Keywords: earthquake, timber structures, lightweight structure.

The selection of environmentally responsible building products and systems is a central aspect of sustainable building. Wood has been used as a building material for centuries. Wood is strong, lightweight, very easy to use and to manufacture into new products. Wood also possesses positive environmental attributes; not only is wood the single major renewable building material, but it also requires less energy to manufacture than any other building material [1].

Wood is also a renewable material. It can be used for construction, furniture, food handling, packaging, pallets and transport applications. At the end of its first life, wood or a wood-based product can be reused, recycled or used as a carbon-neutral source of energy. Respect for the carbon cycle will produce greatest benefits not only from a longer period of carbon storage, but also from the energy and finite resources saved from the production of alternative fossil-based materials [1].

A lightweight glulam timber structure is analyzed. The span of the structure is 33 metres. The static system is a three hinged system with a steel truss. The total length of the building is 65 metres. The purlins are simple supported beams with a span between the main girders of 7.15 metres. A very detailed finite element model of the structure is made.

The concrete structure has the same dimensions as the timber (the total length of the structure, span and spacing between main girders are the same as described earlier). The material chosen is concrete C30/37. The main girder is a prestressed beam of cross-section 35x160 cm.

The structure is analyzed using modal response spectrum analysis according to Eurocode 8 (EN 1998) [2]. As it is intended to compare various spectrum curves, all ground types defined in EC8 are analysed (A, B, C, D and E). Damping is assumed to be 5% for the concrete structure and 7% for the timber structure. The seismic load is applied both horizontally and vertically.

Linear time history analysis is made by using three real accelograms representing earthquakes in Croatia. The earthquakes are selected from two basic criteria: a magnitude of 6 or greater and a peak horizontal acceleration of 2 m/s² or greater.

All ground types defined in EC8 are analysed (A, B, C, D and E). For the purpose of the calculation of the total base shear, square root of sum of squares (SRSS) method is used. The results and discussion concerning the response spectrum and time history are given.

This paper shows that lightweight structures such as timber structures have an excellent response during seismic action (forces and displacements are rather small so that the structure remains elastic). Given all the advantages of these structures, the authors suggest using timber structures in seismically active regions.

1

CEI-Bois, "Tackle Climate Change: Use Wood!", CEI-Bois Roadmap2010, Canada, 2007.

2

Eurocode 8: Design of Structures for Earthquake Resistance, Part 1: General Rules, Seismic Actions Rules for Buildings, CEN. Brussels, 2003.

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