Portal frame construction is a method of building and designing structures, primarily using
steel or steel-reinforced precast
concrete although they can also be constructed using laminated timber such as
glulam. The connections between the
columns and the
rafters are designed to be
moment-resistant, i.e. they can carry bending forces. "They were first developed in the 1960s, and have now become the most common form of enclosure for spans of 20 to 60 m"