Seismic CFST Column-to-Precast Cap Beam Connections for Accelerated Bridge Construction

Concrete-filled steel tubes (CFSTs) frequently are a more efficient and economical structural solution then conventional reinforced concrete and structural steel. For the same size member, CFSTs offer increased strength and stiffness as well as accelerated construction. CFSTs may be used for bridge columns that will yield under earthquake loading, but this requires robust connections capable of sustaining large cyclic loads. To facilitate accelerated bridge construction, precast cap beams and girders are commonly used. Although CFST column-to-foundation connections have been studied, CFST column-to-precast cap beam connections have not. This is the focus of this research study. In contrast to cast-in-place (CIP) components, precast pier cap connections require additional design considerations including construction methodology and limits on geometry. To investigate this connection an integrated analytical and experimental research program was performed. Initially, continuum finite-element methods were used to conduct a parametric study; the results from that study determined the values of the study parameters and selection of the experimental specimens. Three different connection types were studied: (1) an embedded ring CFST, (2) a welded dowel, and (3) an interior reinforced concrete connection. Large-scale, pseudostatic tests were conducted. Results from the experimental investigation showed that the three connection types provide excellent deformability under reversed-cyclic loading and minimized damage in the cap beam.