PSI - Issue 44

Matteo Canestri et al. / Procedia Structural Integrity 44 (2023) 2198–2205 Canestri et al./ Structural Integrity Procedia 00 (2022) 000–000

2204

7

To evaluate the equivalent force acting on the confined masonry element, Eq. (1) can be used:

c  F A   masonry (1) where A masonry and A mortar are the cross- sectional area of the column and the SRG reinforcement, respectively. The stress on the mortar matrix σ m is calculated as proposed by Kent and Park (1969): m mortar A   

   

   

2

  

      

  





2

f 



(2)

m

m

m cm





, m peak

, m peak

where f cm is the mortar matrix compressive strength (Section 2.2), ε m,peak is the corresponding maximum strain value (taken equal to 0.005 mm/mm from the experimental tests on the matrix) and ε m is equal to the axial strain on the column ε c . To properly consider the effect of confinement on a square cross section, a simplification was introduced by dividing the cross-section in two regions: a fully confined area and a unconfined one. Their shapes can be analytically defined by the following parabolic expressions:

  

  

  

  

1

1 4

1

1 4

\ \ \ \ \ \

2

2

(2

)

(2

)

y

x

B W 

x

y

H W 

  

 

  

 

(3)

x

y

W

W

x

y

where B, H, W x and W y are the dimensions reported in Fig. 7 a . In Fig. 7 b , the cross-section of a SRG strengthened masonry column after the test clearly shows the distinction between the confined and unconfined portions, in line with the analytical expression of Eq. (3). In Fig. 7 c , the force vs displacement curves obtained with the analytical model are compared with the experimental ones. It can be observed that a good agreement was found, especially in terms of initial stiffness and peak load, while the prediction of the post-peak phase was less accurate, also due to the scattering of the experimental response.

Fig. 7. (a) Definition of confined and unconfined area for square masonry columns; (b) representative cross section at failure; (c) force vs vertical displacement curves with comparison between experimental and analytical results. 5. Conclusions In the present paper, the effectiveness of the use of SRG for the confinement of masonry columns was studied by testing 8 clay brick masonry columns in uniaxial compression condition. The columns were strengthened with 1 to 3 SRG layers. Comparisons between the behavior of the unreinforced and the strengthened samples, in terms of axial stress vs strain, showed that confined columns exhibited a strength increase proportional to the number of SRG