Junwon Seo

Nonlinear Seismic Response and Parametric Examination of Horizontally Curved Steel Bridges Using 3D Computational Models

AbstractThe seismic behavior of horizontally curved steel bridges is more complex than straight bridges because of their curvature and other parameters. Studies that attempt to develop methods to efficiently predict their seismic response have been somewhat limited to date. A computational modeling approach was examined to assist with understanding the seismic behavior of these bridges. The computational, three-dimensional (3D) bridge models consisting of the concrete deck, steel girders, cross-frames, pier columns and caps, and abutments and footings were created in OpenSees and examined for accuracy via application to a representative, three-span continuous curved steel plate girder bridge in Pennsylvania. Sensitivity studies in the form of tornado analyses were also carried out to investigate the influence of critical curved bridge parameters on the seismic response using a group of representative bridges. Each representative bridge was subjected to an ensemble of synthetic ground motions, and seismic ...

Summary Review of Structural Health Monitoring Applications for Highway Bridges

AbstractThe state-of-the art paper provides an extensive literature review on the work pertaining to structural health monitoring (SHM) systems used to investigate the structural integrity of highway bridges. The focus of this review is on identifying the SHM research efforts that include damage detection, structural capacity evaluation, and remaining service life estimates on such structures. These efforts have spanned a broad range of data processing methods devoted to tracking changes in structural characteristics for damage detection, codified frameworks enabling structural capacity estimating, and reliability analysis to predict remaining life. Our findings are that a large number of studies considered damage detection by data processing methods, whereas a relatively small number of studies were devoted to the estimation of structural capacities and the remaining service life of bridges. We conclude that the critical gaps include a lack of validated SHM systems that use ambient data to examine design...

Lateral Live-Load Distribution Characteristics of Simply Supported Steel Girder Bridges Loaded with Implements of Husbandry

This paper discusses the effect of agricultural live-loads on lateral load distribution characteristics of girder bridges on rural roadways in the United States. In this study, load distribution factors for bridges subjected to agricultural vehicles frequently used on rural roads are calculated based upon codified processes, field test results, and simulations. As part of this work, five simply supported steel girder bridges in Iowa were selected for field tests with four agricultural vehicles and a highway-type truck. Strain sensors were mounted on the bottom flanges of girders at midspan of all five bridges. Strain data resulting from the test vehicles were measured and used to determine girder distribution factors for each bridge. These strain data were also used to calibrate analytical models of the bridges. Over 120 agricultural vehicles were identified and used to analytically load the models. Girder distribution factors were then computed using responses from the vehicle-induced model simulations. Findings revealed that the analytical and field distribution factors were in most cases smaller than code-specified values, as has been observed by others. In some cases, however, these factors exceeded code values. Furthermore, the variability in agricultural vehicles’ characteristics had a significant impact on the live-load distribution factors for each bridge.

Field Validation of a Statistical-Based Bridge Damage-Detection Algorithm

This paper describes a field validation of a second-generation, statistical-based damage-detection algorithm and its ability to detect actual damage in bridges accurately. The algorithm had been theoretically validated previously. For the field tests, in lieu of introducing damage to a public bridge, two sacrificial specimens that simulated damage-sensitive locations of the bridge were mounted on the bridge, and different types and levels of damage in the form of cracks and simulated corrosion were induced in the specimens. Using strain data collected from sensors on the sacrificial specimens and on the bridge, the algorithm correctly identified the damage. Analysis of data from sensors far away from the damaged area revealed a relatively high false-positive rate.

Statistical determination of significant curved I-girder bridge seismic response parameters

Curved steel bridges are commonly used at interchanges in transportation networks and more of these structures continue to be designed and built in the United States. Though the use of these bridges continues to increase in locations that experience high seismicity, the effects of curvature and other parameters on their seismic behaviors have been neglected in current risk assessment tools. These tools can evaluate the seismic vulnerability of a transportation network using fragility curves. One critical component of fragility curve development for curved steel bridges is the completion of sensitivity analyses that help identify influential parameters related to their seismic response. In this study, an accessible inventory of existing curved steel girder bridges located primarily in the Mid-Atlantic United States (MAUS) was used to establish statistical characteristics used as inputs for a seismic sensitivity study. Critical seismic response quantities were captured using 3D nonlinear finite element models. Influential parameters from these quantities were identified using statistical tools that incorporate experimental Plackett-Burman Design (PBD), which included Pareto optimal plots and prediction profiler techniques. The findings revealed that the potential variation in the influential parameters included number of spans, radius of curvature, maximum span length, girder spacing, and cross-frame spacing. These parameters showed varying levels of influence on the critical bridge response.

Probabilistic Vulnerability Scenarios for Horizontally Curved Steel I-Girder Bridges Under Earthquake Loads

Horizontally curved steel I-girder bridges are located in all seismic zones in the United States. Research has shown that damage can occur to steel bridge components under earthquake loads. Probabilistic-based techniques are one tool that can be used to assess more accurately the seismic vulnerability of curved bridges for various damage states and at various seismic hazard levels. To examine probabilistic-based vulnerability criteria efficiently, the study used response surface metamodels (RSMs) in conjunction with Monte Carlo simulations to generate horizontally curved steel I-girder bridge fragility curves. The generated curves were then used to evaluate bridge damage in terms of previously published structure damage states. The use of RSMs reduces the required number of computer simulations needed to generate the fragility curves. The paper summarizes the fragility curve generation procedure for a group of horizontally curved steel I-girder bridges using RSMs in association with Monte Carlo simulation. Probabilistic vulnerability scenarios are presented via application to existing horizontally curved steel bridges located in Pennsylvania, New York, and Maryland to estimate seismic demands for those bridges and to generate fragility curves.

Probabilistic structural integrity evaluation of a highway steel bridge under unknown trucks

Abstract This paper presents fragility curves derived from a best-fit regression model that enable to quantify probabilistic structural integrity of an in-service highway steel bridge under multiple truck passages with uncertain characteristics. The regression model is able to be identified via analytical modelling techniques incorporating the bridge response quantities resulting from unknown five-axle trucks through structural health monitoring system. These quantities coupled with weigh-in-motion (WIM) data obtained from two weigh stations closest to the bridge are used (1) to identify which unknown trucks are presumably to travel over the bridge and (2) to quantify the plausible characteristics of the trucks and the corresponding load ratings determined following the AASHTO Manual. With this information, the regression models can be made to demonstrate load ratings as the truck characteristics change. Based on the best-fitted load ratings, nine significant truck characteristics were looked at in their role in causing a below satisfactory bridge capacity. Key findings reveal that the all axle weights affect the fragility curves though the axle weights are not significantly different, and the most significant axle spacing is the first spacing.

Vulnerability Sensitivity of Curved Precast-Concrete I-Girder Bridges with Various Configurations Subjected to Multiple Ground Motions

Abstract Curved bridges provide a vital benefit to the nation’s infrastructure system by allowing for accessibility and ease of transition in irregular highway layouts. Curved bridges using straight prestressed concrete I-girders with curved decking can fulfill this need. A number of such bridges have been constructed both in seismically and nonseismically active zones. This paper determines the seismic vulnerability sensitivity of the bridges with vastly different configurations via use of conventional fragility-assessment techniques. Experimental design established a statistical setting using core variables to produce a wide variety of hypothetical bridges to represent both as-built and proposed bridge configurations. Each bridge was designed following the strength and serviceability limit states stipulated by current bridge design specifications. As part of the sensitivity analysis, nonlinear time history analyses (NLTHAs) using numerous synthetic ground motions were performed to establish seismic dema...

Influence of Atypical Vehicle Types on Girder Distribution Factors of Secondary Road Steel-Concrete Composite Bridges

This paper investigated the influence of atypical agricultural vehicle parameters on girder distribution factors (GDFs) for two simply supported steel-concrete composite bridges located on secondary roads in the United States. As part of the parametric investigation, field measurements were performed on the bridges under the passage of full-scale agricultural vehicles along each bridge centerline. Strain data obtained from field tests were used to determine field GDFs. Both field data and GDFs were used to calibrate a finite element model of the bridge. Data from over in-use one hundred agricultural vehicles were collected, and then each vehicle was applied to the model to compute analytical GDFs. These vehicles were analytically and statistically investigated to determine the sensitivity of GDFs to vehicle parameters, including maximum vehicle axle load, gage width, and spacing distributions. Based upon field strain investigation for the two bridges, the responses of the central girders were greater than those of the exterior girders, resulting in greater field GDFs for central girders than those of the exterior girders. Results also indicated from the sensitivity study that each girder had different levels of correlation between GDFs and single vehicle parameters.

Evolution of a Bridge Damage-Detection Algorithm

Several of the steps, iterations, and refinements required to develop one of the many pieces of the structural health monitoring (SHM) system puzzle are described. These steps include devising initial concepts, alpha testing, analytical investigation, beta testing, concept upgrades, and field evaluations. Although not necessarily a blueprint for the development of such systems, the report serves as a case study for taking an initial concept through multiple steps that culminate in a validated approach. As SHM becomes a more widely adopted and accepted bridge evaluation protocol, it will be imperative that developers understand the steps required to develop such systems. The work presented is one example of such a process.