Experimental and numerical analysis of the structural behaviour of the groin vaults system of St. John Hospital in Jerusalem

The St. John Hospital is located in a strategic position in the Old City of Jerusalem, between the King David street and the suq spine; even if located in the Christian Quarter, it is close to the other three quarters: Muslim, Jewish and Armenian. In spite of its strategic position, the building is nowadays largely underutilised since currently partially serves as storage for the adjacent shops. The St. John Hospital was significantly changed over time, even through heavy demolition interventions. At present it looks like an irregular volume both in height and in plan, covered by ten groin vaults resting on very stocky pillars. In view of its historical significance, its architectonics features and its strategic position in the heart of the old city, UNESCO has included the St. John Hospital in a list of buildings subjected to “Adaptive reuse projects”, as described in [1,2]. These project profiles include architectural surveys and structural analysis at different scale and an early assessment of the structural condition, mainly aimed at the evaluation of the possible reuse options. In particular, conservation interventions have been recommended for the St. John Hospital, in order to preserve, reinforce and restore the structures of the building. Seeing the historical value of the building and the cited interest for eventual future reuse projects, an experimental and numerical study on the structural behaviour of the vaulted system of St. John Hospital where carried out as described in the paper. In particular, appropriate experimental investigation were carried out on a 1:5 scale groin vault, representative of the real system [3]. The laboratory scaled model was built with materials and construction techniques similar to those of the real building. The load bearing capacity and the collapse mechanisms of the scale model, resulting from a combination of a constant vertical load and a cyclic horizontal load (to simulate a seismic action), are determined from the experimental analysis. The experimental tests have been simulated using a commercial finite element code (ADINA) which implements an effective constitutive model able to simulate the mechanical behaviour of masonry. The parameters defining such model have been calibrated using standard tests carried out on the materials used to manufacture the scale vault. The predictions of the numerical simulations compare well with the structural response of the laboratory test.