3rd Croatian Conference on Earthquake Engineering 3CroCEE

The seismic performance of building structures is governed by the lateral stiffness which is provided by the geometrical and material characteristics of their structural elements and their arrangement in plan and elevation. In general, the procedure for designing the structures to withstand the code-prescribed lateral loads is quite straightforward. However, the performance of the building subjected to realistic seismic loading is also important beyond the deterministically defined safety points that ensure life-safety at fixed return periods. Building structures in North Macedonia are designed according to an outdated code that does not consider the modern developments in the field of performance-based earthquake engineering such as ductility of the cross-section. Thus, the ratio of the column dimensions is not a matter of consideration when designing a structure and the weak beam – strong column concept is ignored in the designer’s check list. Therefore, because of the need for open architectural spaces and aligned interior walls and columns, the designers often rotate the shorter cross-section dimension along the longer beam span. With the aim of investigating the effect of the orientation of the columns in plan on the seismic performance of reinforced concrete frame structures, an existing residential building is analyzed. The existing structure is compared with alternatively designed structural models with different column cross-sections or different orientation of the existing column cross-section in plan. The comparison is performed using nonlinear analysis of the existing structures and the proposed models. Then, a simplified probabilistic assessment of the structural configurations is performed, and the results are presented. Finally, the results are used to stress the need for assessment of the existing structures with the modern approaches employed in the more up-to-date design codes and performance-based earthquake engineering principles.