Seismic Performance and Retrofit-Based Guidelines for DS-4 Unreinforced Masonry Buildings Evidence from Eight Real Case Studies

Marjo Hysenlliu; Altin Bidaj; Enio Deneko; Hysein Bilgin

doi:10.15157/ijitis.2026.9.1.238-261

Authors

Marjo Hysenlliu Department of Mechanics of Structures, Polytechnic University of Tirana, Albania https://orcid.org/0000-0002-0863-2112
Altin Bidaj Department of Mechanics of Structures, Polytechnic University of Tirana, Albania https://orcid.org/0000-0002-1101-6310
Enio Deneko Department of Mechanics of Structures, Polytechnic University of Tirana, Albania https://orcid.org/0009-0000-7236-5242
Hysein Bilgin Department of Architecture and Engineering, Epoka University, Tirana, Albania https://orcid.org/0000-0002-5261-3939

DOI:

https://doi.org/10.15157/ijitis.2026.9.1.238-261

Keywords:

Unreinforced Masonry, Seismic Assessment, DS-4 Damage State, Pushover Analysis, Structural Retrofit, Performance-based Evaluation, Eurocode 8

Abstract

Unreinforced masonry (URM) buildings constitute a substantial share of the existing building stock in many seismic regions and have repeatedly demonstrated poor seismic performance during recent earthquakes. After strong ground motions, a significant portion of these structures are classified as severely damaged (DS-4), a condition that typically requires detailed structural assessment and retrofit in order to restore acceptable safety levels. Although the seismic behaviour of URM buildings has been widely investigated, practical performance ranges derived from real post-earthquake case studies remain limited, particularly for buildings already affected by severe damage. This study presents a seismic performance assessment of eight real URM buildings classified as DS-4 following the 26 November 2019 Albania earthquake. All buildings were subjected to detailed on-site inspections, material characterization through laboratory testing, numerical modelling, and nonlinear static (pushover) analysis. The seismic response was evaluated both in the damaged (existing) condition and after the implementation of retrofit interventions designed in accordance with Eurocode 8 – Part 3. A macro-element modelling approach was adopted to ensure consistency in the evaluation of global capacity, drift limits, and ductility across the dataset. The results provide quantitative insight into the typical seismic capacity of severely damaged URM buildings and demonstrate the level of performance improvement achievable through commonly adopted retrofit strategies. Based on the synthesis of the eight case studies, realistic seismic performance ranges for DS-4 URM buildings are identified, together with target values for retrofitted configurations. The findings are intended to support engineers involved in post-earthquake assessment and retrofit design by providing reference benchmarks grounded in real building behaviour.