What is a portal knee?
Answer:
It's the joint between the vertical support and the more-or-less horizontal roof section of portal type contruction, which resembles frame house construction. See the ref.
Edit: As the ref. points out, a knee joint can be strengthened by gusseting or designed so the two joined members can be braced by steel reinforcements. Either method enables the knee to carry moment loads.
A portal knee or a 'knee joint' is where the rafter and the column are connected at the edge of a building. Usually you would connect using a haunch connection on the underside of the steel members to take the moment, however with a knee (I think) the rafter sits on top of the column and is designed as simply supported so the moment is 0. If you have it I would refer to the Greeno & Chudley Building & Construction book for details.
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