STRUCTURAL GLASS FACADES - USC School of Architecture

analysis eliminates the formation of an overall stiffness matrix, providing an efficient problem
solution. The method is able to accommodate the kind of gross out of balance forces
resulting from geometrical inaccuracies and stiffness differences that characterize tension
structures. (Wakefield 1984, p.89)
It was initially considered that the use of such a method would be impractical as part of a
simplified analysis tool. Dynamic relaxation tools are typically complex computer programs
capable of accommodating a wide range of structural models and incorporating form-finding
and pattern-making processes (as required for fabric membrane structures).
A dynamic relaxation program called DR was developed by Dr. Tejav Dehghanyar (ca. 1993)
and used in the analysis of numerous tension structures since that time (T Dehghanyar
2008, pers. comm., 7 March). DR employs a unique method of applying pulses at key
intervals as a means to dampen the oscillations and achieve convergence. The program
efficiently and consistently achieves a steady-state; such convergence to a steady-state
condition can be a problem with some dynamic relaxation techniques. With his involvement,
the viability of adapting DR for use as a simplified analysis tool was explored. The patterning
and form-finding components of the program were first removed.
A key opportunity for providing a simplified analysis tool is to reduce the necessary inputs
into the system. This simplifies the input process for the user and reduces the demands on
the analytical method. Instead of having to accommodate the infinite variations of a custom
structure model, a parametric model can be defined and the analysis method simplified and
fine-tuned to that model. Here, the requirement for an input model was eliminated entirely,
and instead the user merely inputs dimensions for the basic parameters. The flat grid cable
net discussed below, for example, solves only flat, rectangular grid two-way cable net
structures. Double-curved cable nets will require a new parametric model tuned to the
specific minimal input requirements of such a structure, with the analysis fine-tuned to those
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