Massimo Dalla Benetta

Compression and Sonic Tests to Assess Effectiveness of Grout Injection on Three-Leaf Stone Masonry Walls

The results of an experimental campaign on multi-leaf stone masonry panels (scales 1:1 and 2:3), in original conditions and after consolidation with natural hydraulic lime grout injection are presented. The specimens were constructed with one of the most common structural techniques, widely employed on minor historical buildings throughout Europe. Experimental research included a series of destructive (DT) monotonic and cyclic uni-axial compression tests on three-leaf and single-leaf stone masonry panels. Mechanical tests were complemented by non-destructive tests (NDT) on the walls before and after strengthening. Both NDT and DT allowed assessment of the effectiveness of grout injection as a consolidation technique and gave better insights on its influence on the behavior of this type of masonry. An attempt to establish a relation between sonic velocity and mechanical parameters for this specific type of masonry was also carried out.

Experimental Characterization of Timber Floors Strengthened by in-Plane Improvement Techniques

The rehabilitation of existing timber floors in seismic area should take into account the possibility to use both traditional and more modern materials and techniques. An extensive experimental program carried out at the University of Padova concerned full-scale wooden floors segments strengthened through the application of several solutions, belonging to the following three main categories: planks overlapping, diagonals, and nets.In detail, the following techniques were considered: single and double planking with an orientation of ±45° having different thicknesses; steel, CFRP, SRP or wooden diagonals; natural fibre (hemp) composites applied as nets with resin or vinyl glue; wooden nets applied with hardwood pins and screws.The study is aimed at characterizing the behaviour of strengthened floors for the selection of the most suitable solutions applicable in existing buildings, which are able to provide a proper in-plane stiffness for seismic load distribution among bearing walls. The test set-up was designed and realized on purpose to simulate the in-plane shear behaviour of timber floors. The experimental results and the comparison between unreinforced and strengthened floors under monotonic shear load are presented in the paper.

On-Site Pull-Out Tests of Steel Anchor Spikes Applied to Brickwork Masonry

Externally Bonded (EB) composite materials are becoming a widespread solution for strengthening interventions on masonry buildings, even Cultural Heritage structures, due to several positive aspects mainly related to their high strength-to-weight ratio. In recent years, beside common epoxy-based Fibre-Reinforced Polymers (FRP), steel-based composites have been proposed: they are composed by unidirectional high-strength steel cords that can be coupled to either organic (Steel Reinforced Polymers, SRP) or inorganic (Steel Reinforced Grouts, SRG) matrices, in relation to their optimized spacing. The bond behaviour of all these EB composites has a strong influence over the effectiveness of interventions, since the detachment of reinforcements from the substrate generally represents the weaker failure mechanism. In order to improve this aspect, several anchorage devices have been proposed, being spikes, among them, one of the most suitable for masonry supports. Spikes are made of a bundle of fibres partly in the form of a bar, to be inserted and glued into a hole drilled in the substrate, and partly loose, to be spread and connected to reinforcement strips. Despite their importance also from a design point of view and considering the variety of shapes and materials, there are still few investigations in this field, being clear that both the spike-to-reinforcement and the spike-to-masonry connections need to be studied. Focused on the spike-to-masonry connection, this paper is aimed at investigating the performance of steel cord spikes applied to existing clay brick masonry, by means of overall 39 pull-out tests carried out taking into account the bonded length (equal to the hole depth), the type of embedding material and the number of steel cords forming the anchorage. The main results of this experimentation are herein presented and discussed.

Mechanical Characterization of Masonry Typologies in Israel via Flat Jack Tests

During the last decade, the Laboratory of the Department of Civil, Architectural, and Environmental Engineering department at the University of Padova, together with a Spin-Off of the same University, Expin srl, and the consultant engineering company Schaffer & Ronen ltd., carried out more than fifty on site single and double flat jacks on masonry panels of a relevant sample of existing masonry buildings in different historical sites in Israel. Typical Israeli masonry used in historical buildings consists of limestone, calcar (sand) stone, and Basalt stone masonry, with mostly lime based mortar as a binder. Double flat jack tests were employed on two main types of stone walls: single-faced and two-faced stone wall (the most common stone masonry arrangement). From these tests it was possible to obtain the characterization of the mechanical properties of the stone masonry panels tested, belonging to different construction eras and masonry types. Double flat jack tests were mainly carried out following the local state of stress determination via single flat jack. The paper presents the results with a classification of the masonry types mechanical characteristics. This ongoing work, to be complemented with laboratory tests in future stages, may represent a preparatory work for the development of reference characteristic values of the different masonry types of the country, to be included in Israeli technical standards.