Seismic Design and Response of Bare and Masonry-Infilled Reinforced Concrete Buildings. Part Ii: Infilled Structures

Abstract

The effects of masonry infills on the global seismic response of reinforced concrete structures is studied through numerical analyses. Response spectra of elastic SDOF frames with nonlinear infills show that, despite their apparent stzening effect on the system, infills reduce spectral displacements and forces mainly through their high damping in the first large post-cracking excursion. Parametric analyses on a large variety of multi-storey infilled reinforced concrete structures show that, due to the hysteretic energy dissipation in the infills, if the infilling is uniform in dl storeys, drifts and structural damage are dramatically reduced, without an increase in the seismic force demands. Soh-storey effects due to the absence of infills in the bottom storey are not so important for seismic motions at the design intznsity, but may be very large at higher motion intensities, if the ultimate strength of the infills amounts to a large percentage of the building weight. The Eurocode 8 provisions for designing the weak storey elements against the effects of infill irregularity are found to be quite effective, in general, for the columns, but unnecessary and often counterproductive for the beams.

Empirical-Based Infill Model Accounting for in-Plane/Out-of-Plane Interaction Applied for the Seismic Assessment of Ec8-Designed Rc Frames

“…Each infill wall was introduced in the structural model through a single equivalent strut whose non-linear behaviour is modelled based on Panagiotakos and Fardis proposal [3][4]. The ratio of the softening over the elastic stiffness, α, was set to -3.6%.…”

“…OOP acceleration can produce infills' collapse by their overturning, which is a great risk for life safety as well as an obstacle to escape/rescue operations during seismic emergency [2]: in this sense, the OOP collapse of infill walls is associable to the attainment of the Life Safety Limit State (LS). A great number of experimental and analytical works concerning the IP behaviour of URM infills is available in literature ( [3][4][5][6], among many others) and some analytical and experimental works have been proposed about their OOP behaviour, especially in recent years ( [7][8][9][10][11][12][13][14][15], among others), and concerning the IP-OOP interaction phenomena, i.e., the effects of IP actions on the OOP behaviour and vice versa. For instance, several authors showed through analytical and experimental studies how the IP displacement demand affects the OOP response of infills in terms of capacity and demand acting on them.…”

Eurocode-based seismic assessment of modern heritage RC structures: The case of the Tower of the Nations in Naples (Italy)

“…Tuff and concrete infills are modeled through an equivalent strut macro-model [29]. They are two crossing diagonal axial springs (link) that can carry compression only.…”

Empirical Unreinforced Masonry Infill Macro-Model Accounting for in-Plane/Out-of-Plane Interaction

“…Clearly, Pdam/Pundam cannot be higher than 1 and must be equal to 0 if IDR≥IDRu, i.e., the OOP capacity drops to zero at the infill IP collapse. If IP tests were stopped prior to the complete infill's resistance loss, IDRu was calculated by applying Fardis and Panagiotakos [6] proposal.…”

“…A very large number of experimental tests and modelling proposals concerning infills' IP behaviour are proposed in literature, e.g. in [6][7][8][9][10], among many others. Moreover, infills are subjected to Out-Of-Plane (OOP) seismic accelerations, which may provoke the collapse with overturning from the structural frame.…”