Seismic assessment of the out-of-plane performance of traditional stone masonry walls.Costa, A.A. (2012). Tese de doutoramento.

The present Thesis focuses on the experimental characterization and numerical study of the out-of-plane behaviour of stone masonry walls for quasi-static and dynamic loads.
Several in-situ experiments on existing constructions were performed in order to characterize the quasi-static behaviour of unreinforced and strengthened specimens with techniques commonly used in pre/post-earthquake interventions. For this purposes, a new test setup to perform field tests within reasonable time interval and costs was developed and validated with an extensive tests campaign on damaged constructions after the 1998 Azores earthquake. The efficiency of different strengthening techniques was assessed and compared among them and simple analytical calculations proved to be efficient and conservative solutions when applied to force-based assessment of existing masonry walls.
The dynamic behaviour of masonry walls was also evaluated resorting to shaking table tests as well as numerical simulations. Shaking table tests performed at LNEC (Lisbon, Portugal) on full scale ne-storey sacco stone masonry facades were made especially devoted to the out-of-plane behaviour, where the selection of the input ground motions revealed to be decisive to trigger the overturning mechanism. The behaviour of the facades was found to be significantly influenced by the presence of the masonry multiple leaves, being the instability achieved by the overturning of the outer leaf and local masonry assemblages’ effects.
A novel proposal for simulating the dynamic response of local mechanisms was made resorting to multibody dynamics, where masonry portions (of a given local mechanism) are simulated through kinematic chains (rigid bodies) with concentrated nonlinearity at contact surfaces. The restitution coefficient, an important parameter to correctly describe the dynamic rocking behavior of rigid bodies, was determined by lab experimental tests of cantilever masonry walls for 2-sided rocking, where the dynamic properties of the wall are reproduced by an equivalent structure based on a proposed methodology named as Equivalent Block Approach (EBA).
Finally, the multibody dynamics approach was validated against two shaking table test results: the shaking table test presented herein and the test performed on a two-storey height double leaf stone masonry facade tested at EUCENTRE (Pavia, Italy). Promising results were obtained and some comments are included regarding static and dynamic analysis of local mechanisms resorting to simplified models. At the end, a proposal for seismic assessment of existing structure is made, where both the in-plane and out-of-plane behaviours are taken into account.


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