Massive Abutments


The abutments to the arch in this structure have been mad in the form of an inverted U rigid frame. If the abutments are made heavy and rigid, then the arch may be lighter so it may be more economical to use the large mass of concrete at the lower elevation to save concrete in the arches. In a monumental structure, such as an auditorium, the side spaces can be used as archways for access to the seating area.

Instead of the U frame, which is subjected to very heavy bending moments, a triangular frame may be used with the apex at the springing of the arch. The structural members of this abutment can be quire thin because they follow the thrust line of the forces better than does the U frame.

An architectural problem of the short shell structure is the proper design of the end walls. On a long span structure there will be large blank areas that require careful architectural treatment to make the structure pleasing.