The “Memorandum on Bridge Design and Construction," issued by the Ministry of War Transport in 1945 (London, H.M.S.O., price 1s.) contains, under the heading “Multiple Span Bridges,” the following paragraph (italics have been added by the author):
“The cantilever and suspended span type of construction is suitable for a bridge of several spans located on a horizontal curve. The beams should be arranged as chords to the curve, and the footpath slab may be cantilevered from the outside beams, so that its outer end (and the bridge parapet) is made to follow the curve. Though curved continuous beam structures have been built, it is preferable to avoid them, except in cases where the curves are of large radius, for where the beams are arranged as chords of the curve there is a change of direction at the supports where a considerable amount of tensile reinforcement is placed in reinforced concrete beams. An excessive
change of direction in steel beams, in addition to introducing complications in the
construction of the beams, produces undesirable torsional stresses in the flanges.
When the beams themselves are curved continuously, and not arranged as chords to the curve, somewhat complicated torsional stresses are induced, and design calculations become involved.”
Dr. H. Gottfeldt