FAQ - Portal Frame Generator
Portal Frame Generator
The Portal Frame Generator does not know what the moment diagram of the frames generated in Metal 3D will be like; therefore a default value of 1 is provided. Users must change this value to that indicated in the selected code. Regarding the braced distance, the program does generate the data correctly.
The program generates a buckling coefficient for the weak axis of the bars making up the bottom chord of the truss. When this value is multiplied by the length of the span of the bar, the result is equal to the length of the bottom chord. This coefficient can be excessive if there is transverse bracing at intermediate points of the bottom chord. The user must indicate the correct value depending on how the bottom chord is really braced.
The load data, geometry, node description and bar check parameters can all be modified in Metal 3D so to adapt the model to a similar situation which cannot be generated in the Portal Frame Generator.
Check the following points:
Change the units to International System and check that the data introduced is coherent in the various sections (dead load, live load,…) to avoid strange results from arising.
The type of attachment can be decisive. The optimum selection is Rigid fixing. Consult this option in the User manual
The loads generated by the program are uniform and applied along the length of the external chords.
If the purlins are generated with a large separation, and the chords are part of a truss, the load generation may not be adequate, as these are really point loads which can produce unforeseen local bending moments in the chords, and hence the sections designed in Metal 3D will be smaller than those really required.
If the truss or frame is not one of the types included in the program, it cannot be generated.
In this case, what can be done is generate a similar one in the Portal Frame Generator and then modify it later on in Metal 3D to adapt it to the real situation.
Alternatively, it can be created completely in Metal 3D but the user will have to introduce the loads him/herself and corresponding loadcases, which are generated automatically by the Portal Frame Generator. For this reason, the first option is the better option.