The characteristics of the load -bearing masonry
Ordinary built -in masonry buildings have one Good compression resistance for static loadshowever they suffer from poor traction resistance. Therefore seismic actions of medium-high intensity can induce traction stresses that exceed the main capacity of the material.
Furthermore, often the box behavior of the wall structure, especially if old, is never perfect but presence Deformable strokes and deformable floors which compromise seismic safety by activating partial reversals of the walls and serious damage on their plan.
Player masonry: an innovative solution
These critical issues are resolved by the new construction method of Army masonry that combines full brick blocks or semipies (with a drilling less than 45%), reinforced with a minimum quantity of horizontal armor for the cut resistance (in the joints of Malta) and vertical for the flexion resistance (in special housings prepared in the blocks).
The horizontal bars must have a minimum diameter of 5 mm and must be inserted in the Malta beds with intensity not exceeding 60 cm (i.e. 3 block courses), anchoring them adequately to the ends of the walls by hooks or folds around the vertical bars. The percentage of horizontal armor, calculated with respect to the gross area of the vertical section of the wall, cannot be less than 0.04%, nor greater than 0.5%. The vertical armor consists of at least 2 cm² (1 8) to be placed at the ends of each supporting wall, to each intersection between bearing walls, in correspondence with each opening and in any case with those with no more than 4 m.
The insertion of the armor bars gives the traction resistance that is missing from traditional brick construction, as well as exploiting better compression resistance of the blocks. This ensures a improvement of the main verification parameters (die -cast, cutting, reduction of movements), and better dissipation of seismic energy, or the ductility obtained through a controlled deformation. In fact, the relief of the damage found during the last large seismic events on buildings built in armed masonry has proven itself considerably reduced compared to traditional masonry buildings.
Regulatory references and construction techniques
The armed masonry finds its first regulatory references within the Ministerial Decree 19/01/1996 To then remain among the newly built techniques provided for in subsequent technical standards up to the current NTC 2018 which govern its design and minimum quantity of armor.
The armed masonry construction involves a traditional continuous reinforced concrete foundation equipped with a recovery bars to tie the vertical walls and the creation of floors connected to the entire perimeter through reinforced concrete curbs, in order to Ensure box behavior that must have any wall structure.
THE floors They will be able to configure both in the traditional type in lamentocement, and in steel and tables, or in wood, with suitable stiffening insole for the diaphragm action and with light not exceeding 5 meters. The roof structures are always provided in non -push mode. The planimetries They must remain as compact and symmetrical as possible compared to two orthogonal axes, however guaranteeing the possibility of building at higher heights compared to the classic brick masonry. The thickness of the walls It must not be less than 24 cm (20 cm for low seismicity areas) and, gross of openings, have continuity in elevation up to the foundation, avoiding false walls.
Advantages of armed masonry
Armed masonry does not require specialized labor and it turns out competitive Compared to the costs of the most traditional ordinary masonry buildings and reinforced concrete frame.
Its technology uses simpler and easy to design static schemes because they are requested less restrictive but more reliable and compatible rules with the stresses in the seismic field. In particular, compared to the reinforced concrete frame structures, the structural scheme of the armed masonry cannot be affected by the usual overturning or serious cracking of the rear -end collision panels that characterizes the seismic response of many frame existing buildings.
It can also be used for the execution of existing buildings for its ability to react flexiblely to seismic movements.
