Date of Award

12-2016

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Civil Engineering

Committee Member

Thomas E. Cousins, Committee Chai

Committee Member

Bryant G. Nielson

Committee Member

Brandon E. Ross

Abstract

The Five Forks Bridge in Liberty, SC (Figure 7-1) is one of approximately 450 prestressed concrete channel bridges that the SCDOT oversees. Some of these channel bridges, such as the Five Forks Bridge, have unknown structural properties and flexural capacity. The Five Forks Bridge is a prestressed concrete channel bridge consisting of 33 girders that form three simple spans each 30 ft. in length. There are no formal design calculations available for some of these bridges and there are multiple prestressed strand designs that may describe the physical properties of each bridge. This project seeks to reveal the structural characteristics of the Five Forks Bridge and similar bridges through live load tests, laboratory channel tests, and analysis. A channel girder similar to those in the Five Forks Bridge was tested in a four point bending arrangement to experimentally determine the cracking moment and nominal strength of the girders that make up these bridges. Hand calculations were also carried out to compare the theoretical values for nominal strength, cracking moment, distribution factor for moment, and dynamic load allowance. After completion of the channel test, a forensic investigation was carried out in which the end of the girder was chipped away to discover the actual strand properties and layout. Comparisons of the live load test, channel test, and hand calculations revealed that the experimental nominal strength of the girders is 3% greater than theoretical calculations predict, the bridge possesses less load transfer than the AASHTO LRFD equations assume, and the bridge is insufficient to support the demand of the HL-93 design load set. The original load rating factors were modified with the experimental results and the Forks Bridge passed the legal load rating level with a rating factor of 1.14. No posting is needed for the Five Forks Bridge for all legal loads, but it is recommended that the SCDOT carry out future load ratings with assumed conservative bridge properties unless a nondestructive test is conducted.

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