Keywords: masonry column, finite element analysis, cohesion, internal friction angle, Drucker-Prager criterion, failure, fiber reinforced polymer, compressive strength, confinement level.

Earthquakes can destroy many unreinforced masonry (URM) buildings which exhibit little ductility particularly in the absence of adequate shear walls and columns. Nearly thirty percent of buildings in Turkey are URM constructions. There are also a large number of historical buildings and monuments in Turkey and Mediterranean region creating an important cultural heritage. A steady growth in the application of fiber reinforced polymers (FRPs) for strengthening of masonry structures against earthquake hazard and static overloading is therefore beneficial for the maintenance of the architectural cultural heritage. The confinement of masonry columns and walls with fiber reinforced polymers prevents brittle failure of structural masonry elements subjected to compressive overloads and seismic actions. Besides the experimental research, it is also necessary to focus on theoretical and computational aspects when dealing with the behavior of confined masonry. The aim of this paper is to present a practical modelling approach for the nonlinear finite element analysis (NLFEA) of FRP-confined masonry columns under concentric loading. A computational study, using the finite element program LUSAS 14-5 [1], on the fracture behavior of concrete elements confined with CFRP jackets has been conducted by the application of the Drucker-Prager criterion [2,3,4,5]. The behavior of FRP-confined masonry columns tested by Krevaikas and Triatafillou [6] has been simulated by means of the proposed approach. New relations for material parameters cohesion and internal friction angle affecting the compression constitutive laws are obtained by fitting of the experimental behavior of both unconfined and confined masonry columns. While the failure of unconfined specimens is determined by reaching the tensile strength, the analyses of the confined columns are terminated when reaching the tensile strength of the FRP material. The behaviour of FRP-confined masonry columns has been simulated by means of the proposed approach. The model results are in good agreement with the test results for unconfined and confined square sections with at most two layers of FRP material. A discrepancy exists between the calculated and measured stress-strain plots of columns heavily confined with FRP and an underestimation occurs for their load carrying capacities.

1

LUSAS 14-5, Finite Element System, Examples manual, FEA Ltd., Surrey, U.K.

2

H.O. Köksal, B. Doran, B.T. Turgay, "A practical approach for modeling FRP wrapped concrete columns", Constr. Build. Mater., 23, 1429-1437, 2009. doi:10.1016/j.conbuildmat.2008.07.008

3

B. Doran, "Numerical simulation of conventional RC columns under concentric loading", Materials & Design, 30(6), 2158-2166, 2009. doi:10.1016/j.matdes.2008.08.033

4

H.O. Köksal, B. Doran, E. Ozsoy, S.N. Alacali, "Nonlinear modeling of concentrically loaded reinforced blockwork masonry columns", Can. J. Civ. Eng., 31(6), 1012-23, 2004. doi:10.1139/l04-058

5

H.O. Köksal, C. Karakoç, H. Yildirim, "Compression behavior and failure mechanisms of concrete masonry prisms", J. Mater. Civ. Eng., 17(1), 107-115, 2005. doi:10.1061/(ASCE)0899-1561(2005)17:1(107)

6

T.D. Krevaikas, T.C. Triantafillou, "Masonry confinement with fiber-reinforced polymers", J. Compos. Constr., 9(2), 128-135, 2005. doi:10.1061/(ASCE)0899-1561(2005)17:1(107)

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