Specimen Details

The experimental program consisted of testing three full-scale bridge decks with a span-to-depth ratio of 12.5 to evaluate the structural performance of MMFX steel as main flexural reinforcement in comparison to the use of conventional Grade 60 steel. The bridge decks were identical in all aspects except for the type and amount of steel used in each. The bridge decks consisted of two spans and two cantilevers, supported in composite action by three pre-cast post-tensioned concrete girders having cross-sectional dimensions of 24 x 10 in. (610 x 254 mm). The overall nominal dimensions of the bridge decks were 21’ — 10” x 13’ — 2” x 8 5/8” (6655 x 4013 x 220 mm). The supporting girders were post-tensioned using deformed prestressing bars of 1 in. (25 mm) diameter with ultimate strength of 150 ksi (1034 MPa). Each girder was prestressed by four bars resulting in a total prestressing force of 360 kips (1601 KN) per girder.

The first and third bridge decks were reinforced with MMFX steel, while the second bridge deck was reinforced with conventional Grade 60 steel for comparison purposes. The test matrix is given in Table 1 and the reinforcement details for the three bridge decks are shown in Figure 1. It should be noted that the reinforcement ratio (p) is calculated using the total slab thickness. The first and second bridge decks were constructed with the same reinforcement ratio using MMFX and conventional Grade 60 steel, respectively. However, the third bridge deck was reinforced with MMFX steel using only two-third of the reinforcement ratio used for the first deck in an attempt to utilize the higher

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M. Pandey et al. (eds), Advances in Engineering Structures, Mechanics & Construction, 139-152.

© 2006 Springer. Printed in the Netherlands.

Bridge Deck

Steel Type

Bottom Reinforcement

Top Reinforcement

Transverse

Longitudinal

Transverse

Longitudinal

First

MMFX

#5 @ 6.75” (#16 @ 170) p = 0.54%

#5 @ 10” (#16 @250) p = 0.36%

#5 @ 6.75” (#16 @ 170) p – 0.54%

#4 @ 14” (#13 @360) p = 0.17%

Second

Grade 60

#5 @ 6.75” (#16 @ 170) p = 0.54%

# 5 @ 10” (#16 @250) p = 0.36%

#5 @ 6.75” (#16 @ 170) p = 0.54%

#4 @ 14” (#13 @360) p = 0.17%

Third

MMFX

#5 @ 10” (#16 @250) p = 0.36%

#5 @ 10” (#16 @250) p = 0.36%

#5 @ 10” (#16 @250) p = 0.36%

#4 @ 14” (#13 @360) p = 0.17%

Fig. 1. Reinforcement details for the three bridge decks.

tensile strength of MMFX steel. It should be noted that the first bridge deck was designed to simulate the same reinforcement ratio of an actual bridge that was built in Johnston County, North Carolina in 2004. The three bridge decks had the same span and thickness of the bridge, and supported by girders designed to have the same torsional stiffness as the actual bridge.