The need for new retrofitting techniques is the consequence of an increasing interest in the conservation of historic construction. The global behavior of a stone masonry structure is often governed by the level of connection between masonry wall leaves and the overall quality of the masonry material. This paper presents the results of an investigation carried out on site and in the laboratory on multi-leaf stone masonry panels strengthened using stainless steel rod inserted in a grouted fabric sleeve. The aim is to increase the collaboration between weakly connected masonry leaves. Pull-out tests were conducted on site on full-scale stone masonry wall panels, with the aim of studying the force required to pull out a connector under uniaxial tension. Several wall panels were assembled in the laboratory using solid calcareous stones and weak mortar and the effectiveness of the connectors was tested in shear and compression on both virgin and damaged panels. The experimental tests allowed the analysis of the behavior of the multi-leaf panels. Experimental results show that a substantial improvement of the wall panels' mechanical behavior can be achieved by applying transverse connectors.

The proposed paper reports the results of a research on the behaviour of injected anchors in historical masonry. The purpose of this investigation was to develop a methodology to be used as a preliminary design stage for structural interventions in order to pre-qualify the real strength of this kind of anchors. Several preliminary tests in laboratory with test specimens made of concrete and masonry and a first series of in situ tests on different types of masonry were conducted to analyse the behaviour of the anchorage and of the mortar. As this test is not included in National Standard, the studied standardised methodology could be adopted as a Guideline.

No abstract

The paper reports the results of a research on the static consolidation of an important XV century tower by Bramante belonging to an important monumental complex located in the Po Valley which was showing worrying structural conditions . The tower, 19 m high, very thin, lacking connections in the highest part, showed overturnings of the four façades not in plumb by over 150mm; Due to the presence of architectural terracotta elements, it was not possible to intervene on the external facades. This is why the authors decided to create a sort of hoop from inside using a U (120 mm) steel profile fastened to the walls by means of steel pins anchored with epoxy resins. The pins ( 12 mm, 350 mm length) have been positioned at a distance of 50 cm inclined by 30° alternatively downwards and upwards in order to get at minimum of 2+2 courses of bricks. Then, by a series of steel tie rods it was possible to tie the opposite walls. Finally, triangular frames have been positioned on the 4 corners in order to avoid teething collapse in case of great stress. Before starting with the strengthening work, as described above, experimental tests, supported by the Bossong company, were conducted to verify tensile stress resistance of each pin. The tests studied different solutions in terms of diameter and anchoring material. The tensile tests , carried out by using a specific hydraulic puller equipped with a dynamometer and a displacement transducer, showed very high allowable loads , between 20 and 60 kN/pin depending on the pin and fastening type. According to data obtained, the most suitable solution was chosen; it was also used in other parts of the castle. The behavior of the reinforced structure , which withstood the February 2012 earthquake without any problem demonstrated the validity of the proposed technique which is an interesting, non invasive solution for historical buildings.