The Effect of Masonry Infill Model Selection on the Seismic Response of Reinforced Concrete Frame Structures

<p>In many countries, reinforced concrete (RC) frames are widely utilized as the primary building structure. The infill is typically composed of traditional masonry (brick elements connected with mortar), commonly without isolation from the frame. It is noted that in engineering practice, seismic force calculations for RC frame buildings are often conducted on models that exclude masonry infill, even when the infill is not isolated from the frame through specific construction elements. In such cases, the walls are considered only as a permanent load. Consequently, the contribution of non-insulated (bonded) masonry infill to changes in bearing capacity, stiffness, and ductility of the RC frame, affecting stresses and horizontal movement during seismic activity, is frequently disregarded. To assess the consequences of prevalent calculation models, four representative types of RC frame models with masonry infill were analysed herein. The study demonstrated that differently conceptualized models of the same building impact dynamic characteristics, including forces and displacements of the main frame structure. The dynamic analysis revealed that inadequate treatment of the frame and non-insulated infill connection in the design phase can lead to dangerous phenomena such as "soft floors," significant torsion, and the effects of short columns going unnoticed. Therefore, this paper underscores the importance of appropriately addressing non-insulated infill in the calculation model in routine design practices. Additionally, it advocates for the issuance of precise instructions for special construction measures that would effectively isolate masonry infill from the frame when such a solution is justified.</p>