Report on a special investigation of the City of Moorland for the period January 1, 2008 through October 31, 2013

Report on a special investigation of the City of Moorland for the period January 1, 2008 through October 31, 2013

Investigation of the Effect of Reheating Asphalts on the Test Results, MLR-84-09, 1984

All noncomplying penetration and absolute viscosity results must be verified before being reported. This verification of test results is done by reheating and retesting the identical sample that is suspect. The District Laboratories are required to submit penetration and absolute viscosity correlation samples to the Central Laboratory. These samples are the identical ones tested by the District Laboratories. When the Central laboratory tests these correlation samples they are also considered to be reheated and retested. Reheating a sample will harden the asphalt to some degree and possibly cause a change in the test results. This investigation was conducted to determine how much change in penetration and absolute viscosity could be expected by reheating and retesting asphalt samples.

Investigation of Video Crack and Patch Surveying for Pavement Management, MLR-92-01, 1992

The Iowa DOT has been using the AASHTO Present Serviceability Index (PSI) rating procedure since 1968 to rate the condition of pavement sections. A ride factor and a cracking and patching factor make up the PSI value. Crack and patch surveys have been done by sending crews out to measure and record the distress. Advances in video equipment and computers make it practical to videotape roads and do the crack and patch measurements in the office. The objective of the study was to determine the feasibility of converting the crack and patch survey operation to a video recording system with manual post processing. The summary and conclusions are as follows: Video crack and patch surveying is a feasible alternative to the current crack and patch procedure. The cost per mile should be about 25 percent less than the current procedure. More importantly, the risk of accidents is reduced by getting the people and vehicles off the roadway and shoulder. Another benefit is the elimination of the negative public perceptions of the survey crew on the shoulder.

Investigation of Steel-Stringer Bridges: Superstructures and Substructures, Volume I, TR-522, 2007

There are hundreds of structurally deficient or functionally obsolete bridges in the state of Iowa. With the majority of these bridges located on rural county roads where there is limited funding available to replace the bridges, diagnostic load testing can be utilized to determine the actual load carrying capacity of the bridge. One particular family or fleet of bridges that has been determined to be desirable for load testing consists of single-span bridges with non-composite, cast-in-place concrete decks, steel stringers, and timber substructures. Six bridges with poor performing superstructure and substructure from the aforementioned family of bridges were selected to be load tested. The six bridges were located on rural roads in five different counties in Iowa: Boone, Carroll, Humboldt, Mahaska, and Marshall. Volume I of this report focuses on evaluating the superstructure for this family of bridges. This volume discusses the behavior characteristics that influence the load carrying capacity of this fleet of bridges. In particular, the live load distribution, partial composite action, and bearing restraint were investigated as potential factors that could influence the bridge ratings. Implementing fleet management practices, the bridges were analyzed to determine if the load test results could be predicted to better analyze previously untested bridges. For this family of bridges it was found that the ratings increased as a result of the load testing demonstrating a greater capacity than determined analytically. Volume II of this report focuses on evaluating the timber substructure for this family of bridges. In this volume, procedures for detecting pile internal decay using nondestructive ultrasonic stress wave techniques, correlating nondestructive ultrasonic stress wave techniques to axial compression tests to estimate deteriorated pile residual strength, and evaluating load distribution through poor performing timber substructure elements by instrumenting and load testing the abutments of the six selected bridges are discussed. Also, in this volume pile repair methods for restoring axial and bending capacities of pile are developed and evaluated.

Investigation of Steel-Stringer Bridges: Superstructures and Substructures, Volume II, TR-522, 2007

Problems with unknown bridge foundations in Iowa are often associated with timber substructures. Timber piles are subject to biological and physical deterioration, which makes quantifying in-service pile capacity difficult. Currently there are no reliable means to estimate the residual carrying capacity of an in-service deteriorated pile; and thus, the overall safety of the bridge cannot be determined. The lack of reliable evaluation methods can lead to conservative and costly maintenance practices. This research study was undertaken to investigate procedures for assessing bridge substructures, and evaluating procedures for rehabilitating/strengthening/replacing inadequate substructure components. The report includes an extensive literature review, a field reconnaissance study of 49 bridges, a survey of substructure problems from the perspective of County Engineers, a laboratory study aiming to correlate nondestructive tests to residual pile strength and stiffness values, nondestructive and destructive load tests for 6 bridges with poor substructures, and finally a laboratory study evaluating selected repair methods.

Report on a special investigation of the West Des Moines Community School District - Western Hills Elementary School for the period May 22, 2012 through March 31, 2015

Report on a special investigation of the West Des Moines Community School District - Western Hills Elementary School for the period May 22, 2012 through March 31, 2015

Investigation of Improved Utility Cut Repair Techniques to Reduce Settlement in Repaired Areas, Phase II, TR-566, 2010

Trench maintenance problems are caused by improper backfill placement and construction procedures. This report is part of a multiphase research project that aims to improve long-term performance of utility cut restoration trenches. The goal of this research is to improve pavement patch life and reduce maintenance of the repaired areas. The objectives were to use field-testing data, laboratory-testing data, and long-term monitoring (elevation survey and falling weight deflectometer testing) to suggest and modify recommendations from Phase I and to identify the principles of trench subsurface settlement and load distribution in utility cut restoration areas by using instrumented trenches. The objectives were accomplished by monitoring local agency utility construction from Phase I, constructing and monitoring the recommended trenches from Phase I, and instrumenting trenches to monitor changes in temperature, pressure, moisture content, and settlement as a function of time to determine the influences of seasonal changes on the utility cut performance.

Investigation of Electromagnetic Gauges for Determination of In-Place Density of HMA Pavements, TR-576, 2009

This study evaluated the use of electromagnetic gauges to determine the adjusted densities of HMA pavements. Field measurements were taken with two electromagnetic gauges, the Pavement Quality Indicator (PQI) 301 and the Pavetracker Plus 2701B. Seven projects were included in the study with 3 to 5 consecutive paving days. For each day/lot 20 randomly selected locations were tested along with seven core locations. The analysis of PaveTracker and PQI density consisted of determining which factors are statistically significant, and core density residuals and a regression analysis of core as a function of PaveTracker and PQI readings. The following key conclusions can be stated: 1. Core density, traffic and binder content were all found to be significant for both electromagnetic gauges studied, 2. Core density residuals are normally distributed and centered at zero for both electromagnetic gauges, 3. For PaveTracker readings, statistically one third of the lots do not have an intercept that is zero and two thirds of the lots do not rule out a scaler correction factor of zero, 4. For PQI readings, statistically the 95% confidence interval rules out the intercept being zero for all seven projects and six of the seven projects do not rule out the scaler correction factor being zero, 5. The PQI 301 gauge should not be used for quality control or quality assurance, and 6. The Pavetracker 2701B gauge can be used for quality control but not quality assurance. This study has found that with the limited sample size, the adjusted density equations for both electromagnetic gauges were determined to be inadequate. The PaveTracker Plus 2701B was determined to be better than the PQI 301. The PaveTracker 2701B could still be applicable for quality assurance if the number of core locations per day is reduced and supplemented with additional PaveTracker 2701B readings. Further research should be done to determine the minimum number of core locations to calibrate the gauges each day/lot and the number of additional PaveTracker 2701B readings required.

Investigation of Glass Fiber Composite Dowel Bars for Highway Pavement Slabs, TR-408, 2001

Contractors, engineers, owners and manufacturers want to be certain that a new product or procedure will yield beneficial results when compared to the current method of construction. The following research was conducted in order to compare the performance of epoxy coated dowel bars to dowel bars of alternative shapes and materials such as stainless steel and glass fiber reinforced polymer (GFRP). Research was also done on the effect that dowel bar spacing has on the performance of concrete pavements. Four phases of this research are described in this report.

Investigation of Materials for the Reduction and Prevention of Corrosion on Highway Maintenance Equipment, TR-472, 2009

The issue of corrosion of winter maintenance equipment is becoming of greater concern because of the increased use of liquid solutions of ice control chemicals, as opposed to their application in solid form. Being in liquid form, the ice control chemicals can more easily penetrate into the nooks and crannies on equipment and avoid being cleansed from the vehicle. Given this enhanced corrosive ability, methods must be found to minimize corrosion. The methods may include coatings, additives, cleansing techniques, other methods, and may also include doing nothing, and accepting a reduced equipment lifetime as a valid (perhaps) trade off with the enhanced benefits of using liquid ice control chemicals. In reality, some combination of these methods may prove to be optimal. Whatever solutions are selected, they must be relatively cheap and durable. The latter point is critical because of the environment in which maintenance trucks operate, in which scrapes, scratches and dents are facts of life. Protection methods that are not robust simply will not work. The purpose of this study is to determine how corrosion occurs on maintenance trucks, to find methods that would minimize the major corrosion mechanisms, and to

Feasibility Investigation of Segmentally Precast Bridge Piers for Accelerated Construction, TR-556, 2009

An innovative structural system for pier columns was investigated through a series of laboratory experiments. The columns and connections examined were comprised of precast concrete segments to accelerate construction. In addition some of the columns employed unbonded post-tensioning to self-center the columns when subjected to lateral loads and structural fuses to control large lateral deflections, dissipate energy, and expedite repair in the event of a catastrophic loading event. Six cantilever columns with varying component materials and connection details were subjected to a regimen of vertical dead loads and cyclic, quasi-static lateral loads. One column was designed as a control column to represent the behavior of a conventional reinforced concrete column and provide a basis for comparison with the remaining five jointed columns designed with the proposed structural system. After sustaining significant damage, the self-centering, jointed columns were repaired by replacing the structural fuses and retested to failure to investigate the effectiveness of the repair. The experiments identified both effective and unsatisfactory details for the jointed system. Two of the jointed columns demonstrated equivalent lateral strength, greater lateral stiffness, and greater lateral deformation capacity than the control column. The self-centering capability of the jointed columns was clearly demonstrated as well, and the repair technique proved effective as demonstrated by nearly identical pre and post repair behavior. The authors believe the proposed system to be a feasible alternative to conventional pier systems and recommend further development of details.

Special investigation of the University of Iowa Health Care, Department of Orthopaedics and Rehabilitation, for the period July 1, 1999 through December 31, 2014

Special investigation of the University of Iowa Health Care, Department of Orthopaedics and Rehabilitation, for the period July 1, 1999 through December 31, 2014

Laboratory Investigation of Concrete Beam-End Treatments, RB08-013, 2015

The ends of prestressed concrete beams under expansion joints are often exposed to moisture and chlorides. Left unprotected, the moisture and chlorides come in contact with the ends of the prestressing strands and/or the mild reinforcing, resulting in corrosion. Once deterioration begins, it progresses unless some process is employed to address it. Deterioration can lead to loss of bearing area and therefore a reduction in bridge capacity. Previous research has looked into the use of concrete coatings (silanes, epoxies, fiber-reinforced polymers, etc.) for protecting prestressed concrete beam ends but found that little to no laboratory research has been done related to the performance of these coatings in this specific type of application. The Iowa Department of Transportation (DOT) currently specifies coating the ends of exposed prestressed concrete beams with Sikagard 62 (a high-build, protective, solvent-free, epoxy coating) at the precast plant prior to installation on the bridge. However, no physical testing of Sikagard 62 in this application has been completed. In addition, the Iowa DOT continues to see deterioration in the prestressed concrete beam ends, even those treated with Sikagard 62. The goals of this project were to evaluate the performance of the Iowa DOT-specified beam-end coating as well as other concrete coating alternatives based on the American Association of State Highway and Transportation Officials (AASHTO) T259-80 chloride ion penetration test and to test their performance on in-service bridges throughout the duration of the project. In addition, alternative beam-end forming details were developed and evaluated for their potential to mitigate and/or eliminate the deterioration caused by corrosion of the prestressing strands on prestressed concrete beam ends used in bridges with expansion joints. The alternative beam-end details consisted of individual strand blockouts, an individual blockout for a cluster of strands, dual blockouts for two clusters of strands, and drilling out the strands after they are flush cut. The goal of all of the forming alternatives was to offset the ends of the prestressing strands from the end face of the beam and then cover them with a grout/concrete layer, thereby limiting or eliminating their exposure to moisture and chlorides.

Report on a special investigation of the University of Northern Iowa, College of Education – Curriculum and Instruction Department for the period January 1, 2012 through October 31, 2014

Report on a special investigation of the University of Northern Iowa, College of Education – Curriculum and Instruction Department for the period January 1, 2012 through October 31, 2014

Special investigation of the City of Casey for the period July 1, 2008 through October 31, 2014

Special investigation of the City of Casey for the period July 1, 2008 through October 31, 2014