G.C. MANOS1; V. SOULIS2

1) Professor, Aristotle University of Thessaloniki, Greece , Civil Engineering, gcmanos@civil.auth.gr

It has been widely observed that masonry infill panels within multi-story reinforced concrete (R/C) framed structures were damaged to a substantial degree under past, strong earthquake activity. Under certain circumstances this interaction of masonry infills with the surrounding R/C frame during the seismic response may result in either beneficial effects, by increasing the stiffness, strength and seismic energy absorption of the structure, or in adverse consequences (damage) to the main R/C structural elements as well as premature damage to the masonry infills. This paper presents first a valid, fully non-linear 2-D numerical model that can capture realistically the in-plane hysteretic behaviour of reinforced concrete (R/C) frames with masonry infills when they are subjected to combined vertical and cyclic horizontal load. This fully non-linear 2-D numerical model accounts for all the non-linear mechanisms that can arise at the R/C frame, the masonry infill and the masonry infill – R/C frame interface. Next, the applicability of this non-linear masonry-infill concrete-frame numerical simulation is utilized to predict realistically the seismic behaviour of a prototype multi-storey R/C plane framed structural formations with masonry infills adopting a step by step “push over” type of analysis. In order to overcome the obstacle of computational time and computer memory requirements, use was made of an equivalent post-elastic “pushover” type of analysis. This equivalent post-elastic “pushover” analysis replaces the fully non-linear 2-D model with an equivalent non-linear diagonal strut in order to account for the masonry infill R/C frame interaction. This equivalent non-linear diagonal strut model draws information on the stiffness and strength variation from, one-storey R/C masonry infilled unit frame formations that compose a given multi-storey structure. These single story unit frame formations can consist of either one bay or can also be multi-bay and are first analysed by the fully non-linear 2-D model in order to calibrate the equivalent non-linear diagonal strut model. By comparing the results of the push over response of the multi-story structures by either the fully non-linear modelling or by the equivalent non-linear diagonal strut model the applicability of the later method of analysis in realistically predicting the masonry infill R/C frame interaction is demonstrated.

Keywords: Simulation, Masonry-infilled R/C frames, Equivalent step-by-step analysis, Pushover analysis