Retaining Wall - Modular Unit Reinforced Earth Tensar Geogrid Reinforcement, HR-549, 1998

This research, initiated in October 1992, was located at the intersection of Blairs Ferry Road and Lindale Drive in the City of Marion. The wall is located on the southeast corner of the intersection. Reinforced retaining wall construction started with a five inch base of roadstone with one inch of sand for leveling purposes. One and one-half to two feet of one inch clean stone was placed behind the blocks. A four inch perforated plastic pipe was placed approximately nine inches from the bottom of the one inch clean stone. The Tenswal, tensar geogrid was placed at every third layer. Openings in the Tenswal are hooked over plastic dowels in the blocks. The tenswal reaches from the face of the wall back 5' to 8'. The cost for constructing this wall was $124,400. The wall has performed well for the past five years. The wall improves the aesthetics of a high traffic volume intersection of an urban area. Many positive comments have been received by the city regarding its appearance. The City of Marion has been pleased with the wall and has used this type of wall on subsequent projects.

Reinforced Slope with Geogrids, HR-548, 1997

The objective of this research study is to evaluate the performance, maintenance requirements and cost effectiveness of constructing reinforced slope along a concrete bikeway overpass with a Geogrid system such as manufactured by Tensar Corporation or Reinforced Earth Company. This final report consists of two separate reports - construction and performance. An earlier design report and work plan was submitted to the Iowa DOT in 1989. From the Design Report, it was determined that the reinforced slope would be the most economical system for this particular bikeway project. Preliminary cost estimates for other design alternatives including concrete retaining walls, gabions and sheet pile walls ranged from $204/L.F. to $220/L.F. The actual final construction cost of the reinforced slope with GEDGRIDS was around $112/L.F. Although, since the reinforced slope system was not feasible next to the bridge overpass because of design constraints, a fair cost comparison should reflect costs of constructing a concrete retaining wall. Including the concrete retaining wall costs raises the per lineal foot cost to around $122/L.F. In addition to this initial construction cost effectiveness of the reinforced slope, there has been little or no maintenance needed for this reinforced slope. It was noted that some edge mowing or weed whacking could be done near the concrete bikeway slab to improve the visual quality of the slope, but no work has been assigned to city crews. It was added that this kind of weed whacking over such steep slope is more difficult and there could possibly be more potential for work related injury. The geogrid reinforced slope has performed really well once the vegetation took control and prevented soil washing across the bikeway slab. To that end, interim erosion control measures might need to be considered in future projects. Some construction observations were noted. First, there i s no specialized experience or equipment required for a contractor to successfully build a low-to-medium geogrid reinforced slope structure. Second, the adaptability of the reinforced earth structure enables the designer to best fit the shape of the structure to the environment and could enhance aesthetic quality. Finally, a reinforced slope can be built with relatively soft soils provided differential settlements between facing are limited to one or two percent.

Audit report on the City of Wall Lake, Iowa for the year ended June 30, 2006.

Audit report on the City of Wall Lake, Iowa for the year ended June 30, 2006.

Instrumentation and Monitoring of Precast Bridge Approach Tied to an Integral Abutment Bridge in Bremer County, SPR 0000-005, 2010

Approach slab pavement at integral abutment (I-A) bridges are prone to settlement and cracking, which has been long recognized by the Iowa Department of Transportation (DOT). A commonly recommended solution is to integrally attach the approach slab to the bridge abutment. This study sought to supplement a previous project by instrumenting, monitoring, and analyzing the behavior of an approach slab tied to a integral abutment bridge. The primary objective of this investigation was to evaluate the performance of the approach slab. To satisfy the research needs, the project scope involved reviewing a similar previous study, implementing a health monitoring system on the approach slab, interpreting the data obtained during the evaluation, and conducting periodic visual inspections of the bridge and approach slab. Based on the information obtained from the testing, the following general conclusions were made: the integral connection between the approach slab and the bridge appears to function well with no observed distress at this location and no relative longitudinal movement measured between the two components; the measured strains in the approach slabs indicate a force exists at the expansion joint and should be taken into consideration when designing both the approach slab and the bridge and the observed responses generally followed an annual cyclic and/or short term cyclic pattern over time; the expansion joint at one side of the approach slab does not appear to be functioning as well as elsewhere; much larger frictional forces were observed in this study compared to the previous study.

Examination report on the City of Wall Lake, Iowa for the period July 1, 2012 through June 30, 2013

Examination report on the City of Wall Lake, Iowa for the period July 1, 2012 through June 30, 2013

Recruiting and Retaining Women and Minorities in Public Sector Engineering Positions, HR-348, 1995

The objective of phase one of this research was to assess the degree to which currently employed Iowa Department of Transportation (DOT) employees would be affected by a more aggressive policy to recruit and retain women and minority engineers. The DOT's "Future Agenda" was used as a baseline to focus on efforts to update and implement a recruitment plan that would target underrepresented classes. The primary question that emerged out of phase one was how could the Iowa DOT strengthen its ties with Iowa State University (ISU) to produce increased numbers of in-state applicants for engineering positions. This introduced the objective of phase two, which was to identify problem areas resulting in unacceptably high attrition rates for women, minorities, and to a lesser degree, Caucasian men in the College of Engineering at ISU, particularly Civil and Construction Engineering (CCE). Past research has focused on (1) projected shortages of qualified civil engineers, (2) the obstacles confronting women in a traditionally male-oriented profession, and (3) minorities who are often unprepared to succeed in the rigors of an engineering curriculum because of a lack of academic preparedness. The researchers in this study, in contrast, chose to emphasize institutional reasons why women, minorities, and some Caucasian men often feel a sense of isolation in the engineering program. It was found that one of the key obstacles to student retention is the lack of visibility of the civil engineering profession. The visibility problem led to the hypothesis that many engineering students do not have a clear conception of what the practice of civil engineering entails. It was found that this may be a better predictor of attrition than the stereotypical assumption that a majority of students leave their engineering programs because they are not academically able to compete. Recommendations are offered to strengthen the ties between ISU's Department of CCE and the Iowa DOT in order to counter the visibility issue. It was concluded that this is a vital step because over the next 5-15 years 40% of DOT engineers currently employed will be phasing into retirement. If the DOT expects to draw sufficient numbers of engineers from within the state of Iowa and if increasing numbers of them are to be women and minorities, a university connection will help to produce the qualified applicants to fulfill this need.

Experimental Project No. 621, Pavement Instrumentation, HR-293, 1992

This document contains a discussion of the reasons why the project did not succeed. A detailed discussion of the steps taken by the Iowa Department of Transportation to make the experiment work are contained in this document, along with recommendations for future projects.

Pavement Instrumentation, HR-293, 1988

The report documents the development and installation of an instrumented pavement on I-80 in Iowa for the purposes of demonstration and answering current pavement questions. Its two primary objectives include documentation of the installation and verification of existing design procedures through monitoring of the continuous traffic stream reactions in the pavement. Some 120 instruments were installed in a forty foot segment of reconstructed pavement. The instruments included concrete strain gages, weldable strain gages on dowels, LVDT-deflection gages and temperature sensors in the concrete and base material. Five tubes were placed under three joints and two midslabs to measure the relative moisture and density at the interface between the pavement and base with atomic equipment. The instruments were placed ahead of the paving and over 92% of the instruments responded after paving. Planning requirements, problems encountered and costs of installation are presented. The site will use piezoelectric cables in a weigh-in-motion arrangement to trigger the data collection, a microcomputer controlled data acquisition system to analyze multiple sensors simultaneously, and telemetry to monitor the site remotely. Details provide the first time user of instrumentation with valuable information on the planning, problems, costs and coordination required to establish and operate such a site.

Agreed-upon procedures report on the City of Wall Lake, Iowa for the period July 1, 2013 through June 30, 2014

Agreed-upon procedures report on the City of Wall Lake, Iowa for the period July 1, 2013 through June 30, 2014

Instrumentation of Paver Vibrators, MLR-95-10, 1999

Premature deterioration of Portland Cement Concrete (PCC) pavements led to investigations for causes of the concrete failures. Evidence of parallel longitudinal cracks in deteriorating pavements, with crack spacings similar to paver vibrator spacings, made it clear that the vibrators were related to the cause for deterioration. After a number of field trips observing paving operations and measuring vibrator frequencies, it soon became clear that the paver vibrators were, in many cases, not running in compliance with the Iowa DOT specification. The specified frequency was from 5000 to 8000 revolutions per minute (rpm). The pavers visited did not have a monitoring system to give a continuous frequency readout for any of it's vibrators. Occasionally, during a paving operation, frequency readings were taken on some vibrators with a hand held tachometer. However, that degree of monitoring was found to be far from providing the quality of information and control necessary to maintain compliance to the Iowa DOT specification. A paver vibrator monitoring system, which would operate continuously while paving and cover all vibrators, was determined to be essential. The output must be visible to the paver operator and inspector at all times.

Field Instrumentation, Testing, and Long-Term Monitoring of High-Mast Lighting Towers in the State of Iowa, TR-518, 2006

As a result of the collapse of a 140 foot high-mast lighting tower in Sioux City, Iowa in November of 2003, a thorough investigation into the behavior and design of these tall, yet relatively flexible structures was undertaken. Extensive work regarding the root cause of this failure was carried out by Robert Dexter of The University of Minnesota. Furthermore, a statewide inspection of all the high-mast towers in Iowa revealed fatigue cracks and loose anchor bolts on other existing structures. The current study was proposed to examine the static and dynamic behavior of a variety of towers in the State of Iowa utilizing field testing, specifically long-term monitoring and load testing. This report presents the results and conclusions from this project. The field work for this project was divided into two phases. Phase 1 of the project was conducted in October 2004 and focused on the dynamic properties of ten different towers in Clear Lake, Ames, and Des Moines, Iowa. Of those ten, two were also instrumented to obtain stress distributions at various details and were included in a 12 month long-term monitoring study. Phase 2 of this investigation was conducted in May of 2005, in Sioux City, Iowa, and focused on determining the static and dynamic behavior of a tower similar to the one that collapsed in November 2003. Identical tests were performed on a similar tower which was retrofitted with a more substantial replacement bottom section in order to assess the effect of the retrofit. A third tower with different details was dynamically load tested to determine its dynamic characteristics, similar to the Phase 1 testing. Based on the dynamic load tests, the modal frequencies of the towers fall within the same range. Also, the damping ratios are significantly lower in the higher modes than the values suggested in the AASHTO and CAN/CSA specifications. The comparatively higher damping ratios in the first mode may be due to aerodynamic damping. These low damping ratios in combination with poor fatigue details contribute to the accumulation of a large number of damage-causing cycles. As predicted, the stresses in the original Sioux City tower are much greater than the stresses in the retrofitted towers at Sioux City. Additionally, it was found that poor installation practices which often lead to loose anchor bolts and out-of-level leveling nuts can cause high localized stresses in the towers, which can accelerate fatigue damage.

Field Instrumentation, Testing, and Long-Term Monitoring of High-Mast Lighting Tower No. 1 at the I-35/US 18 Interchange Near Clear Lake in the State of Iowa Phase 3, TR-562, 2009

The current study was initiated to quantify the stresses induced in critical details on the reinforcing jacket and the tower itself through the use of field instrumentation, load testing, and long-term monitoring. Strain gages were installed on the both the tower and the reinforcing jacket. Additional strain gages were installed on two anchor rods. Tests were conducted with and without the reinforcing jacket installed. Data were collected from all strain gages during static load testing and were used to study the stress distribution of the tower caused by known loads, both with and without the reinforcing jacket. The tower was tested dynamically by first applying a static load, and then quickly releasing the load causing the tower to vibrate freely. Furthermore, the tower was monitored over a period of over 1 year to obtain stress range histograms at the critical details to be used for a fatigue evaluation. Also during the long-term monitoring, triggered time-history data were recorded to study the wind loading phenomena that excite the tower.

Timber Abutment Piling and Back Wall Rehabilitation and Repair, TR-616, 2012

Based on previous National Bridge Inventory data, the state of Iowa has nearly 20,000 bridges on low-volume roads (LVRs). Thus, these bridges are the responsibility of the county engineers. Of the bridges on the county roads, 24 percent are structurally deficient and 5 percent are functionally obsolete. A large number of the older bridges on the LVRs are built on timber piling with timber back walls. In many cases, as timber abutments and piers age, the piling and back wall planks deteriorate at a rate faster than the bridge superstructure. As a result, a large percentage of the structurally deficient bridges on LVRs are classified as such because of the condition of the timber substructure elements. As funds for replacing bridges decline and construction costs increase, effective rehabilitation and strengthening techniques for extending the life of the timber substructures in bridges with structurally sound superstructures has become even more important. Several counties have implemented various techniques to strengthen/repair damaged piling, however, there is minimal data documenting the effectiveness of these techniques. There are numerous instances where cracked and failed pilings have been repaired. However, there are no experimental data on the effectiveness of the repairs or on the percentage of load transferred from the superstructure to the sound pile below. To address the research needs, a review and evaluation of current maintenance and rehabilitation methods was completed. Additionally, a nationwide survey was conducted to learn the methods used beyond Iowa. Field investigation and live-load testing of bridges with certain Iowa methods was completed. Lastly, laboratory testing of new strengthening and rehabilitation methods was performed.

Attachment of Combination Rails to Concrete Parapets Utilizing Epoxy Adhesive Anchors, RPFP-IOWA-1, 2015

The Iowa Department of Transportation (IaDOT) was interested in investigating the use of epoxy adhesive anchorages for the attachment of posts used in the BR27C combination bridge rail system. Alternative anchorage concepts were developed using a modified version of the ACI 318-11 procedures for embedded anchor design. Four design concepts were developed for review by IaDOT, including: (1) a four-bolt square anchorage, (2) a four-bolt spread anchorage, (3) a twobolt centered anchorage, and (4) a two-bolt offset anchorage. IaDOT representatives selected the four-bolt spread anchorage and the two-bolt offset anchorage as the preferred designs for evaluation. In addition to these two proposed configurations, IaDOT also requested that the researchers evaluate a third option that had been previously installed on the US-20 bridge near Hardin, IA. The proposed alternative anchorages and the original cast-in-place anchorage for the BR27C combination bridge rail were evaluated through dynamic component testing. The test of the original cast-in-place anchorage was used a baseline for comparison with the alternative designs. Test no. IBP-1 of the original cast-in-place anchorage developed a peak load of 22.9 kips (101.9 kN) at a deflection of 1.5 in. (38 mm). All three of the tested alternative anchorages provided greater load capacity than the original cast-in-place design and were deemed acceptable surrogates. Of the three alternative designs, the two-bolt offset design was deemed the best option.

Agreed-upon procedures report on the City of Wall Lake, Iowa for the period July 1, 2014 through June 30, 2015

Agreed-upon procedures report on the City of Wall Lake, Iowa for the period July 1, 2014 through June 30, 2015