Energy dissipation index for masonry walls with wallposts under vertical seismic effects

An energy dissipation index (EDI = Etot/(Puδu)) is proposed as an independent, dimensionless performance metric derived from a pool of 275 simulated out-of-plane (OoP) pressure–displacement (P–δ) curves obtained from pre-validated three-dimensional finite-element (FE) simulations, of which 223 with a fully identifiable post-peak branch were retained for EDI computation. Five wall categories were investigated spanning interior and exterior walls, with and without wallposts (types I and II) and openings, under three levels of vertical seismic acceleration (Ev = 0, 0.5g, 1.0g) – a parameter shown to have a major impact on OoP response. One-way analysis of variance confirmed highly significant inter-group differences (F = 56.0, p < 10−30, η2 = 0.51). The Pearson correlation between EDI and the response-modification factor (Rp) was r = −0.20 (R2 = 0.041), demonstrating that the EDI captured fundamentally different information. Lognormal fragility curves and reliability indices (β) were derived for each wall category, and a five-level performance classification (insufficient to excellent) is proposed based on the 15th and 85th percentiles. The results showed that exterior walls without openings achieved the highest energy dissipation capacity (median EDI = 23.2), whereas walls with openings exhibited considerable variability at typical demand levels.