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

Uncertainty analysis of FRP reinforced timber beams

Timber has been a popular building material for centuries and offers significant sustainable credentials, high mechanical and durability properties. Availability, ease to use, convenience and economy have made timber the most used construction material in history but, as it is a natural material, uncertainty in its mechanical characteristics is considerably higher than man made structural materials. National codes and engineers usually employ high factor of safety to incorporate timber strength uncertainty in design of new structures and reinforcement of existing ones. This paper presents the results of 221 bending tests carried out on unreinforced and reinforced soft- and hardwood beams (fir and oakwood) and illustrates the reinforcement effect on timber capacity and strength uncertainty. Both firwood and oakwood beams have been tested in flexure before and after the application of a composite reinforcement made of FRP (Fiber Reinforced Polymer) unidirectional sheet. The uncertainty in the strength of reinforced timber is also quantified and modelled. Test results show that the FRP reinforcement is effective for both enhancing the beam load carrying capacity and for reducing strength uncertainties

Effect of transversal steel connectors on the behaviour of rubble stone-masonry walls: two case studies in Italy

Multi-leaf masonry walls are very common in historical constructions and have been primarily designed to resist vertical static loads. Recent earthquakes have shown their high vulnerability against dynam-ic horizontal and static compression loads which can easily produce the detachment of the different leaves and determine important damage and catastrophic consequences. An increasing interest in the conservation of his-toric masonry constructions has produced a need for new consolidation and retrofitting methods. With the aim of increasing the mechanical characteristics, the overall structural behaviour and ultimately the safety of mul-ti-leaf masonry wall panels against out-of-plane collapse mechanisms, several reinforced techniques have been investigated. In this paper, a new strengthening system which consists in the application of a pre-loaded steel bar enclosed into a fabric protective bag-case, is investigated. The steel-bar connector is inserted into a pre-drilled hole made in the masonry in order to bond the masonry leaves and to prevent the detachment dur-ing seismic events; finally cement-based grout is injected at high pressure inside the fabric bag-case. The aim is to increase the collaboration between masonry leaves and increase the wall-capacity. The paper initially de-scribes the reinforcement technique and its fields of application and expected benefits. In the second part, the paper addresses two case studies where this reinforcing method has been recently applied: the medieval castle of Laurenzana, located in the southern Italian region of Basilicata and a coeval 18th-century annex building nearby the Royal Palace of Capodimonte (Naples)

Fiberglass Grids as Sustainable Reinforcement of Historic Masonry

Fiber-reinforced composite (FRP) materials have gained an increasing success, mostly for strengthening, retrofitting and repair of existing historic masonry structures and may cause a significant enhancement of the mechanical properties of the reinforced members. This article summarizes the results of previous experimental activities aimed at investigating the effectiveness of GFRP (Glass Fiber Reinforced Polymers) grids embedded into an inorganic mortar to reinforce historic masonry. The paper also presents innovative results on the relationship between the durability and the governing material properties of GFRP grids. Measurements of the tensile strength were made using specimens cut off from GFRP grids before and after ageing in aqueous solution. The tensile strength of a commercially available GFRP grid has been tested after up to 450 days of storage in deionized water and NaCl solution. A degradation in tensile strength and Young’s modulus up to 30.2% and 13.2% was recorded, respectively. This degradation indicated that extended storage in a wet environment may cause a decrease in the mechanical properties

Saturated R134a flow boiling inside a 4.3 mm inner diameter microfin tube

The refrigerant charge minimization in refrigerating and air-conditioning systems represents a challenging issue due to the new environmental national and international regulations. The use of smaller smooth tubes, such as with the outer diameter around 5 mm, is becoming more and more common in many applications. More recently, the microfin tubes have also started to be reduced in size to cope with the continuously increasing demand of new, efficient, and compact heat exchangers for air-conditioning and refrigeration equipment. This work investigates the performance of R134a during saturated flow boiling inside a microfin tube with internal diameter at the fin tip of 4.3 mm. Boiling heat transfer coefficients, frictional pressure drops, and critical vapor qualities were measured at 30\ub0C of saturation temperature, by varying the refrigerant mass velocity between 100 and 800 kg m 122 s 121 and the vapor quality from 0.1 to 0.95 at four different heat fluxes: 15, 30, 60, and 90 kW m 122. Moreover, the reliability of several models for flow boiling heat transfer and pressure drop estimations was assessed by comparing the experimental results with the calculations

A Numerical Analysis Of Latent Thermal Energy Storage For Refrigerated Trucks

In this work, an innovative insulated wall concept for refrigerated truck is proposed. A 2D transient numerical model of the truck cell is developed and simulated considering the solar radiation from 6 AM to 4 PM of a typical summer day in Vicenza (Italy). The innovative composite wall consists of a traditional polyurethane (PU) insulation layer wrapping a layer of PCM (reference melting temperature of 2 °C) with different thickness from 0.5 cm to 2 cm. The results confirm that the proposed solution is very promising because even the smallest thickness can assure an adequate temperature inside the cell for almost the entire simulated journey

Length of efficacy and effect of implant location in adult tom cats treated with a 9.4 mg deslorelin subcutaneous implant

Objectives The objective of this study was to assess duration of efficacy, side effects and return to fertility following use of the 9.4 mg deslorelin implant (Suprelorin 12; Virbac) in cats, and test whether efficacy and duration of action are influenced by implantation site (interscapular vs periumbilical). Methods Sixteen healthy adult tom cats were checked with (1) reproductive examination, (2) gonadotropin-releasing hormone stimulation test and (3) semen collection until achievement of sterility, then with (1) and (2) only at 2, 4, 6 and 12 months, and every 6 months thereafter until treatment effect disappeared. Results Serum testosterone reached basal levels by 7 days post-treatment. Semen quality improved initially then started to worsen by 1 month post-treatment and after 70 days post-treatment all cats were sterile. Early in the third month post-treatment there was a significant decrease in testicular volume and penile spikes. Testicular histology was normal upon neutering performed after resumption of fertility. No injection site lesions or treatment-related side effects were observed. There was no difference between periumbilical and interscapular placement for all criteria, but there was a trend for the decrease in testicular volume to last longer and for the regression of penile spikes to start sooner after interscapular administration. One of 16 cats did not respond to treatment. Six cats were lost at variable times during the study while fully responding to treatment. In the cats that completed the study, normal fertility was regained after 805 days, on average, but with a variable duration of effect from 750-850 days. Conclusions and relevance Treatment with a 9.4 mg deslorelin implant in male cats was effective for a period of 750-850 days, 1.5-2 times longer than the effect of the 4.7 mg deslorelin implant. Fertility (based on serum testosterone production and presence of penile spikes) was regained at the end of the study. Placing implants in the intrascapular vs periumbilical location did not affect duration of suppression of testosterone production. The interscapular location may be characterised by a better efficacy, although further studies are needed to clarify this issue

Endothelin Receptors Expressed by Immune Cells Are Involved in Modulation of Inflammation and in Fibrosis: Relevance to the Pathogenesis of Systemic Sclerosis

open13noEndothelin-1 (ET-1) plays a pivotal role in vasoconstriction, fibrosis, and inflammation, the key features of systemic sclerosis (SSc). ET-1 receptors (ETA and ETB) are expressed on endothelial cells, smooth muscle cells, and fibroblasts, but their presence on immune cells has not been deeply investigated so far. Endothelin receptors antagonists such as bosentan have beneficial effects on vasoconstriction and fibrosis, but less is known about their potential anti-inflammatory effects. We studied the expression of ET-1 receptors on immune cells (T and B lymphocytes, monocytes, and neutrophils) and the link between ET-1 and inflammation in patients with SSc. We show here that ET-1 exerts a proinflammatory effect in CD4+ T cells, since it induces an increased IFN-γ production; preincubation with antagonists of both receptors reduces IFN-γ production. Moreover, following ET-1 stimulation, neutrophils produce proinflammatory mediators, thus amplifying the effects of activated CD4+ T cells. Our data indicate that ET-1 system is involved in the pathogenesis of inflammation and fibrosis typical of SSc, through the activation of T lymphocytes and neutrophils and the consequent release of proinflammatory and profibrotic cytokines. These findings suggest that dual ET-1 receptors antagonist therapy, besides its effect on vasculopathy, has a profound impact on the immune system favouring antiinflammatory and antifibrogenic effects.openElisa, Tinazzi; Antonio, Puccetti; Giuseppe, Patuzzo; Alessandro, Barbieri; Giuseppe, Argentino; Federico, Confente; Marzia, Dolcino; Ruggero, Beri; Giacomo, Marchi; Andrea, Ottria; Daniela, Righetti; Mariaelisa, Rampudda; Claudio, LunardiTinazzi, Elisa; Puccetti, Antonio; Patuzzo, Giuseppe; Barbieri, Alessandro; Argentino, Giuseppe; Confente, Federico; Dolcino, Marzia; Beri, Ruggero; Marchi, Giacomo; Ottria, Andrea; Righetti, Daniela; Rampudda, Mariaelisa; Lunardi, Claudi