Analysis of behavior and uniaxial compression failure modes in ungrouted hollow concrete block masonry and their implication in design expressions

In this study, new analytical expressions for the design and revision of ungrouted masonry of hollow concrete blocks under gravitational effects were developed. These expressions can predict the compressive strength and modulus of elasticity for full and face-shell mortar beddings. A trend chart was generated, considering various modes of failure for different strength relationships between blocks and mortar. The study revealed that the main international masonry design codes underestimate the compression resistance of masonry when using weak mortar in combination with full mortar bedding. Results obtained using the Finite Element Method indicated that the optimal compression strength ranges were: 62–70 % for weaker mortar than the block with full mortar bedding; 152 % for block weaker than the mortar with full mortar bedding; and close to 67 % with face-shell bedding mortar. • A non-linear 3D FEM for concrete masonry was proposed and verified. • New expressions to predict compressive strength of HCB masonry was proposed. • Deformational analysis in the plastic equivalent strain domain was performed. • Stress-strain state was obtained with mortar stronger than HCB. • Failure modes behavior with the strength ratio between mortar and the HCB are shown.