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Parametric finite element analysis of masonry structures using different constitutive models

Stavroulaki Maria, Liarakos Evaggelos

Πλήρης Εγγραφή

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Περίληψη

The masonry of old structures varies in a wide range: geometry of walls and columns, type anddressing of stones, joint constructions and materials, and others. Also repair work and strengthening techniquesof old masonry have a major influence on the mechanical behavior so additionally material models are neededto describe the seismic behavior of strengthened masonry.The masonry material constituting the structures of monumental and old constructions is often characterizedby very low tensile strength with respect to the compression strength. In parallel, masonry compressionbehaviour is of crucial importance for design and safety assessment purposes, since masonry structures areprimarily stressed in compression. However, the compression failure mechanism of quasi-brittle materials israther complex, especially when compared with tensile failure.The finite element method is usually adopted to achieve sophisticated simulations of the structuralbehaviour. A mathematical description of the material behaviour, which yields the relation between the stressand strain tensor in a material point of the body, is necessary for this purpose. This constitutive model must becapable of predicting the behaviour of the structure from the linear elastic stage, through cracking anddegradation until total loss of strength.Masonry is a composite material made of bricks and mortar, which exhibits distinct directional propertiesdue to the mortar joints which act as planes of weakness. In our research, on the numerical representation themacromodeling of masonry as a composite is used, which is applicable when the structure is composed of solidwalls with sufficiently large dimensions so that the stresses across or along a macro-length will be essentiallyuniform and also is more practice oriented.Nonlinear behaviour of both components should be considered to obtain a realistic model able to describecracking, slip, and crushing of the material. Its yield behaviour is a strong function of hydrostatic pressure andtensile yield stress and compressive yield stress, under uniaxial loading are different. In order to obtain a betterrepresentation, individual yield criteria must be considered, according to different failure mechanisms, one intension and the other in compression. Something which is not so easy in many yield and failure criteria whichare already programmed to finite elements programs.In this paper, some results of a parametric investigation about the applicability of widely used criteria likethe Drucker and Prager, the Parabolic Mohr- Coulomb and the Buyukozturk, in the dynamic analysis ofmasonry wall are presented. The analysis was done, considering various dynamic loads in order to study theinfluence of the selected criterion on the dynamic behaviour locally or globally of the structure. The correlationof the results is concentrated on the effectiveness of the examined criteria to represent the real mechanicalbehavior and the estimation of critical areas. Also the differences which are presented seems to be remarkablewhen complicated dynamic loads are applied.

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