PSI - Issue 64

Veronica Bertolli et al. / Procedia Structural Integrity 64 (2024) 1033–1040 1035 Veronica Bertolli, Lesley H. Sneed, Francesco Focacci, Tommaso D’Antino/ Structural Integrity Procedia 00 (2019) 000–000 3

behavior of the specific FRCM studied. Some models use the mechanical properties of the bare textile (Triantafillou and Papanicolaou (2006), Escrig et al. (2015), Tetta et al. (2018)), while others use the mechanical properties of the cracked FRCM (Ombres (2015)). One model is based on the simplified compression field theory (SCFT) (Wakjira and Ebead (2018)). Italian CNR-DT 215 (2018) and American ACI 549.4R (2020) guidelines are both based on Eq. (1) and Eq. (2), but they compute  fe starting from different hypotheses. CNR-DT 215 (2018) defines  fe from the bond behavior of the specific FRCM studied, whereas ACI 549.4R (2020) computes  fe starting from the ultimate strain and elastic modulus of cracked FRCM. Considering the available literature, a reliable design model for the shear strength contribution of U-wrapped FRCM should be able to take into account the mechanical and bond behavior of the specific FRCM considered (Ombres (2015), Bertolli et al. (2024)) and their variation with different numbers of textile layers (D’Antino et al. (2020)). It should also consider the presence (and amount) of internal transverse steel reinforcement (Gonzalez-Libreros et al. (2017a)).

Fig. 1. Elevation view of U-wrapped RC beam with a main diagonal shear crack having either T-shape or rectangular cross-sections.

In this paper, the contribution provided by EB U-wrapped FRCM to the RC beam shear strength is computed with the models proposed by Italian CNR-DT 215 (2018) and American ACI 549.4R (2020) guidelines. The shear strength predictions of these models are evaluated with respect to a database of experimental results of U-wrapped FRCM shear strengthened RC beams collected from the available literature. Comparison between the analytical predictions of CNR-DT 215 (2018) and ACI 549.4R (2020) and corresponding experimental results allowed to assess the accuracy of their design models, highlighting their different behavior in computing the FRCM reinforcement shear strength contribution when different types of fiber are used. 2. CNR-DT 215 (2018) and ACI 549.4R (2020) models for U-wrapped FRCM shear strength contribution Both the models by the Italian CNR-DT 215 (2018) and American ACI 549.4R (2020) guidelines are based on Eq. (2), and for both d fe is taken equal to the smaller of d f and z (Fig. 1). The model proposed by the Italian CNR-DT 215 (2018) guideline is based on Eq. (2) and computes  fe starting from the bond behavior of the specific interface studied, which can be determined directly with single- or double-lap direct or indirect shear tests (Sneed et al. (2015)). The model relies on the model proposed by D’Antino et al. (2020), neglecting the presence of friction. The value of the compressed strut angle can be 21.8° ≤  ≤ 45°, following the prescriptions of EN 1992-1-1 (2004). This model considers only PD fibers when computing V f .

     

   

   

L

L

1 3

σ

1

max L l 

max

max



fd

eff

l

l

eff

e

f

f

(3)

σ

 

fe

l

 

  

1 3

eff

σ 1

max L l 

 

f

d

e

f

f

L

max





min 0.9 , sin β

f d d

(4)

L



max