Seismic performance evaluation of 2-Dimensional reinforced concrete, steel and mixed frames

ABSTRACT: It is well known that, Turkey and Cyprus are in high seismic activity zone. Therefore designers should consider the seismic effects according to described earthquake. Reinforced concrete and structural steel are the two main materials that are used in construction industry. However, these two materials possess different characteristics in their behavior. In recent years structural steel has become more popular due to some of its characteristics such as being light, ability for being prefabricated, fast erection and ductility levels. Nowadays, with lack of space for the development of cities multi-story structures are more in favor by the building developers and contractors. Demolishing old structures and constructing new high-rise buildings are not always the optimized solution from economic point of view. In recent years using light materials to build extra stories on existing structures is believed to be a good option for the solution of load problem. Under static loads there may not be any serious concern. However the analysis and assessment of seismic performance of these mixed-material frames would be different when compared to conventional structures. Designing such structures would be a challenging task since current design codes do not support the analysis and design solutions for the structures having frames with different damping ratios. The scope of this work is to evaluate the seismic performance of mixed and regular structures. For this, the mixed structural models considered had two parts; a lower part constructed from reinforced concrete and the upper part made constructed of structural steel. In order to investigate and evaluate the seismic performance of mixed structures and compare the results with those of normal structures, the nonlinear time history analysis method was used including geometric and material nonlinearities. In order to achieve a reliable comparison the response of mixed structures under dynamic loads were investigated together with normal structural steel and reinforced concrete structures. Comparison of the results showed that changing the story numbers or structural materials will cause contrasting results. Plain frame dynamic analyses were performed on three different frame structural models. Two regular framed models; fully reinforced concrete and fully structural steel were designed according to codes and the third one was created by combination of the other two models. Keywords: seismic performance, mixed structure, composite framing, time history, dynamic analysis. …………………………………………………………………………………………………………………………