Shear Assessment and Strengthening of Contiguous-Beam Concrete Bridges Using FRP Bars


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Title: Shear Assessment and Strengthening of Contiguous-Beam Concrete Bridges Using FRP Bars

Author(s): P. Valerio, T.J. Ibell and A.P. Darby

Publication: Special Publication

Volume: 230


Appears on pages(s): 825-848

Keywords: bridges; fiber-reinforced polymers; prestressed concrete; reinforced concrete; shear; strengthening

Date: 10/1/2005

Many concrete bridges related to railways in the U.K. consist of prestressedrectangular concrete beams, post-tensioned together transversely to aid lateraldistribution of load; this bridge type has been repeatedly flagged as having insufficientshear capacity. Sixteen tests on small-scale beams, which are scaled-down replicamodels of the actual bridge beams, are presented. The specimens are tested under afour-point loading system and are both prestressed (PRC) with and without stirrups andnon-prestressed (RC) with and without stirrups, to provide full understanding of theirshear behaviour. Four further tests are then presented on RC beams strengthened inshear with FRP bars inserted from the soffit into pre-drilled holes and fixed in placeusing epoxy resin; this method allows strengthening in cases where the webs areinaccessible. Comparisons are made with current code predictions for the strength ofall specimens. The results show that unstrengthened RC beams behave mostly asexpected and as predicted by codes, while for PRC beams a great variation in shear-carrying capacity following shear cracking is observed for different span-to-depthloading ratios. The proposed FRP strengthening scheme is effective and providessignificant improvement to the shear-carrying load capacity.