Comparative Study between Rigid Frames and Truss Steel Structures

Jesús M Martínez, Pablo G Montero, Carlos N Peguero, José I Díaz Huedo

Abstract


Until the beginning of the 1980’s, the steel structure most widely used in Spain
for building bays was a truss structure erected on posts. Since then, we have seen a
tendency towards the use of rigid frames, which is the most common structure at
present. Aside from the obvious functional advantages of rigid frames, it is commonly
thought that rigid frames are now more economical to build.
The purpose of this study is to determine whether rigid frames are actually more
economical to build than post and trusses. For that, we have compared different
standard bays of rigid frames and “English” trusses; with a series of spans, ranging from
10 to 30 m; and a series of post heights from 3 to 6 m, calculating and evaluating both
their metallic structures and the foundations. The spacing between bays was 5 m.
The following conclusion was reached: when only the cost of the steel structure
is considered, a rigid frame is more economical than a truss on posts with spans up to 30
m. However, if foundation costs are also taken into account, the rigid frame is more
costly with spans of over 20 m, due to the big size of rigid frame foundations. As spans
increase, the truss structure becomes much more economical.

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