Design of Integrated Beams

The analysis of the MasterFrame model will have produced the moments and forces that the composite beams are required to carry and therefore the beams can be designed without having to re-input all the loading information, section sizes, span lengths, etc. All this information will be taken from the MasterFrame model automatically.

Stiffnesses and deflections 

When a composite frame model is analysed for the first time the program doesn't yet know how much slab is being taken into account in the stiffness of each of the composite members. Hence the first analysis is based on the steel stiffnesses only. The composite design should then be carried out by the user for all the composite beams in the frame. At this point the program will have picked up the composite stiffnesses and the next analysis of the frame will take account of these stiffnesses resulting in updated moments and forces. The composite design of the members should be rechecked at this stage.

This process is reflected in the deflections of the composite beams in the model. The deflections in the first loadcase are based on the composite stiffness of the model. The 2nd, 3rd, 4th and 5th loadcase deflections are based on the steel only stiffness. The deflections in all subsequent loadcases are based on the composite stiffnesses of the beams. These deflections are used in the deflection checks for the composite beams.

For further information on how the deflection values are calculated and a comparison of those deflections shown in the MasterFrame results with those calculated in the composite design go to Calculation of Composite Beam Deflections.

Design Briefs

Once the model has been set up, analyse it and move to the Design menu.  Move down this menu and select the Composite Deck Steel Beam Member Design option. Your model will now be in the composite beam designer. The first time you come into the composite design, you will need to set up the design briefs for all the members in each model. On the top menu go to the MasterFrame menu and select Create ALL Composite Design Briefs. A design brief will be applied to each of the composite beams. You only need to do this the first time.

If further composite members are added to the frame, you can copy and paste a brief from an existing member on to the new member using the

Use the  search button to select a member to which a brief has already been attached.

You can use the  apply button to apply the current brief to a different member instead.

The  design whole group option will highlight all beams that are identical within the frame. These highlighted beams will all be designed in one go, saving you having to find and design each one in turn. All their member numbers will appear at the start of the beam calcs.

Design Groups

Design groups can be used to:

a) Define a common set of design parameters for a group of members

b) Specify that a group of members must be designed to have the same section size

Although not essential, design groups are recommended since they allow a more controllable and rational design to be achieved, particularly when allowing the composite design program to perform an automatic design.

For further details on design groups see the MasterFrame manual, Steel and Composite Member Design Groups.

Design 

The design of the composite beams is basically the same as the stand alone design. You will notice that certain entries on the bottom tabs have been greyed out. These entries are dimensions, loadings, deck profiles and slab thicknesses that have been set up in the MasterFrame model and are not available to be changed in the design end of the model.

To use the auto design click on the 'auto design'  option. The program will attempt to size the current beam, studs and mesh for the moments and forces in the beam. Note that it doesn't take account of any openings when carrying out an automatic design. To auto design all the composite beams click on the 'auto design all'  option.

When all the beams in a model have been designed, a 'scan for failures'  can be carried out. This will check all the briefs and highlight any that are failing. This is especially useful if a global parameter has been changed, eg, the concrete grade, to ensure all the beams still pass. Any failing briefs will be highlighted and you can move from failing brief to failing brief using the 'find next failure'  option. All the maximum unity values on all the composite beams can be displayed using the  button. Or you can display only those that are failing using the  button.

Occasionally, you may wish to precamber beams in composite construction. Use the precamber icon  to link a precamber to the beams. This takes account of the dead load deflection in an unpropped beam. The values can be displayed on the graphics with the  button. You can define the ratio of dead load deflection to precamber for. The precamber can be rounded up to a value, eg, every 5mm and a lower limit before the precambering begins can be set.

Option to only precamber beams above a certain length. Option to limit precamber to a % of beam length.