40 research outputs found
Optimizing Steel Railway Truss Bridge Health Monitoring
No full textProblems - Steel Railway Trusses • Aging • Large system – bridge AND railway • Labor intensive condition eval • Reported conditions: Stringer-to-floor beam connections [Haghani 2012] Stringer flange clip angle cracks [Haghani 2012] Unequal eyebars stress distribution [DelGrego 2008] Displaced eyebar pins [DelGrego 2008
Problems – Condition Evaluation • Visual inspection: Prescribed frequency Costly Subjected to human interpretation • Sensors: Focused on a single bridge Extensive array Costl
Probabilistic Vulnerability Scenarios for Horizontally Curved Steel I-Girder Bridges under Earthquake Loads
No full text 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. </jats:p
Steel Pin and Hanger Assembly Replacement Options
No full textA number of steel beam bridges exist in the United States that contain pin and hanger assemblies. Pin and hanger assemblies are fracture critical members whose failure would result in collapse of the bridge or render it unable to perform its expected functions. As these bridges continue to age, many assemblies have deteriorated to a point where retrofit or replacement has to be considered and performed to maintain intended safety and performance. States have taken various approaches to address the pin and hanger assembly retrofit and replacement options. However, there is no single report that summarizes these approaches. This report documents steel pin and hanger assembly retrofit and replacement options via a literature review and synthesis that explores options that have been studied and implemented in the United States. In conjunction with the literature review, a survey was developed in conjunction with the Bureau of Sociological Research (BOSR) at the University of Nebraska-Lincoln to assist with identifying implemented strategies and evaluate best practices. Information was solicited from 50 states and was used in conjunction with the literature review to develop flowcharts that would assist NDOR personnel with assessing various options and their consequences when pin and hanger assembly retrofit or replacement options are being considered for bridges in the state
Nonlinear Seismic Response and Parametric Examination of Horizontally Curved Steel Bridges Using 3D Computational Models
No full textNonlinear Seismic Response Analysis of Curved and Skewed Bridge System with Spherical Bearings
No full textA three-dimensional (3D) modeling approach to investigate nonlinear seismic response of a curved and skewed bridge system is proposed. The approach is applied to a three-span curved and skewed steel girder bridge in the United States. The superstructure is modeled using 3D frame elements for the girders, truss elements for the cross-frames, and equivalent frame elements to represent the deck. Spherical bearings are modeled with zero-length elements coupled with hysteretic material models. Nonlinear seismic responses of the bearings subjected to actual ground motions are examined in various directions. Findings indicate that the bearings experience moderate damage for most loading scenarios based on FEMA seismic performance criteria. Further, the bearing responses are different for the loading scenarios because of seismic effects caused by interactions between excitation direction and radius of curvature
Assessment of Load Sharing Members in an Anti-ram Bollard System
No full textDue to the increased frequency, scale, and danger of malicious attacks carried out by Vehicle Borne Improvised Explosive Devices (VBIEDs), anti-ram bollards have become a key element in the protection of critical structures. This study focused on the evaluation of above grade load sharing members in a steel anti-ram bollard system in an attempt to develop efficient load sharing mechanisms that improve the structure’s ability to resist vehicle impacts, while concurrently remaining aesthetically pleasing to the general public. A computational assessment was completed using calibrated LS-DYNA finite element models to determine if effective load sharing member configurations and designs could be established so that further optimization of the entire anti-ram system was possible. It was determined that efficient above-grade load sharing could improve the crashworthiness of the anti-ram bollard systems that were studied. Of the configurations that were investigated, the most effective load sharing member design was a single HSS member connecting the vertical bollards near their exposed free ends
Evaluation of Live-Load Lateral Flange Bending Distribution for a Horizontally Curved I-Girder Bridge
No full textThis paper focuses on levels of live-load lateral bending moment (bimoment) distribution in a horizontally curved steel I-girder bridge.Work centered primarily on the examination of (1) data from field testing of an in-service horizontally curved steel I-girder bridge and (2) results from a three-dimensional numerical model. Experimental data sets were used for calibration of the numerical model and the calibrated model was then used to examine the accuracy of lateral bending distribution factor equations presented in the 1993 Edition of the (AASHTO) Guide Specifications for Horizontally Curved Bridges. It is of interest to examine these equations for potential use in preliminary design even though they have been eliminated during recent AASHTO specification modifications that addressed curved bridge analysis, the 2005 Interims to the AASHTO LRFD Bridge Design Specifications. In addition, they were developed using idealized computer models and small-scale laboratory testing with very few field tests of in-service full-scale curved steel bridges conducted to support or refute their use. Results from such experimental and numerical studies are presented and discussed herein
