Abstract: Masonry structures can be considered as the simplest type of structures concerning its assemblage but, at the same time, it is one of the most complex construction materials in terms of mechanical properties and correct behaviour assessment. In this context, the work herein presented aims at describing an experimental testing campaign recently carried out in order to characterize the out-of-plane behaviour of traditional masonry constructions. Taking advantage of the existence of a traditional two-storey masonry building abandoned after the 1998 Azores earthquake, several in-situ tests were defined and performed with the application of quasi-static cyclic loads at the building top level in the out-of-plane direction. In addition, the efficiency of retrofitting and/or strengthening techniques applied during the 1998 Azores reconstruction process was also experimentally evaluated. Finally, an overall discussion of these techniques is presented, resorting also to previous tests’ results carried out by the same authors, aiming at inferring and suggesting quantifications of strengthening techniques’ contributions for future interventions on existing buildings. For this purpose, simple analytical mechanical approaches were adopted in order to provide numerical estimates of strength that were found in good agreement with the experimental results.
Abstract: Stone masonry is one of the oldest building techniques used worldwide and it is known to exhibit poor behaviour under seismic excitations. In this context, this work aims at assessing the in-plane behaviour of an existing double-leaf stone masonry pier by experimental testing. Additionally, a detailed 3D finite element numerical analysis based on micro-modelling of the original pier is presented (fully describing the geometry and division of each individual elements, namely infill, blocks and joints) aiming at simulating the experimental test results. This numerical strategy can be seen as an alternative way of analysing this type of constructions, particularly useful for laboratory studies, and suitable for the calibration of simplified numerical models. As part of a wider research activity, this work is further complemented with the presentation of an effective retrofit/strengthening technique (reinforced connected plaster) to achieve a significant improvement of its in-plane cyclic response which is experimentally verified in the results presented herein.
Abstract: The present work reports on an in situ experimental test campaign carried out on abandoned traditional masonry houses after the 9th July 1998 earthquake that seriously hit the Faial island of Azores. For the testing purposes, an experimental test setup was developed based on a self-equilibrated scheme, which is herein described reporting on the advantages and drawbacks of this in situ test setup.
Five specimens were tested aiming at characterizing the out-of-plane behavior of stone masonry walls and strengthening solutions recommended for post-earthquake interventions. A detailed comparison between solutions' efficiency is presented including a cost vs benefit analysis.
In order to assess the efficiency of the developed test setup for other applications on stone masonry walls, an in-plane test on an existing URM panel is also presented. Several related issues are discussed, namely the advantages of dealing with the real boundary conditions and the capacity of providing valuable information of the response, as well as a detailed analysis of the obtained results.
The authors believe that this work provides an increase in knowledge on the seismic behavior of the existing masonry constructions, resulting from the development of an in situ test setup and the efficiency quantification of strengthening solutions. Therefore, the work is thought to positively contribute for the preservation of architectural heritage and for its seismic vulnerability reduction.
Abstract: 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 one-storey sacco stone masonry façades 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 façades 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 behaviour 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 façade 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.
