Numerical Analyses of Mortar Incorporating the Variation in Poisson’s Ratio with Increasing Axial Load

A.LÜBECK(1), G. MOHAMAD(2), F. S. FONSECA(3), A. S. MILANI(4) and H. R. ROMAN(5)

(1)Professor, DECC, UFSM, Santa Maria, 97105-900,Brazil, andrelubeck@gmail.com

(2)Professor, DECC, UFSM, Santa Maria, 97105-900,Brazil, gihad@ufsm.br

(3)Professor, DCEE, Brigham Young University, Provo, 84602, USA, fonseca@byu.edu

(4)Professor, Civil Engineering, UNIPAMPA, Alegrete, 97546-550, Brazil, alissonmilani@unipampa.edu.br

(5)Professor, Civil Engineering Department, UFSC, Florianópolis, 88040-900, Brazil, humberto.roman@ufsc.br

This article is a revised and expanded version of a paper entitled Numerical Analyses of Mortar Incorporating the Variation in Poisson’s Ratio with Increasing Axial Load presented at 10IMC – 10th International Masonry Conference, 9-11 July 2018 Milan (Italy).

ABSTRACT .The work presented herein evaluated the influence of compressive strength and confinement on the stress-strain behaviour of axially loaded mortar specimens by means of experimental and numerical analyses. Two mortars were tested, with volume proportions of cement : lime : sand of 1:0.5:4 and 1:1:6. From these two specimen heights, 50 and 140mm, with diameter of 45mm, resulting in diameter/height ratios of 1.0 and 0.3, were manufactured. The experimental results indicated that the confinement and strength of the mortar influence its stress-strain behaviour, the larger the confinement, the more, nonlinear the behaviour. In addition, the results indicated that the Poisson’s ratio and tangent modulus of elasticity vary with increasing applied load. Two numerical models were tested using the same finite element mesh, boundary conditions and load. The first model was based on the Total Strain Smeared Crack Model and the second model accounted for the observations from the experimental phase with a nonlinear “elastic phased” analysis, which updates the modulus of elasticity and the Poisson’s ratio at each new phase. The tangent modulus of elasticity was calculated directly from the experimental results while the Poisson’s ratio was approximated using the model proposed by OTTOSEN [16]. The numerical model based on the total strain smeared crack was not able to reproduce the behaviour of the compressed mortar near failure while the phased model presented satisfactory results, even close to failure, when cracking is significant.

KEYWORDS: mortar, confinement, stress-strain behaviour, numerical model, compressive strength.