Shear modulus and stiffness of brickwork masonry: An experimental perspective
Masonry is a composite non-homogeneous structural material, whose mechanical properties depend on the properties of and the interaction between the composite components - brick and mortar, their volume ratio, the properties of their bond, and any cracking in the masonry. The mechanical properties of masonry depend on the orientation of the bed joints and the stress state of the joints, and so the values of the shear modulus, as well as the stiffness of masonry structural elements can depend on various factors. An extensive testing programme in several countries addresses the problem of measurement of the stiffness properties of masonry. These testing programs have provided sufficient data to permit a review of the influence of different testing techniques (mono and bi-axial tests), the variations caused by distinct loading conditions (monotonic and cyclic), the impact of the mortar type, as well as influence of the reinforcement. This review considers the impact of the measurement devices used for determining the shear modulus and stiffness of walls on the results. The results clearly indicate a need to re-assess the values stated in almost all national codes for the shear modulus of the masonry, especially for masonry made with lime mortar, where strong anisotropic behaviour is in the stiffness properties.
Behaviour of Structures - Churches
Church buildings in the Maitland diocese were investigated for damage after the Newcastle earthquake of Dec. 1989. Although most of the damage was in Newcastle, the author focuses on damage in the Maitland area.
MASONRY FAILURE CRITERION UNDER BIAXIAL STRESS STATE
Masonry is a material that exhibits distinct directional properties because the mortar joints act as planes of weakness. To define failure under biaxial stress, a 3D surface in terms of the two normal stresses and shear stress (or the two principal stresses and their orientation to the bed joints) is required. This paper describes a method to define a general anisotropic (orthotropic) failure surface of masonry under biaxial stress, using a cubic tensor polynomial. The evaluation of strength parameters is performed using existing experimental data through a least-squares approach. The validity of the method is demonstrated by comparing the derived failure surface with classical experimental results. The ability to ensure the closed shape of the failure surface, the unique mathematical form for all possible combinations of plane stress, and the satisfactory approximation with the results of the real masonry behavior under failure conditions are some of the advantages of the proposed method.