THE EFFECT OF GEOMETRIC IMPERFECTIONS ON THE BUCKLING RESPONSE OF A THIN MASONRY SHELL STRUCTURE SUBJECTED TO EARTHQUAKE LOADS Eftychia DICHOROU 1 , Matthew J. DEJONG 2 , ABSTRACT The presence of initial geometric imperfections in thin masonry shell structures might be particularly important in an earthquake, as they can cause reductions to their load-carrying capacity. This paper aims to assess the effect of geometric imperfections on the seismic capacity and buckling load of an 8mx10m unreinforced, thin masonry shell structure. The structure has the same geometry as the Droneport Prototype that was constructed as part of the Venice Architecture Biennale 2016. An elastic buckling analysis is performed on the design shell geometry using finite element modelling. Repeated simulations are conducted to investigate the sensitivity of buckling to reductions in shell thickness. These analyses include the presence of initial shape and thickness imperfections which are likely to arise in the construction stage. To quantify the initial imperfection parameters, the actual shell geometry of the Droneport Prototype was surveyed using a laser scanner. The sensitivity of buckling to initial geometric imperfections is examined by performing analyses on multiple imperfection patterns that are generated from a tool which is based on the random field theory and uses the laser scan data as input. Comparison of the results enables determination of the extent to which imperfections influence the seismic collapse of thin masonry shells, including identification of the extreme thinness limits at which seismic buckling becomes an issue. The inclusion of a realistic representation of the imperfections that might occur in the construction of a shell structure during the design process is novel and important, to ensure seismic safety, making the design of thin masonry shells more robust in moderate earthquake-prone regions. Keywords: Masonry shells; Earthquake design; Geometric imperfections; Laser scanning; Buckling analysis 1. INTRODUCTION Tile vaulting is a centuries-old construction technique which has recently revived interest due to the development of powerful form-finding tools for the analysis and design of masonry structures (Davis et al., 2012). These innovative computational tools that are based on interactive three-dimensional equilibrium methods, enabled traditional tile vaulting to become a flexible and versatile technique through which, the expressive free-forms of modern architecture could be made possible (López et al., 2016). The contemporary tile vaulting has become particularly attractive for the developing world, as it can also provide a sustainable design alternative. The ability of tile vaulted systems to effectively support their own weight through their optimized form, while using sustainable earth-based materials such as soil-pressed tiles, their extreme thinness which reduces the volume of material required for their construction, and the self-supportive nature of masonry which reduces the need of excessive formwork, are the main parameters which contribute towards the achievement of significant financial and environmental benefits (Ramage et al., 2010). However, the use of minimal formwork for the construction of thin masonry shells can lead to the unavoidable generation of geometric imperfections. Several studies have shown that the presence of initial geometric imperfections on shell structures can cause reductions to their load-carrying capacity (Chen et al., 2016), making their effect in an event of an earthquake to be particularly important. Accounting for the initial geometric imperfections that may occur in the construction of a shell structure during the design process, is therefore vital for ensuring a 1 PhD Candidate, Department of Engineering, University of Cambridge, Cambridge, UK, ed468@cam.ac.uk 2 Doctor, Department of Engineering, University of Cambridge, Cambridge, UK, mjd97@cam.ac.uk