Circular base plates with a gap under large eccentric load

Circular base plates are commonly used for cylindrical columns, such as pylons in cabled-stayed bridges, lighting poles, electric power line posts, and even buildings. In some structures and conditions, a little gap is considered between the base plate and foundation. In this case, the whole forces are transmitted to the foundation via bolts. There are several explicit methods for design of rectangular base plates, which can be found in the AISC steel design guide series and in many other books, but an explicit method has not yet been presented for design of circular base plates. Therefore, in this study, we propose a procedure for designing circular base plates with large eccentric loads in which there is a little gap between base plate and foundation through analytical and numerical methods. It is assumed that the utmost compressive anchor bolt reaches to the allowable compressive stress and also critical section for calculation of base plate thickness to be the edge of the column. Comparison of theoretical and finite element analysis confirms the assumptions. Considered parameters in this study are the axial load and its eccentricity, thickness of base plate, and diameter of anchor bolts. It is concluded that the mentioned status is very useful for columns with large eccentric axial forces, because it causes the thickness of the base plate to be less in comparison with the other cases in which a gap is not considered.