1 Université catholique de Louvain, Unité de Génie Civil et Environnemental, Louvain-la-Neuve, Belgium 2 Université catholique de Louvain, Centre for Systems Engineering and Applied Mechanics, Louvain-la-Neuve, Belgium Received: 21 April 2008 – Accepted: 23 April 2008 – Published: 2 June 2008 Correspondence to: S. Blaise ([email protected]) Published by Copernicus Publications on be...