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In geometric nonlinear analysis of space frames, if the displacements are so small that the
change of geometry is negligible, the equilibrium equations in undeformed configuration using
.' '
second order terms of strain statements provides
an
acceptable
approximate
solution
the
to
nonlinear problem.
However
large
displacements
and
finite
III
rotations these equations must be formed with respect to initial configuration using an Updated or Total Lagrangian Formulation.
In nonlinear analysis of space frames in addition to the stiffness matrix that changes at each step,
the transformation mat_ix is changed as well.
In this paper using an updated lagrangin version
the slope-deflection equations are developed in deformed configuration of the member and the.
transformation matrices are <;a1culated easily at each step. The Posterior calculation of residual


force vector provides a rapid procedure for the analysis of geometrically nonlinear space frames.
Several examples demonstrate the good agreement of results with those provided in the litrature.