Progressive instability in circular masonry columns

TL;DR

This paper investigates the progressive instability of circular masonry columns under eccentric loads using two analytical approaches, revealing how material response and aspect ratio influence stability and damage, and providing a practical design formula.

Contribution

It introduces a comparative analysis of semi-analytical and plastic-damage models for masonry columns, highlighting their applicability and differences in predicting instability and damage.

Findings

Material response type is less critical for high aspect ratio columns.

Tensile strength significantly increases limit load at high eccentricities.

The no-tension model accurately predicts damage zones at low eccentricities.

Abstract

The instability behaviour of eccentrically loaded circular masonry columns is investigated. Two approaches are considered for the analysis. One is based on a semi-analytical formulation of the relevant boundary-value problem for a no-tension material response; the other employs a plastic-damage-contact constitutive model, the CraftS model, to capture the complex microstructural behaviour of the material. The latter has been implemented in the finite element program LUSAS and has been already successfully employed to describe progressive instability in eccentrically loaded brickwork wallettes of rectangular cross section. Equilibrium paths and limit load estimations are computed for both analysis approaches for a range of column aspect ratios and load eccentricities. It is shown that the type of material response becomes less important for specimens with height-to-diameter aspect ratios greater than 7.5 and for loads applied to points in the kernel of the cross section, while for higher eccentricities the presence of a tensile strength increases considerably the limit load. The damage evolution predicted by the models is also investigated for selected cases, showing that the formulation based on the no-tension material is able to capture with good agreement the damaged zone of the column for loads with low eccentricities. For the same type of loading, a useful design formula is provided.