Figure 5.2 shows a symmetrical frame with a symmetrical load. It is a simple matter to take advantage of this symmetry. The joint on the line of symmetry will not undergo any rotation, nor any horizontal displacement. Furthermore, half the load will be carried on the left side of the frame, the other half - on the right side of the frame. Consequently, only half the members need be specified. To ensure that the symmetry conditions are satisfied, one can restrain the centre joint against rotation and against horizontal displacement, i.e. the flags flagXY and flagY are set to 1. The following listing shows the input to the program for the frame (frame2dat file). SMAP is a program used for comparison. A historical note on SMAP is the preamble of this book.
