On The Spot Damage Detection Methodology for Highway Bridges, July 2010

Vibration-based damage identification (VBDI) techniques have been developed in part to address the problems associated with an aging civil infrastructure. To assess the potential of VBDI as it applies to highway bridges in Iowa, three applications of VBDI techniques were considered in this study: numerical simulation, laboratory structures, and field structures. VBDI techniques were found to be highly capable of locating and quantifying damage in numerical simulations. These same techniques were found to be accurate in locating various types of damage in a laboratory setting with actual structures. Although there is the potential for these techniques to quantify damage in a laboratory setting, the ability of the methods to quantify low-level damage in the laboratory is not robust. When applying these techniques to an actual bridge, it was found that some traditional applications of VBDI methods are capable of describing the global behavior of the structure but are most likely not suited for the identification of typical damage scenarios found in civil infrastructure. Measurement noise, boundary conditions, complications due to substructures and multiple material types, and transducer sensitivity make it very difficult for present VBDI techniques to identify, much less quantify, highly localized damage (such as small cracks and minor changes in thickness). However, while investigating VBDI techniques in the field, it was found that if the frequency-domain response of the structure can be generated from operating traffic load, the structural response can be animated and used to develop a holistic view of the bridge’s response to various automobile loadings. By animating the response of a field bridge, concrete cracking (in the abutment and deck) was correlated with structural motion and problem frequencies (i.e., those that cause significant torsion or tension-compression at beam ends) were identified. Furthermore, a frequency-domain study of operational traffic was used to identify both common and extreme frequencies for a given structure and loading. Common traffic frequencies can be compared to problem frequencies so that cost-effective, preventative solutions (either structural or usage-based) can be developed for a wide range of IDOT bridges. Further work should (1) perfect the process of collecting high-quality operational frequency response data; (2) expand and simplify the process of correlating frequency response animations with damage; and (3) develop efficient, economical, preemptive solutions to common damage types.

Snowmobile Reference Guide, 2013

This booklet contains rules and regulations most likely needed for motorized recreational use in Iowa. However, it is not a complete list of all regulations or laws, nor is it a legal document. For more information, please reference Iowa Code Chapters 321 and 321G and Iowa Administrative Code, Chapter 571.

Off-Highway Vehicle Reference Guide, 2012

This booklet contains rules and regulations most likely needed for motorized recreational use in Iowa. However, it is not a complete list of all regulations or laws, nor is it a legal document. For more information, please reference Iowa Code Chapters 321 and 321G and Iowa Administrative Code, Chapter 571.

08018-010 Walnut Creek Final Report

In 2004 Walnut Creek was placed on the 303d list of impaired water bodies for lack of aquatic life with biological causes. Sediment from farmland as well as the stream banks was listed as the most likely stressor. In response to this listing a preliminary watershed assessment was completed by the six counties which have land in the Walnut Creek watershed. Walnut Creek flows through portions of Shelby, Pottawattamie, Montgomery, Mills, Page, and Fremont Counties before reaching its confluence with the West Nishnabotna River. The preliminary study assessed resource concerns and evaluated anticipated landowner participation levels for the six Huc 12 sub-watersheds which divide the Walnut Creek basin. These preliminary assessments revealed a priority sub-watershed which lies between US Hwy 6 and Hwy 34. A development grant was then funded by the Division of Soil Conservation to conduct a detailed assessment of this area. The detailed assessment involved an assessment of the uplands as well as the stream itself. A better understanding of the resource concerns was gained through the assessment, allowing for a comprehensive watershed plan to be developed. A variety of best management practices will be necessary for our project to be a success, many of which will be funded by other sources besides the WIRB. This grant is the first request for funding submitted by the East Pottawattamie and Montgomery SWCDs’. This grant will serve as the first critical step in building what is destined to be a true watershed success story.

Economics of Using Calcium Chloride vs. Sodium Chloride for Deicing/Anti-Icing, TR-488, 2008

The use of chemicals is a critical part of a pro-active winter maintenance program. However, ensuring that the correct chemicals are used is a challenge. On the one hand, budgets are limited, and thus price of chemicals is a major concern. On the other, performance of chemicals, especially at lower pavement temperatures, is not always assured. Two chemicals that are used extensively by the Iowa Department of Transportation (Iowa DOT) are sodium chloride (or salt) and calcium chloride. While calcium chloride can be effective at much lower temperatures than salt, it is also considerably more expensive. Costs for a gallon of salt brine are typically in the range of $0.05 to $0.10, whereas calcium chloride brine may cost in the range of $1.00 or more per gallon. These costs are of course subject to market forces and will thus change from year to year. The idea of mixing different winter maintenance chemicals is by no means new, and in general discussions it appears that many winter maintenance personnel have from time to time mixed up a jar of chemicals and done some work around the yard to see whether or not their new mix “works.” There are many stories about the mixture turning to “mayonnaise” (or, more colorfully, to “snot”) suggesting that mixing chemicals may give rise to some problems most likely due to precipitation. Further, the question of what constitutes a mixture “working” in this context is a topic of considerable discussion. In this study, mixtures of salt brine and calcium chloride brine were examined to determine their ice melting capability and their freezing point. Using the results from these tests, a linear interpolation model of the ice melting capability of mixtures of the two brines has been developed. Using a criterion based upon the ability of the mixture to melt a certain thickness of ice or snow (expressed as a thickness of melt-water equivalent), the model was extended to develop a material cost per lane mile for the full range of possible mixtures as a function of temperature. This allowed for a comparison of the performance of the various mixtures. From the point of view of melting capacity, mixing calcium chloride brine with salt brine appears to be effective only at very low temperatures (around 0° F and below). However, the approach described herein only considers the material costs, and does not consider application costs or other aspects of the mixture performance than melting capacity. While a unit quantity of calcium chloride is considerably more expensive than a unit quantity of sodium chloride, it also melts considerably more ice. In other words, to achieve the same result, much less calcium chloride brine is required than sodium chloride brine. This is important in considering application costs, because it means that a single application vehicle (for example, a brine dispensing trailer towed behind a snowplow) can cover many more lane miles with calcium chloride brine than with salt brine before needing to refill. Calculating exactly how much could be saved in application costs requires an optimization of routes used in the application of liquids in anti-icing, which is beyond the scope of the current study. However, this may be an area that agencies wish to pursue for future investigation. In discussion with winter maintenance personnel who use mixtures of sodium chloride and calcium chloride, it is evident that one reason for this is because the mixture is much more persistent (i.e. it stays longer on the road surface) than straight salt brine. Operationally this persistence is very valuable, but at present there are not any established methods to measure the persistence of a chemical on a pavement. In conclusion, the study presents a method that allows an agency to determine the material costs of using various mixtures of salt brine and calcium chloride brine. The method is based upon the requirement of melting a certain quantity of snow or ice at the ice-pavement interface, and on how much of a chemical or of a mixture of chemicals is required to do that.

1014-008 Walnut Creek Watershed Final Report

In 2004, Walnut Creek was placed on the 303d list of Impaired Waters due to a low biotic index (lack of aquatic life) during IDNR stream sampling events. Sediment originating from agriculture, streambank erosion, and channelization were listed as the most likely sources impacting aquatic life. In an effort to address these concerns, a preliminary study was completed of the multi-county watershed to identify priority areas. A Watershed Development & Planning Assistance Grant was then funded by the IDALS-DSC to conduct a detailed assessment of these prioritized sub-watersheds. The impending assessment of the watershed and the stream corridor revealed ample opportunities to address gully, sheet and rill erosion while addressing in-stream water velocity issues that plagued the riparian corridor. A comprehensive plan was developed comprised of a variety of best management practices to address the identified concerns. In 2009, this plan was submitted to the WIRB Board by the East Pottawattamie and Montgomery SWCDs and $489,455 was awarded to address concerns identified during watershed assessment inquiries. Despite adverse weather conditions, which has hampered conservation construction recently, this project has held fast to pre-project goals due to the fortitude of the project sponsors and the overwhelming participation by the watershed landowners. Unfortunately, state budget shortfalls are bringing project progress to a halt. As specified in the original WIRB funding request, practice funding for Year 3 was to come from the Division of Soil Conservation’s Watershed Protection Fund (WSPF). Due to Iowa’s budgetary restraints, the Walnut Creek WSPF application, which was submitted this spring, was not funded since no new applications in the state were funded. If funded again, this grant will serve as the critical step in continuing what is destined to be a true watershed success story.

High Priority Corridors for Access Management Near Large Urban Areas in Iowa, 2002

This research project was intended to produce a strategy for addressing current and future access management problems on state highway routes located just outside urban areas that serve as major routes for commuting into and out of major employment centers in Iowa. There were two basic goals: (1) to develop a ranking system for identifying high-priority segments for access management treatments on primary highways outside metro and urban areas and (2) to focus efforts on routes that are major commuting routes at present and in the future. The project focused on four-lane expressways and two-lane arterials most likely to serve extensive commuter traffic. Available spatial and statistical data were used to identify existing and possible future problem corridors with respect to access management. The research team developed a scheme for ranking commuter routes based on their need for attention to access management. This project was able to produce rankings for corridors based on a variety of factors, including proportion of crashes that appear to be access-related, severity of those crashes, and potential for improvement along corridors. Frequency and loss were found to be highly rank correlated; because of this, these indicators were not used together in developing final priority rankings. Most of the highest ranked routes are on two-lane rural cross sections, but a few are four-lane expressways with at-grade private driveways and public road intersections. The most important conclusion of the ranking system is that many of the poor-performing corridors are located in a single Iowa Department of Transportation district near two urban areas--Des Moines and Ames. A comprehensive approach to managing access along commuting corridors should be developed first in this district since the potential benefits would be highest in that region.