Constitutive Models for Tuff Masonry under Uniaxial Compression

The uniaxial monotonic compressive behavior of tuff masonry has been studied by laboratory tests carried out along the directions parallel and orthogonal to the mortar bed joints. Based on the experimental results, different nonlinear stress-strain models have been defined for each loading direction to account for the orthotropy of masonry and to describe strain-softening behavior. Maximum likelihood, mean, and characteristic stress versus strain diagrams have been derived by means of different techniques of statistical analysis to be employed in the structural analysis of both new and existing constructions. Two different analytical models have been obtained via nonlinear regression analysis for defining stress-strain curves for tuff masonry to be used in the current design/assessment procedures. Such constitutive models require only the peak compressive strength and the relevant yielding strain as input data. The allowable strain ductility of masonry can also be explicitly taken into account. Strength, deformability, and ductility parameters have also been identified to run equivalent linear analyses. To this end, simple relationships are provided to define both Young’s and shear moduli from compressive strength.