Numerical prediction of crack formation in historic masonry buildings

This article investigated mechanical behavior of the masonry of historic buildings. It was assumed that reliable cracking processes can be obtained by modeling masonry as a continuous medium and using the Jointed Masonry Model (JMM). The paper gives an analytical review of JMM, identifying the input parameters required for its use. Laboratory tests of brick blocks and mortar for uniaxial compression were carried out and the results of these tests are presented. It is proposed to use the triaxial compression test methodology for rocks for cylindrical samples drilled from bricks. Based on the obtained laboratory data, a method for obtaining input parameters for JMM was proposed. To verify the obtained input parameters of JMM, the construction of a numerical model to predict the stress-strain state of historic masonry buildings was proposed. As an example, old workshop buildings located in the area near St. Petersburg were considered. The results of numerical calculations were compared with the results of building facades surveys for the presence of cracks and opening widths in them. It was found that the zones of the greatest shear deformations were formed mainly in the corners of window and door openings, mainly in the right and left parts of the model. Their position had a qualitative convergence with the results of surveys. The process of formation and qualitative change of zones of limiting compressive and tensile stresses that were formed in the walls of buildings was analyzed using different sets of input parameters of JMM. The influence of dilatancy effects on the stress-strain state was also considered. The study found that a reliable description of the mechanical condition of historic masonry can be obtained using JMM, whose input parameters should be based on the results of laboratory tests. The conducted work showed that along with classical methods of surveys it was possible to use methods of numerical modeling to predict areas where crack propagation occur for historic masonry buildings.