Analytical Results

The predicted and experimental load-deflection envelopes for the three bridge decks are compared as shown in Figure 21. It can be seen that the predicted load-deflection behaviors of the three bridge decks compared very well with the measured values. The initial and post-cracking stiffnesses were very accurately predicted by the analytical model. In addition, the ultimate load was very reasonably predicted considering the fact the two spans of the second and third bridge decks failed in two different modes. However, the predicted ultimate deflection was slightly less than the experimental values; this is due to the nature of the smeared cracking methodology adopted by the program. For validation purposes the contours of the principal strain at failure and the portion of the first bridge deck that failed due to punching failure are shown in Figure 22. The strain contours depict the punching shear cone developed which matches very well the experimental failure shear cone.

Conclusions

1. The ultimate load carrying capacity of the three bridge decks tested in this investigation was eight to ten times the service load specified by AASHTO Design Specifications (1998).

2. Punching shear failure was the primary mode of failure for the three bridge decks tested.

3. Punching failure resulted in sudden decrease of the load carrying capacity, while flexural failure resulted in gradual decrease of the load carrying capacity.

4. Bridge decks reinforced with MMFX steel exhibited same deflection at service load but de­veloped more load carrying capacity when compared to decks reinforced with Grade 60 steel with the same reinforcement ratio.

5. Bridge decks reinforced with 33% less MMFX steel developed the same ultimate load carrying capacity and deflection at service load as those reinforced with Grade 60 steel. This is attributed to the higher strength of the MMFX steel compared to Grade 60 steel.

References

American Association of State Highway and Transportation Officials, 1998, ? “AASHTO LRFD Bridge Design Specifications”, Washington, D. C.

American Concrete Institute (ACI), 2002, “Building Code Requirements for Structural Concrete”, ACI 318-02, Farmington Hills, Michigan.

James, R. G., 2004, “ANACAP Concrete Analysis Program Theory Manual”, Version 3.0, Anatech Corporation, San Diego, CA, 2004.

Kinnunen, S. and Nylander, H., 1960, “Punching of Concrete Slabs without Shear Reinforcement”, Transactions of the Royal Institute of Stockholm, Sweden, No. 158.

Marzouk, H. and Hussein, A., 1991, “Punching Shear Analysis of Reinforced High-Strength concrete Slabs”, Canadian Journal of Civil Engineering, 18, 954-963.

Mufti A. A. and Newhook, J. P., 1998, “Punching Shear Strength of Restrained Concrete Bridge Deck Slabs”, ACI Structural Journal, 95(4), July-August, 375-381.

OHBDC, 1991, “Ontario Highway Bridge Design Code”, Ministry of Transportation of Ontario, Downsview, Ontario

Rashid, Y. R., 1960, “Ultimate Strength Analysis of Prestressed Concrete Pressure Vessels”, Nucl. Eng. & Design, pp. 334-344.