TIMBER-BASED SEISMIC RETROFIT TECHNIQUES FOR EXISTING MASONRY STRUCTURES IN NORTH EUROPE

This paper presents the results of an application of seismic retrofitting techniques to an existing masonry structure in Oslo. Due to low seismicity, the Norwegian National annex of 1998-1 (EC8-1, Standard Norge, 2021) allows omission from seismic design of several structures. Furthermore, the EC8-3 Norwegian National annex (Standard Norge, 2013) states that, unless the probability of collapse in the case of an earthquake changes significantly as result of a general refurbishment of the structure, it is not necessary to perform seismic retrofitting of the building. However there are cases where, depending on the geographical site, intended use or changes to the lateral force resisting structure, it is necessary to perform seismic analysis and possibly strengthen the building’s resistance to seismic forces. In this paper, a real case study is used to investigate how the effect of changes to shear walls due to a refurbishment intervention can reduce the capacity of a masonry building, and how two combined timber based retrofit systems can reduce the probability of collapse after the interventions: timber posts working as “strong-backs” with nailed OSB connected to the internal surface of the masonry walls; OSB panels applied to the timber floor.