  A discrete tensegrity framework can be thought of as a graph in Euclidean
n-space where each edge is of one of three types: an edge with a fixed length
(bar) or an edge with an upper (cable) or lower (strut) bound on its length.
Roth and Whiteley, in their 1981 paper "Tensegrity Frameworks", showed that in
certain cases, the struts and cables can be replaced with bars when analyzing
the framework for infinitesimal rigidity. In that case we call the tensegrity
"bar equivalent". In specific, they showed that if there exists a set of
positive weights, called a positive "stress", on the edges such that the
weighted sum of the edge vectors is zero at every vertex, then the tensegrity
is bar equivalent.
  In this paper we consider an extended version of the tensegrity framework in
which the vertex set is a (possibly infinite) set of points in Euclidean
n-space and the edgeset is a compact set of unordered pairs of vertices. These
are called "continuous tensegrities". We show that if a continuous tensegrity
has a strictly positive stress, it is bar equivalent and that it has a
semipositive stress if and only if it is partially bar equivalent. We also show
that if a tensegrity is minimally bar equivalent (it is bar equivalent but
removing any open set of edges makes it no longer so), then it has a strictly
positive stress.
  In particular, we examine the case where the vertices form a rectifiable
curve and the possible motions of the curve are limited to local isometries of
it. Our methods provide an attractive proof of the following result: There is
no locally arclength preserving motion of a circle that increases any antipodal
distance without decreasing some other one.
