Deformation behavior of unreinforced masonry structures

• Head of project: Prof. Dr. A. Dazio
• Assistants: Dr. Katrin Beyer, Ahmad Abo El Ezz

The seismic design action defined by the Swiss design code has increased steadily over the past decades. For this reason, and despite the moderate seismicity of the country, current requirements render the design of unreinforced masonry (URM) structures almost impossible. This applies even to the lower seismic zones with design ground accelerations of 10% g and less. It is widely accepted that force-based design methodologies for URM structures implemented in most current codes have the tendency to be rather conservative while displacement-based methodologies show the potential of leading to more rational and economic structures. However, important data regarding the deformation behaviour of URM structures are still missing. The objective of this project is therefore to quantify better the deformation behaviour of URM structures so that displacement-based approaches can be applied in practice.

The project consists of two major parts: The first concerns the out-of-plane behaviour and the second the in-plane behaviour. The out-of-plane behaviour is investigated by means of shaking table tests and numerical models with the aim of determining and quantifying parameters that have a major influence on the out-of-plane behaviour of URM walls. In the second part of the project, which deals with the in-plane behaviour, the global behaviour of URM structures is analysed taking into account the load-deformation characteristics of spandrel beams. Numerical simulations have shown that spandrel beams influence the global wall behaviour significantly. Since URM spandrel beams have never been tested, quasi-static cyclic tests on such beams will be conducted. The results will be used to develop a mechanical model of the spandrel beams and also to refine the global analysis of URM structures. For the latter different approaches are followed which comprise the development of own analysis software as well as the application of commercial packages. The final goal is to develop practice-oriented guidelines for the nonlinear static analysis of URM structures with and without reinforced concrete slabs.