Abstract
Two full-scale building specimens were tested on the shake-table at the EUCENTRE Foundation laboratories in Pavia (Italy), to assess the effectiveness of an innovative timber retrofit solution, within a comprehensive research campaign on the seismic vulnerability of existing Dutch unreinforced masonry structures. The buildings represented the end-unit of a two-storey terraced house typical of the North-Eastern Netherlands, a region affected by induced seismicity over the last few decades. This building typology is particularly vulnerable to earthquake excitation due to lack of seismic details and irregular distribution of large openings in masonry walls. Both specimens were built with the same geometry. Their structural system consisted of cavity walls, with interior load-bearing calcium-silicate leaf and exterior clay veneer, and included a first-floor reinforced concrete slab, a second-floor timber framing, and a roof timber structure supported by masonry gables. A timber retrofit was designed and installed inside the second specimen, providing an innovative sustainable, light-weight, reversible, and cost-effective technique, which could be extensively applied to actual buildings. Timber frames were connected to the interior surface of the masonry walls and completed by oriented strands boards nailed to them. The second-floor timber diaphragm was stiffened and strengthened by a layer of oriented-strand boards, nailed to the existing joists and to additional blocking elements through the existing planks. These interventions resulted also in improved wall-to-diaphragm connections with the inner leaf at both floors, while steel ties were added between the cavity-wall leaves. The application of the retrofit system favored a global response of the building with increased lateral capacities of the masonry walls. This paper describes in detail the bare and retrofitted specimens, compares the experimental results obtained through similar incremental dynamic shake-table test protocols up to near-collapse conditions, and identifies damage states and damage limits associated with displacements and deformations.
Highlights
During the last few decades, gas extraction activities have exposed the region of Groningen, in the North-East area of The Netherlands, to induced seismicity
This paper describes in detail the bare and retrofitted specimens, compares the two experimental dynamic responses up to near-collapse conditions, and identifies damage states and damage limits associated with displacements and deformations
The building prototypes reproduced some relevant features of an end unit of common Dutch terraced houses of the late ‘70s–early ‘80s, with perimeter cavity walls consisting of inner load-bearing calcium-silicate leaf and exterior clay veneer, connected by steel ties
Summary
During the last few decades, gas extraction activities have exposed the region of Groningen, in the North-East area of The Netherlands, to induced seismicity. Following a series of low-intensity earthquake events which caused minor, yet diffuse damage in the region, a comprehensive research project was conceived to assess and eventually mitigate the local seismic risk (Dost et al 2012; Dost and Kraaijpoel 2013; Bommer et al 2016). Two-storey terraced houses built in the late ‘70s–early ‘80s (Fig. 1) constitute one of the most common and earthquake-vulnerable building typologies within the Groningen region This residential typology combines structurally-independent adjacent units, with discontinuous floors and roofs usually supported by single-wythe calcium-silicate (CS) walls. Two identical full-scale specimens, representing the end-unit of a typical two-storey terraced house, with unfavorable construction details, were designed, built, and tested on the shake-table of the EUCENTRE Foundation. Further details on the shared data can be found in Miglietta et al (2019)
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