عنوان مقاله [English]
In this study, the application of one steel structural system called steel frames with knee element connections (KCF) is investigated for seismic resistant structures. In these structural systems, ends of beams are connected to columns by hinges (simple connection), and ends of knee elements are connected to columns and beams by hinges as well. This configuration creates one zonular rigid connection instead of concentrated rigid connection in moment resisting frame (MRF). This structural system has several advantages for example, it provides more flexibility in architecture design, and it avoids the construction difficulties of rigid connections, which need an advanced technology of manufacturing and inspection. Besides, some defects of moment resisting frames such as insufficient lateral stiffness and large lateral displacements are avoided too. Using this system, the repairing cost of the buildings after a moderate earthquake could be greatly reduced because the knee members can be easily fixed or replaced. In addition, this system is a suitable technique for retrofitting the damaged or existing buildings. This study applied finite-element analysis to this frames and compared seismic performance factors, collapse mechanism and material usage of frames under pushover and cyclic analyses in ABAQUS software. Results showed the relative advantages in connection with KCF with respect to MRF rigid connection such as increase of lateral stiffness and strength and improvement in hysteretic behavior of KCF with respect to MRF. However, the lateral torsional buckling (LTB) of beam in KCF must be considered more than MRF beam's because of different configurations in beam to column connection. In addition two tree-story four-bay frames of each stractural system were designed according to ASCE7-SEI10 and AISC360-10 criteria without any special seismic design approach to case studies and their pushover and incremental dynamic analyses (IDA) were carried out using the ``OPENSEES'' software. Seismic performance evaluation results according to FEMA-P695 criterion and fragility curves showed that collapse mechanism of KCFs is similar to MRFs mechanism's; this structural system has a better seismic performance and low probability to collapse compared to the MRFs. For the main result from this study, one can use the seismic design factors ($\omega_0$, R, $C_d$) of ordinary moment resisting frames (OMRF) of ASCE7- SEI10 for design of KCFs in ordinary ductility level without any special consideration in seismic design.