Shear strengthening of precast prestressed bridge I-girders using shape memory reinforcement: Fid-Bau Portal

Shear strengthening of precast prestressed bridge I-girders using shape memory reinforcement

Yaqub, Muhammad Arslan / Czaderski, Christoph / Matthys, Stijn

Abstract Existing bridge infrastructure requires careful monitoring, assessment and in some cases application of a suitable rehabilitation system to ensure proper operation through the service life of the structure. A large number of existing concrete bridge structures are composed of prestressed concrete (PC) I-girders that, either due to aging or more stringent design provisions, require rehabilitation. Research in the past has revealed challenges associated to shear strengthening of I-shaped girders with externally bonded fibre reinforced polymer (FRP). Given the concave shape of the cross section with bonded FRP, there is a tendency of severe debonding at the web-flange interface. Therefore, interest arises for more reliable solutions for shear strengthening of such an important cross section that is widely used in the concrete bridge industry. In search of an effective shear strengthening solution for PC I-girders, this study reports a detailed experimental program that uses memory steel reinforcement in the form of plain strips or ribbed rebars that are used as externally applied shear reinforcement in order to enhance the shear capacity. When fixed to the cross section, memory steel has an intrinsic property of recovering pre-induced strains during heating and subsequent cooling, as a result of which lateral prestressing is applied to the cross-section. Iron-based shape memory alloy (Fe-SMA) strips were wrapped and anchored at the top of the PC I-girder cross section, while, ribbed Fe-SMA rebars were used as near surface mounted (NSM) reinforcement. Each system was assessed in two different ways i.e. with and without heating/activation of the Fe-SMA shear reinforcement, in order to observe the difference between passive and active (prestressed) shear reinforcement. Fe-SMA shear strengthening provided an increase of 40 to 47% in the shear capacity of the studied PC bridge I-girders, whereby four full scale shear tests were executed in comparison to that of a control specimen without strengthening. The activated Fe-SMA shear strengthening configurations helped in controlling shear crack widths and showed better serviceability performance compared to the passive counterparts. Truss analogy for shear design has been applied to assess the shear contribution of Fe-SMA shear reinforcement, resulting in close estimation.

Highlights • Large-scale experiments on 10 m prestressed I-girders. • Iron based shape memory alloy reinforcement as externally applied shear reinforcement. • Different shear strengthening configurations. • Iron based shape memory alloy ribbed bars and plane strips were used. • Prestressed versus nonprestressed shear strengthening.