D. H. CAMILLERI

Managing Partner DhiPeriti Building Consultancy Services Floriana FRN 1400 Malta.

dhc@dhiperiti.com

ABSTRACT

The Maltese archipelago has been inhabited since 3000BC and the evidence of occupation is preserved within the fabric of the cultural heritage. It is not clear whether it was the central Mediterranean location of the limestone resource which attracted the Temple Builders around 3000BC and resulted in the high concentration of Neolithic temples. Malta’s stable semi-arid Mediterranean climate resulted in durability for its compact limestone resource the use of which followed the tradition of excavated burial chambers and for many centuries the use of caves by the Maltese as residences. A French study defines a compact stone having a crushing strength lying between 10N/mm2 and 40N/mm2, a soft stone <10N/mm2, and a hard stone >40N/mm2 [1]. There is little preservation of structures from the Arab occupation from 870 up to 1090. However the construction methods in vernacular construction used in Malta from this point to the mid-20th Century derive from the methods first introduced at this time. Some of this early work which included using weak rubble construction was destroyed in the earthquake of 1693. The expertise of the military engineers of the Knights of St. John who began to build Valletta in 1570 was shared with Maltese masons and led to significant structural improvements. The British period 1813-1964 brought along the Royal Engineers and introduced the neo-classical/gothic into masonry constructions. Steel joists were introduced and widely utilised in this period, embedded in masonry floor slabs. Building regulations were also introduced which had an effect on floor plans, with the traditional central courtyard layout overtaken by construction with a backyard. The British masonry codes of practice resulted in the construction of up to 8-storey cellular residential constructions rather than the previous maximum of 5 storeys. The aesthetics together with the  reverberation” {associated with seismic resistance} proportions of masonry spaces is introduced. The role of the structural engineer in designing a building is to establish their numerical competence with respect to both the aesthetic proportions and the impact which these have on the “reverberation” characteristics. A comparison is then drawn between the BS and EC masonry codes with the characteristic strengths for the Maltese masonry building block outlined in the respective codes. The seismic rigidity of the Maltese masonry constructions is then outlined according to EC8. The effect of blast loadings is also considered. It is found that a only a small number of buildings constructed in masonry and 8 storeys high, with ages just exceeding 100 years conform with the characteristic strengths in the EN masonry codes. The rigidity of these regular planned masonry constructions when subjected to low seismic risk is confirmed as adequate, however this is not so as when subjected to blast loadings. An appendix is provided which introduces a calculation for the verification of thin  masonry slabs, which was an important Maltese building element up to the mid-1960s. The importance of this structural check becomes necessary, when the building use is to be changed resulting in additional loading.

KEYWORDS: globigerina Franka limestone, vernacular construction, historic development.