NCHRP 12-93: Contribution of Steel Casing to Single Shaft Foundation Structural Resistance

Principal Investigator: Michel Bruneau

PhD Student: Hadi Kenarangi

Start Date: 6/13/2013

End Date: 1/31/2017

Abstract: Bridges are often constructed with a single enlarged shaft foundation supporting a column. In many cases the shaft foundation is constructed with a permanent steel casing. The steel casing is typically ignored in design when calculating the structural resistance of the shaft; only the reinforced concrete section of the shaft is considered for structural resistance. Bridge designers would like to account for the added structural resistance of the steel casing but there is limited research data as to when the steel casing and concrete inner core act as a composite section. This research project is conducted to determine under which conditions the shaft can be considered a composite section, which would be beneficial to design and could significantly reduce construction cost. The final deliverable of this research will be proposed revisions to the AASHTO LRFD Bridge Specifications for a single shaft foundation supporting a column to account for the contribution of steel casing including reinforced concrete confinement and composite action on structural resistance.