Full Size Test of an AASHTO Type IV Bridge


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Title: Full Size Test of an AASHTO Type IV Bridge

Author(s): Ignacio Martin

Publication: Concrete International

Volume: 3

Issue: 6

Appears on pages(s): 36-41

Keywords: beams (supports); bridges (structures); cracking (fracturing); deflection; failure; failure mechanisms; flexural strength; girders; loads (forces); precast concrete; prestressed concrete; research; safety factor; strains

Date: 6/1/1981

Cracks in AASHTO Type IV precast bridge beams cast doubts on the strength of these precast prestressed concrete products. It was decided to test one of these beams to failure. As the strength of the precast beam was questioned, the test was limited to the girder without the deck slab. This facilitated the test setup because it was necessary to apply smaller loads to fail the beam, but the type of failure to be expected was a sudden compression failure rather than the ductile tension failure that would be expected of the beam in the bridge. Static loads to simulate the dead load, live load, and twice the live load were applied to the beam, using three concentrated loads. Failure was induced by subjecting the beam to a monotonically increasing equivalent uniform loading. The beam behavior during the test was excellent, as evidenced by the measured deflections, section rotations, end rotations, and crack pattern and distribution. The beam failed at a bending moment 13 percent higher than the predicted failure moment for design conditions. The cracks at the ends of he beam did not increase or progress during the test. It may be concluded that the tested beam behaved as predicted by prestressed concrete theory.