Performance limits of brick masonry spandrels

Spandrel elements in unreinforced brick masonry buildings with timber floors consist of a masonry spandrel supported by either a timber lintel or a masonry arch. When subjected to seismic loading, the force-deformation relationship of such spandrel elements can be described by a piecewise linear relationship which distinguishes two principal regimes: The first regime describes the behaviour up to peak strength of a largely uncracked spandrel. The second regime is associated with a residual strength mechanism after the formation of major cracks in the spandrel. The residual strength of brick masonry spandrels is often less than 80% of their peak strength. Hence, according to established rules in seismic engineering for estimating the ultimate drift capacity of structural members, the residual strength would typically be neglected when assessing the seismic behaviour of existing buildings. However, the residual strength mechanism is typically associated with a rather large deformation capacity and it is therefore argued that it should be considered. Moreover, small cracks due to, for example, previous earthquakes or differential foundation settlements might reduce the peak strength of the spandrel but will have little influence on its residual strength. This paper discusses on the basis of experimental and numerical results the different limit states of brick masonry spandrels subjected to seismic loading, which characterise the two regimes and the ultimate rotation capacity of the spandrel.