Nondestructive Testing and Identification for Bridge Rating. Phase 2. Steel-Stringer Bridges

摘要

Nondestructive dynamic field testing and structural identification studies onthree (2, 20, and 43-years old) steel-stringer bridges are presented. The bridges were rated by code procedures and by field-calibrated comprehensive 3-D finite-element models developed by structural indentification. Experimentally measured and analytically simulated modal flexibilities were correlated with bridge deflections obtained under proof-load level truck-load tests. Test results indicated that all three bridges, although constructed as noncomposite, exhibited composite action between the slab and girders. While the composite action was near-perfect in the 2-year old bridge, the older bridge exhibited partially-composite behavior due to deterioration of the chemical bond and friction. The rating factors obtained by field-calibrated models exceeded the corresponding operating rating factors by about two and half to four times for the three test bridges. The rating process and the resulting factors helped to identify and conceptualize a number of unresolved important issues that influence bridge rating and management.