General tab

On the General tab, you can set up the basics for the portal frame. This commences with which design code is to be used - British Standard or EuroCode. By default the EuroCode will use equations 6.10a and 6.10b. You can change this so it uses 6.10 instead should you wish.

The base partial fixity can be specified. This is normally accepted as 0/10/20 meaning that in ultimate cases the base fixity is zero, ie, pinned for design, but 20% fixity for the service cases to allow a reduction in the frame deflection. The bases can be set to fully pinned or fixed if that is how you wish to consider your frame. The As Is option allows the column base fixities, specified in the Columns input tab and elsewhere, to take precedence.

Automatic haunch optimisation - the eaves and apex haunches can be set to be automatically optimised based on the rafter section size. The haunch usually has the flange removed (deducted) and possibly the root fillet too.  Additional web can also be removed. The end plate thickness is also specified. Based on all these criteria the program calculates the maximum section depth of the haunch based on the rafter section size. A node is placed on the column at the point where the haunch bottom flange coincides with the column flange.

On plan           - measure haunch length on plan from centreline of column, as opposed to the default of measuring it up the rafter slope.

Underside           - measure column height to underside of haunch, as opposed to the default of the intersection of the column and rafter centrelines.

Clear span           - measure span between inner faces of columns, as opposed to the default of the column centrelines.

Outer face           - measure the overall span between the outer faces of the external columns.

The basic dead, live and services loading is included as an area plan load in kN/m2. Note that the dead and service loadings are separated to allow for a minimum loading of dead plus wind uplift without any service loading being included. The frame spacing is automatically picked up from the frame geometry. These are multiplied together to give a line load on the members ready for analysis.

A combination of all the necessary load cases can be added by ticking the appropriate boxes. You can add or omit the wind and snow loading from the automatic generation of load cases, add service cases for each ultimate load case, include P-delta analysis in all load cases and use only the envelope (critical) load cases for analysis. The last option only becomes active after at least one analysis cycle has been completed for all load cases, from which the critical cases can be detected. The notional cases can be included as well as basic cases for each load group. In a typical 3D frame it would not be uncommon to have as many as 200 load cases.

A frame can be analysed elastically or plastically as desired. In plastic analysis there are options to find the plastic load factor, ignore plastic hinges or allow rafter haunch hinges to possibly form.

For sway stability the default is to use the horizontal notional loads to obtain the elastic critical load factors. Alternatively you can use the buckling analysis method instead.