Shake Table Testing of a Two-Span Bridge Specimen with Unbonded, Pre-tensioned Rocking Columns

The dynamic, system performance of the precast pre-tensioned system was evaluated by shake table testing of a two-span, three-bent bridge at the NEES Facility at the University of Nevada, Reno.

The bridge was quarter scale, had two-column bents with 12in. (0.305m) diameter columns, and 30ft (9.14m) span lengths. The overall bridge geometry was similar to that of one previously tested at the University of Nevada, Reno that used conventional non-prestressed columns, cast-in-place concrete columns.

Clear heights of 6ft (1.83m), 8ft (2.44m), and 5ft (1.52m) were used for bents 1, 2 and 3 respectively. The column bases were embedded 22 in. (0.56m) inside the cast-in-place combined footing using a wet socket connection (Haraldsson et al. 2014). The tops of the column were integrally grouted into the superstructure using a hybrid-bar-socket connection (Davis et al. 2012). The column longitudinal reinforcement consisted of 6-#3 bars and 4-3/8 in. diameter epoxy coated prestressing strands.

Both low- and high-amplitude earthquake excitations were used to investigate the bridge response. The excitations were based on the 90 deg. and 360 deg. components of the Century City Country Club North (CCN90/CCN360) record from the 1994 Northridge California Earthquake; the 360 deg. component of the Sylmar- Olive View Med. Center (SYL360) record from the 1994 Northridge California Earthquake; and the 0 deg. component of the Takatori (TAK000) record from the 1995 Kobe, Japan Earthquake.