Estudo numérico do comportamento mecânico de paredes de alvenaria estrutural com cortes

Abstract

An unplanned chase made in structural masonry for the passage of pipes is a common situation. These chases can compromise the cross section of the walls and their strength capacity. The Brazilian standardization for structural masonry defines few guidelines for chases in structural walls, while some international standards are more complete in this respect; however there is a lot of heterogeneity in the dimensional limits and positions allowed for the chases. It is also observed that the mode that the chases must be considered in the evaluation of the structural safety of the masonry is presented superficially by the standards, and little research is presented on this subject. This work initially presents a numerical evaluation using the finite element method of the mechanical behavior of structural masonry walls with chases, through which it is proposed to equate the effect of these chases on the mechanical strength of the walls. Additional criteria are defined for the resistance reduction factor (R) calculated through the slenderness of the masonry in the Brazilian standard ABNT NBR 16868 (2020). A macro modeling was performed with solid elements, and the effect of the percentage of depth of chases in relation to the thickness of the walls was evaluated, as well as the influence of the direction (horizontal or inclined) and the location of the chases. The contribution of the flanges is also evaluated for different height/length ratios. It was concluded that the simplified approach of disregarding the chase thickness of the wall determine its slenderness (λ), and consequently the strength reduction factor (R), was invalidated in the present study, considering that the numerical models provided lower reduction coefficients for any wall group studied. It is also suggested a maximum limit for the slenderness of the walls equal to 33, considering the residual thickness of the masonry in the chase region. A simplified 3D model is proposed, where the wall is simulated with one material, and other more refined, where the mortar joints are considered. Finally, the LDEM models are a good alternative for representing the behavior of the chased walls and to predict the strength, and failure mechanisms within this kind of structure.