Anti-seismic construction

MARLES potres

Wood is, in addition to stone and brick, one of the oldest building materials, with solid wood structures already being built a thousand years ago. As a vivid example, let us mention the nine storey Sakyamuni Pagoda of Fogong Temple with a height of 67.3 m, the product of Chinese architecture, which was built in 1056 and still stands today despite the twelve earthquakes that have been recorded in the area.

The Sakyamuni Pagoda of Fogong Temple

Throughout history, we can find many examples of wooden structures that have successfully survived seismic loads. In Slovenia, there are also examples of Marles prefabricated houses with a wooden frame structure surviving earthquakes. After the earthquake in Posočje in 1976, more than 100 Marles wooden frame buildings were erected in that area. All these buildings survived the earthquake of 1998 without damage. This is a result of the fact that the seismic safety of Marles houses is verified by computational methods and practical tests in laboratories. This way, we can ensure our buildings are really safe in case of earthquakes. Finally, we largely participated with our buildings in the framework of the project of reconstruction following the earthquake in the region of Posočje.

Despite the fact that seismic danger has become less important in the mindsets of people since much time has elapsed since the earthquakes and that investors are reluctant to invest additional resources into seismic safety, we at Marles are aware of the importance of taking into account seismic load and carefully plan the design of earthquake-resistant prefabricated houses.  

Buildings in which the supporting construction is made of wood are called light-weight wooden buildings. They are manufactured mainly of wood, or only the supporting structure is made up of wooden elements and smaller cross-sections. The elements are interconnected by mechanical fasteners in wooden frames, so such structures are called wood frame structures. Sheathing boards attached with mechanical fasteners to the frame structure bearing the vertical load provide the frame structure with stability under the influence of horizontal loads such as wind and earthquakes. Thus, with proper design of the wood frame construction, careful planning and knowledge of the reaction of wood load-bearing elements to a horizontal load, Marles prefabricated houses are made earthquake-resistant and wind-resistant and are therefore safe wooden buildings.

However, the characteristics and the general assessment of behaviour of wooden structures during an earthquake cannot be generalised to all types of light-weight wooden structures, as prefabricated buildings differ significantly from one another in the very base of the wall element due to the use of various materials and fasteners. It is known that it’s difficult to make calculations for buildings with wood frame structures due to the large number of mechanical fasteners. This is the main reason why engineering knowledge about the behaviour of such structures, compared to structures from other materials, in seismic areas is often still highly deficient. That is why the mentioned knowledge has been nurtured and developed by Marles over decades and is also used in practice on a daily basis. Basic information required to calculate the whole structure includes the experimental behaviour of the contact between the sheathing board and the wooden frame exposed to a cyclically changing load. Based on the correlation of experimental and computational results for the basic wall unit in the wooden structure, the dynamic response of different structures under seismic load can be predicted with reliability and thus the comprehensive seismic safety of our buildings can be provided.