FRP-strengthened RC slabs anchored with FRP anchors

Abstract

Existing reinforced concrete (RC) structure can be strengthened upon the addition

of externally bonded high-strength light-weight fibre-reinforced polymer (FRP)

composites. An abundance of research over the last two decades has established

the effectiveness of the externally bonded FRP via extensive experimental testing.

Perhaps the most commonly occurring failure mode though is premature

debonding of the FRP and debonding generally occurs at strains well below the

strain capacity of the FRP. Debonding failures are undesirable as they are

typically brittle and represent an under-utilisation of the FRP material. A

straightforward means to prevent or at least delay debonding is by the addition of

mechanical anchors, however, research to date on anchors is extremely limited. Of

the various anchor concepts examined to date by researchers, this dissertation will

focus on anchors made from FRP which are herein referred to as FRP anchors.

The details and results of a program of research on the performance of FRP

anchors in FRP-strengthened structures are presented in this dissertation. An

extensive review of exiting literature helps establish knowledge gaps which serve

to justify the need and the scope of the research reported herein. A novel bow-tie

FRP anchor concept is then proposed and tested in smaller-scale single-shear

FRP-to-concrete joint assemblages as well as larger-scale simply-supported FRP-strengthened

RC slabs. The anchors are shown to increase the strength and slip

capacity of the joints by up to 41 % and almost 600 %, respectively, in

comparison with unanchored control joints. The anchors are then shown to

increase the load and deflection capacity of slabs by 30 % and 110 %, respectively,

above an unanchored control slab. In addition to strength, it is the ability of FRP

anchors to introduce deformability into FRP-strengthened RC slabs which is

particularly beneficial in order to produce safer structures.

An analytical model is then developed which is based on a novel quad-linear

moment-curvature response which can capture the complete load-deflection

response of the FRP-strengthened slabs anchored with FRP anchors. The

analytical modeling approach enables closed-form equations to be derived which

can then be used by design engineers to relatively easily construct load-deflections

responses and accurately predict member responses. Following the

concluding comments for the project as a whole, future research topics of

relevance are identified.