Granite plates as structural slabs in Brazilian buildings: application of reliability concepts

Abstract

Polished finishing granites are greatly accepted for claddings because of the plates’ shape, design and color variety. The features depend on the geological conditions that occur during the formation process, which include the mineralogy of the stone, the fluids formed during the process, the grain size of the minerals and the way in which the minerals interact with each other. One of the noblest uses of stone plates is in non-adherent covering systems (without mortar), such as ventilated façades and pedestrian paving systems. Currently, the methodology for non-adherent systems uses the allowable stress design criteria. In recent years, the number of papers indicating reliability analysis as an important design tool for natural stones has increased. However, a lack of information concerning the design methodology still happens. Therefore, the structural properties assessed as complementing these studies were: compressive strength, three-point flexural tensile strength, Young’s modulus and Poisson’s ratio. A granite slab design example was also presented. First, the thickness of the plates was determined based on the formulation proposed by Timoshenko [Strength of materials (original language, Portuguese), Volume II. Editora Ao Livro Técnico S. A., Rio de Janeiro, 1977], using the allowable stress design criteria. Next, the reliability analysis was performed by Monte Carlo simulation. Results showed that the Desireé White granitic plate presented a higher reliability index than the Capão Bonito Red granitic plate. This result seems to be paradoxical, owing that the Capão Bonito Red presented a higher value of mean flexural strength than the Desireé White. The minimal safety factors to satisfy the target reliability value of 3.8 as recommended by the standard EN 1990:2002 (Eurocode) were found to be 2.61, 1.98 and 2.72, respectively, for the three stone types.