Abstract
This paper investigates composite-to-brick strengthening systems with flexible adhesive made of polyurethane (Carbon Fibre Reinforced Polyurethane (CFRPU) and Steel Reinforced Polyurethane (SRPU)) and epoxy resin (Carbon Fibre Reinforced Polymer (CFRP) and Steel Reinforced Polymer (SRP). The specimens were tested in a single lap shear test (SLST). LVDT displacement transducers (LVDT – Linear Variable Differential Transformer) and digital image correlation method (DIC) based measurement systems were used to measure displacements and strains. The obtained results were applied in a numerical analysis of the 3D model of the SLST specimen, with flexible adhesives modeled as a hyper-elastic model. The DIC and LVDT based systems demonstrated a good correlation. Experimental and numerical analysis confirmed that composite-to-brick strengthening systems with flexible adhesives are more effective on brittle substrates than stiff ones, as they are able to reduce stress concentrations and more evenly distribute stress along the entire bonded length, thus having a higher load carrying capacity.
Highlights
Composite strengthening of masonry structures is one of the most popular methods for improving load capacity and ductility of existing masonries
In the calculations of Fibre Reinforced Polymers (FRP)/SRP and FRCM/SRC (TRM/SRM), the influence of adhesive properties is neglected
The results presented in this paper indicate that properties of adhesives in composite-to-substrate strengthening systems should be taken into consideration
Summary
Composite strengthening of masonry structures is one of the most popular methods for improving load capacity and ductility of existing masonries. When maximum loads were reached, these adhesives caused serious damages to masonry substrates These strengthening methods were found to be irreversible to and incompatible with masonry substrates, a factor that resulted in the heritage structure authorities’ disapproval of their application. The effectiveness of such composites bonded on stiff epoxies was determined to be low, because of the short effective bonding length and the generated high stress concentrations, responsible for the fracture in a brittle substrate. This problem prompted the search for a new, more compatible and effective strengthening system that utilized mineral mortars or highly deformable polyurethanes
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