Author ORCID Identifier

https://orcid.org/0009-0009-5753-4170

Semester

Fall

Date of Graduation

2025

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Civil and Environmental Engineering

Committee Chair

Onur Avci

Committee Member

Michael Seek

Committee Member

John Quaranta

Abstract

Press-brake-formed tub girders have welded internal angle bracing that is believed to be necessary for torsional stability under eccentric loading. However, this bracing creates fatigue weld hotspots overtime, which are subject to cracking. This study was performed to assess the torsional behavior of the Valmont U12 press-brake-formed tub girder (PBFTG) under various configurations using finite element analysis (FEA) modeling and experimental laboratory testing. The primary objective was to (1) determine the necessity of various angle bracing throughout the beam, and the effects removing said braces has on the torsional stiffness of the girder and (2) investigate the use of stay-in-place forms (SIPs) as a possible source of torsional stability.

SIP formwork is commonly used in PBFTGs as concrete formwork, but is not considered a form of structural bracing under the American Association of State Highway and Transportation Officials (AASHTO) guidelines. After all internal bracing was removed, SIP forms were progressively added to the bridge and torsion testing was performed for each SIP added. Experimental cantilever testing was performed on SIP forms using combinations of screw patterns and end-types to obtain a diaphragm stiffness and connection strength value of the SIP forms. This diaphragm stiffness was then used in the finite element analysis of the PBFTG torsion testing to better represent the SIP forms used, and validate the results.

By performing laboratory testing on a 40-foot PBFTG and simultaneously modeling the test in the finite element analysis software SAP2000, the study was able to conclude that the center three angle braces provided no significant torsional stability to the girder, and could be removed in future production of the 40-ft Valmont U12 beam. Additionally, the study concluded that the diagonal bracing at beam ends proved to be necessary for torsional stability. Lastly, the study found that SIP forms do improve the torsional stability as the forms are added to the beam.

Download

Share

COinS