Analytical and Experimental Study of the Contribution of Steel Casing to Single Shaft Foundation Flexural and Shear Resistance
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The objective of this dissertation is to investigate how to account for the contribution of steel casing to the structural resistance of the single shaft foundations that are encased in a permanent steel casing and are supporting a Reinforced Concrete (RC) column at their top. To investigate the contribution of the existing steel casing to the structural resistance and seismic response of the single shaft foundations of bridges, the composite action between the steel casing and the interior RC shaft has been investigated by means of analytical studies and two series of tests including thirteen large scale cyclic flexural and shear tests of Reinforced Concrete Filled Steel Tube (RCFST) shafts. The bond at the concrete-to-steel tube interface is a controlling parameter in achieving the composite action in RCFSTs. This bond is provided by means of sufficient existing friction at the interface. In case of lack of sufficient friction, shear transfer mechanisms can be used at the interface at the top of the shaft and below the point of maximum moment below the soil level. Equations were proposed for designing such transfer mechanisms and also for calculating the shear strength of RCFSTs. Revisions were proposed to existing AASHTO documents.