reference ©2012 Civil-Comp Ltd

Paper 116

A Study of the Out-of-Plane Behaviour of Unreinforced Masonry Walls using a "Unit and Interaction" Micro-Modelling Approach

E. Bultot and L. Van Parys
Risk Research Team, University of Mons, Belgium

Keywords: out-of-plane loads, unreinforced masonry, numerical simulation, unit and interaction, micro-modelling, contact laws.

full paper (pdf) - reference

Most of the masonry walls involved in real buildings are supported on three or four sides; these boundary conditions lead to the consideration that walls are subject to bi-axial bending when out-of-plane loads are applied. Consequently the wall undergoes a combination of horizontal, vertical and diagonal bending.

The research project described in this paper is directed towards the development of a simple analytical method for the verification of the out-of-plane behaviour of unreinforced masonry (URM) walls. This analytical approach relies on the results of a preliminary numerical study. This paper presents the early steps of the research as well as preliminary results concerning the validation of the numerical modelling.

This paper contains three parts. The first part presents the "unit and interaction" micro-model approach developed in the framework of this research. The micro-modelling approach effectively models each masonry unit with respect to the effective unit-joint pattern and provides the highest care in managing the interactions between them. The innovative character of the numerical modelling approach which is proposed concerns the recourse to specific contact laws for managing the manner whose adjacent units will interact together. These laws will govern the behaviour of the interfaces based on the local normal and shear stress states. This method will be efficient to identify the effective failure mode susceptible to occur during the out-of-plane loading of unreinforced masonry walls (taking into account the morphology, the boundaries, etc.).

In the second part, the accuracy of the "unit and interaction" micro-model approach to capture horizontal, vertical and diagonal bending failure modes of the URM walls and the resistant mechanisms is verified by applying this concept to three illustrative examples, one for each bending type. The comparisons of the results of the numerical simulations with those from the experimental tests are conclusive: the failure modes obtained are similar to those observed during the tests.

Finally, the third part presents two case studies: the "unit and interaction" concept was applied to two URM walls subject to two-way out-of-plane bending. In the two cases, observations of deformations of the wall and stresses permit the identification of a failure mechanism similar to those predicted by the yield line theory.