Simplified methods enable faster calculations if pure flexural state (slabs, simple bending) or membrane state (plane stress structure, compression/ tension) occurs. For complex states (shells) with additional membrane forces (N x N xy , N y ) acting, there are no simplified algorithms worked out. Implementation of the analytical approach is the only allowable course of action.
Since modeled shells often work as slabs (with slight membrane forces acting), the possibility to calculate moments according to the selected simplified method still remains and these design moments are superimposed with longitudinal forces N x , N y .
It should be emphasized here that this course of action is justified only for relatively small membrane forces and it is the user who is responsible for implementation of this procedure.
In the performed tests, the differences between the results obtained by calculating reinforcement using the analytical method and the simplified ones have not exceeded 5% of reinforcement area (the simplified methods yielded a slightly greater maximum reinforcement).
The analytical method is the most complicated in regard to the computational procedure. Duration of calculations by means of the analytical method (except calculations of slabs with unidirectional reinforcement) may considerably lengthen (depending on a structure, the duration grows from 100% to 500%) as compared to Wood&Armer or NEN methods.