In the last decades, considerable improvements have been achieved in the seismic design of buildings thanks to the implementation of concepts such as ductility and energy dissipation. Consequently, new structures are not only able to perform better during seismic events, but are also more efficient in terms of balance between life safety and costs.Conversely, historic centres are still considerably affected by earthquakes. To understand the extent of seismic-related damage in historic centres, it may suffice to think that the ICOMOS World Report 2008-2010 on Monuments and Sites in Danger reports no less than five earthquakes, Chile 2010, Sichuan 2008, Haiti 2010, L’Aquila 2009 and Christchurch 2010, all of which impacted and endangered heritage buildings and assets.The lack of good quality connections among structural elements greatly affects the dynamic performance of heritage masonry structures and is the cause of out-of-plane failures of masonry panels, which are most frequently recurring, most dangerous in terms of human lives and most damaging from the point of view of conservation.Although it is recognised that the strengthening of connections is of capital importance for damage reduction and prevention, ad-hoc solutions are missing from the technical literature. Furthermore, design codes are vague when it comes to define the assessment and design procedures to be followed when implementing innovative strengthening system in historic structures.This dissertation aims to tackle such technical gaps by developing a new strengthening system and compiling a draft protocol for its validation and design.Two typologies of dissipative devices are designed to address the out-of-plane mechanisms of wall panels and limit cracking in the historic substratum, in accordance with both the principles of multilevel performance design and of the preservation of historic assets. The prototypes are validated through experimental assessment, on-site application to a case study and computational modelling. The recurring structural features and issues surveyed in the aftermaths of major seismic events feed into the validation process; the weakness of historic structural connections, the characteristics of original materials, traditional construction techniques as much as current practice are all taken in due consideration.Throughout the validation process, great importance is given to the relevance of experimental and computational results to the task of creating a systematic process, which can provide guidance to those facing the challenge of creating and implementing innovative structural solutions through a broad variety of methodologies. The research project contributes to the collection of quantitative data and, even more importantly, it amounts to a first step towards the development of validation and design procedures. These, although not exhaustive of the broad variety of scenarios typical of heritage structures, constitute the basis for further developments and research challenges, as highlighted in the conclusions.Ultimately the thesis aims to address the missing link between research, market and practice. In spite of the peculiarities and limits of each case, research should indeed strive to provide targeted, yet flexible solutions that end users will be able to apply in compliance with the requirements of current codes.
|Date of Award||7 Jan 2016|
|Supervisor||Mark Wilson Jones (Supervisor) & Dina D'Ayala (Supervisor)|