Bond slip behaviour of deep mounted carbon fibre reinforced polymer strops confined with a ductile adhesive in clay brick masonry

Retrofitting clay brick masonry using Deep Mounted (DM) Carbon Fibre Reinforced Polymer (CFRP) strips embedded in grooves filled with a ductile adhesive considerably increases the out-of-plane flexural capacity of slender unreinforced masonry walls. In order to investigate the bond-slip behaviour of CFRP-strips in a viscous-elastic adhesive, an extensive experimental program was initiated. Direct pull-out tests were conducted with clay brick masonry. Two parameters were investigated, namely, the type of adhesive (2 types) and the groove widths (10 and 15 mm). The second part of the experimental program focused on the pull-out capacity when surface treatment (primering or sandblasting) was applied to the CFRP-strips. \u3cbr/\u3eIn literature dealing with bond behaviour the critical bond length was found using masonry prisms of approximately 350 mm in height. In the current study with CFRP strip application in conjunction with ductile epoxy, the critical bond length was not reached for specimens of nearly 1000 mm in length. This finding was an indication of a significantly improved stress distribution over the length of the embedded CFRP-strip as the appearance of peak stresses was prevented. No premature brick splitting was initiated despite the depth of the groove being 65% of the specimen thickness, whereas in literature this phenomenon was reported for groove depths of only 30%

Analytical modelling of the out-of-plane behavior of CFRP and ductile adhesive reinforced clay brick masonry walls

In an experimental testing program three different ductile adhesive reinforced masonry configurations were involved. The first configuration consisted of a carbon fibre reinforced polymer (CFRP) strip placed in the heart of the masonry wallettes with a visco-elastic epoxy. The second configuration had an additional surface treatment based on a polymer. The third configuration was similar to the second one, however with a cement based surface treatment with imbedded CFRP net. The results of the experimental tests confirmed the strong increase in both the moment- and flexural capacity and supported the previously stated significant gain in ductility. The purpose of the research was to model out of plane behaviour of QSRM. A discrete model is described that can be used to determine the structural behaviour of non-load bearing clay brick masonry walls which are enhanced by applying the aforementioned reinforcement configurations. The model consists of stiff masonry blocks and discrete joints at the locations of the first cracks. The relation between the internal moment and the rotation in the discrete joint is based on the bond behaviour of the CFRP strips and, when it is applied, the polymer finish. The bonding behaviour of the CFRP strips is derived from pull-out tests. The results of the model are compared with results from experimental research after the out of plane behaviour of clay brick masonry walls has been enhanced with the ductile adhesive configurations. From this comparison it is concluded that the model is able to describe the experimental out of plane behaviour

Experiments to determine the out-of-plane behavior of CFRP and ductile adhesive reinforced clay brick masonry walls

The reinforcement systems with ductile adhesive have shown to remarkably increase the out-of plane flexural capacity of unreinforced masonry (URM). Extensive laboratory scale out-of-plane (OOP) experiments have been conducted with construction material that is representative for the masonry found in Groningen. The research purpose was to gain more understanding on the out of plane behaviour of carbon fibre reinforced polymer (CFRP) and ductile adhesive reinforced masonry. In the experimental testing program three different reinforcement configurations have been involved. The first configuration consisted of a CFRP strip placed in the heart of the masonry wallettes with a visco-elastic epoxy. The second configuration had an additional surface treatment based on a polymer. The third configuration was similar to the second one, however with a cement based surface treatment with imbedded CFRP net. The results of the experimental tests confirmed the strong increase in both the moment- and flexural capacity and supported the previously stated significant gain in ductility

In-plane behaviour of clay brick masonry wallettes retrofitted with single-sided fabric-reinforced cementitious matrix and deep mounted carbon fibre strips

\u3cp\u3eThe in-plane shear behaviour of a new seismic retrofit concept which combines two standalone retrofit measures for in-plane and out-of-plane strengthening of masonry walls was investigated. The in-plane reinforcement consists of a single-sided carbon fabric-reinforced cementitious matrix (FRCM) overlay, while the out-of-plane reinforcement consists of deep mounted carbon fibre reinforced polymer strips embedded in a viscous-elastic epoxy. An experimental program was undertaken in which clay brick masonry wallettes were subjected to the diagonal compression test to assess the effectiveness of the strengthening system on the in-plane behaviour. The obtained results showed that the single-sided carbon FRCM overlay increased the shear capacity with 80%, compared to the unstrengthened control specimens. Moreover, by testing two different FRCM overlay thicknesses it was found that a thicker matrix layer does not increase the shear capacity of wallettes. However, wallettes provided with a thicker FRCM overlay did show a higher level of ductility. Furthermore, the obtained experimental results showed that the presence of only the aforementioned out-of-plane reinforcement does not affect the in-plane strength of masonry wallettes loaded under shear, and even prevented the disintegration after reaching the failure load compared to the unstrengthened control specimens. Finally, an existing analytical model as well as the Eurocode 8 design provisions were compared to the found failure mechanisms and failure loads. The analytical model developed showed good correspondence with the experimental values for both the failure mechanism and failure load, with an experimental/model ratio (φ) of 0.98, while Eurocode 8 proved to lead to conservative values.\u3c/p\u3

Mechanical characterization and out‐of‐plane behavior of fabric‐reinforced cementitious matrix overlay on clay brick masonry

The mechanical behavior of carbon fiber-reinforced polymer (CFRP) fabric-reinforced cementitious matrix (FRCM) overlay on clay brick masonry was characterized by means of double-shear bond, tensile, and out-of-plane tests. Different bond lengths in the range 55-250 mm were analyzed during the double-shear bond tests. The failure mechanism was slippage of the CFRM mesh, with peak stresses in the fabric around 500 N/mm2 per 100 mm bond length. Tensile tests were performed following AC434.13 with FRCM coupons of 10 and 15 mm thickness, where the mechanical behavior was divided into three stages. The four-point bending experiments on FRCM-reinforced prisms showed that the CFRP mesh provided significant added value in both moment capacity (>110%) and deformation capacity (>2800%), when compared to specimens reinforced with solely a cementitious matrix. Additionally, no significant difference was observed between the envelope of the cyclically tested specimen and the statically loaded specimens. A model was proposed where, in contrast to existing design models, the influence of the cementitious matrix layer also was considered. Using the modified tensile test results as input parameters for the model, a good estimation of the experimental results was obtained