Local Effects in the Seismic Design of RC Frame Structures With Masonry Infills

Abstract eng:
For the prevention of local effects that may occur on the load-bearing elements of newly designed masonry infilled RC frames, additional measures are foreseen in modern seismic design codes. In particular, European code regulations impose special detailing and confinement requirements for structural elements in RC frames with adherent masonry infills. Moreover, the verification of adjacent columns for increased shear demands is required, estimated based on approximate values of horizontal shear strength of the infill, and through the application of capacity design principles along the contact length. With the aim to verify the efficiency of the current design approach and provide additional recommendations related to local effects due to the presence of masonry infills in RC frames, in this study a series of nonlinear dynamic analyses on typical newly designed building configurations with different masonry infill typologies of varying strength and stiffness properties has been performed at increasing levels of seismicity. The analyses are carried out using a simple numerical model representing the masonry infill as a single diagonal strut. Although such model cannot directly capture the local effects in the contact region, it allows, a posteriori, the calculation of effective shear demands on the columns. For a number of considered prototype buildings, a comparison of effective shear demands obtained from analyses and shear design forces required by the code has been carried out. Furthermore, a simplified procedure for the verification of columns in RC frames exposed to increased shear demands due to the presence of masonry infills as a function of expected inter-storey drift demands has been proposed. Hence, starting from existing code recommendations, the given method allows the evaluation of shear design forces in compliance with effective shear demands, accounting for different masonry infill typologies, the position of the infill along the height of the building and the seismic ground motion intensity.

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