Structural Analysis and Overlay Design of Pavements Using the Road Rater, MLR-84-3, 1986

In recent years the Iowa DOT has shifted emphasis from the construction of new roads to the maintenance and preservation of existing highways. A need has developed for analyzing pavements structurally to select the correct rehabilitation strategy and to properly design a pavement overlay if necessary. This need has been fulfilled by Road Rater testing which has been used successfully on all types of pavements to evaluate pavement and subgrade conditions and to design asphaltic concrete overlays. The Iowa Road Rater Design Method has been simplified so that it may be easily understood and used by the widely diverse groups of individuals which may be involved in pavement restoration and management. Road Rater analysis techniques have worked well to date and have been verified by pavement coring, soils sampling and testing, and pavement removal by block sampling. Void detection testing has also been performed experimentally in Iowa, and results indicate that the Road Rater can be used to locate pavement voids and that Road Rater analysis techniques are reasonably accurate. The success of Road Rater research and development has made deflection test data one of the most important pavement management inputs.

Structural Characterization of UHPC Waffle Bridge Deck and Connections, TR-614, 2014

The AASHTO strategic plan in 2005 for bridge engineering identified extending the service life of bridges and accelerating bridge construction as two of the grand challenges in bridge engineering. These challenges have the objective of producing safer and more economical bridges at a faster rate with a minimum service life of 75 years and reduced maintenance cost to serve the country’s infrastructure needs. Previous studies have shown that a prefabricated full-depth precast concrete deck system is an innovative technique that accelerates the rehabilitation process of a bridge deck, extending its service life with reduced user delays and community disruptions and lowering its life-cycle costs. Previous use of ultra-high performance concrete (UHPC) for bridge applications in the United States has been considered to be efficient and economical because of its superior structural characteristics and durability properties. Full-depth UHPC waffle deck panel systems have been developed over the past three years in Europe and the United States. Subsequently, a single span, 60-ft long and 33-ft wide prototype bridge with full-depth prefabricated UHPC waffle deck panels has been designed and built for a replacement bridge in Wapello County, Iowa. The structural performance characteristics and the constructability of the UHPC waffle deck system and its critical connections were studied through an experimental program at the structural laboratory of Iowa State University (ISU). Two prefabricated full-depth UHPC waffle deck (8 feet by 9 feet 9 inches by 8 inches) panels were connected to 24-ft long precast girders, and the system was tested under service, fatigue, overload, and ultimate loads. Three months after the completion of the bridge with waffle deck system, it was load tested under live loads in February 2012. The measured strain and deflection values were within the acceptable limits, validating the structural performance of the bridge deck. Based on the laboratory test results, observations, field testing of the prototype bridge, and experience gained from the sequence of construction events such as panel fabrication and casting of transverse and longitudinal joints, a prefabricated UHPC waffle deck system is found to be a viable option to achieve the goals of the AASHTO strategic plan.

Synthetic Fabric to Improve Structural Capacity in Asphalt Overlays, HR-516, 1984

Iowa's first field application of synthetic engineering fabrics was on research project HR-158, "Prevention of Reflective Cracking in Asphalt Overlays". This research placed in September 1971 used three different engineering fabrics. A final report concluding generally favorable performance was distributed in May 1977. There have been a number of Iowa engineering fabric installations since that initial project.

Hydro-Surface Preparation and Coating for Painted Structural Steel, TR-407, 1999

Cities and counties in Iowa have more than 8,890 steel bridges, most of which are painted with red lead paint. The Iowa Department of Transportation (Iowa DOT) maintains less than 35 bridges coated with red lead paint, including seven of the large border bridges over the Mississippi and Missouri Rivers. Because of the federal and state regulations for bridge painting, many governmental agencies have opted not to repaint, or otherwise maintain, lead paint coatings. Consequently, the paint condition on many of these bridges is poor, and some bridges are experiencing severe rusting of structural members. This research project was developed with two objectives: 1) to evaluate the effectiveness of preparing the structural steel surface of a bridge with high pressure water jetting instead of abrasive blasting and 2) to coat the structural steel surface with a moisture-cured polyurethane paint under different surface preparation conditions.

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.

Protection of Structural Concrete Substructures, Construction Report, HR-220, 1981

It is the objective of this project to determine, via field tests, the long term effectiveness of several available systems as their ability to protect concrete surfaces against the intrusion of chloride ions. Early concepts of this project included utilizing personnel from several offices within the Highway Division of the Iowa Department of Transportation. Cooperation and coordination with regularly scheduled activities were considered imperative. A meeting for this purpose was held on April 16, 1980. This meeting was attended by the investigators, Mr. Bernard C. Brown, Office of Materials, Mr. Richard Merritt, District 6 Materials Engineer, Mr. John Saunders, District 6 Maintenance Engineer, and Mr. James Phinney, Resident Maintenance Engineer.