Principal Investigator
Chris Williams

Director, AMPP

About the research

The main purpose of the proposed research is to develop a mix design procedure for high RAM mixtures with both rejuvenators and fractionated RAM materials for the Iowa Department of Transportation (DOT) and local public agencies by thoroughly understanding complex interactions between fractionated RAM and rejuvenators. The main objectives of this research are to: (1) examine the effects of various rejuvenators and different methods of RAP stockpile fractionation on the volumetric mix design properties, (2) evaluate long-term oven aging of both laboratory and field rejuvenated/fractionated high RAM mixtures and (3) develop specifications for evaluating asphalt mixtures with rejuvenators and high fractionated RAM contents.

Project Details
STATUS

In-Progress

PROJECT NUMBER

24-882, HR-3049

START DATE

01/01/24

END DATE

12/31/24

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

An electrically conductive concrete (ECON) heated pavement system (HPS) utilizes the inherent electrical resistance of concrete to maintain the pavement surface at above-freezing temperatures and thus prevent snow and ice accumulation on the surface. Such a sustainable concrete pavement system can improve its infrastructure resiliency by allowing it to be safe, open, and accessible during even harsh winter storms. The primary objective of this project is to to enhance the practicality of the ECON mix design and ECON HPS field implementation by conducting necessary tests to establish a defined range of electrical conductivity compliant with national electrical safety specifications for executing the construction of the Iowa City Bus Stop Enhancement Project. This will be achieved through execution of the following primary tasks: (1) project management; (2) formulating robust production, transportation, and quality control/assurance (QC/QA) protocols; (3) determining electrical safety protocols; (4) developing implementation plans with recommendations; and (5) producing a final project report. The outcomes of this project will include both best-practice guidance on the steadfast and uniform quality of ECON mixture production as well as a defined range of electrical conductivity for the ECON HPS, ensuring both performance and safety. Such outcomes could result in successful implementation of the ECON HPS for the Iowa City Bus Stop Enhancement Project.

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

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.

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