Construction of the Iowa Highway 60 Precast Prestressed Concrete Pavement Bridge Approach Slab Demonstration Project, HR-1085, 2007

Reconstruction of bridge approach slabs which have failed due to a loss of support from embankment fill consolidation or erosion can be particularly challenging in urban areas where lane closures must be minimized. Precast prestressed concrete pavement is a potential solution for rapid bridge approach slab reconstruction which uses prefabricated pavement panels that can be installed and opened to traffic quickly. To evaluate this solution, the Iowa Department of Transportation constructed a precast prestressed approach slab demonstration project on Highway 60 near Sheldon, Iowa in August/September 2006. Two approach slabs at either end of a new bridge were constructed using precast prestressed concrete panels. This report documents the successful development, design, and construction of the precast prestressed concrete bridge approach slabs on Highway 60. The report discusses the challenges and issues that were faced during the project and presents recommendations for future implementation of this innovative construction technique.

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.

Demonstration Project using Railroad Flatcars for Low-Volume Road Bridges, TR-444, 2003

The use of Railroad Flatcars (RRFCs) as the superstructure on low-volume county bridges has been investigated in a research project conducted by the Bridge Engineering Center at Iowa State University. These bridges enable county engineers to replace old, inadequate county bridge superstructures for less than half the cost and in a shorter construction time than required for a conventional bridge. To illustrate their constructability, adequacy, and economy, two RRFC demonstration bridges were designed, constructed, and tested: one in Buchanan County and the other in Winnebago County. The Buchanan County Bridge was constructed as a single span with 56-ft-long flatcars supported at their ends by new, concrete abutments. The use of concrete in the substructure allowed for an integral abutment at one end of the bridge with an expansion joint at the other end. Reinforced concrete beams (serving as longitudinal connections between the three adjacent flatcars) were installed to distribute live loads among the RRFCs. Guardrails and an asphalt milling driving surface completed the bridge. The Winnebago County Bridge was constructed using 89-ft-long flatcars. Preliminary calculations determined that they were not adequate to span 89 ft as a simple span. Therefore, the flatcars were supported by new, steel-capped piers and abutments at the RRFCs' bolsters and ends, resulting in a 66-ft main span and two 10-ft end spans. Due to the RRFC geometry, the longitudinal connections between adjacent RRFCs were inadequate to support significant loads; therefore, transverse, recycled timber planks were utilized to effectively distribute live loads to all three RRFCs. A gravel driving surface was placed on top of the timber planks, and a guardrail system was installed to complete the bridge. Bridge behavior predicted by grillage models for each bridge was validated by strain and deflection data from field tests; it was found that the engineered RRFC bridges have live load stresses significantly below the AASHTO Bridge Design Specification limits. To assist in future RRFC bridge projects, RRFC selection criteria were established for visual inspection and selection of structurally adequate RRFCs. In addition, design recommendations have been developed to simplify live load distribution calculations for the design of the bridges. Based on the results of this research, it has been determined that through proper RRFC selection, construction, and engineering, RRFC bridges are a viable, economic replacement system for low-volume road bridges.

Field Testing of Railroad Flatcar Bridges Volume I: Single Spans, TR-498, 2007

Based on the conclusions of IHRB Project TR-444, Demonstration Project Using Railroad Flat Car Bridges for Low Volume Road Bridges, additional research on the use of RRFC bridges was undertaken. This portion of the project investigated the following: (1) Different design and rating procedures; (2) Additional single span configurations plus multiple span configurations; (3) Different mechanisms for connecting adjacent RRFCs and the resulting lateral load distribution factors; (4) Sheet pile abutments; and (5) Behavior RRFCs that had been strengthened so that they could be used on existing abutments. A total of eight RRFC bridges were tested (five single span bridges, two two-span bridges, and one three-span bridge). Based on the results of this study a simplified design and rating procedure has been developed for the economical replacement bridge alternative. In Volume 1, this volume, the results from the testing of four single span RRFC bridges are presented, while in Volume 2 the results from the testing of the strengthened single span bridge plus the three multiple span bridges are presented.

Field Testing of Railroad Flatcar Bridges Volume II: Multiple Spans, TR-498, 2007

Based on the conclusions of IHRB Project TR-444, Demonstration Project Using Railroad Flat Car Bridges for Low Volume Road Bridges, additional research on the use of RRFC bridges was undertaken. This portion of the project investigated the following: (1) Different design and rating procedures; (2) Additional single span configurations plus multiple span configurations; (3) Different mechanisms for connecting adjacent RRFCs and the resulting lateral load distribution factors; (4) Sheet pile abutments; and (5) Behavior RRFCs that had been strengthened so that they could be used on existing abutments. A total of eight RRFC bridges were tested (five single span bridges, two two-span bridges, and one three-span bridge). Based on the results of this study a simplified design and rating procedure has been developed for the economical replacement bridge alternative. In Volume 1, the results from the testing of four single span RRFC bridges are presented, while in Volume 2,this volume, the results from the testing of the strengthened single span bridge plus the three multiple span bridges are presented.

Optimization and Management of Materials in Earthwork Construction, TR-501, 2010

As a result of forensic investigations of problems across Iowa, a research study was developed aimed at providing solutions to identified problems through better management and optimization of the available pavement geotechnical materials and through ground improvement, soil reinforcement, and other soil treatment techniques. The overall goal was worked out through simple laboratory experiments, such as particle size analysis, plasticity tests, compaction tests, permeability tests, and strength tests. A review of the problems suggested three areas of study: pavement cracking due to improper management of pavement geotechnical materials, permeability of mixed-subgrade soils, and settlement of soil above the pipe due to improper compaction of the backfill. This resulted in the following three areas of study: (1) The optimization and management of earthwork materials through general soil mixing of various select and unsuitable soils and a specific example of optimization of materials in earthwork construction by soil mixing; (2) An investigation of the saturated permeability of compacted glacial till in relation to validation and prediction with the Enhanced Integrated Climatic Model (EICM); and (3) A field investigation and numerical modeling of culvert settlement. For each area of study, a literature review was conducted, research data were collected and analyzed, and important findings and conclusions were drawn. It was found that optimum mixtures of select and unsuitable soils can be defined that allow the use of unsuitable materials in embankment and subgrade locations. An improved model of saturated hydraulic conductivity was proposed for use with glacial soils from Iowa. The use of proper trench backfill compaction or the use of flowable mortar will reduce the potential for developing a bump above culverts.

Design Guide for Improved Quality of Roadway Subgrades and Subbases, TR-525, 2008

The performance of a pavement depends on the quality of its subgrade and subbase layers; these foundational layers play a key role in mitigating the effects of climate and the stresses generated by traffic. Therefore, building a stable subgrade and a properly drained subbase is vital for constructing an effective and long lasting pavement system. This manual has been developed to help Iowa highway engineers improve the design, construction, and testing of a pavement system’s subgrade and subbase layers, thereby extending pavement life. The manual synthesizes current and previous research conducted in Iowa and other states into a practical geotechnical design guide [proposed as Chapter 6 of the Statewide Urban Design and Specifications (SUDAS) Design Manual] and construction specifications (proposed as Section 2010 of the SUDAS Standard Specifications) for subgrades and subbases. Topics covered include the important characteristics of Iowa soils, the key parameters and field properties of optimum foundations, embankment construction, geotechnical treatments, drainage systems, and field testing tools, among others.

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.

Iowa ABC Connections, RB06-013, 2015

For several years the Iowa Department of Transportation (DOT), Iowa State University, the Federal Highway Administration, and several Iowa counties have been working to develop accelerated bridge construction (ABC) concepts, details, and processes. Throughout this development, much has been learned and has resulted in Iowa being viewed as a national leader in the area of ABC. However, at this time, the Office of Bridges and Structures does not have a complete set of working standards nor design examples to accompany ABC portions of the bridge design manual (now called the Load and Resistance Factor Design/LRFD Bridge Design Manual). During the fall of 2013, the Iowa DOT constructed a bridge on IA 92 in Cass County using an ABC technique known as slide-in bridge construction. During the design of the Cass County Bridge, several questions were raised about the performance of critical design and construction details: the pile-to-pile cap connection and the polytetrafluoroethylene (PTFE) coated bearing pads on which the bridge would slide. The timing of this specific need and the initiation of this project offered a unique opportunity to provide significant short- and long-term value to the Office of Bridges and Structures. Several full-scale laboratory tests, which included several variations of the pile-to-pile cap connection and bearing pad slides, were completed. These tests proved that the connection was capable of achieving the desired capacity and that the expected coefficient of friction of the bearing pads was reasonably low. Finally, a design tool was developed for the Office of Bridges and Structures to be used on future projects that might benefit from a precast pile cap.

Material and Construction Optimization for Prevention of Premature Pavement Distress in PCC Pavements, Phase III Final Report, 2008

Mixture materials, mix design, and pavement construction are not isolated steps in the concrete paving process. Each affects the other in ways that determine overall pavement quality and long-term performance. However, equipment and procedures commonly used to test concrete materials and concrete pavements have not changed in decades, leaving gaps in our ability to understand and control the factors that determine concrete durability. The concrete paving community needs tests that will adequately characterize the materials, predict interactions, and monitor the properties of the concrete. The overall objectives of this study are (1) to evaluate conventional and new methods for testing concrete and concrete materials to prevent material and construction problems that could lead to premature concrete pavement distress and (2) to examine and refine a suite of tests that can accurately evaluate concrete pavement properties. The project included three phases. In Phase I, the research team contacted each of 16 participating states to gather information about concrete and concrete material tests. A preliminary suite of tests to ensure long-term pavement performance was developed. The tests were selected to provide useful and easy-to-interpret results that can be performed reasonably and routinely in terms of time, expertise, training, and cost. The tests examine concrete pavement properties in five focal areas critical to the long life and durability of concrete pavements: (1) workability, (2) strength development, (3) air system, (4) permeability, and (5) shrinkage. The tests were relevant at three stages in the concrete paving process: mix design, preconstruction verification, and construction quality control. In Phase II, the research team conducted field testing in each participating state to evaluate the preliminary suite of tests and demonstrate the testing technologies and procedures using local materials. A Mobile Concrete Research Lab was designed and equipped to facilitate the demonstrations. This report documents the results of the 16 state projects. Phase III refined and finalized lab and field tests based on state project test data. The results of the overall project are detailed herein. The final suite of tests is detailed in the accompanying testing guide.

Electronic Construction Collaboration - Phase 1, 2009

Bridge construction projects are becoming increasingly complex as the demand for context-sensitive solutions, aesthetic designs, and accelerated bridge construction becomes more prevalent. In addition, the Iowa Department of Transportation (Iowa DOT) is entering a phase of design and construction of large border bridges, such as the I-80 (let 2008 for $56 million) and US 34 bridges over the Missouri River and I-74 over the Mississippi River. Compared to typical construction projects, these bridges generate more contractor Requests for Information (RFIs), Value Engineering (VE) proposals, Requests for Changes (RFCs), and shop drawings. Management of these submittals is a significant challenge for Resident Construction Engineers (RCEs) and other Iowa DOT staff. In addition, some submittals require cross-departmental and project consultant reviews. Commercially available software exists for managing submittals and project collaboration teams; in-house solutions may also be possible. Implementation is intended to speed construction submittal review time, reduce incidence of delay claims, and free up Iowa DOT staff from project management administrative tasks. Researchers from Iowa State University working with the Iowa DOT conducted a multi-pronged approach to indentify a web-based collaboration solution for Iowa DOT bridge projects. An investigation was launched to determine the functional needs of the Iowa DOT. Commercially available software programs were also evaluated to find what functionality is currently available. A Request for Proposals (RFP) was written to select a commercial web-based collaboration solution for pilot testing. In the second phase of research, a solution will be selected and implemented on two pilot projects. Lessons learned from these pilot projects will assist the Iowa DOT in developing and implementing a long-term solution to improve the management of Iowa DOT bridge projects.

Constructability in the Bridge Design Process, Progress Report, HR-320, 1990

Information concerning standard design practices and details for the Iowa Department of Transportation (IDOT) was provided to the research team. This was reviewed in detail so that the researchers would be familiar with the terminology and standard construction details. A comprehensive literature review was completed to gather information concerning constructability concepts applicable to bridges. It was determined that most of the literature deals with constructability as a general topic with only a limited amount of literature with specific concepts for bridge design and construction. Literature was also examined concerning the development of appropriate microcomputer databases. These activities represent completion of Task 1 as identified in the study.

Demonstration and Field Evaluation of Alternative Portland Cement Concrete Pavement Reinforcement Materials, Construction Report, HR-1069, 1998

The function of dowel bars is the transfer of a load across the transverse joint from one pavement slab to the adjoining slab. In the past, these transfer mechanisms have been made of steel. However, pavement damage such as loss of bonding, deterioration, hollowing, cracking and spalling start to occur when the dowels begin to corrode. A significant amount of research has been done to evaluate alternative types of materials for use in the reinforcement of concrete pavements. Initial findings have indicated that stainless steel and fiber composite materials possess properties, such as flexural strength and corrosion resistance, that are equivalent to the Department of Transportation specifications for standard steel, 1 1/2 inch diameter dowel bars. Several factors affect the load transfer of dowels; these include diameter, alignment, grouting, bonding, spacing, corrosion resistance, joint spacing, slab thickness and dowel embedment length. This research is directed at the analysis of load transfer based on material type and dowel spacing. Specifically, this research is directed at analyzing the load transfer characteristics of: (a) 8-inch verses 12-inch spacing, and (b) alternative dowel material compared to epoxy coated steel dowels, will also be analyzed. This report documents the installation of the test sections, placed in 1997. Dowel material type and location are identified. Construction observations and limitations with each dowel material are shown.