Low Cost Techniques of Base Stabilization, HR-312, 1994

This project was initiated in 1988 to study the effectiveness of four different construction techniques for establishing a stable base on a granular surfaced roadway. After base stabilization, the roadway was then seal coated, eliminating dust problems associated with granular surfaced roads. When monies become available, the roadway can be surfaced with a more permanent structure. A 2.8 mi (4.5 km) section of the Horseshoe Road in Dubuque County was divided into four divisions for this study. This report discusses the procedures used during construction of these different divisions. Problems and possible solutions have been analyzed to better understand the capabilities of the materials and construction techniques used on the project. The project had the following results: High structural ratings and soil K factors for the BIO CAT and Consolid bases did not translate to good roadway performance; the macadam base had the best overall performance; the tensar fabric had no noticeable effect on the macadam base; and the HFE-300 performed acceptably.

Cracking and Seating to Retard Reflective Cracking - Hamilton County, HR-277, 1993

The crack and seat (C & S) method of rehabilitating concrete pavements has been proposed to reduce the incidence of reflective cracking in asphalt overlays. These cracked pieces help reduce the thermal effects on lateral joint movement while the seating of slab pieces reduces vertical movement. This 1986 project demonstrated that a 0.6 m x 0.9 m (2 ft x 3 ft) cracking pattern was optimal to retard reflective cracking in an asphalt overlay. The best performance among three C & S test sections was section 4 with a 0.6 m x 0.9 m (2 ft x 3 ft) cracking pattern and 7.6 cm (3 in) overlay. Structural ratings determined from the Road Rater™ indicated little difference between each C & S section with varying AC thicknesses and crack spacings. Although reflection cracking is reduced in the early years after construction, the effectiveness of the C & S method diminishes over time.

Total Cost of Transportation Analysis of Road and Highway Issues, HR-388, 2002

In the administration, planning, design, and maintenance of road systems, transportation professionals often need to choose between alternatives, justify decisions, evaluate tradeoffs, determine how much to spend, set priorities, assess how well the network meets traveler needs, and communicate the basis for their actions to others. A variety of technical guidelines, tools, and methods have been developed to help with these activities. Such work aids include design criteria guidelines, design exception analysis methods, needs studies, revenue allocation schemes, regional planning guides, designation of minimum standards, sufficiency ratings, management systems, point based systems to determine eligibility for paving, functional classification, and bridge ratings. While such tools play valuable roles, they also manifest a number of deficiencies and are poorly integrated. Design guides tell what solutions MAY be used, they aren't oriented towards helping find which one SHOULD be used. Design exception methods help justify deviation from design guide requirements but omit consideration of important factors. Resource distribution is too often based on dividing up what's available rather than helping determine how much should be spent. Point systems serve well as procedural tools but are employed primarily to justify decisions that have already been made. In addition, the tools aren't very scalable: a system level method of analysis seldom works at the project level and vice versa. In conjunction with the issues cited above, the operation and financing of the road and highway system is often the subject of criticisms that raise fundamental questions: What is the best way to determine how much money should be spent on a city or a county's road network? Is the size and quality of the rural road system appropriate? Is too much or too little money spent on road work? What parts of the system should be upgraded and in what sequence? Do truckers receive a hidden subsidy from other motorists? Do transportation professions evaluate road situations from too narrow of a perspective? In considering the issues and questions the author concluded that it would be of value if one could identify and develop a new method that would overcome the shortcomings of existing methods, be scalable, be capable of being understood by the general public, and utilize a broad viewpoint. After trying out a number of concepts, it appeared that a good approach would be to view the road network as a sub-component of a much larger system that also includes vehicles, people, goods-in-transit, and all the ancillary items needed to make the system function. Highway investment decisions could then be made on the basis of how they affect the total cost of operating the total system. A concept, named the "Total Cost of Transportation" method, was then developed and tested. The concept rests on four key principles: 1) that roads are but one sub-system of a much larger 'Road Based Transportation System', 2) that the size and activity level of the overall system are determined by market forces, 3) that the sum of everything expended, consumed, given up, or permanently reserved in building the system and generating the activity that results from the market forces represents the total cost of transportation, and 4) that the economic purpose of making road improvements is to minimize that total cost. To test the practical value of the theory, a special database and spreadsheet model of Iowa's county road network was developed. This involved creating a physical model to represent the size, characteristics, activity levels, and the rates at which the activities take place, developing a companion economic cost model, then using the two in tandem to explore a variety of issues. Ultimately, the theory and model proved capable of being used in full system, partial system, single segment, project, and general design guide levels of analysis. The method appeared to be capable of remedying many of the existing work method defects and to answer society's transportation questions from a new perspective.

Development of Concepts for Pavement Management, MLR-79-04, 1979

Sufficient evidence was not discovered in this brief search to alter the general opinion that the Serviceability (Present Serviceability Index-PSI) - Performance Concepts developed by the AASHO Road Test provides the optimum engineering basis for pavement management. Use of these concepts in Iowa has the additional advantage in that we have a reasonable quantity of historical data over a period of time on the change in pavement condition as measured by PSI's. Some additional benefits would be the ability to better assess our needs with respect to those being recommended to Congress by AASHTO Committees. These concepts have been the basis used for developing policies on dimensions and weight of vehicles and highway needs which the AASHTO Transport Committees have recommended to the United States House Committee on Ways and Means. The first recommendation based on these concepts was made in the mid 1960's. Iowa's participation in the evaluation for this recommendation was under the direction of our present Director of Transportation, Mr. Raymond Kassel. PSI Indexes had to be derived from subjective surface ratings at that time. The most recent recommendation to Congress was made in November of 1977. Based on the rationale expressed above, a pilot study of the major part of the rural interstate system was conducted. The Objective of the study was to measure pavement performance through the use of the Present Serviceability Index (PSI) - Pavement Performance concepts as developed by the AASHO Road Test and to explore the usefulness of this type of data as a pavement management tool. Projects in the vicinity of the major urban centers were not included in this study due to the extra time that would be required to isolate accurate traffic data in these areas. Projects consisting of asphalt surface courses on crushed stone base sections were not included.

Field Evaluation of Electro-Reflective Measuring Apparatus (ERMA), MLR-81-01, 1981

The Electro-Reflective Measuring Apparatus (ERMA) was developed by the Minnesota Department of Highways in 1974 to measure the retro-reflective characteristics of pavement marking materials. Minnesota researchers recommended that due to the increased cost of pavement marking materials and reduced availability of these materials, ERMA can and should be used as a maintenance management tool to determine when painting is necessary rather than according to a fixed time schedule. The Iowa DOT Office of Materials built an ERMA device patterned after Minnesota's design in 1976. Subsequent efforts to calibrate and correlate this ERMA device to District Paint Foremen ratings proved unsuccessful, and ERMA modification or abandonment was recommended in 1979. Lyman Moothart, Materials Lab. Tech. 4, modified the ERMA device in 1980 and correlation attempts to District Paint Foremen ratings conducted in November 1980 have been moderately successful. A Paint/No Paint ERMA value has been established which will identify about 90% of the painting needs but will also include about 40% of the marking lines not needing repainting. The Office of Maintenance should establish a trial ERMA program to study the accuracy and potential cost savings of using ERMA to identify pavement marking needs.

Development of Bridge Load Testing Process for Load Evaluation, TR-445, 2003

Recent reports indicate that of the over 25,000 bridges in Iowa, slightly over 7,000 (29%) are either structurally deficient or functionally obsolete. While many of these bridges may be strengthened or rehabilitated, some simply need to be replaced. Before implementing one of these options, one should consider performing a diagnostic load test on the structure to more accurately assess its load carrying capacity. Frequently, diagnostic load tests reveal strength and serviceability characteristics that exceed the predicted codified parameters. Usually, codified parameters are very conservative in predicting lateral load distribution characteristics and the influence of other structural attributes. As a result, the predicted rating factors are typically conservative. In cases where theoretical calculations show a structural deficiency, it may be very beneficial to apply a "tool" that utilizes a more accurate theoretical model which incorporates field-test data. At a minimum, this approach results in more accurate load ratings and many times results in increased rating factors. Bridge Diagnostics, Inc. (BDI) developed hardware and software that are specially designed for performing bridge ratings based on data obtained from physical testing. To evaluate the BDI system, the research team performed diagnostic load tests on seven "typical" bridge structures: three steel-girder bridges with concrete decks, two concrete slab bridges, and two steel-girder bridges with timber decks. In addition, a steel-girder bridge with a concrete deck previously tested and modeled by BDI was investigated for model verification purposes. The tests were performed by attaching strain transducers on the bridges at critical locations to measure strains resulting from truck loading positioned at various locations on the bridge. The field test results were used to develop and validate analytical rating models. Based on the experimental and analytical results, it was determined that bridge tests could be conducted relatively easy, that accurate models could be generated with the BDI software, and that the load ratings, in general, were greater than the ratings, obtained using the codified LFD Method (according to AASHTO Standard Specifications for Highway Bridges).

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.