CRACK PREDICTION IN MASONRY STRUCTURES

The paper deals with a numerical procedure available for the analysis of unreinforced masonry structures. The model is capable of predicting the likelihood of cracking and the expected crack widths. Masonry is modelled on a discrete system of rigid blocks connected by unilateral elastic contact constraints. The numerical algorithm is based on the introduction of suitable distortion terms capable to generate internal coactions such as to give back the compatibility in the sign conditions where tensile stresses are not admissible. The distortion terms can be interpreted as cracks caused in the material because of the no-tension behaviour. A convenient way to define the ‘contact device ’ which links adjacent blocks, through which a mortar joint could be simulated, is to consider a sort of Drucker’s model consisting of a set of elastic links orthogonal to the contact surface between two adjacent blocks, and an additional link tangent to the same contact surface. In accordance with the assumption that only compressive forces can be transmitted from one element to another, no tensile strength in the joints is considered. Through the results of the numerical procedure it is possible both to define and locate the cracking pattern, highlighting the actual reacting structure, within the apparent one, and to evaluate the width of the cracks located in the joints.