Geometrically nonlinear effects in the flexural response of masonry walls strengthened with composite materials

Abstract

The geometrically nonlinear effects in the out-of-plane flexural response of unreinforced masonry walls strengthened with externally bonded composite materials are analytically investigated. The investigation aims to explore the stabilizing or destabilizing influence of the arching action formed under realistic supporting conditions (restricted longitudinal deformations) of the wall, and to quantify the contribution of the strengthening system to improving the stability characteristics of the wall. The localized buckling effects associated with the development of compressive stresses in the FRP strip are also examined. Variational principles, large displacements kinematics, compatibility conditions between the structural components (masonry units, mortar joints, FRP strips, and adhesive layers), and the assumption of oneway flexural action are used for the formulation of the nonlinear analytical model. The cracking of the mortar joints, which is essential to the development of the arching action, and the formation of debonded zones are also considered. A numerical example that highlights the geometrically nonlinear effects in the response of the strengthened wall and examines the influence of the slenderness ratio is presented. The results quantify the potential increase of the limit point load and deflection due to the externally bonded composite system. They also quantitatively reveal the wrinkling phenomenon of the compressed FRP strip and the shear and peeling stress concentrations that develop in the vicinity of the cracked mortar joints, the debonded regions, and the wrinkled FRP layer. The paper closes with concluding remarks.

Buckling-driven debonding in stiff block: compliant joint structural assemblies patched with composite materials

“…As a result, the transfer of compressive stresses to the FRP reinforcement due to the presence of the compliant joint and their destabilization effect on the debonding process were not studied. The effect of geometrical nonlinearity on the response of FRP strengthened masonry walls was studied in Hamed and Rabinovitch (2007). This work revealed a global limit-point behavior and the localized wrinkling of the FRP layer near the joint.…”

“…Armor plates composed of ceramic tiles, rubber joints, and outer composite layers (Mahdi and Gillespie 2004), sandwich panels with embedded rigid inserts (Found et al 1997;Burchardt 1998;Thomsen and Rits 1998;Thomsen 1998;Mamalis et al 2002;Bozhevolnayaa et al 2004;Bozhevolnayaa and Lyckegaard 2005;Rabinovitch 2007), and coating for electronic packaging (Anderson et al 2009), are examples of such applications. Another example is found in masonry walls upgraded with externally bonded composite materials and fiber reinforced polymers (FRP).…”

“…The assembly of rigid structural units, flexible and brittle joints, and thin bonded FRP layers is characterized by unique structural phenomena, many of them concentrated near the joints. These include the cracking of the joint under tension, the development of stress concentrations at the interfaces and near irregular points (Hamed and Rabinovitch 2007), and the debonding of the layered structure. The localized effects near the joint are further amplified by the development of compressive stresses in the externally bonded reinforcement.…”

“…This obstacle is an outcome of the differences in the orders of magnitude of the characteristic length scales and elastic properties of the components (building blocks, joints, adhesive layers, FRP layers) and the irregularities near the joint. These features make the FE analysis of the upgraded wall computational effort demanding, subjected to divergence, or highly sensitive to the modeling parameters (Davidson et al 2005;Hamed and Rabinovitch 2007). Rabinovitch (2008a,b) applied the cohesive zone concept to the analysis of beams strengthened with composite materials.…”

Analysis of brick masonry walls strengthened with fibre reinforced polymers and subjected to eccentric compressive loads

“…In this line, the analytical approach presented in the codes [16,17] might be taken as a valuable reference. For more specific models, the works by Hamed et al [24,31] are significant for addressing the out-of-plane response of FRP-strengthened masonry walls. These papers consider experimental and analytical approaches and take into account the influence of geometric parameters like the slenderness of the wall.…”