PSI - Issue 78

Paolo Morandi et al. / Procedia Structural Integrity 78 (2026) 1293–1301

1298

conditions, infills are assumed to be significantly damaged or, in any case, no longer fully interacting with the structural system. The displacement limits (drift capacities) corresponding to the OP, DL, and SD limit states provided in the Guidelines are reported in Table 1 for the various masonry infill typologies, and are consistent with those in the prEC8 1-2 (2025). It should be noted that these deformation limits, derived from a preliminary evaluation of the results of a dataset with in-plane cyclic tests on frames with non-ductile infills (Dataset NDI, 2023) and ductile infills (Dataset DI, 2023), are still under review. In the case where different infill types coexist on the same floor, the most restrictive displacement limit must be adopted. The same applies to double-layer infill or partition walls, where the two wythes are of different types: the lower displacement limit shall be used. In the case of infill walls with openings, the limits provided in Table 1 should be reduced by at least 20%. Table 1. Drift capacity in function of the different infill typologies ( θ are the inter-storey drifts, h s the inter-storey height).

5. Local effects on RC structural members due to infills In the case of infill walls in direct contact with the frame, it is necessary to verify the shear force acting on the RC columns due to the horizontal component of the compression strut induced by the presence of the infills. Fig. 5 illustrates the shear and bending moment distribution on a column resulting from the local thrust of the diagonal strut. This thrust increases with the stiffness and strength of the infill and may lead to brittle failures at the ends of columns that are not sufficiently strong. The Guidelines report that RC columns should be designed to resist the shear force generated by the thrust of the diagonal strut from the infill wall, acting over a length l c at the column ends. The following condition should be satisfied: , , ≥ , , (3) where V C,Rd,lc is the shear resistance over the length l c at the ends of the RC columns, and V C,Ed,lc is the shear force over the same length, caused by the horizontal component of the infill thrust. It is recommended that the length l c of the columns, over which the compression force of the diagonal strut from the infill wall is applied, be verified in shear with respect to the lower value, V C,Ed,lc , of the following two shear forces: V C,Ed,w , which is the maximum horizontal component of the force transmitted by the diagonal strut of the infill wall (for example equals f v t w L w , where f v is the shear strength, t w and L w the thickness and the length of the infill) and V C,Ed,M which assumes that the flexural resistance of the column M C,Rd develops at both ends of the contact length l c ( γ Rd is the overstrength factor, equal to 1.30 for ductility class “A” and 1.10 for class “B”): , , = � , , = ; , , = 2 , � (4) Other methods are also presented in the Guidelines, including the approach proposed by Hak et al. (2013), which introduces an “activation” reduction factor ( ≤ 1) of the maximum lateral force of the strut as a function of the in-plane drift at SD, the method described in prEC8-1-2, and the criterion developed by Di Trapani et al. (2024) for estimating shear demands on columns when the infill is explicitly modelled using diagonal struts. Finally, a method for the evaluation of the additional shear on the columns caused by the thrust of ductile infills with sliding joints has been introduced in the Guidelines according to studies by Pelucco et al. (2025) and Preti et al. (2019).