A moment frame can be used to provide shear strength for narrow-walled structures when standard framing solutions are inadequate. In all cases, beam and column sizes and connection details need to be designed by a structural engineer.
A moment frame can be used to provide shear strength for narrow-walled structures when standard framing solutions are inadequate. In all cases, beam and column sizes and connection details need to be designed by a structural engineer.

A.Christopher DeBlois, a structural engineer with Palmer Engineering in Tucker, Ga., responds: This is a problem frequently encountered in townhouse construction, with the fundamental difficulty arising from the fact that townhouses must be designed structurally as if each unit were a completely separate building.

Fire separation can't be compromised, so there can be no positive structural connection between units. Add to that the standard architectural desire for narrow, deep units with lots of glass on the front and rear walls and big garage-door openings at the lowest level in front or back, and you have a recipe for serious structural trouble.

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