PSI - Issue 78

Hadi Monsef Ahmadi et al. / Procedia Structural Integrity 78 (2026) 1745–1752

1751

4.2. Application of suggested hybrid configurations with different ductile web plate thickness

The effectiveness of the proposed hybrid retrofitting system was assessed through nonlinear static (pushover) analyses. The study compares unreinforced masonry (URM) walls strengthened with rigid steel grid plates of different thicknesses and hybrid configurations obtained by adding ductile thin steel web plates ( td = 1–3 mm thick) at selected grid locations. Table 1 reports the maximum lateral strength (Fmax) for each configuration, along with the non-dimensional coefficient α, which represents the normalized strength with respect to a reference case for each grid thickness ( t = 5, 10, 20, and 30 mm), evaluated from the work of Zizi et al. (2010). The results show that hybrid configurations consistently achieve higher lateral strength compared to their corresponding rigid grid-only systems. For instance, the configuration SPSW-G-10-3, consisting of a 10 mm rigid grid combined with 3 mm ductile inserts, reaches a 58% strength increase over the SPSW-G- 10 configuration (α = 1.58). Similarly, SPSW -G-30-3 reaches over twice the base shear of the SPSW-G- 5 reference (α = 2.35). These results confirm that the strategic insertion of ductile thin web plates within the rigid grid system leads to a substantial improvement in structural capacity.

Table 1. Maximum lateral strength and normalized strength coefficient (α) for retrofitted masonry walls with rigid and hybrid steel plate systems

t

td Fmax

Fmax (This study)

α (t =5 mm)

α (t=10 mm)

α (t=20 mm)

α (t=30mm)

(Zizi et al. 2021)

Specimens

mm mm kN

kN

-

-

-

-

SPSW-G-5 SPSW-G-10 SPSW-G-20 SPSW-G-30 SPSW-G-5-1 SPSW-G-5-2 SPSW-G-5-3 SPSW-G-10-1 SPSW-G-10-2 SPSW-G-10-3 SPSW-G-20-1 SPSW-G-20-2 SPSW-G-20-3 SPSW-G-30-1 SPSW-G-30-2 SPSW-G-30-3

5

-

620 720 800 880

- - - -

1.00 1.16 1.29 1.42 1.25 1.44 1.64 1.41 1.65 1.83 1.65 1.91 2.14 1.85 2.11 2.35

0.86 1.00 1.11 1.22 1.08 1.24 1.41 1.22 1.42 1.58 1.42 1.64 1.84 1.59 1.81 2.03

0.77 0.90 1.00 1.10 0.97 1.12 1.27 1.09 1.27 1.42 1.28 1.48 1.66 1.44 1.63 1.82

0.70 0.82 0.91 1.00 0.88 1.02 1.16 0.99 1.16 1.29 1.16 1.34 1.51 1.31 1.48 1.65

10 - 20 - 30 -

5 5 5

1 - 2 - 3 -

777.94 896.47 1019.91 878.13 1022.90 1136.05 1025.34 1182.44 1327.02 1150.81 1307.26 1459.57

10 1 - 10 2 - 10 3 - 20 1 - 20 2 - 20 3 - 30 1 - 30 2 - 30 3 -

5. Conclusions This study presents a numerical investigation on a hybrid retrofitting system for unreinforced masonry walls, combining rigid steel grids and ductile thin steel web plates. The analysis was carried out in multiple stages: first, the mechanical behavior of steel plate configurations was evaluated; subsequently, the most promising solutions were applied to masonry walls to assess their seismic performance. The results of pushover analyses show that the introduction of ductile web plates within rigid grids leads to a substantial increase in lateral strength, especially when the inserts are strategically distributed. The use of hybrid