Portal frame

Abstract

A portal frame is disclosed for use around portals in, for example, a light-framed construction. The portal frame includes a pair of vertically-oriented shearwalls, and a header extending between and connected to the shearwalls. The portal frame may be used around a variety of portals formed in a construction, including for example doors, garage doors and windows. By forming a portal frame using a pair of shearwalls connected to a header, the portal frame in embodiments of the present invention is able to effectively reduce the loads exerted on a foundation by the shearwalls in comparison to a shearwall acting alone (i.e., one that is not part of a portal frame).

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a portal frame for opposing lateral forces, and in particular to a portal frame including a pair of shearwalls to improve the ability of the portal frame to withstand lateral forces such as those generated in earthquakes, high winds, floods and snow loads.[0003]2. Description of the Related Art[0004]Shearwalls were developed to counteract the potentially devastating effects of natural phenomena such as seismic activity, high winds, floods and snow loads on the structural integrity of light-framed constructions. Prior to shearwalls and lateral bracing systems, lateral forces generated during these natural phenomena often caused the top portion of a wall to move laterally with respect to the bottom portion of the wall, which movement could result in structural failure of the wall and, in some instances, collapse of the building. Shearwalls within wall sections of light-framed constructions...

AI Technical Summary

Benefits of technology

[0009]By forming a portal frame using a pair of shearwalls connected to a header, the portal frame in embodiments of the present invention is able to effectively reduce the loads exerted on a foundation by the shearwalls in comparison to a shearwall acting alone (i.e., one that is not part of a portal frame). In one embodiment, the portal frame is essentially pinned to the underlying foundation at the bases of the shearwalls. In such embodiments, very little, if any, moment demand is taken up at the connection point of the shearwalls with the foundation. Thus the demands on the foundation and anchoring mechanisms may be greatly reduced.

Problems solved by technology

Prior to shearwalls and lateral bracing systems, lateral forces generated during these natural phenomena often caused the top portion of a wall to move laterally with respect to the bottom portion of the wall, which movement could result in structural failure of the wall and, in some instances, collapse of the building.

Typically, the load capacity for such shearwalls is limited not by the ability of the wall itself to withstand lateral loads, but rather the ability of the anchorage system and / or the diaphragm or foundation to withstand the large moment forces generated by the shearwall under the lateral loads.

Portal frames are often subjected to larger lateral forces due to the absence of any structural materials within the portal itself.

Images