School of Civil and Environmental Engineering
Ph.D. Thesis Defense Announcement
Effective Cross-Frame Framing Arrangements and Simplified Design for Straight Skewed and Nonskewed Steel I-Girder Bridges
By Ajit Manohar Kamath
Advisors:
Dr. Donald W. White (CEE), Dr. Ryan J. Sherman (CEE)
Committee Members: Dr. Yang Wang (CEE), Dr. Russell Gentry (ARCH), Dr. Francesco Russo (Russo Structural Services)
Date and Time: August 15, 2023, 12-2 pm EST
Location: Mason Classroom 2117 and Zoom Meeting Link: https://gatech.zoom.us/j/98759436135?pwd=NFk3NFlBbXNkcnJPaWtqYVhUYVQzdz09&from=addon
Straight skewed steel I-girder bridges exhibit three-dimensional behavior due to deformation compatibility considerations. Differential vertical displacements occur because intermediate cross frames connect to the girders at different locations along the girder lengths due to the skew. The cross frames twist the girders because of their high in-plane stiffness, imparting approximately equal twist rotations at the cross-frame-to-girder connections. The continuity effects with the girders can result in large cross-frame forces. Traditionally, many of these structures have been designed using 1D line girder analysis (LGA). Gaps in understanding the influence of cross-frame framing arrangements on three-dimensional behavior make the application of LGA challenging. This research discusses the influence of cross-frame framing arrangements on the three-dimensional behavior of straight skewed bridges under dead, live, and fatigue loads based on the 10th Edition of the AASHTO LRFD Specifications, and develops limits on and improvements in the application of LGA procedures. A 3D FEA parametric study was completed considering a range of geometric variables and cross-frame framing arrangements. Six framing arrangements, consisting of contiguous, staggered, and variations of lean-on framing, were studied for moderately skewed (skew index, Is ≤ 0.3) and highly bridge geometries (0.3< Is < 0.97). The influence of the framing arrangement on the bridge’s three-dimensional behavior is assessed and guidelines are provided for developing effective framing arrangements and application of LGA procedures for straight skewed and nonskewed bridges. Recommendations are provided for the selection of framing arrangements and sizing of cross frames.