historic masonry walls strengthened with gfrpstrips under compression and shear

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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

Analysis of the experimental flexural behaviour of a concrete beam grid reinforced with CFRP bars

Abstract In recent years the use of composite materials as reinforcement in concrete beams has increased whenever durability is the main controlling parameter. Many studies have been performed on the behaviour of concrete beams but few have analysed the structural behaviour of plane elements like slabs or grids. The paper analyses the experimental flexural behaviour of a concrete beam grid reinforced with CFRP bars. An one-third scale experimental model of a real concrete floor, was tested in bending. The experimental results show the flexural behaviour in terms of cracking phases and deflection until the failure. The experimental model was affected by the cracking of concrete even under low loads. The experimental model is analysed both by elastic theory of orthotropic plate and a FEM code. An approximate method of calculation, based on an orthotropic plate model, is developed that considers modified bending rigidities for orthogonal directions

Experimental analysis of bond-slip effects in RC beams strengthened with NSM CFRP rods

The use of the near surface mounted (NSM) fiber reinforced polymer (FRP) technique for retrofitting RC beams is a mainstream. Nevertheless, the bond mechanisms of FRP rods between rods and adhesive resin and/or rod–resin with concrete surfaces are not known completely. This paper investigates the experimental bond-slip effects of circular and rectangular carbon-FRP (CFRP) rods inserted in grooves in RC elements through experimental pull-out and bending tests, and using theoretical models. Five RC beams were built and subjected to bending loading; three of the ones strengthened using NSM CFRP rods were subjected to bending until failure. The experimental results showed changes in the response of beams such as stiffness in the elastic phase, reduction of ultimate capacity and ductility due to bond-slip effects. On the other hand, strain measurements on CFRP rods recorded by pull-out tests theoretically valid the linear elastic analysis capable of defining the behavior of CFRP rods before loss of bond. Finally, the comparison between experimental results and theoretical data opens a discussion concerning bond-slip effects in cracked RC beams strengthened with NSM CFRP rods and leads to the definition of actual strain limits for FRP under service loads

Clay block masonry under compression and shear with different mortar joints

Proc. CIB-W023 38th Commission meetin