Quality of the Traditional Timber Houses in Croatia Proven in the M6.2 2020-Year Petrinja Earthquake

Traditional timber houses are still preserved in almost all villages in Pokuplje, a region in the continental part of Croatia. Due to the high-quality oak wood, abundant in nearby forests, and due to the method of construction, with horizontal timber elements (logs or, in later period, planks), connected well with carpentry joints, traditional timber houses have very good durability. Some houses withstood weathering and earthquakes for more than 400 years of their existence. These old structures proved their seismic resistance also in the damaging to heavily damaging 2020-year Petrinja earthquake (Richter scale Magnitude 6.2). This earthquake caused serious damage to many improperly built buildings, on bridges, roads and some of levees around Petrinja. The old timber houses, on the other hand, suffered only from some minor plaster cracks. The seismic resistance of traditional timber buildings is due to the high-quality oak wood and to the proper structural design with carpentry joints that allow micro-displacement. The timber walls, made of horizontal timber elements, connected with carpentry joints, were constructed on a base frame, made of strong timber beams. These frames were placed on isolated stone foundations which allow sliding and thus dissipation of seismic energy. As the displacements in horizontal direction are not hindered, when the earthquake occurs, the upper structure moves, thus dissipating a lot of energy.