Wind Connections with Simple Framing

Abstract

If a multi-story building is designed with simple framing (Type 2, AISC Specification Sect. 1.2), the frame must be braced to resist horizontal wind loads. This bracing may be provided by X-bracing, shear walls or "wind connections". Wind connections are normally designed to carry only the moments due to wind, without regard to the additional moments caused by gravity loading of the girders. This assumption that a connection is "intelligent" and "knows" which moments to carry and which not to carry may seem paradoxical. However, the validity of such a connection in providing wind bracing for a simple frame can be justified. The moment-rotation characteristic of a typical riveted or bolted moment connection is shown in Fig. 1. The shape of the curve depends on the stiffness of the connection and can only be determined by test. Tee-stub connections, for instance, usually have a steeper slope than does the typical "cap and seat angle" moment connection. The actual shape of the curve, however, does not effect the performance of the connection as a "wind connection" in conjunction with simple framing.