An application of sequentially linear analysis to settlement damage prediction for masonry façades

In Amsterdam, the North-South metro-link is being constructed underneath the urban historical city centre. This implies that historical masonry facades and monuments face the risk of being damaged due to the settlements imposed by the subsurface building activities. The situation is critical because we have the combination of very soft soil, timber pile foundations and brittle un-reinforced masonry. A representative Amsterdam masonry façades from 18-19th century is analysed. A crucial aspect of large-scale masonry structural behaviour is that cracks may initiate, gradually propagate and then suddenly snap to a free surface, thus the final fracture is localized and often highly brittle. Existing Newton-Raphson based non-linear finite element techniques face difficulties in modelling this, whilst softening results in negative stiffness, sharp snap-backs and bifurcations. In this paper, the sequentially linear analysis is proposed as an alternative approach. The paper illustrates the potential of numerical models to gain insight in the risks and in the need for mitigating measures to preserve the architectural heritage.