Seismic Retrofitting of Rectangular Bridge Piers with Deficient Lap Splices Using Ultrahigh-Performance Fiber-Reinforced Concrete

Abstract

The effectiveness of an innovative retrofitting method using ultrahigh-performance fiber- concrete (UHPFRC) was investigated experimentally on RC bridge piers with deficient lap splice details. The objective is to study the performance of the proposed retrofitting technique for eliminating the bond failure mode in lap splice regions of rectangular columns with a cross-sectional aspect ratio exceeding 2. The strengthening technique consists of substituting the normal concrete around lapped bars in the splice region by UHPFRC. The test program includes unidirectional reverse cyclic tests conducted on five rehabilitated and one control rectangular large-scale specimens. The longitudinal reinforcement ratio ranged from 1.30 to 1.67% with bar diameters (db) equal to 25, 30, 35, and 45 mm. A splice length at the column base of 24db and stirrup spacing of 300 mm were used for all specimens to replicate column design practice before the introduction of modern seismic design specifications. The selected self-compacting UHPFRC mix contained 234 kg/m3 (3% by volume) of 10 × 0.20-mm straight fibers. The failure of all retrofitted specimens was progressive and ductile because they all failed due to the successive rupture of the dowel bars in the footing at a very high displacement ductility ratio. The lapped splice splitting failure mode was eliminated, whereas no longitudinal bar buckled. The UHPFRC cover integrity contributed to eliminate all failure modes associated with concrete damage (crushing, spalling). Recommendations for applying the proposed technique to deficient column rehabilitation are suggested.