Analysis and design of two-way slabs strengthened in flexure with FRCM

Fabric reinforced cementitious mortar (FRCM), an emerging sustainable retrofit technique, has seen very limited research and applications on two-way reinforced concrete (RC) slabs. In this study, a three-dimensional finite element (FE) model is developed for FRCM-strengthened slabs, incorporating concrete nonlinearity, cracking, debonding and rupture. After validation with experimental results from literature, an extensive parametric study was performed, examining the effects of FRCM coverage area as a ratio of the width of FRCM reinforcement (w(FRCM))-to-span (S); the use of discontinuous FRCM strips; internal steel reinforcement ratio (rho(s)); compressive strength of concrete (f(c)'); and aspect ratio of slab (alpha). The study showed that ultimate strength (P-u) increases sharply by 84% as (w(FRCM)/S) increased from zero to 0.25, then only by 19% from (w(FRCM)/S) of 0.25 to 1.0. In general, P-u increased with f(c)' and rho(s) but was not affected by alpha. Two existing models were evaluated and found to be unconservative or insensitive to key parameters. A regression analysis was performed on data from the parametric study, resulting in two expressions for the FRCM effective strain (epsilon(fe)) and much better predictions for P-u.