[CCoE Notice] FW: [CCOE Notice] PhD Dissertation Presentation (correction)

[Abercrombie, Irene F]

*correction of date, marked in red
PhD Dissertation Defense
Shear Behavior and Design of High Strength Concrete Prestressed Bridge Girders


Emad Leon Labib

 Date: Thursday  Friday, July 13, 2012
Time: 9:00 am
Location: CE Conference Room 107
Committee Chair: Dr. Yi-Lung Mo
Committee Members: Dr. Thomas T. C. Hsu
Dr. Abdeldjelil "DJ" Belarbi
Dr. Ashraf S. Ayoub
Dr. Mohamad Mansour
Dr. Gangbing Song


Prestressed Concrete (PC) I-beams are used extensively as the primary superstructure components in highway bridges. A simple semi-empirical equation was developed by the University of Houston (UH) to predict the shear strength of PC I-beams with normal strength concrete. The UH-developed equation is a function of shear span to effective depth ratio, concrete strength, web area and amount of transverse steel. This research work validates the UH-developed equation for (1) high strength concrete by testing ten 25-feet long full-scale PC I-beams with three variables, namely concrete strength, shear span to depth ratio greater than 1.60 and transverse steel ratio, (2) conservative design of the end zone where shear span to depth ratio is not greater than 1.60 to prevent premature failure due to shear-bond.
Ten modified Tx28 PC beams derived by scaling down the real TxDOT cross section with depth 54 inches and divided into three groups (A, F, and C) based on the concrete compressive strength were tested for the first objective. Beams in Group A were designed to have a balanced condition in shear. A pair of beams each belonging to Group F and Group C were designed to have a balanced condition while remaining beams were designed as over-reinforced sections. Each group of the PC beams was tested with different shear span to effective depth ratio.
The research findings proved that the shear capacities of PC beams depend mainly on the compressive strength of concrete and the shear span to effective depth ratio. The validity of the proposed UH-developed equation was ascertained using the beam test results. The UH-developed equation was found to accurately predict the ultimate shear strength of PC beams having concrete strength up to 17,000 psi. The UH method assumes that the concrete shear contribution in a PC beam is through the shear resistance of concrete along the 45 degree failure surface. The present study showed that this assumption remains valid for high strength concrete.
If the beam has been tested using a small span-to-depth ratio (not greater than 1.6), the web-shear capacity may be less than the recommended capacity if inadequate strand anchorage length is provided at the end of the girders. The beam may fail at a reduced load due to crushing at the intersection of web to flange, or splitting of the bottom flange due to strand pullout. Six beams of Tx-series with three different sizes and different percentage of transverse steel were tested in this research work to study the behavior of the end zone region.
Simulation of Concrete Structures (SCS), a finite element program recently developed at UH, is being used to predict the shear behavior of the tested beams with shear span to depth ratio greater than 1.6.






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