Keywords: unreinforced, masonry, out-of-plane, bending, seismic, design, ABAQUS.

In the German market, unreinforced masonry is still the main construction material for residential homes. Research to determine the in-plane capacity of cyclic shear walls has been carried out during recent years. For example within the framework of the European research project ESECMaSE [1] resulting in feasible seismic design approaches. A very important aspect, the out-of-plane stability of unreinforced masonry walls, still needs to be further investigated. Out-of-plane failure was one of the main problems observed in unreinforced masonry structures after the earthquake events in Germany especially in the upper stories where low vertical load levels and amplified accelerations are present.

In order to properly design unreinforced masonry walls subjected to out-of-plane loading, a detailed knowledge of the seismic input at each story and the behaviour of walls with different boundary conditions and geometries is necessary. Seismic codes such as EC 8 [2] or NZS 1170.5 [3] provide simplified procedures to determine the seismic input according to the position of the structural element within a building. The verification is mainly carried out based on slenderness criteria and geometry limitations or by using simple design approaches as defined in EC 6 [4]. Where simplified approaches are not applicable, the dynamic stability has to be checked by using realistic acceleration time histories which is a difficult task for practicing engineers considering the complex behaviour of masonry structures subject to seismic loading.

Numerical models of masonry walls are currently under development using the finite element toolkit ABAQUS. The simulations will help to better understand the out-of-plane behaviour of unreinforced masonry structures within the context of the entire building. The research will help to critically check and improve the simple design procedures available at present.

1

ESECMaSE, "Enhanced Safety and Efficient Construction of Masonry Structures in Europe", http://www.esecmase.org

2

DIN EN 1998-1:2004, "Eurocode 8: Design of structures for earthquake resistance - Part 1: General rules, seismic actions and rules for buildings", German version, Deutsches Institut für Normung e.V., Beuth Verlag, Berlin, April, 2006.

3

NZS 1170.5:2004, "Structural Design Actions - Part 5: Earthquake actions", Standards New Zealand, Wellington, New Zealand, December, 2004.

4

DIN EN 1996-1-1:2005, "Eurocode 6: Design of masonry structures - Part 1-1: General rules for reinforced and unreinforced masonry structures", German version, Deutsches Institut für Normung e.V., Beuth Verlag, Berlin, January, 2006.

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