Improved Serviceability Criteria for Steel Girder Bridges

Abstract

Current AASHTO LRFD Bridge Design Specifications Service I deflection limits are in place with the purpose to prevent deformation-induced structural damage and psychological user discomfort from excess bridge vibration. Previous research has shown that deflection criterion alone is insufficient in controlling excess bridge vibrations and structural deterioration of the concrete deck. Previous research shows that natural frequency criteria better controls excess vibration than deflection criteria alone. In addition, previous research shows no significant correlation between deflection and structural deformation of the concrete deck slab. To better control excess bridge vibrations and deformation-induced structural deterioration, two new separate criteria formulations are proposed. The first formulation consists of a natural frequency criteria transformed into deflection-type terms familiar to the typical bridge engineer. The second proposed formulation directly controls the acting flexural strain in the concrete deck to control deformation-induced structural damage. The proposed serviceability criteria are applied to a database of 185 steel girder bridges. Both the as-built behavior and the design optimized behavior are examined and compared with current AASHTO serviceability criteria. The proposed user comfort and deformation-induced damage serviceability formulations are intended to be incorporated into ongoing Federal Highway Administration and bridge industry long-term bridge performance research where serviceability criteria is an important component.