Unbonded Pretensioned Columns for Accelerated Bridge Construction in Seismic Regions

A new concept was developed to accelerate the construction of highway bridge bents, to improve their seismic resilience, and to make them more durable. On-site construction activities are accelerated by precasting the columns and cap beams and by using socket connections at the bottoms of the columns and grouted connections at the top. Unbonded pretensioning of the columns increases both the bridge's seismic resilience (through improved recentering) and its durability (through reduced cracking), whereas precasting improves quality control. Previous researchers have incorporated unbonded posttensioning into structural systems to reduce postearthquake residual displacements, but pretensioning is preferable in terms of construction convenience, speed, and quality control. Epoxy coating also adds corrosion resistance to the pretensioned strands. Two cantilever concrete subassemblies, representing the top and bottom connections for a column, were subjected to constant axial load and cyclic lateral loading. The tests demonstrated that the new system recenters better than does a comparable RC column. Furthermore, the inelastic action was restricted to the columns, thereby validating the capacity protection of the connection regions. (C) 2017 American Society of Civil Engineers.