Experimental and numerical analysis on flexural behavior of improved U-bar joint details for accelerated bridge construction

Abstract

U-bar loop connection is achieving widespread applications in the precast deck panel systems for accelerated bridge construction (ABC), while the welding operations on U-bars poses massive inconvenience and serious cost to the on-site assembly of precast deck panels. To eliminate the heavy welding operations and provide guidelines for design and detailing of U-bar loop connection, a total of nine specimens associated with three U-bar joint details are designed and examined through four-point bending tests. The experimental results suggest that welded splices can be omitted without affecting the moment capacity of wet joints. A notched double-loop connection is further developed to resolve fit-up issues resulting from the interference between studs and U-bars. The joint details involve setting notches at both ends of precast panels and placing additional looped bars in the specifically designed notches. The looped bars inserted in notches overlap with U-bars embedded in precast panels, therefore achieving the continuity of longitudinal reinforcement. The U-bar joints exhibit flexural failure characteristics and satisfactory bearing capacity in the experiment. Furthermore, the influence of lap length, concrete and steel grade, and lacer bars on the flexural behavior of U-bar joints is investigated based on 182 FE models, and the minimum lap length for spliced U-bars in notched double-loop connection is thereby determined. Besides, the proposed equations provide an estimate for the minimum lap length with reasonable accuracy.