Date of Graduation

2018

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Civil and Environmental Engineering

Committee Chair

Karl E Barth

Committee Co-Chair

Gregory K Michaelson

Committee Member

John P Zaniewski

Abstract

The Short Span Steel Bridge Alliance (SSSBA) is a group of bridge and culvert industry leaders (including steel manufacturers, fabricators, service centers, coaters, researchers, and representatives of related associations and government organizations) who have joined together to provide educational information on the design and construction of short span steel bridges in installations up to 140 feet in length. Within the SSSBA technical working group, a modular, shallow press-brake-formed steel tub girder was developed. This new technology consists of cold-bending standard mill plate width and thicknesses to form a trapezoidal box girder. The steel plate can be uncoated or galvanized steel, as each is an economical option. Once the plate has been press-brake-formed, shear studs are welded to the top flanges. A reinforced concrete deck is cast on the girder in the fabrication shop and allowed to cure, forming a composite modular unit. The composite tub girder is shipped to the bridge site, expediting construction and reducing traffic interruptions.;The increased use of the press-brake-formed tub girders has led to the recognition that long-term service life testing of different steel types in this system have not been investigated. The cold-bending of the steel plate into the desired tub-girder shape creates residual stresses in the bends of the girder. At this time, the majority of prefabricated bridge elements undergoing fatigue testing are of traditional structural shapes. It is currently unknown if the high heat of galvanization affects the residual stresses in the bends of the tub girder.;The scope of this project is to determine if hot-dip galvanization affects the fatigue performance of a cold-bent shallow press-brake-formed steel tub girder. Two composite steel tub girders were constructed, one composed of an uncoated steel tub and the second composed of a galvanized steel tub. The composite system was fatigue loaded simulating a 75-year life in a rural environment. At a predetermined number of load cycles, a Service II load was applied to the system to observe the performance of the specimen. Strain gages were applied to the webs and bottom flange of each section to determine the actual moments induced in the system. Experimental results were used to evaluate any difference in the performance of the different steels used in the composite tub girder system. Results from this project show the type of steel does not have an influence on the fatigue performance of press-brake-formed tub girders.

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