How can I analyze a flat membrane with normal pressure? Since the normal degrees of
freedom initially have zero stiffness, the solver throws them away before cable action can be
One procedure is to solve an initial load step with negative thermal strain instead of pressure
using SSTIF,ON. The pressure can be applied in the second load step and the thermal strain removed.
If SHELL181 is used NLGEOM,ON must be set for SSTIF,ON to be active. SHELL63 can be used without
NLGEOM,ON and therefore is a better choice for this analysis.