An Experimental Study on the Effect of Water on Historic Brickwork Masonry

Architectural heritage is deeply threatened by extreme weather events due to ongoing climatic change. Since these phenomena are becoming more and more serious, their effects cannot be neglected when a reliable assessment of a historic masonry structure is required. In this paper, the phenomenon of rising damp was studied, focusing on the influence of water on the unit weight of masonry walls made from fired clay bricks and lime mortar. This study consists of a basic experimental research on the variations in the unit weight of masonry undergoing an ageing treatment, which was simulated through some cycles of capillary water absorption and temperature changes. The experimental study proves that penetrating damp causes an increase in masonry unit weight of more than 20%. This basic result is significant in the structural assessment of historic masonry buildings. Subsequent papers will analyze the interaction with strengths parameters

Out‐of‐plane reinforcement of masonry walls using joint-embedded steel cables

The out-of-plane mechanism (rocking) of walls often causes fatalities and collapses of historic buildings during earthquakes. This paper addresses the problem of assessing the seismic resistance of walls subjected to out-of-plane bending, before and after reinforcement. A new retrofitting method, consisting in the use of high-strength steel cables fully embedded in the mortar bed joints was studied. An experimental investigation using full-scale brickwork specimens was therefore conducted in an attempt to assess the walls’ structural response when these are subject to out-of-plane loads. Test results demonstrated that it is possible to increase the out-of-plane capacity with the proposed method. A simplified macro-element procedure is also presented along with recommendations for the calculation of the walls’ capacity before and after the application of the steel cable reinforcement. Predictions of the magnitude of horizontal force required to cause out-of-plane failure using the proposed procedure and quasi-static analysis procedures are compared with the results of laboratory experiments

Experimental evaluation of shear and compression strength of masonry wall before and after reinforcement: Deep repointing

Masonry presents some inadequacies due to its almost total lack of tensile strength. Typical damage to multiple leaf walls during earthquakes is the loss of bond between the leaves with consequent collapse of the external leaf. Retrofitting or repair of this damage is a very difficult task. In many cases grout injection or wall jacketing fail due to incompatibility with the construction technique of the walls. A complementary technique to the grouting has been proposed by the authors. Experimental results and applications of the technique on site have shown positive characteristics and the results of tests carried out on site show, in some cases, increases in shear strength and stiffness of the masonry walls

Calibration of a visual method for the analysis of the mechanical properties of historic masonry

The conservation and preservation of historic buildings affords many challenges to those who aim to retain our building heritage. In this area, the knowledge of the mechanical characteristics of the masonry material is fundamental. However, mechanical destructive testing is always expensive and time-consuming, especially when applied to masonry historic structures. In order to overcome such kind of problems, the authors of this article, proposed in 2014 a visual method for the estimation of some critical mechanical parameters of the masonry material. Based on the fact that the mechanical behavior of masonry material depends on many factors, such as compressive or shear strength of components (mortar and masonry units), unit shape, volumetric ratio between components and stone arrangement, that is the result of applying a series of construction solutions which form the "rule of art". Taking into account the complexity of the problem due to the great number of variables, and being on-site testing a not-always viable solution, a visual estimate of the mechanical parameters of the walls can be made on the basis of a qualitative criteria evaluation. A revision of this visual method is proposed in this paper. The draft version of new Italian Building Code have been used to re-calibrate this visual method and more tests results have been also considered for a better estimation of the mechanical properties of masonry

Use of natural resins in repairing damaged timber beams – An experimental investigation

Different techniques including the application of steel elements, composite materials and polymeric resins have been used in the past to repair damaged timber beams. However, there is a growing need to replace these materials with those with minimal environmental impact. In addition, stringent requirements of conservation authorities on the compatibility between repair and parent materials have also necessitated search for innovative repair materials for timber beams. Therefore, an increasing shift of focus towards the use of materials derived from natural sources in repairing and reinforcing timber structures is currently experienced. This paper presents the results of an exploratory study on the use of natural resins (rosin and bone glue) in repairing oak timber beams. 15 oak timber beams with cross section dimensions of 67 x 67 mm and 1100 mm in length were tested in four-point bending to failure. Undamaged, damaged (unrepaired) and damaged but repaired timber beams (with rosin and bone glue) were tested. The effectiveness of the repair material and technique was analysed based on the bending capacity and mid span deflection at failure. The initial results show negligible effectiveness of rosin in repairing timber beams. In fact, about 16% reduction (average) in load carrying capacity with a corresponding 5% decrease (average) in maximum displacement was recorded. Relatively higher level of effectiveness was recorded with the use of bone glue (about 10 % average increase in load carrying capacity). However, over 30% corresponding average increase in the maximum displacement was also recorded. Further work investigating different repair techniques and other natural resins is presently underway

Masonry wall panels retrofitted with thermal-insulating GFRP-reinforced jacketing

Today there is a need to provide thermally efficient walls, while at the same time to increase the mechanical properties of old unreinforced masonry walls that will not require large amounts of energy in the retrofitting or deconstruction processes. To address this problem, this paper gives the results of shear tests carried out on masonry panels made of solid bricks retrofitted with a new technique based on the use of glass fiber-reinforced polymers (GFRP) grids inserted into a thermal insulating jacketing. This was made of different low-strength lime-based mortars. Tests were carried out in laboratory and results were used for the determination of the shear modulus and strength of the wall panels before and after the application of the GFRP reinforcement. Retrofitted panels exhibited a significant enhancement in the lateral capacity when compared to the control panels. The thermal performance of the proposed mortars was also investigated both with and without GFRP. Low values of thermal conductivity were found, especially for the samples with GFRP; a reduction of the thermal transmittance value in the 34–45 % range was also obtained by applying 45 mm layer of coating in conventional masonry walls

The Relationship between Article 4 (1)(b) Cross-Border Merger Directive and the European Merger Regulation

In a time when protectionism is re-emerging as a strong policy stance on a global scale, the opposition to cross mergers based on public interest grounds may once more become more frequent. The lack of a common policy at the EU level leaves each Member State free to set its own framework to oppose mergers based on the public interest. However, such frameworks need to comply with Article 4(1)(b) of the Cross-Border Merger Directive (CBMD) which expressly introduces a non-discrimination principle in respect of MS’s provision which regulate the opposition of public interest. This paper compares the protection offered under Article 4(1)(b) with the one offered under the EU Merger Regulation (EUMR). It shows that the protections under the EUMR are greater and that the EUMR provides a robust ex ante assessment of public interest claims raised against the merger. However, it also shows that the role of the EUMR in the protection of mergers against public interest opposition is limited. This limitation stems from the threshold for establishing a Union dimension within the meaning for that Regulation. This Chapter suggests that, while the scope of the CBMD covers more mergers, the real playing field of public interest opposition is prior to the merger—during the takeover by a foreign company or the change of control in the terms of the EUMR

Sustainable Strengthening Techniques for Masonry Structures

Reducing the energy consumption is an important objective of the construction industry and this also applies for renovation, retrofit and refurbishment of existing buildings. Masonry buildings often need to be retrofitted and the use of Fibre Reinforced Polymeric (FRP) materials has proven to be a viable solution. With the inevitable declining of fossil fuels, carbon fibres and epoxy resins must be substituted with greener materials. This paper reports the results of several experimental investigations recently conducted by the authors using glass fibre meshes embedded into an inorganic matrix (known as FRCM: Fibre Reinforced Cementitious Matrix) to reinforce historic masonry constructions. This strengthening technique has been applied in laboratory to reinforce masonry wall panels, tile brickwork vaults and to construct masonry ring-beams at eaves level of existing buildings. The mechanical behaviour of the reinforced masonry elements have been significantly enhanced and test results demonstrate that is possible to avoid the use of more traditional composite reinforcements like high-strength carbon fibres and epoxy resins to bond the reinforcing materials to the masonry substrate

Shear resistance of screwed timber connections with parallel to grain FRP reinforcements

Several applications involving the use of Fibre Reinforced Polymers (FRP) glued on the tension side of timber beams are available in literature. However, some drawbacks (durability, product cost and health and safety restrictions, difficulties in removal) have limited an intensive use of organic adhesives (i.e. epoxy resins, etc). A possible solution could be the use of metal screws, changing the nature of the connection from chemical to mechanical. This paper describes an experimental investigation on the mechanical behaviour of externally bonded FRP composites using steel screws. Two different composite materials have been considered: Carbon Fibre Reinforced Polymer (CFRP) and Glass Fibre Reinforced Polymer (GFRP) and three different metal screw types have been used. FRP strengthening was then applied to timber blocks and shear tested conducted to study the performance of the screwed connection. The response of the screwed connection was recorded: catastrophic collapse did not occur, as the connection failed gradually for slippage phenomena produced by screw yielding and wood displacement. The slippage between timber and FRP plate has been recorded and tests described in this paper demonstrated that the effectiveness of screwed FRP strengthening could be compromised by these phenomena

The Failure of Masonry Walls by Disaggregation and the Masonry Quality Index

The visual method for assessment of the structural behaviour of historic masonry walls, known by the acronym MQI (Masonry Quality Index) was introduced in 2002 by a team of researchers from the University of Perugia, Italy. This is based on a visual survey of the faces and the cross section of a wall panel, and it aims at verifying if a wall complies with the “rules of the art”. Based on this analysis, it is possible to calculate a numerical index: numerous tests, carried out on site by the authors to validate the method, have demonstrated that the index is able to provide useful information about the mechanical characteristics and structural response, in general, of the analysed wall panel. The failure mode of a wall panel under the action of an earthquake is a critical aspect. In general, the failure modes can be categorized in two classes: masonry disaggregation and the development of a local or global mechanism of wall elements (macroelements). Several theoretical models and numerical simulations only consider the latter. In this paper, application of the MQI method is further investigated, with particular emphasis to those masonry typologies which are more prone to collapse by disaggregation during a seismic event. Under the action of an earthquake, some types of masonry are typically unable to deform and to split in macroelements, and another type of failure occurs: this is the so-called “masonry disaggregation” or “masonry crumbling”. This type of failure anticipates the ones resulting from macroelement methods or stress analysis. As a conclusion, these latter methods become completely inappropriate and potentially hazardous, as they overestimate the seismic capacity of the building under investigation. The MQI method has been adapted to assess the structural response of different types of masonry under the action of an earthquake. In detail, the aim was to verify when the phenomenon of masonry disaggregation is likely to occur