Evaluation of bracing systems in horizontally curved steel I-girder bridges
Open Access
- Author:
- Sharafbayani, Mohammadreza
- Graduate Program:
- Civil Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- September 05, 2012
- Committee Members:
- Daniel G Linzell, Dissertation Advisor/Co-Advisor
Jeffrey A Laman, Committee Member
Andrew Scanlon, Committee Member
Thomas E Boothby, Committee Member - Keywords:
- Plate Girder Bridge
Curved Bridge
Bracing System
Constructability
Service
Finite Element Method - Abstract:
- This work examined the effects of an innovative torsional bracing system, “skewed bracing,” on the behavior of horizontally curved I-girder bridges with non-skewed abutments. More specifically, the influence of this bracing system was studied on the performance of curved I-girder bridges during construction and while in-service. For this, the performance of the skewed bracing system was compared against that for a common type of bracing for horizontally curved bridges; bracing oriented normal to girder web. Studies were completed using three-dimensional, nonlinear finite element analysis. The first part of the study examined the effect of the proposed skewed braces on the behavior of non-composite horizontally curved I-girder bridges during construction and compared that behavior to existing bracing systems. Studies, first, completed on a single-span bridge having small radii of curvature indicated better load sharing between the girders during construction when skewed bracing was used. The significance of these benefits was extended through a number of parametric studies that investigated varying bridge plan geometries by examining different cross frame connection details, bracing type, brace spacings, girder number, and number of spans. For all cases examined, the skewed bracing, compared to normal-to-web bracing, was found to improve the structural behavior during construction, while generally required fewer intermediate braces. The second part of this research examined the performance of the skewed bracing arrangement on behavior of in-service, composite bridges. First, elastic behavior of the bridge members under unfactored live loading cases was investigated. Similar to the behavior of the non-composite girders under construction dead load, the skewed bracing, compared with the normal-to-web bracing arrangement, resulted in a slightly more uniform load sharing among the structural members in the composite bridge under the unfactored live loads. Next, the effect of changing the bracing arrangement on inelastic behavior of the girders and the concrete deck under an elevated ultimate loading case was studied. The skewed bracing, although used smaller number of intermediate braces, improved the inelastic behavior of girders and concrete deck.