Timber and earthquakes

In the recent years several studies have proven that timber is a suitable and reliable building material also under extreme loading, such as the one caused by earthquakes, because of its light weight and high strength. Our group mainly focuses on the seismic performance of timber diaphragms and their connections to walls, both in as-built and strengthened configurations.

This research field is quite recent because in the Netherlands earthquakes were very rare in the past and not diffused across the country. However, gas extraction in the Northern region (Province of Groningen) caused local settlements of the ground, and finally also frequent sudden earthquakes.

In an area in which this problem was completely unknown and never experienced before, it is crucial to help people in finding again a safer and more comfortable feeling with respect to the place where they live. Therefore, it is necessary to characterize the seismic response of typical buildings belonging to this context, in order to quantify their own resistance in existing as-built configurations. Starting from this knowledge, it is then possible to create and design proper strengthening interventions, where they are needed, and also to build new earthquake-safe structures.

One of the most diffused characteristics of these existing buildings is the presence of flexible and light timber floors, which are often unable to efficiently transfer high seismic shear forces and can lead even to out-of-plane collapses of the surrounding walls due to their excessive deflection.

Especially for the Dutch context, in which small structural elements are normally used and each part of a building was designed just considering basic static rules, the development of suitable strengthening techniques proves to be necessary for these timber diaphragms and their connections to the (mainly) unreinforced masonry walls.

Our research in this framework is therefore related to the following key topics:

• Improvement of the in-plane stiffness of timber diaphragms by means of light and reversible techniques;
• Enhancement of the energy dissipation of the diaphragms, which leads to lower shear forces transferred to the walls;
• Development of analytical and numerical models as a basis of a correct design of the strengthening intervention according to specific needs and building conditions;
• Effective and reversible strengthening techniques for the improvement of the stiffness of floor-to-wall joints.