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Attached beams model the effect of a beam acting compositely with the FE surface. The presence of the beam is used to modify the stiffness of the FE surface, to account for the stiffness and position of the beam relative to the centroid of the FE surface.
When a beam is attached to an FE surface, it is assumed to act compositely with the FE surface. Thus it is assumed that there will be shear transfer between the beams and the slab. It is not possible to assume that the beam provide vertical support only, so it is not possible to have the beam support the slab as an independent structural element.
Within the Attached Beam menu, there are a number of options to quickly define the position of the attached beam relative to the FE surface centreline. The control the position of the beam relative to the FE surface local z axis. It is also possible to input an offset value to manually determine the position of the attached beam.
Within the Attached Beam menu, there are also options to define the width of the concrete flange to be used when considering the beam cross section properties. There is also the option to calculate the bending of the beam element itself for use in the automated design of the steel or concrete designer.
When modelling attached beams, the line element is only modelled as the attached element itself. For an attached steel beam this means the line element should be sized as the steel section itself. In the case of concrete elements, since the FE surface is modelling the slab, the attached element need only be modelled as the additional concrete element. For example, with a downstand beam, the depth of the concrete line element would be set as the overall beam depth minus the slab thickness.
The Attached Beams area can be accessed from the top menu within Masterframe by going to Properties>FE Surface Attached Beams. Alternatively, the Attached Beam tab can by going to any of the other FE menu items and then selecting the Attached Beams tab. The layout of the attached beam tab is shown below.
To select a line element in the model to make an attached beam, select the .png){kind=small}
icon to enter the select mode, then position the mouse pointer over the line element and select using the left mouse button. The selected element will highlight in red (when viewing the wire frame model) and the member number will appear in the member area in the right hand pane.
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When attaching a beam, there are three options to position the beam relative to the FE surface. These are:
Centre - the centroid of the attached beam will coincide with the centreline of the FE surface.
Bottom - the centroid of the attached beam will be positioned such that the top of the beam will be coincident with the bottom of the FE surface.
Top - the centroid of the beam is positioned such that the underside of the attached beam will be coincident with the top surface of the FE surface.
The position of the centroid of the attached beam can be further modified or refined by inputting an Additional z direction offset. This input moves the attached beam offset by the input amount in the local FE surface z-axis.
The beam-plate offset settings apply to all the beams in an attached beam grouping. To set different offsets for beams, additional grouping of attached beams need to be created. This is done by clicking on the .png){kind=small}
icon.
For each set of attached beams, the .png)
For each set of attached beams, the Combined Beam-Plate results can be set to control how the stiffness and results for the attached beams are determined. These options are:
Use Combined Beam-Plate Results - the axial force in the FE surface is used along with the offset of the centroid of the beam element to calculate the bending moment in the beam.
Flange width side 1 - the width of the concrete flange width on side 1 for use in the combination of results when calculating the bending moments in the beam
Flange width side 2 - the width of the concrete flange width on side 2 for use in the combination of results when calculating the bending moments in the beam
To create multiple groupings of attached beams, click on the icon and setup and select the members as required.