Evaluation of the Performance of A709 Grade 65 QST Bridge Steel

The primary goal for this project was to evaluate the efficacy of A709 Grade QST 65 steel for use in Iowa bridge projects. The objectives of the project were as follows: Identify the current state of use of A709 Grade QST 65 steel in bridge projects; Identify the ductility and strength characteristics of A709 Grade QST 65 steel through full-scale laboratory testing; Identify the fatigue characteristics of A709 Grade QST 65 steel through cyclic fatigue testing; Observe and compare bridge construction similarities and differences to conventional steel construction using a new bridge planned over Sand Creek in Buchanan County, Iowa; Compare relative costs of using A709 Grade QST 65 steel versus conventional steel; and, Measure the live load response at various points in time on the Sand Creek Bridge, which was constructed using A709 Grade QST 65 steel. The ductility and strength of the steel was observed through the various laboratory tests completed for this project as well as the testing performed by others. Minimum requirements for this steel grade have been established, and the results of this study indicate that the requirements were met and surpassed. The modified design of this first-in-the-nation bridge using Grade QST 65 steel over Sand Creek allowed for a reduction in beam size for this relatively short-span, low-traveled bridge due to the increased strength of the steel beams. The total steel cost for these beams resulted in a 20% material cost savings. The results should give confidence to engineers considering use of this steel grade on bridge construction projects with longer spans and higher traffic counts

Assessment, Repair, and Replacement of Bridges Subjected to Fire

Although bridge fires are not frequent events, they pose impacts on safety, traffic flow, and the economy given bridge repairs or replacement can be costly. A lack of information and the tools needed to evaluate fire damage to concrete bridges and to aid in decisions for both immediate and long-term use of fire-damaged bridges was the impetus for this research. On October 30, 2019, multiple items within a homeless encampment were set on fire beneath the I-29 northbound bridge over the Perry Creek conduit in Sioux City, Iowa. The fire was exacerbated when a propane tank became engulfed by the flames. The bridge girders and deck were particularly vulnerable to the ground fire because of the minimal ground clearance (about 6 ft) in comparison to that of most other bridges. Despite this unfortunate incident, it provided an opportunity to learn more about the residual condition and strength of the bridge girders through a research study. The Iowa Department of Transportation (DOT) elected for the removal and replacement of the bridge, which allowed for girders to be removed and undergo testing. Three fire-damaged girders were selected from the bridge, carefully removed, and transported to the Iowa DOT maintenance yard in Ames, Iowa. Each girder was visually assessed and selected based on the apparent level of damage incurred: one low-level, one mid-level, and one higher-level. The goal was to compare and contrast apparent levels of damage and assess the impacts each level of damage had on the serviceability and strength of the girder. This report provides the results and recommendations resulting from the completed load testing. The results will assist in providing more technical information with respect to fire-damaged girders to help bridge owners to develop guidelines for assessment and repair

Re-Tightening the Large Anchor Bolts of Support Structures for Signs and Luminaires: Phase II

(c) 1033985The Minnesota Department of Transportation (MnDOT) funded two projects in an effort to mitigate anchor bolt connection loosening and develop improved pre-tensioning steps for its sign, luminaire, and traffic signal (SLTS) structures. The Phase I study proposed new pre-tensioning procedures, completed laboratory testing, did an in-depth literature review, and set up instrumentation. The next part of the work started by implementing the proposed procedures in the field and suggesting revisions to be investigated further in Phase II. Through this work, the structural monitoring objective was to better understand field fatigue forces on the anchor rods and develop a testing procedure to replicate field stresses accurately in the laboratory. In the Phase II project, lessons learned from both the field results and additional literature review were tested in the laboratory to balance the efficiency and efficacy of the revised pre-tensioning procedures. Feedback from stakeholders and experience from in-field inspections were considered for the revised procedures. Testing methods and conclusions were validated with finite element models and structural health monitoring. This final report brings all aspects of the work together and recommends improved procedures and additional studies

Field Demonstration of an Innovative Box Beam Connection

The objective of this project was to demonstrate the field implementation of an innovative longitudinal joint design developed during a previous phase of research. To achieve this objective, a yet-to-be-constructed box girder bridge in Washington County, Iowa, was selected to demonstrate the construction and performance of the joint. In order to evaluate the joint\u2019s performance, a seven-day period of field monitoring was conducted shortly after construction was completed. In addition, long-term evaluation of the joint was performed through the completion of live load field tests and deck concrete crack inspections. The live load tests were performed every 12 months, and crack inspections of the bridge deck were performed every six months. During the field tests and monitoring, temperature, strain, and displacement data were collected at critical locations and analyzed to evaluate joint performance with respect to cracking resistance and load distribution. The results indicate that the innovative joint is sufficient to resist early-age longitudinal joint cracking. Joint cracks that were seen on another box girder bridge with traditional narrow joints were not observed in this case. The innovative joint performed well with respect to load distribution. The whole bridge superstructure behaved as an integrated structure regardless of the transverse location of a passing truck. In addition, the box girder bridge was constructed using integral abutments, which added transverse restraint and positively affected the strain distribution at the joint ends

Multi-Span Lateral Slide Laboratory Investigation: Phase II

With slide-in bridge construction (SIBC), the bridge superstructure is constructed off the final alignment and then slid laterally from the temporary worksite onto the in-place substructure. Once the sliding is complete, closure joints between the bridge super- and sub-structure are cast to establish continuity. The cementitious materials and reinforcement design used to complete the closure joints affect when the bridge can be opened to traffic or construction loading. The goal of this research was to investigate the performance of closure joints using ultra-high performance concrete (UHPC) and noncontact lap-spliced reinforcing steel bar, with a specific focus on determining when a noncontact lap-splice has sufficient strength to either open a bridge or expose it to additional construction loading. The research was also conducted to explore an alternative material to UHPC\u2014hybrid composite synthetic concrete (HCSC)\u2014which may be able to provide sufficient early-age capacity when used in the same way. A series of laboratory tests were performed on 96 samples including four noncontact lap-splice connection designs with different rebar development lengths and joint filling materials. A time-dependent pull-out test was performed on each design with a focus on the performance at the material early age. Each sample was loaded with a pull-out force until failure. The ultimate capacity of each sample was captured and analyzed. Based on the test results, recommendations for the selection of UHPC/HCSC closure joints reinforced with lap-spliced rebars were developed

Investigation of the Causes of Transverse Bridge Deck Cracking

Transverse cracks in concrete bridge decks sometimes initiate in the early stages of the bridge service life, usually just after construction. Cracks in the bridge deck can accelerate the deterioration of the deck concrete, provide a direct pathway for the intrusion of water and chlorides to the deck reinforcement, and detract from the aesthetics. This eventually results in increased maintenance costs and reduced bridge service life. The goal of this research was to identify factors that consistently lead to the formation of early-age transverse cracks for mitigation in the future. To obtain a comprehensive evaluation and include as many factors as possible in the research, the primary research investigation was conducted in three stages with varying numbers of bridges and factors considered in each stage. The first stage was carried out on 2,675 bridges constructed in Iowa between 1900 and 2020. The goal of this stage was to identify the correlation between deck cracking and six parameters: deck concrete type (high-performance concrete [HPC] or non-HPC), maximum span length, maximum structure length, Iowa Department of Transportation (DOT) District, year built, and main structure type. The second stage was conducted to include additional bridge parameters\u2014but with a smaller number of bridges. A group of 20 bridges was selected after reviewing inspection reports for 116 bridges constructed between 2013 and 2018. Various bridge parameters in three main categories, structural, construction, and material, were investigated. The third stage was carried out based on data collected from six field visits while deck concrete was being placed. The parameters investigated in this stage included evaporation rate (lb/ft2/h), air temperature (\ub0F), concrete temperature (\ub0F), relative humidity (%), and wind speed (mph). The results from the three investigation stages were compared with the research results documented in another Iowa DOT report. Based on the research findings from each stage of investigation, the various parameters were classified as having either direct correlation, no correlation, slight positive correlation, or slight negative correlation

Advancing Bridge Load Rating: State of Practice and Frameworks

693JJ319D000020 TO693JJ320F000170The U.S. has more than 600,000 bridges, making the distributed load rating and posting processes across the nation a significant effort that does and can benefit from improvements in efficiency. Bridge load rating, posting, and overweight permitting processes evolve due to the regulatory requirements regarding the frequency of inspections and relevant changes to bridges that necessitate re-rating them. These factors include changes to the dead load, strength of members, and any maintenance or rehabilitation work. As such, States are interested in modifying their procedures to implement technology and improved means and methods to reduce the time associated with load rating. Being able to load rate bridges efficiently and accurately is a necessity, particularly in the use case of permit load routing. Based on the extensive findings during the information collection processes for this project, frameworks for future bridge load rating, posting, and overweight permitting were developed to improve productivity, efficiency, and consistency by closing process gaps and through the application of newer technologies. The newer technologies include digital twin concepts; integrating various (new) data; creating, updating, and reusing models; integrating sensing data (bridge, traffic, weigh-in-motion); and better analysis methods. This work may help develop the state of practice

Evaluation of the Use of IRI Data to Estimate Bridge Dynamic Impact Factor (DIF)

The objectives of this project were to correlate international roughness index (IRI) data (which are widely collected and directly related to bridge deck roughness) to impact factors and develop a process for determining the impact factor to use for all bridges in Iowa. To achieve the project objectives, a sample of 20 bridges was selected for bridge monitoring to collect dynamic strain data. To estimate the static strain data, the locally weighted scatterplot smoothing (LOWESS) function was used to smooth the dynamic strain time history. The dynamic impact factor (DIF) value was then calculated using maximum dynamic and static strain data. IRI data were extracted from PathWeb, a web-based application provided by the Iowa Department of Transportation (DOT) for all bridges considered in the field test program. Once the bridge was identified in PathWeb, the IRI data from four locations near each bridge deck approach were extracted and used to study the relationship between the IRI and DIF. Based on the results from this research, these were the key findings: \u2022 The DIF value decreases as the bridge skew angle increases. Based on linear regression, the DIF value decreases about 0.037 to 0.043 per 10-degree increment of bridge skew. \u2022 The DIF value decreases as the bridge deck condition index increases, meaning that the dynamic response is lower when the bridge deck condition is better. \u2022 For bridges with zero skew, the DIF value increased by 0.006 per 100 in/mile increment of the IRI value. According to the research findings, an equation was developed for the prediction of DIF on existing bridges with consideration of the bridge skew and the maximum IRI value near the bridge deck approach. Although the proposed equation was validated using data from 13 bridges, the researchers recommend using the equation with the limitation that the actual bridge dynamic response could deviate \ub110% from the equation predicted value

Study of the Impacts of Implements of Husbandry on Bridges Volume III: Appendices

The objectives of this study were to develop guidance for engineers on how implements of husbandry loads are resisted by traditional bridges, with a specific focus on bridges commonly found on the secondary road system; provide recommendations for accurately analyzing bridges for these loading effects; and make suggestions for the rating and posting of these bridges. To achieve the objectives, the distribution of live load and dynamic impact effects for different types of farm vehicles on three general bridge types\u2014steel-concrete, steel-timber, and timber-timber\u2014were investigated through load testing and analytical modeling. The types of vehicles studied included, but were not limited to, grain wagons/grain carts, manure tank wagons, agriculture fertilizer applicators, and tractors. Once the effects of these vehicles had been determined, a parametric study was carried out to develop live load distribution factor (LLDF) equations that account for the effect of husbandry vehicle loads. Similarly, recommendations for dynamic effects were also developed. The live load distribution factors and dynamic load allowances are covered in the first volume of the report. Finally, suggestions on the analysis, rating, and posting of bridges for husbandry implements were developed. Those suggestions are covered in the second volume of the report. This third volume of the report contains six appendices that include the 19 mini-reports for field tested and analytically modeled steel-concrete, steel-timber, and timber-timber bridges, the farm implement and bridge inventories for the project, and survey responses

Evaluation of Galvanized and Painted Galvanized Steel Piling

This project investigated the long-term protection of steel piles with galvanized and painted galvanized coatings using a corrosion chamber to accelerate corrosion effects in the laboratory. Further investigation was completed through observation of painted galvanized piles installed in the field at a newly constructed bridge in Buchanan County, Iowa. The primary objective of this research was to evaluate the effectiveness of galvanized and painted galvanized piles in extending bridge service life in a cost-effective manner. An economic evaluation was conducted comparing the use of a larger H-pile section, a galvanized coating, and a painted galvanized coating to protect the piles against corrosion. One solution to achieve a 100-yr design life is to increase the section size of the pile to allow for section loss without compromising the required pile capacity While the cost to increase the pile size was determined to be less than the premium for galvanizing or galvanizing and painting the piles for the bridge in this study, a cost-benefit evaluation for each protection measure is suggested knowing that costs can vary widely depending on specific project requirements, location, market prices, etc. This is an interim report, and the research team plans to continue to collect additional annual data from the Buffalo Creek Bridge in Buchanan County for future analysis