Mechanical parameters of historical masonry

Reference values of the mechanical parameters for different types of masonry. Normative references and usual values.

The first regulatory reference on the resistance parameters of existing masonry is provided by

CIRCULAR OF THE MINISTRY OF PUBLIC WORKS 30 JULY 1981 No. 21745
(SUPERIOR COUNCIL PRESIDENCY – CENTRAL TECHNICAL SERVICE)

LAW 14 MAY 1981 N. 219 – ART. 10.

INSTRUCTIONS RELATING TO THE TECHNICAL STANDARD FOR THE REPAIR AND STRENGTHENING OF MASONRY BUILDINGS DAMAGED BY EARTHQUAKE.

INSTRUCTIONS FOR THE APPLICATION OF THE TECHNICAL STANDARD FOR THE REPAIR AND STRENGTHENING OF BUILDINGS DAMAGED BY THE EARTHQUAKE.

In particular, Table 1 provides the following values:

Taking the solid brick and bastard mortar masonry as a reference, the reference values are t = 12 N / cmq and s = 300 N / cmq.

The note ordinance 3274 of 2003, in attachment 11.D reports different values but in some way attributable to the “Bolognese” type masonry:

In fact, since it is specified that these values (minimum and maximum), for historical masonry, refer to “hangings simply combined or poorly connected”, in the case of a typical Bolognese masonry performed in a workmanlike manner, the values can be multiplied reference for solid brick and lime mortar masonry for the improvement coefficient 1.3, obtaining the following average value:

s medio = (180 + 280) /2*1.3 = 300 N / cmq, corresponding to that indicated in Circular 21745 of 1981.

For single-headed Bolognese masonry it seems correct to apply the same improvement coefficient 1.3 as it is the single brick block that is also diatonic over the entire thickness.

The D.M. 14/1/2008 – Technical standards for constructions (NTC08) significantly increases some of these parameters; perhaps from 2003 (2005 if we consider the OPCM3431) to January 2008 a significant number of tests have been carried out …

whoever had news of it and wanted to share it would help the common understanding. On the other hand, paragraph C8A.2 of Circular 617 contains large excerpts of the text of OPCM3274.

On this update of resistances I found an article by Borri and De Maria (CUTTING BEHAVIOR OF EXISTING WALLS: EXPERIENCES AND EXPERIMENTS ALSO IN THE LIGHT OF THE EARTHQUAKE IN EMILIA) in which a numerical comparison is made between the cases of resistance of the masonry panel with mortar of poor or good characteristics:

The authors continue with the consideration that: “Currently, according to the NTC 2008, if no direct tests are carried out, the values shown in table C.8.A.2.1 can be assumed for the “brick and lime” type, which, however, can be much higher than the actual ones (therefore safety disadvantage) if the mortar is very poor,
or much lower than the real ones if the mortar is very good (see figure above). “

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