Design of pr frames with top and seat angle connections using the direct analysis method

Partially restrained (PR) connections are connections that possess stiffness and moment characteristics that fall between the extreme cases of pinned and rigid. This paper proposes a design methodology for PR frames that takes into consideration the semi-rigid nature of the connections, including their loading/unloading behavior under combined gravity and wind loads. Top and seat angle connections, modeled using the three-parameter power model, are used to demonstrate the proposed design procedure. To simply the design, two linearized connection stiffness values calculated on the basis of expected connection loads are used. The analysis is carried out using the American Institute of Steel Construction (AISC) direct analysis method in which notional horizontal loads, expressed as a fraction of the gravity load, are applied to the PR frames in conjunction with the use of reduced member axial and bending stiffness. Examples are given to demonstrate the validity of the proposed method of PR frame design.