This paper is primarily concerned with the formation of barrel-vault s
pace trusses derived from a flat configuration by posttensioning. To o
btain a fairly general picture of the shape-formation process by means
of posttensioning; both gently and sharply curved barrel-vault models
are studied. The structures are devised to be near mechanisms during
the posttensioning operation. They are considered to be near mechanism
s because only the flexural stiffness of the top chords provides any a
ppreciable resistance to deformation apart from friction and self weig
ht. Therefore, no appreciable axial force is induced in the members of
the structures during the shape-formation process. The result of expe
rimental and theoretical work on the shape formation of barrel-vault s
pace trusses by means of posttensioning is presented here. The shape-f
ormation process, referred to as self-erection, can lead to significan
t economies in the construction of large-span lightweight structures b
y eliminating or minimizing the need for scaffolding and heavy cranes.