Verification of Drift Demands in the Design of RC Buildings With Masonry Infills

Abstract eng:
Given the significant influence that masonry infill typologies constructed in full contact with adjacent structural elements may have on the seismic response of RC structures, the importance of integrated verification methods, accounting for the presence of non-structural infill in the structural design phase is frequently pointed out. Nevertheless, in practice, masonry infills are regularly considered only in terms of mass and vertical loads. This choice may be justified according to European code provisions, as long as possible adverse effects such as consequences of irregularities in plan and elevation or increased local shear demands in regions of interaction are prevented. On the other hand, calculations required to ensure the achievement of given performance objectives related to different limit states should not be limited to structural elements only, but also have to result in a satisfactory response of non-structural components. In order to limit the in-plane infill damage, inter-story drift limitations are commonly imposed in the design of RC structures. However, the commonly adopted approach, relying on the verification of bare frame drift demands against a code-defined drift limit that is independent of the building configuration and adopted infill typologies, may not always guarantee satisfactory results. Specifically, in function of the deformation capacity of the infill, expected extents of damage may not be sufficiently limited, or on the contrary overly conservative design choices, for example related to the size of structural elements, may be imposed. The careful evaluation of expected drift demands and their verification against appropriate drift limits related to the available deformation capacity is particularly important at higher levels of seismic action, for the damage control of weaker infill typologies, or in the case of building configurations with scarcely distributed infills. The present study has focused on possible improvements regarding commonly adopted procedures for the verification of inter-story drift demands in the design of RC structures with masonry infills. In particular, the possibility to control drift demands corresponding to infilled configurations against the critical drift limit in function of the infill deformation capacity was envisaged. Therefore, a simple parameter that accounts for structural properties of the load-bearing system and quantifies the presence of different masonry infills was adopted, implying a relationship between drift demands of bare and infilled configurations. Accordingly, a simplified approach is proposed to verify the expected inter-storey drift demands of the RC building with masonry infills, based on related values for the corresponding bare configuration. To support the described procedure, results of extensive parametric studies, including nonlinear dynamic analyses of selected frame and wall-frame dual systems designed according to current European seismic code recommendations are presented and the practical application of the proposed approach is discussed in the light of current design provisions.

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