Re-Analyse a model

The members forces and deflections are determined by the frame analysis in Masterframe. These results are displayed near the top of the calculation window. The MasterFrame analysis is based on the original members sizes in the model. For beams and column elements, the software will adjust the deflection values based on the member section modulus of the selected section. Therefore, in the member design, as the section modulus changes, the deflection values will be adjusted based on the section modulus. However, the shear force and bending moments are not adjusted and remain as per the last frame analysis.

In the case of a cantilever, the deflection of the cantilever will not update, since the deflection of the cantilever is made up of two components. The first component is the deflection of the member itself under load. However, the second component is the rotation of the structure at the connected end of the cantilever. This is based on the distribution of bending moments in the frame and is determined by the relative stiffnesses of the cantilever and the members connected to joint at the connected end of the cantilever.

For continuous beams and columns and for cantilevers, the moments and forces in the members are dependent on the section size. Hence, in these cases, once the members have been designed, the model needs to be re-analysed and the sections checked to ensure that the behaviour of the members under the modified member forces and deflections is still satisfactory. For simply supported beams and columns in simple construction, the analysis would be updated after design to account for the modified member forces due to any changes in the loading and member self-weight.

A re-analysis of the frame can be done by exiting the steel design and going back into MasterFrame and carrying out the analysis from the Analysis menu item. However, it is also possible to carry out a re-analysis of the model within the steel design module.

The re-analysis of the model with the updated section sizes can be carried out by clicking on the  icon. Alternatively, the frame reanalysis can be done by going to File > Re-analyse.

Particularly in 3D frames with continuous members, it is advisable, after the frame design is complete, to rerun the analysis and then check the member design is still satisfactory, to account for any changes in the distribution of the bending moments and shear forces as a result of the modification of the members in the model.

See the next item 'Checking a Model for Design Failures' for how to quickly locate any failing design briefs.