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The paper examines the seismic response of an existing externally braced steel frame high-rack structure and analyses the effects of mass eccentricities that can be realistically achieved by asymmetric positioning of the stored payload. Apart from the symmetric, three different extreme payload distributions with varying occupancy levels have been considered, with the payload mass concentrated: (i) at the topmost part of the structure, (ii) at the upper corner of the structure and (iii) at the outermost edge of the structure. The seismic performance has been analysed by using unidirectional non-linear dynamic analyses as well as by non-linear static analyses, with the structure's response observed in the cross-aisle direction in which it is possible to account for the effects of torsional twist. The results showed that most unfavourable payload eccentricities might increase the seismic risk leading to local instability of the rack columns. From a seismic point of view, a fully occupied structure does not present the most critical condition. It is obtained at an intermediate occupancy level, which allows more space to produce horizontal and/or vertical eccentricities. Very small occupancy levels in turn produce smaller induced seismic forces and might therefore not be of critical concern. The paper concludes that the payload distribution concentrated symmetrically at the topmost part is the most critical for the central part of the rack structure and that concentrating the payload eccentrically at the outermost edge is the most critical for the flexible side of the structure, while shifting the payload to one of the upper corners is generally not of critical concern.

The seismic retrofitting measures which are appropriate for buildings belonging to the architectural heritage are limited, since the extent to which such buildings are allowed to be altered is severely limited. In the paper the possibilities which exist for the implementation of base isolation in the case of the seismic upgrade of unreinforced masonry (URM) structures belonging to the valuable architectural heritage have been investigated. A new methodology for the modelling of URM buildings, based on an equivalent frame model with plastic hinges, was used for this purpose. A case study involving a typical neo-renaissance masonry building is presented, in which base isolation is implemented, and a comparison is made with the response of the building in its original state. A refined approach for the selection of proper isolation devices is proposed which is based on the nonlinear static (pushover) analysis of such buildings and on the desired level of seismic protection, with reference to the code-based damage limit Downloaded by [University of Bath] at 12:53 29 June 2016 A c c e p t e d M a n u s c r i p t 2 states. Additionally, the incremental nonlinear dynamic analyses were also applied in order to estimate what increases in seismic safety could be achieved if the employed base isolation system was used in the case of different seismic intensities. Running head: Protection of Heritage Arch. with Seismic Isolation