Strengthening of Existing Single Span Steel Beam and Concrete Deck Bridges, HR-238, Part II, 1985

The unifying objective of Phases I and II of this study was to determine the feasibility of the post-tensioning strengthening method and to implement the technique on two composite bridges in Iowa. Following completion of these two phases, Phase III was undertaken and is documented in this report. The basic objectives of Phase III were further monitoring bridge behavior (both during and after post-tensioning) and developing a practical design methodology for designing the strengthening system under investigation. Specific objectives were: to develop strain and force transducers to facilitate the collection of field data; to investigate further the existence and effects of the end restraint on the post-tensioning process; to determine the amount of post-tensioning force loss that occurred during the time between the initial testing and the retesting of the existing bridges; to determine the significance of any temporary temperature-induced post-tensioning force change; and to develop a simplified design methodology that would incorporate various variables such as span length, angle-of-skew, beam spacing, and concrete strength. Experimental field results obtained during Phases II and III were compared to the theoretical results and to each other. Conclusions from this research are as follows: (1) Strengthening single-span composite bridges by post-tensioning is a viable, economical strengthening technique. (2) Behavior of both bridges was similar to the behavior observed from the bridges during field tests conducted under Phase II. (3) The strain transducers were very accurate at measuring mid-span strain. (4) The force transducers gave excellent results under laboratory conditions, but were found to be less effective when used in actual bridge tests. (5) Loss of post-tensioning force due to temperature effects in any particular steel beam post-tensioning tendon system were found to be small. (6) Loss of post-tensioning force over a two-year period was minimal. (7) Significant end restraint was measured in both bridges, caused primarily by reinforcing steel being continuous from the deck into the abutments. This end restraint reduced the effectiveness of the post-tensioning but also reduced midspan strains due to truck loadings. (8) The SAP IV finite element model is capable of accurately modeling the behavior of a post-tensioned bridge, if guardrails and end restraints are included in the model. (9) Post-tensioning distribution should be separated into distributions for the axial force and moment components of an eccentric post-tensioning force. (10) Skews of 45 deg or less have a minor influence on post-tensioning distribution. (11) For typical Iowa three-beam and four-beam composite bridges, simple regression-derived formulas for force and moment fractions can be used to estimate post-tensioning distribution at midspan. At other locations, a simple linear interpolation gives approximately correct results. (12) A simple analytical model can accurately estimate the flexural strength of an isolated post-tensioned composite beam.

Strengthening of an Existing Continuous-Span, Steel-Stringer, Concrete-Deck Bridge, HR-333, 1993

The need to upgrade understrength bridges in the United States has been well documented in the literature. The concept of strengthening steel stringer bridges in Iowa has been developed through several Iowa DOT projects. The objective of the project described in this report was to investigate the use of one such strengthening system on a three-span continuous steel stringer bridge in the field. In addition, a design methodology was developed to assist bridge engineers with designing a strengthening system to obtain the desired stress reductions. The bridge selected for strengthening was in Cerro Gordo County near Mason City, Iowa on County Road B65. The strengthening system was designed to remove overstresses that occurred when the bridge was subjected to Iowa legal loads. A two part strengthening system was used: post-tensioning the positive moment regions of all the stringers and superimposed trusses in the negative moment regions of the two exterior stringers at the two piers. The strengthening system was installed in the summers of 1992 and 1993. In the summer of 1993, the bridge was load tested before and after the strengthening system was activated. The load test results indicate that the strengthening system was effective in reducing the overstress in both the negative and positive regions of the stringers. The design methodology that was developed includes a procedure for determining the magnitude of post-tensioning and truss forces required to strengthen a given bridge. This method utilizes moment and force fractions to determine the distribution of strengthening axial forces and moments throughout the bridge. Finite element analysis and experimental results were used in the formulation and calibration of the methodology. A spreadsheet was developed to facilitate the calculation of these required strengthening forces.

Iowa Power Fund Board Project Report Update, November 12, 2008

ISU’s proposed research will (1) develop methods for designing clean and efficient burners for low‐Btu producer gas and medium‐Btu syngas, (2) develop catalysts and flow reactors to produce ethanol from medium‐Btu synthesis gas, and (3) upgrade the BECON gasifier system to enable medium‐Btu syngas production and greatly enhanced capabilities for detailed gas analysis needed by both (1) and (2). This project addresses core development needs to enable grain ethanol industry reduce its natural gas demand and ultimately transition to cellulosic ethanol production.

Alternatives for Rural Roads, HR-242, 1989

Much of the nation's rural road system is deteriorating. Many of the roads were built in the 1880s and 1890s with the most recent upgrading done in the 1940s and 1950s. Consequently, many roads and bridges do not have the capacity for the increased loads, speed, and frequent use of today's vehicles. Because of the growing demands and a dense county road system (inherited from the land settlement policies two centuries ago), revenue available to counties is inadequate to upgrade andmaintain the present system. Either revenue must be increased - an unpopular option - or costs must be reduced. To examine cost-saving options, Iowa State University conducted a study of roads and bridges in three 100 square mile areas in Iowa: • A suburban area • A rural area with a large number of paved roads, few bridges, and a high agricultural tax base and •A more rural area in a hilly terrain with many bridges and gravel roads, and a low agricultural tax base. A cost-benefit analysis was made on the present road system in these areas on such options as abandoning roads with limited use, converting some to private drives, and reducing maintenance on these types of roads. In only a few instances does abandonment of low traffic volume roads produce cost savings for counties and abutting land owners that exceed the additional travel costs to the public. In this study, the types of roads that produced net savings when abandoned were: • A small percentage (less than 5 percent) of the nonpaved county roads in the suburban area. However, net savings were very small. Cost savings from reducing the county road system in urbanized areas are very limited. • Slightly more than 5 percent of the nonpaved county roads in the most rural area that had a small number of paved county roads. • More than 12 percent of the nonpaved roads in the rural area that had a relatively large number of paved county and state roads. Converting low-volume roads to low-maintenance or Service B roads produces the largest savings of all solutions considered. However, future bridge deterioration and county liability on Service B roads are potential problems. Converting low-volume roads to private drives also produces large net savings. Abandonment of deadend roads results in greater net savings than continuous roads. However, this strategy shifts part of the public maintenance burden to land owners. Land owners also then become responsible for accident liability. Reconstruction to bring selected bridges with weight restrictions up to legal load limits reduces large truck and tractor-wagon mileage and costs. However, the reconstruction costs exceeded the reduction in travel costs. Major sources of vehicle miles on county roads are automobiles used for household purposes and pickup truck travel for farm purposes. Farm-related travel represents a relatively small percent of total travel miles, but a relatively high percentage of total travel costs.

Evaluation of Lightweight Profilers for Construction Smoothness Evaluation, MLR-02-02, 2004

High-speed non-contact laser profilers have become the standard testing equipment for pavement management ride quality testing. The same technology used in the high-speed profilers is now being used in lightweight profilers for construction smoothness testing. The lightweight profilers have many advantages over the California 25-ft profilograph. Despite the many advantages of the lightweight profilers, there is resistance from the contracting industry toward eliminating the 25-ft profilograph for construction ride testing. One way to reduce or overcome the resistance is to evaluate and demonstrate the advantages/disadvantages of the lightweight profiler in actual field use in Iowa. The objective of the study was to purchase a lightweight profiler and to evaluate its suitability for construction smoothness quality verification and quality acceptance on Iowa projects. A lightweight profiler, an Ames Engineering, Inc. LISA single laser unit, was received in February 2003 for the study. Based on the work done during the 2003 construction season, the following conclusions can be made: (1) For hot mix asphalt surfaces, the LISA correlated well with the contractors' profilographs; (2) LISA results are significantly affected by longitudinal tining on portland cement concrete pavements, requiring a laser system upgrade to give accurate results; (3) A significant timesaving was realized by using the LISA; (4) Increasing visibility and reducing time in the construction zone improved safety; (5) One person with limited lifting capabilities could set up and operate the LISA; and (6) With the current Iowa Department of Transportation specification, the LISA cannot totally replace the profilograph, since bridges and short segments with no adjoining pavement would still require a profilograph.

Financial Needs of Iowa's County Roads, TR-608, 2012

The TR-608 project developed methods and processes for determining current and future Iowa secondary (county) road needs. These tools will be permanently maintained and operated by the Iowa County Engineers Association Service Bureau to provide ongoing need determination services for the state’s ninety-nine county road departments. The systems established via this project will annually tally and report a) how much funding is needed to sustain the county roads long term, b) the adequacy of the secondary roads for the traffic they carry and c) what upgrade needs exist. A “Trend Projection Engine” will also be available to project from current circumstance, with continuation of known revenue and cost trends, to estimate potential outcomes occurring in the next fifteen years. Now that it has been developed, the TR-608 system will continue as an ongoing resource of county road and bridge numbers, condition, trends and issue information for use by counties, either individually or collectively.

West 1 St Street/ IA 57 from Highland Drive to Center Street/Franklin Street, Blackhawk County, Iowa, Project # STP-57-2(28)--2C-07, Environmental Assessment and Section 4(f) De Minimis Impact Finding, 2015

From Proposed Action: "Iowa Northland Regional Council of Governments (INRCOG) and the City of Cedar Falls, in coordination with the Iowa Department of Transportation (Iowa DOT) and the Federal Highway Administration (FHWA), are proposing to upgrade and modernize an approximate 4,900-foot segment of Iowa Highway 57 (IA 57), locally known as West 1st Street, in Cedar Falls, Black Hawk County, Iowa."