borri@unipg.it
Le carenze strutturali del patrimonio edilizio italiano, prime fra tutte la scarsa qualità meccanica delle murature e la mancanza di collegamenti tra i diversi elementi strutturali, emergono drammaticamente in occasione dei terremoti, pur con aspetti e sfumature di volta in volta differenti, ma con esiti comunque troppo spesso infausti e luttuosi.
Nel presente lavoro si prende spunto da alcune osservazioni generali sul comportamento degli edifici in muratura, svolte in Emilia Romagna dopo il recente terremoto. Dopo una classificazione ragionata delle principali problematiche osservate, si focalizza l’attenzione su alcuni aspetti del comportamento della muratura in laterizio sottoposta ad azioni orizzontali parallele al proprio piano e si propongono alcune tecniche innovative di rinforzo che si ritengono idonee per tali tipologie murarie. Si mostrano inoltre i risultati delle prime sperimentazioni condotte su murature in mattoni e malta di scarsa qualità, sia non rinforzate che rinforzate con intonaco armato con GFRP. Le sperimentazioni illustrate consistono in prove in situ di compressione diagonale in un edificio di San Felice sul Panaro (MO). Infine si valutano gli effetti del rinforzo mostrando i risultati dell’analisi pushover prevista dalle vigenti NTC 2008 su due edifici.
The structural vulnerabilities of the Italian building heritage, first of all the poor quality of masonry from a mechanical point of view and the lack of connection between the different structural elements, come to light dramatically during earthquakes, even with aspects each time different, but with outcomes, however, too often unfortunate and tragic.
This paper draws on some general observations on the behavior of masonry buildings, carried out in Emilia Romagna after the recent earthquake. After a rational classification of the main problems observed, the attention is focused on certain aspects of the behavior of brick masonry subjected to horizontal actions parallel to its plane and propose some innovative techniques of reinforcement that seem to be appropriate for these types of masonry. We also show the results of the first experimental tests on walls made of bricks and poor quality mortar and on the same walls reinforced with a GFRP grid. The experimental tests consist in diagonal compression tests on a building in San Felice sul Panaro (MO). Finally, it is assessed the effect of reinforcement showing the results of pushover analysis of two buildings as required by the current Italian Building Code (NTC 2008).
It should be noted that the current Italian Building Code and the commercial structural software take into account only partially the resistant contributes of such masonry type and, on the contrary, underestimate some weakness aspects. In particular, as it will be seen, the texture of the bricks and the quality of the mortar can strongly influence the mechanical behavior of such types of masonry and that the current Italian Building Code take it into account in a very superficial way, proposing values of strength and deformability that for the walls of bricks appear in many cases (and in particular in Emilia) far from reality.
Therefore it is possible to remark once again the importance of a correct characterization of these types of masonry, in order to properly assess the behavior that can be expected from those walls.
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