Steel girder ends in bridges can be susceptible to corrosion damage from deicing salts, water, and other contaminants that leak from failed deck expansion joints. When corrosion becomes significant, it can decrease the sectional properties of steel girder ends and eventually reduce structural resistance against bearing and shear. Conventional methods that are typically used to repair corrosion-damaged girders require a substantial amount of time and resources to complete and often cause public inconvenience due to traffic lane closures. Thus, there is a critical need for practical, rapid, and cost-efficient repair solutions suitable for implementation by local DOT maintenance teams. The main concept of the proposed Sandwich Panel repair method is to encase the corroded region in a filler material, such as cementitious grout or an alternative, and reinforce it with threaded rods. To expedite installation and eliminate the need for formwork removal, two bent thin steel plates installed on both girder sides serve as stay-in-place formwork. Therefore, this repair method eliminates the labor-intensive steps of jacking, welding, and formwork disassembly, making it more cost-effective and less time-consuming. The structural performance of the Sandwich Panel repair method was validated through five large-scale experimental tests, considering parameters such as (1) threaded rod layout, (2) filler material, and (3) support conditions. This study primarily focused on the repair of steel girders without full-depth stiffeners, whose bearing strength is more sensitive to web deterioration. The repair successfully restored, and even exceeded, the design web crippling capacity of the W24 & times; 68 steel girder, calculated in accordance with AASHTO LRFD methodology. A complementary parametric study was conducted using finite-element models that were benchmarked against experimental results and validated the efficacy of the repair.

This study presents structural redundancy evaluations of three two-girder steel bridge systems using finite element analysis to assess their capacity and behavior under fracture conditions. Following AASHTO System Redundant Members (SRM) Guide Specifications, detailed three-dimensional finite element analysis (FEA) models were developed in ABAQUS to simulate member fractures at critical locations and evaluate bridge responses under Redundancy I and II load combinations. The analysis includes two-girder bridges using geometries typical of real bridge applications. Multiple fracture scenarios across different spans were evaluated to identify controlling limit states and failure modes. Results demonstrate that two-girder systems may have redundancy challenges as a result of limited load sharing between intact and fractured girders. This limitation results from low torsional stiffness and relatively flexible lateral bracing and floor beams, which severely restrict load redistribution. When one girder fractures, the remaining intact girder carries substantially increased loads, causing the fractured girder to behave as a cantilever beam. The controlling failure mode was identified as buckling at section changes near piers on fractured girders, with high displacement differences between intact and fractured girders. These behaviors may reduce reserve capacity below Redundancy I and II thresholds. Analysis revealed that the evaluated two-girder bridges did not meet SRM qualification requirements because of inadequate load transfer mechanisms between the two main load-carrying members. This research provides bridge engineers with critical guidance on the need for careful evaluation when two-girder systems are evaluated for redundancy performance.

Corrosion at steel girder ends is caused by deicing salts, water, and other environmental debris, leading to a loss of cross-sectional area and a reduction in structural resistance against shear and bearing. This study investigates the effect of corrosion-induced section loss on the residual strength of steel girders through full-scale experimental testing. Six girders with different end configurations, including unstiffened, partially stiffened, and fully stiffened ends, were tested to evaluate failure mechanisms and strength reduction. Observed failure modes included shear buckling, web local crippling, and shear rupture, with web local crippling found to be more sensitive to section loss, particularly in girders without full-depth stiffeners. Residual strength estimates for unstiffened girders aligned well with equations proposed by prior research, developed through parametric studies that considered individual corrosion parameters. In contrast, current methods for estimating shear strength reduction remain limited, demonstrated through the comparison of experimental results with current methods. Girders with partial-depth transverse connection plates exhibited enhanced resistance to web local crippling. These results underscore the importance of girder end configuration and corrosion characteristics in evaluating residual strength and highlight the need for improved methods that account for detailed corrosion topology and end restraint conditions.

Despite the historical tendency toward proportioning and spacing braces based on rules of thumb, modern specification guidance stipulates that cross-frame design be supported with a rational analysis, which is commonly aided by computer software. While cross-frame research has advanced over the last 30 years, the relatively vague nature of specification language related to rational analysis is still utilized and often misunderstood by engineers leading to uneconomical chase-your-tail design solutions-particularly related to the fatigue limit state. To improve the design specifications and economy, an extensive analytical parametric study was conducted to quantitatively investigate the sensitivity of load-induced cross-frame response in varying bridge geometries. The study included multiple three-dimensional analyses on 4,104 unique steel I-girder bridges. Among other observations, the results demonstrated that load-induced cross-frame forces are generally higher in heavily skewed systems. From these studies, two primary recommendations are proposed to improve specification guidance on fatigue design of cross-frames. First, designers can avoid overly conservative and iterative designs by utilizing staggered and/or discontinuous cross-frame configurations, thereby alleviating force demands in heavily skewed systems. Second, the study concluded that refined analyses are not warranted in straight bridges with little to no support skew since cross-frame force magnitudes are generally not significant. Geometric limits based on skew and connectivity indexes are proposed to serve as the delineation between when a refined analysis is recommended.

Across the U.S.A., steel girder bridges experience significant deterioration caused by corrosion, and the current repair methods for corroded steel girders require considerable time and cost. Corrosion is typically found at end-span locations above girder supports at abutments and piers caused by deicers and water leaking from the deck joints. Therefore, there is a need for effective, rapid, and robust repair strategies that can be implemented by bridge maintenance personnel. This paper presents five innovative repair methods for rehabilitating corroded steel girder bridges. The five innovative repair methods were evaluated to select two repair procedures that can be implemented by the local Department of Transportation (DOT) in Indiana. During the evaluation process, typical and critical requirements associated with repair methods for corrosion-damaged steel girders were considered, including robustness, reduction of implementation cost, and time. Furthermore, feedback from the local DOT in Indiana was collected to identify any additional requirements. The evaluation was completed by choosing two innovative repair methods through a selection process called the house of quality matrix, which is a commonly used tool in the consumer product industry. After completing the evaluation, two repair methods, "sandwich panel" and "web strengthening with diagonally oriented angles," were selected.

Many of the current fatigue design specifications for cross frames, especially those in composite steel bridge systems, have primarily been based on computational studies and component-level laboratory experiments. To fully understand the behavior of cross frames when subjected to in-service truck traffic and to critically evaluate legacy design provisions, in-service field monitoring of cross frames in various composite systems is important. Therefore, select cross frames in three bridges in the greater Houston area were instrumented with strain gage sensors-one straight bridge with normal supports, one straight bridge with skewed supports, and one horizontally curved bridge with radial supports. For each bridge, rainflow counting techniques and other postprocessing procedures were implemented for a monitoring period of one month to compare the measured cross-frame response. Among other key observations, the measured data demonstrated that load-induced force effects in the cross frames of the skewed bridge system exceeded those in the bridges with normal or radial supports and that cross-frame response was highly sensitive to the longitudinal and transverse truck positions. In all cases, though, the measured damage accumulated on all instrumented cross-frame members during their respective monitoring periods, if extrapolated to the entire service life, would likely not cause significant load-induced cracking in the critical welded gusset-to-member connections.

Ultrasonic testing is utilized to ensure weld quality during the fabrication of steel bridges by identifying discontinuities that are classified as either acceptable or rejectable. The classification of a discontinuity can be affected by differences in the acoustic properties of the material under test and the reference standard used for calibration. Differences in wave velocity affect the refracted angle and amplitude of refracted shear waves. As a result, indications can be missed or incorrectly classified, or incorrectly located in the material. The objective of this research study was to characterize the acoustic wave velocities in a sample of contemporary steels to better understand the range over which velocities may vary for common steels. To address this objective, a series of velocity measurements have been conducted for shear waves propagating through different directions in steel plates of different strengths and reported manufacturing processes. The study also examines the loss of signal amplitude that results from changes in the refracted angle of shear waves used for the inspection of welds. Beam splitting that may occur in anisotropic materials and the potential impact on signal amplitudes is also presented. It was shown in the research that relatively small differences in velocity between the material under test and the reference standard cause a loss of sensitivity of the test. Data presented in the paper documents wave velocity and anisotropic ratios for a population of contemporary bridge steels used for the fabrication of steel bridges and an assessment of how velocity differences affect the amplitude of reflected shear waves.

An exploratory study was conducted for some bridges in the state of Indiana that evaluated the implementation potential of the AASHTO Guide Specifications for Internal Redundancy of Mechanically-Fastened Built-Up Steel Members (IRM Guide Specification) and the AASHTO Guide Specifications for the Analysis and Identification of Fracture Critical Members and System Redundant Members (SRM Guide Specification). The outcomes for the project included (1) determining if the application of the Guide Specifications on a wider scale would be beneficial to INDOT; (2) identifying which bridges or members were “truly” non-redundant in the selected bridges, thus allowing a more targeted inspection program that would minimize the risk associated with member failures; (3) developing a more targeted inspection program for the bridges eligible to be classified as IRMs and SRMs, and (4) proposing a strategy to move forward with a state-wide implementation plan to analyze other bridges presently classified as having NSTMs. This report addresses the bridge selection process used in determining the list of structures in the state of Indiana for IRM and SRM evaluation, as well as a detailed description of the IRM and SRM evaluation processes.

In compliance with recent (2022) federal legislation found in the Code of Federal Regulations Part 650 Subpart C, risk-based inspection (RBI) practices for determining inspection intervals for highway bridges are now permitted. The RBI approach allows for a systematic assessment of risk and prioritizes inspection resources where they are most needed. However, to ensure an optimal level of safety and serviceability, it is necessary to utilize reliable inspection techniques in conjunction with an appropriate inspection interval, as emphasized by National Cooperative Highway Research Program (NCHRP) Report 782. Utilizing ineffective inspection techniques may lead to uncertainty about the element's condition and thus increase the risk associated with the component. Therefore, this paper proposes a framework that integrates a new factor, called the inspection effectiveness factor (IEF), into the RBI process to rationally estimate the inspection interval considering the reliability of the inspection technique. The inspection interval in the proposed approach is determined based on the damage mode, associated likelihood, consequences, and effectiveness of the inspection technique, offering a rational approach for decision-makers in estimating the inspection interval of bridges and identifying appropriate inspection techniques for different defects. The effectiveness of the proposed method is validated through experts' judgment. In addition, the proposed approach is demonstrated through a case study utilizing historical inspection reports.

Previous research on large-scale fracture tests on mechanically fastened built-up steel members subjected to flexural or axial loads demonstrated resistance to complete member fracture due to cross-boundary fracture resistance (CBFR). This paper builds on and expands that work through additional experimental and analytical research into behavior of two-channel mechanically-fastened built-up axial steel members following fracture of a single component. Finite element based parametric studies were conducted to characterize the static load redistribution behavior of axial members comprised of two channels, following a fracture event. FEMs were calibrated using experimental data obtained from full-scale testing. Simplified solutions were developed to estimate the after-fracture load capacity and the fatigue stress range in a remaining channel. The solutions are used to evaluate the internal redundancy of mechanically fastened built-up two-channel members. If this member type is found to be internally redundant during an evaluation, the developed solutions can then be used to reliably predict fatigue life of the member in the faulted state and establish the special inspection interval according to the relevant provisions of AASHTO.

The variability in ultrasonic attenuation of narrow-gap improved electroslag welds (NGI-ESW) and submerged arc welds (SAW) was assessed through experimental testing of machined weld specimens with side drilled hole (SDH) reflectors. The specimens were assessed using a 2.25 MHz conventional UT probe and a 5 MHz PAUT probe. NGI-ESW welds had significant variability depending on the position of the sound path in relation to the structure of the weld, with increased average attenuation and increased scatter in amplitude when sound passed through any portion of the weld metal. One NGI-ESW specimen was fabricated from with thermo-mechanically controlled processed (TMCP) base metal which resulted in additional scatter for scans through the base metal due to acoustic anisotropic behavior. SAW welds had much less attenuation variations than the NGI-ESW welds, but scans through the weld metal had larger amplitude variations than scans through the base metal only.

Impact energy tests are an efficient method of verifying adequate toughness of steel prior to it being put into service. Based on a multitude of historical correlations between impact energy and fracture toughness, minimum impact energy requirements that correspond to desired levels of fracture toughness are prescribed by steel bridge design specifications. Research characterizing the fracture behavior of grade 485 and 690 (70 and 100) high-performance steel utilized impact, fracture toughness, and crack arrest testing to verify adequate performance for bridge applications. Fracture toughness results from both quasi-static and dynamic stress intensity rate tests were analyzed using the most recently adopted master curve methodology. Both impact and fracture toughness tests indicated performance significantly greater than the minimum required by material specifications. Even at the AASHTO Zone III service temperature, which is significantly colder than prescribed test temperatures, minimum average impact energy requirements were greatly exceeded. All master curve reference temperatures, both for quasi-static and dynamic loading rates, were found to be colder than the Zone III minimum service temperature. Three correlations between impact energy and fracture toughness were evaluated and found to estimate reference temperatures that are conservative by 12 to 50 °C (22 to 90 °F) on average for the grades and specimen types tested. The evaluation of two reference temperature shifts intended to account for the loading rate was also performed and the results are discussed.

Corrosion in the girders of steel girder bridges often occurs due to the deicing salts, water, and other debris that leak through the deck joints into the web and bottom flange at the girder ends. Corrosion causes loss of cross-sectional area leading to a reduction in section properties of the member, which eventually results in a reduction in structural resistance against shear and bearing. In this study, seven full-scale tests were performed on decommissioned steel girders acquired from bridges scheduled for demolition in Indiana. Two of the four girders had severe corrosion with cracks and holes in the bottom of the web induced by corrosion, while four girders had moderate section loss induced artificially. All seven girders were subjected to shear loading to determine the residual shear and bearing capacity. Test results revealed a reduction in strength due to section loss compared to nominal sections. Failure modes observed during these four large-scale experiments were shear buckling, shear rupture, and web local crippling. Finite element models were developed and benchmarked to the experimental results. Parametric studies were performed for unstiffened and stiffened girders and included different corrosion scenarios by varying parameters such as corrosion height, length, and thickness loss. Results were analyzed to investigate the effect of each parameter and a modification factor was developed to estimate the residual shear and bearing capacity of corroded girders.

A study to investigate the effects of taper on vortex shedding coherence on High Mast Lighting Towers (HMLT) with models of eight-, twelve-, and sixteen-sided polygonal cross-section was performed in Purdue’s Boeing Low-Speed Wind Tunnel. Partial tower models were mounted on springs to recreate a flutter phenomenon seen on high mast lighting towers and data was taken using a stationary configuration within the wind tunnel. The model was later oscil-lated at specified frequencies and amplitudes and the resulting wake and surface pressures were recorded and compared to the stationary cases. The re-searchers aim to study the characteristics of a “lock-in” phenomenon, that is, a region of pole height where there is a vortex cell with a single shedding frequency, instead of different shedding frequencies for different diameters as Strouhal theory dictates. Results show the existence of vortex cell shedding for clamped models. Using a motor and a forcing cam to recreate the elastic movement of the HMLT in ambient conditions has yielded a specific range of diameters to determine the size of the locked in vortex cells. According to standard Department of Transportation manufacturing standards for tapered HMLT, the lock in distance for small excitations (0.254 cm) would be approximately 305 cm in tower height.

The detail category for base metal at the toe of transverse stiffener-to-flange and transverse stiffener-to-web fillet welds is defined as Category C' in the current AASHTO LRFD Bridge Design Specifications (2020, 9th Ed.) and as Category C in the AREMA (2020) Manual for Railway Engineering and the AISC Steel Construction Manual (2017, 15th Ed.). These are often referred to as short attachments due to their very short length (< 2 in.) in the direction of the primary stress range. Sometimes it is necessary to place a stiffener or a connection plate at an angle different than perpendicular to the web, such as in skewed bridges. Increases in the effective length of the stiffener along the flange in the longitudinal direction are seen as the plate is rotated away from being perpendicular to the web. The other extreme occurs when the stiffener is rotated completely 90° and is perfectly parallel to the web and the longitudinal stress range. In this instance, this is identical to the long attachment and classified as Category E (length > 4 in.). The current specifications and manuals, on the other hand, do not have classification on how to address the potential effects on fatigue performance of angles in between these two extremes. This paper summarizes finite element analysis studies based on local stress and structural hot-spot stress approaches that were conducted to investigate and classify welded attachments placed at angles other than 0° (transverse) or 90° (longitudinal) for a variety of stiffener geometries and thicknesses. This study includes new classification for incorporating the findings into the AASHTO LRFD Bridge Design Specifications, AREMA Manual for Railway Engineering, and the AISC Steel Construction Manual.

Over the past decade, there has been considerable interest in the development of quantitative analytical procedures to determine if a primary steel tension member (PSTM) is a fracture critical member (FCM). Traditionally, this designation has most often been arbitrarily determined based simply on the bridge geometry, for example, the number of girders in the cross section, rather than an evaluation of the bridge in the faulted state. Clearly, such a redundancy evaluation must address the loading scenarios concurrent with failure of the PSTM, the likelihood of the member failure, the acceptable probability of load exceeding resistance in the faulted state, and the application of vehicular live load models. This research was conducted to develop a load model and load combinations that are specific to evaluating the performance of a bridge in the event a steel member was to fracture. Specifically, two load combinations were developed to evaluate the strength of a steel bridge, one for the event in which the failure of a PSTM occurs, and another for a post-failure service period. The development adhered to the reliability-based principles and procedures applied in the calculation of load combinations currently used in bridge engineering to facilitate direct implementation and to ensure consistency with current steel bridge design and evaluation procedures contained in the AASHTO LRFD Bridge Design Specifications.

The behavior of shear studs affect load transfer between the steel girder and the concrete deck. This aspect of behavior has vital importance in the evaluation of redundancy for composite steel bridges with fracture critical members (FCMs) in which the fracture of a member is being evaluated. It is important to include proper shear stud properties which cover the shear, tensile, and combined shear and tensile behavior to prevent erroneous conclusions when evaluating the redundancy of such bridges. In this study, a shear stud damage methodology was developed by calibrating finite element (FE) analysis to existing experimental data and other methodologies. The numerical results from FE models were used to develop new modification factors for the existing methodologies and develop an approach to more accurately model the strength, stiffness, and ductility of stud damage behavior for a range of typical shear stud, haunch, and flange configurations.

Inspection agencies have been increasingly implementing unmanned aerial systems (UAS) for bridge inspections. Currently, UAS are typically used for long-range monitoring and surveillance tasks, but bridge managers are hopeful that they may be utilized for detailed inspection, such as condition assessments and the inspection of fracture critical members (FCMs) in the near future. As an assistive tool for visual inspections, the accuracy of UAS-assisted inspections is unknown. This study investigates the relationship between the characteristics of the individual inspectors and a set of performance metrics associated with UAS-assisted FCM inspections. Four bridge inspectors used a UAS to inspect a series of full-sized bridge specimens with known fatigue cracks. The inspection videos were later shared with 19 bridge inspectors for a desk review. The performance of each inspector was evaluated and compared with the results from 30 hands-on inspections of the same specimens. The results showed that an inspector's past experience with UAS, licensure, and academic degree could have a significant influence on one or more of the three defined performance metrics. The comparison between the results of the UAS-assisted inspections and the hands-on inspections revealed that crack detection was comparable. However, the hands-on inspections were more accurate.

Ultrasonic testing results can be affected by differences in acoustic properties of the material under test such as attenuation and velocity. Weld flaws can be missed or incorrectly rated, or incorrectly located in the material. The goal of this study was improving the quality of ultrasonic testing of welds. The objective of the study was to assess the variation in acoustic properties of structural steels used for the construction of highway bridges. This paper discusses the results of measurements of the acoustic properties of 43 different material heats that show different grades of steel plate used in bridges. Normal incidence shear wave transducers were used to measure shear wave speeds and acoustic anisotropy ratios. Results showed significant variations in wave velocities in the different steels that is unaddressed in contemporary welding codes for bridges in the US.