Detection and localization of debonding damage in composite-masonry strengthening systems with the acoustic emission technique

Different types of strengthening systems, based on fiber reinforced materials, are under investigation for external strengthening of historical 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 and durability of the strengthening solution. In this paper, the effectiveness of the Acoustic Emission (AE) technique for debonding characterization and localization on Fiber Reinforced Polymer (FRP)- and Steel Reinforced Grout (SRG)-strengthened clay bricks is investigated. The AE technique proofs to be efficient for damage detection during accelerated ageing tests under thermal cycles and during experimental shear bond tests. AE data demonstrated the thermal incompatibility between brick and epoxy-bonded FRP composites during the accelerated ageing tests and debonding damage was successfully detected, characterized and located during the shear bond tests.- (undefined

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

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

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

Effect of environmental aging on the numerical response of FRP-strengthened masonry walls

Recent durability studies have shown the susceptibility of bond in fiber-reinforced polymer (FRP) strengthened masonry components to hygrothermal exposures. However, it is not clear how this local material degradation affects the global behavior of FRP-strengthened masonry structures. This study addresses this issue by numerically investigating the nonlinear behavior of FRP-masonry walls after aging in two different environmental conditions. A numerical modeling strategy is adopted and validated with existing experimental tests on FRP-strengthened masonry panels. The model, once validated, is used for modeling of four hypothetical FRP-strengthened masonry walls with different boundary conditions, strengthening schemes, and reinforcement ratios. The nonlinear behavior of the walls is then simulated before and after aging in two different environmental conditions. The degradation data are taken from previous accelerated aging tests. The changes in the failure mode and nonlinear response of the walls after aging are presented and discussed.The first author acknowledges the financial support of the Portuguese Science Foundation [Fundacao de Ciencia Tecnologia (FCT)] through grants SFRH/BD/80697/2011 and SFRH/BPD/92614/2013

Simulation of moisture transport in fired-clay brick masonry structures accounting for interfacial phenomena

This paper presents a numerical study on moisture transport in brick masonry walls with a special focus on the simulation of their hygric performance as well as the hydraulic phenomena at the brick-mortar interface. A diffusivity model based on Fick's law is used to describe the moisture transport accounting for both liquid and water vapor movement. The necessary hygric parameters are obtained directly from experimental tests or determined by curve fitting. The proposed model is validated with respect to water absorption and drying tests. The good-fitness of the results is qualitatively assessed and an overall good agreement is found between the simulated and measured curves. It is demonstrated that the chosen liquid water diffusivity expression needs to be adjusted to represent drying processes; the necessary adjustment is made through a diffusivity factor implemented in the original analytical expression. The interface impact on water absorption is introduced as a hydraulic resistance. Moreover, it is hypothesized that the presence of successive interfaces entails an additive in-series effect. Conversely, the interfacial impact on drying is negligible. Finally, the proposed model is extended to different modeling approaches commonly used for mechanical studies of masonry. The necessary input data, modeling methodology, advantages and disadvantages associated with each modeling strategy are also discussed. The present study points out the need of studying water absorption in multi-layered structures made up of constituents with relatively similar hygric behavior. In such cases, the impact of imperfect contact at the interface between materials is not negligible.Article publishing charge (APC) funded by agreement between Portugal (FCT/FCCN) and Elsevie

Experimental investigation on the long-term durability of bond between FRP and masonry substrates

The characterization of long-term behavior of bond between Fiber-Reinforced Polymers (FRPs) and masonry substrates in a service environment is a crucial issue for design purposes, which requires a full body of experimental and theoretical information. Most of the research in this area has been devoted to FRP-concrete specimens, and the available data for FRP-strengthened masonry components are still lacking. This paper presents the experimental investigation on degradation of bond between glass FRP composite sheets and masonry bricks by performing accelerated aging tests. Masonry bricks strengthened with GFRP sheets are prepared following the wet lay-up procedure and exposed to thermal cycling and constant relative humidity. Single-lap shear bond tests are finally performed for investigating the degradation of the bond after exposure to environmental conditions and the results are presented

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

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