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Composite design

GSA integrates with Oasys Compos to carry out detailed design of steel-concrete composite beams. With GSA and Compos, you can follow a seamless workflow from a whole building model in GSA to detailed, per-beam calculations in Compos.

This feature requires Oasys GSA 10.3 or later, and Oasys Compos 8.7 or later.

In GSA, you can set up a model that specifies the following information:

  • Composite beam layout
  • Shear stud size and spacing
  • Web openings in a beam
  • Slab mesh reinforcement
  • Slab openings
  • Loads

GSA's Composite 1D member design task will use the above information and the analysis results to:

  • Determine the available width of the slab for each composite beam, taking into account the beam layout, slab dimensions and slab openings.
  • Determine the load on the beam by back calculating equivalent loads from the beam's shear force, bending moment and axial force diagrams.
  • Create a Compos file for each composite beam that includes both SLS and ULS loads.

Modelling Guidelines​

The GSA model must be set up in a particular way to be able to send composite beams to Compos:

  • Composite beams must be modelled as 1D members in the Design Layer, with Member type set to Composite Beam.
  • Composite beams must have properties that are either "Catalogue", "I Section" or "General I Section"
  • The slabs that the beam is composite with must be modelled as 2D members, with
    • Member type set to Slab,
    • 2D analysis type set to Load Panels, and
    • a Load Panel type 2D property with Physical Properties defined.
  • The beam z-axis and the slab z-axis must be parallel (e.g. the slab must sit perfectly flat on the top flange.)
  • A composite beam must be surrounded by slabs with the same property and the same orientation.
  • Slabs supported on composite beams may not overlap.

Rationale​

When checking a single composite beam, design codes generally treat the beam and some portion of the slab as a 1D beam element. The GSA-Compos link requires that the slab be analysed as a load panel to make it possible to accurately and conservatively determine the loads on each composite beam.

  • The Composite Beam member type is the signal to GSA that this is a candidate for composite design.
  • Modelling the slab as a load panel allows GSA to calculate the loads on the beam, without requiring the modeller to calculate 1D loads.
  • Compos does not have the ability to rotate a beam relative to the slab, therefore GSA will not attempt to create a Compos file if the beam and slab are not aligned.
  • Compos does not allow multiple slab definitions along a beam, so GSA will not attempt to create a Compos file if there are multiple types of slab supported on a beam.

Loading​

When setting up a composite design task, you must specify ULS and SLS load cases for construction dead, construction live, final dead and final live cases.

You must set up load cases for each of these. You can choose to create 8 individual load cases and apply the appropriate load factors in the case definition, or you can create 4 SLS load cases, and choose to have GSA apply the code-specific load factors to these cases to create the ULS cases.