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Title: Live Load Distribution Factors in an I Girder Concrete Bridge with Excessive Vibration and Partial Deck Girder Composite Action

Author(s): Ikram Efaz

Publication: Web Session



Appears on pages(s):



Date: 10/17/2021

The current AASHTO provision for live load distribution factor (LLDF) of prestressed concrete I-girder bridges depends on several factors, such as span length, spacing and stiffness of girder. However, it does not take into account the effect of partially composite deck-girder interaction. The current study evaluated the LLDF of a newly constructed partially composite prestressed concrete I-girder bridge with excessive vibration issue on SH 75 in Dallas, TX. Impact Echo (IE) scans of the top of the deck revealed severe delamination at the cast-in-place (CIP)-precast deck panels and deck-girders interfaces. In addition, an initial and follow-up static load tests as well as vibration measurements showed that the excessive vibration was due to delamination-induced loss of composite action. Even though the theoretical calculated LLDF per AASHTO LRFD Bridge Design Specification for one lane loaded condition was 0.52, the LLDF values obtained from the load test were in the range of 0.26 to 0.43. It was concluded that the 21% to 50% significant reduction in the LLDF compared to the theoretical value was the result of stiffness degradation due to partial composite action. This finding necessitates developing a LLDF provision for partially composite prestressed concrete I-girder bridges that can be readily used for load rating.