Structural efficiency of the ‘Pombalino Frontal’ infilled with mortar

On November 1st, 1755, occurred a huge earthquake in Portugal which hit and destroyed Lisbon. In a previous paper, where we presented some research about pombalino system, we referred and noted that we were just in 1755, when the creation and development of the ‘pombalino building’ occurred, so the concept of stress and deformation had not yet appeared, but, despite this, the military engineers of the kingdom were able to create a remarkable construction system with anti-seismic characteristics. In the vertical frontal truss of the Pombaline System, the spaces between the vertical and horizontal plumbs are filled with mortar that contained small elements of stone and ceramic residues. This form of filling was not carried out in order to close the space, because at the time, even in the Pombaline building, the solution adopted to close space was different. This filling was designed by the engineers to provide the building with an additional energy dissipation system, although at the time humanity has not yet developed the concepts and theory of structural analysis and, obviously, the characterization and definition of the dynamic behaviour of a structure had not yet been achieved. The frontal element design suggests their engineers’ designers had at that time an accurate knowledge about the dynamic phenomenology involved in the seismic behaviour of the pombaline building. In this article we present structural calculations performed on a ‘frontal pombalino’ standard, used in the ‘Pombalino cage’, which demonstrate that the military engineers had not only a perfect understanding of the St. André cross potential, but they also know the role played by the filling mortar in the seismic response of the Pombaline building. The infill cracks when a seismic occurs and a large number of slits are formed, and each crack acts as an energy dumper (a power sink).