Irregularity Effects of Masonry Infills on Nonlinear Seismic Behaviour of RC Buildings

Abstract

Despite extensive research studies, the seismic response of infilled reinforced concrete buildings remains an open problem due to both the complexity of the interaction between the infill and the frame and the large number of parameters involved. Thus, guidelines for both modelling and analysis are still lacking and the infill walls are normally treated as nonstructural components in seismic codes. However, it may be not conservative to neglect the influence of infills. In fact, the infill masonry walls may significantly affect the stiffness, strength, and energy dissipation capacity of RC buildings, even when they are regularly distributed. Recognizing this influence and its importance on the vulnerability of infilled frames, Eurocode 8 requires amplifying seismic action effects due to infills. In this paper, the effectiveness of the Eurocode 8 design provisions for infill irregularity in plan and/or elevation was investigated. To this aim, different in-plan layouts of infill walls were selected as marginal cases for which Eurocode 8 does not require amplification of the action effects due to the presence of infills, or the additional measures to counteract these effects are not mandatory. The seismic vulnerability of the infilled RC buildings was evaluated using nonlinear static and nonlinear dynamic analyses. Both cracking and crushing of masonry and stiffness and strength degradation were considered in the analysis. The effect of the layout of the masonry infills on the seismic response in terms of resistance and displacement was evaluated. Results show that in one of the case studies here examined, it is not conservative to neglect the influence of infill panels. In fact, structural failure due to torsion and soft-storey effects may occur even in cases where Eurocode 8 does not require the amplification of the action effects. Finally, the total shear demand on columns may be underestimated, even in cases where the code provisions for infills irregularity are not mandatory, and the additional shear demand in the columns induced by the masonry infill is very low.

A moderately refined and efficient regional seismic damage simulation method considering building irregularity

“…Nevertheless, numerous studies demonstrated that the irregular arrangement of infill walls in RC frames can cause serious damage to structures under earthquake excitation (Ferraioli and Lavino, 2020;Hermanns et al, 2014). Thus, this paper suggests that the shear micro-springs representing the nonlinear behavior of infill walls can be embedded into the MRLEs of the frame structures, and also use the pinching model to simulate their hysteretic behavior.…”

Pushover Analysis in Seismic Engineering: A Detailed Chronology and Review of Techniques for Structural Assessment

“…Seismic analysis procedures are categorized into linear and nonlinear methods, each further divided into static and dynamic procedures. The linear static technique is widely used due to its simplicity [10,11], while linear dynamic techniques offer diverse approaches for studying time-varying structural reactions during seismic events [12,13]. Figure 1 illustrates the combination of these seismic analysis procedures.…”

Influence of Chained Masonry on the Seismic Response of Reinforced Concrete Buildings

“…It also represents in our country the majority of the urban heritage, especially in the north and in the highlands, which is generally known as areas very vulnerable to earthquakes. Here, we are concerned with the observation and study between these walls linked to frames without gap and the masonry walls, which is called "chained masonry walls" that is a special case of infill masonry [1,2].…”