Experimental performance and modeling study of a 30-year-old bridge with steel bearings

The strength and deformation characteristics of 30-year-old steel bridge bearings, both fixed and expansion, are presented on the basis of field and laboratory experiments. The interaction between the deck and the substructure is analyzed. Field experiments were performed on a two-span, slab-on-girder bridge at Niagara Falls, New York, where the bridge deck was cyclically loaded over the central pier by alternating the placement of a hydraulic jack, forcing the spans apart in transverse and longitudinal directions. For the transverse tests, a ratio of about 1.5 of high lateral force to tributary weight was observed without bearing failure. Overall deformation was due mostly to diaphragm action between the deck and bearings, with only minimal movement in the bearings themselves. For longitudinal loading the expansion bearings did not slide on the bronze-steel sliding surface as expected, but the sole plate slid at a friction coefficient of about 0.6. An analytical study of the longitudinal test is presented in an attempt to account for the effects of girder depth and to identify the abutment stiffness from the results of the field experiments. The conclusion is that such bearings should behave satisfactorily in the event of a moderate earthquake such as may be expected in the eastern and central United States.

Experimental performance and modeling study of a 30-year-old bridge with steel bearings Report