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This paper presents an experimental and numerical study on different retrofit solutions for stone masonry buildings with timber diaphragms in earthquake-prone regions, aiming at enhancing wall-to-diaphragm connections, diaphragms’ stiffness, and masonry properties. The experimental results of incremental dynamic shake-table tests on three full-scale two-story buildings, complemented by material and component characterization tests, are initially summarized. The first building specimen was unstrengthened. The second one was retrofitted at the floor and roof levels with improved wall-to-diaphragm connections and a moderate increase in diaphragm stiffness. Connections were also improved in the third specimen together with a significant enhancement of diaphragm stiffness. The calibration of two numerical models, versus the experimental response of the retrofitted building specimens, is then presented. The models were further modified and reanalyzed to assess the effects of masonry mechanical upgrades, which could be achieved in practice through deep joint repointing or various types of jacketing. These solutions were simulated by applying correction coefficients to the masonry mechanical properties, as suggested by the Italian building code. The effectiveness of the experimentally implemented and numerically simulated interventions are discussed in terms of strength enhancement and failure modes.

A unidirectional shaking-table test on the half-scale prototype of a natural stone masonry building aggregate was performed as part of an extensive experimental and numerical research project, investigating the seismic vulnerability of historical buildings in the city of Basel, Switzerland. The prototype structure was characterized by architectural and construction details typical of Basel’s heritage residential building stock. The specimen represented a building aggregate consisting of two adjacent structural units, poorly connected on one side as if they were built at different times. The building specimen was three-story high and was built using double-leaf random stone masonry walls with undressed blocks and river pebbles. Timber floors, simply supported by the transverse walls, constituted flexible diaphragms in their plane. The two units were covered by roofs with different truss configurations, pitches, and side-gable wall heights. Steel wall-to-diaphragm connections were pre-installed but not initially fastened to the prototype; similarly, longitudinal and transverse steel tie-rods were also pre-installed at each floor without anchor plates. Both retrofit strategies were activated after a significant damage level was reached during the dynamic tests. This paper describes the seismic behavior of the prototype, analyzing the response of the bare masonry structure at various stages of the incremental dynamic test and investigating the effects of the retrofit interventions. The analysis focuses in particular on the dynamic behavior evolution, on the hysteretic response, and on the lateral displacement demand, in relation to the damage limit states associated with the observed mechanisms.

This paper focuses on the unidirectional dynamic shake-table test performed on a prototype of a natural stone masonry building aggregate. The half-scale prototype was designed to reproduce the features of existing unreinforced stone masonry building aggregates, typical of the historical centres in many European cities, including the city of Basel, Switzerland. The three-storey-high aggregate prototype consisted of two weakly connected structural units, with double-leaf undressed stone masonry walls incorporating a limited percentage of river pebbles. The specimen included flexible timber floor diaphragms and side-gabled timber roofs with different heights above the two units. Scaling the material mechanical properties of the specimen was necessary to satisfy similitude relationships without alter-ing accelerations and material densities. An incremental, unidirectional dynamic test was performed up to near-collapse conditions of the prototype, using input ground motions selected to be compatible with realistic seismic scenarios for the region of Basel. This paper summarizes the main characteristics of the specimen and illustrates the evolution of its dynamic response and damage mechanisms.