Structural assessment of a masonry vault in Portugal

This paper reports on a structural safety assessment and performance evaluation of the upper choir of the Santa Maria de Belém Church in the Jerónimos monastery, Lisbon, one of the most important cultural heritage buildings in Portugal. The possibility of adding a new 20 t organ to the upper choir and its effects on the church structure's response are presented. A refined and a simplified finite-element model is developed to investigate the structure's performance under self-weight and seismic actions. A sensitivity analysis is performed to investigate the effect of masonry mechanical properties and rib cross-sections on the structural response, given the difficulty in accurately obtaining this information. The results show that the safety level of the structure is acceptable, even in the case of adding a heavy new organ

Debonding damage analysis in composite-masonry strengthening systems with polymer- and mortar-based matrix by means of the acoustic emission technique

Different types of strengthening systems, based on fiber reinforced materials, are under investigation for external strengthening of historic masonry structures. A full characterization of the bond behavior and of the short- and long-term failure mechanisms is crucial to ensure effective design, compatibility with the historic substrate and durability of the strengthening solution. Therein, non-destructive techniques are essential for bond characterization, durability assessment and on-site condition monitoring. In this paper, the acoustic emission (AE) technique is evaluated for debonding characterization and localization on fiber reinforced polymer (FRP) and steel reinforced grout-strengthened clay bricks. Both types of strengthening systems are subjected to accelerated ageing tests under thermal cycles and to single-lap shear bond tests. During the reported experimental campaign, AE data from the accelerated ageing tests demonstrated the thermal incompatibility between brick and epoxy-bonded FRP composites, and debonding damage was successfully detected, characterized and located. In addition, a qualitative comparison is made with digital image correlation and infrared thermography, in view of efficient on-site debonding detection.The authors acknowledge the financial support of the Research Foundation-Flanders (FWO) for the mobility grant offered to Els Verstrynge.info:eu-repo/semantics/publishedVersio

Hygrothermal durability of bond in FRP-strengthened masonry

Fiber reinforced polymers (FRPs) are accepted as an efficient material for external strengthening of masonry structures. Previous researches have shown that the bond between FRP and the substrate plays an important role in the effectiveness of this strengthening technique. Extensive investigations have been devoted to the characterization of the short-term bond behavior, while its durability and long-term performance requires further studies. In this regard, a full experimental program for investigating the environmental durability of bond in FRP-strengthened masonry is crucial for understanding the degrading mechanisms. This paper presents the results of an experimental program aimed at investigating the hygrothermal durability of bond in FRP-strengthened bricks. Accelerated ageing tests were performed on the FRP-strengthened brick elements and the bond degradation was periodically investigated by visual inspection and by conventional single-lap shear bond tests. The changes in the properties of material constituents have also been monitored. The obtained results are presented and critically discussed.This work was developed within the framework of the RILEM Technical Committee "223-MSC: Masonry Strengthening with Composite Materials". The financial support from the project FP7-ENV-2009-1-244123-NIKER of the 7th Framework Program of the European Commission is gratefully acknowledged. The first author also acknowledges the financial support of the Portuguese Science Foundation (Fundacao de Ciencia e Tecnologia, FCT), through grant SFRH/BD/80697/2011

Meso-scale three-dimensional modeling of bond in FRP-strengthened masonry

Performance of masonry elements externally strengthened with fiber reinforced polymers (FRPs) is intrinsically dependent on the bond behavior between the composite material and masonry substrate. Therefore, a sound understanding of the interface behavior is crucial at the design stage. In this paper, a three-dimensional model based on the smeared crack modeling approach is presented for investigating the bond behavior in FRP-strengthened masonry elements. The threedimensional aspects of bond behavior in FRP- strengthened masonry elements are investigated. Moreover, the effect of mortar joints in the bond behavior of strengthened masonry prisms is studie

Recent developments in durability of FRP-masonry systems

Fiber reinforced polymers (FRPs) are being more and more used for external strengthening of masonry structures. Therefore, characterization of the short and long-term behavior of bond between FRP composites and masonry substrates in a service environment is crucial for design purposes. A full body of experimental and theoretical investigations is required for durability assessment of FRP strengthened structures. However, most of the research in this area has been devoted to FRP-concrete specimens, and the available data for FRP- strengthened masonry components is still lacking. This paper presents recent experimental results of a large experimental campaign under development at the University of Minho. The aim is to characterize the short and long-term behavior of bond in FRP-strengthened masonry elements. Debonding tests have been performed on masonry bricks strengthened with different FRP materials for investigating the short-term aspects of the bond behavior. Accelerated ageing tests have been performed on FRP-strengthened masonry elements and the degradation of the bond due to environmental conditions is investigated. The environmental conditions consist of the coupling effect of temperature cycles and relative humidity. The degradation of bond has been measured by performing conventional single-lap shear bond tests

Moisture-induced degradation of interfacial bond in FRP-strengthened masonry

Externally bonded strengthening of masonry structures using Fiber Reinforced Polymers (FRPs) has been accepted as a promising technique. Although the effectiveness of FRPs in improving the performance of masonry components has been extensively investigated, their long-term performance and durability remain poorly addressed. This paper, tackling one of the aspects related to durability of these systems, presents an experimental investigation on the effect of long-term (one year) water immersion on the performance of GFRP-strengthened bricks. The tests include materials' mechanical tests, as well as pull-off and single-lap shear bond tests, to investigate the changes in material properties and bond behavior with immersion time, respectively. The effect of mechanical surface treatment on the durability of the strengthened system as well as the reversibility of the degradation upon partial drying are also investigated. The experimental results are presented and critically discussed.The second author acknowledges the financial support of the Ministerio da Ciencia, Tecnologia e Ensino Superior, FCT, Portugal, under the grant SFRH/BPD/92614/2013

Application of acoustic emission technique for bond characterization in FRP-masonry systems

The acoustic emission (AE) technique is used for investigating the interfacial fracture and damage propagation in GFRP-and SRG-strengthened bricks during debonding tests. The bond behavior is investigated through single-lap shear bond tests and the fracture progress during the tests is recorded by means of AE sensors. The fracture progress and active debonding mechanisms are characterized in both specimen types with the aim of AE outputs. Moreover, a clear distinction between the AE outputs of specimens with different failure modes, in both SRG-and GFRP-strengthened specimens, is found which allows characterizing the debonding failure mode based on acoustic emission data.(undefined

Accelerated hygrothermal aging of bond in FRP-masonry systems

This paper addresses the results of accelerated hygrothermal (coupled temperature and moisture) tests on FRP-strengthened clay bricks aimed at investigating bond degradation mechanisms. The exposures are selected to simulate different environmental conditions and the bond degradation is periodically investigated by visual inspection and by conventional single-lap shear bond tests. The changes in the properties of material constituents have also been monitored and the results are presented and critically discussed. A decay model is then adopted for simulating the observed degradation in the specimens. The model, once validated, is used for long-term performance prediction of FRP-masonry systems and the results are compared with the environmental reduction factors proposed by available design guidelines.The first author acknowledges the financial support of the Portuguese Science Foundation (Fundacao de Ciencia e Tecnologia, FCT), through grant SFRH/BD/80697/2011

Bond behaviour and durability of FRP composites applied externally to masonry structures

The several advantages associated to the use of FRP composites for civil structural applications (mainly reinforced concrete and masonry) has led to a considerable increment in use during the last years. However, the performance of FRP composite strengthening systems when exposed to harsh environmental conditions is a matter of great concern, which justifies the recent research efforts towards the characterization of the deterioration effects. This paper discusses some of the most relevant environmental agents and their effect on the durability of FRP-strengthened concrete and masonry constructions. The results of a comprehensive series of accelerated ageing tests (water immersion and hygrothermal exposure) on external GFRP-strengthened masonry and respective constituent materials recently carried out at University of Minho are presented and discussed in detail.The financial support from the project FP7-ENV-2009-1-244123-NIKER is gratefully acknowledged. The Portuguese Science Foundation through grant contract SFRH/BD/80697/2011

Characterization of debonding in FRP-strengthened masonry using the acoustic emission technique

The acoustic emission (AE) technique is used for investigating the interfacial fracture and damage propagation in GFRP- and SRG-strengthened bricks during debonding tests. The bond behavior is investigated through single-lap shear bond tests and the fracture progress during the tests is recorded by means of AE sensors. The effect of hygrothermal conditions on the debonding characteristics and failure mode is also investigated by performing accelerated ageing tests. Accelerated ageing tests resulted in a change of failure mode in GFRP-strengthened specimens which helped in assessment of AE output in different failure modes, but no conclusive strength degradation was observed in the specimens. The results show that the average and cumulative AE energy are correlated to the FRP slip and debonding fracture energy in GFRPstrengthened specimens, respectively. The fracture progress and active debonding mechanisms are characterized using results from the AE technique. Moreover, a clear distinction between the AE outputs of specimens with different failure modes, in both SRG- and GFRP-strengthened specimens, is found which allows characterizing the debonding failure mode based on acoustic emission data. The tests performed in this study are also a contribution towards the application of AE techniques for on-site health monitoring of strengthened masonry structures.Fundação para a Ciência e Tecnologi