عنوان مقاله [English]
Column base connections are commonly used to connect steel columns to concrete foundations in seismically designed Steel Moment Resisting Frames (SMRFs). These connections are economical for mid-to high-rise frames in which exposed base plate connections (affixed to the footing with anchor) are impractical owing to the necessity of thick base plates and numerous anchor rods. The bolts are cast into the concrete base in location tubes or cones and fit anchor plates to prevent pullout. High-strength grout is poured into the space below the plate. Column base connections are one of the most critical structural connections. Understanding the behavior and performance of these connections come in handy for designing this type of connections, especially in the seismic design of the structures. Such column bases are often only subject to axial compression and shear. However, uplift and horizontal shear may be a design case for column bases in braced bays. The way in which horizontal shear forces are transferred to the foundation is not well researched. Some designers check the resistance of the holding down bolts, and ensure that they are adequately grouted. This practice has been successfully followed for portal frame bases, which carry a significant shear. In column base connection, it can be said that the rotational stiffness is the only feature that links uncertainty in column base connection to structures such that a change in them can change rotational stiffness and, as a result, change the dynamic characteristics and seismic response of structures. In the present study, by considering the sensitivity mentioned above, the effects of rotational stiffness and the strength capacity of column base connection on behavior and seismic performance of steel moment frame have been evaluated by Modal Pushover Analysis (MPA) and Nonlinear Dynamic Analysis (NLDA) methods. The results show that the rotational stiffness of the column base connection effects on the dynamic properties of structures such as pushover curve, story drift, and ductility as well as the analysis of models together with different rotational stiffness showed that structures in combination with semi-rigid rotational stiffness are much better in designs.