Title:
Fibres as shear reinforcement in RC beams: an overview on assessment of material properties and design approaches
Author(s):
Barros, J.A.O.; Foster, S.J.
Publication:
Symposium Paper
Volume:
343
Issue:
Appears on pages(s):
111-120
Keywords:
Shear capacity, Mode I fracture parameters, Inverse analysis, Analytical models. fib Bulletin 95: Shear 111 https://
DOI:
Date:
10/1/2020
Abstract:
For the development of reliable physical-mechanical models for predicting the behaviour
of fibre reinforced concrete structures at service and strength limit conditions, constitutive
models simulating comprehensibly the governing phenomena must be used. In this context,
simulating the post-cracking mechanisms of the fibres, and their symbiotic relationship with
the cementitious matrix that surrounds them, is required for the development of realistic
modelling approaches that accurately represent empirical observations. Several experimental
test setups and inverse analysis procedures have been proposed to derive the fundamental
stress-crack width ( –w) law, but a consensus still does not exists on the best strategy for its
determination. In structures governed by shear, fibre reinforcement increases the stiffness and
shear stress transfer across a crack, but a methodology to capture the contribution of fibres in
this regards is challenging. To overcome this, a clear strategy is needed in deriving
relationships that simulate fibre reinforcement mechanisms in the mobilized fracture modes
and, also, develop design approaches capable of capturing the relevant contributions of the
fibres. This study firstly reviews current inverse analysis models used to describe the tensile
(Model I fracture) relationship for FRC and, secondly, discusses a newly proposed model,
referred to as the integrated shear model (ISM). The ISM is developed from mesoscale
observations from gamma- and X-ray imaging on FRC elements under Modes I and II
fracture conditions. The resulting model is compared to test data reported in the literature and
a good correlation is observed.