ASDIP STEEL includes the design of continuous steel and composite beams per the latest AISC 360. The structural design of steel or composite beams includes the checking of multiple limit states for shear, bending, and deflections, in order to comply with the design code provisions. But how do you know if your design can be improved further? How do you identify the lightest steel sections? How do you optimize your design? This article shows the optimization process for steel and composite beams design using ASDIP STEEL software.
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In the design of composite beams it’s important to consider the loads that will be applied before and after the composite action takes place. In the pre-composite stage, the steel beam acts alone to support the construction loads, therefore the flexural behavior depends on the unbraced length Lb for the limit state of lateral-torsional buckling. On the other hand, in the composite stage, the provided shear connectors will transfer the final loads across the interface in a composite action. The number and spacing of connectors will determine whether the section is fully or partially composite.
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What are the checks in composite beams design?
In addition to the shear and bending strength checks, the design of a steel or composite beam includes the calculation of deflections under the action of different loads in both the pre and post-composite stages. The calculated deflections will be checked against allowable limits. The screen shot above shows a summary of the results of a continuous composite beam.
Evidently all the design checks described above are dependent on the structural properties of the steel and composite sections. Let’s consider two main cases:
- An existing beam will have new and heavier loads, so the adequacy of the beam needs to be checked. In this case, the structural properties of the section are known and we can do all the checks described above. No problem.
- A new beam needs to be designed and installed. In this case the section properties are unknown, and there are only some constraints in beam depth due to space limitations to accommodate HVAC, piping, etc, above the ceiling. The same design checks described above need to be done, but this time there are literally dozens of different possible sections in the AISC Manual that could be installed. How to proceed to find the right section?
Of course you could check all possible sections in the depth range, one by one, then set apart the winners and discard the losers, and then pick your best winner. All this plan sounds very nice in theory, but it might take you hours of hard work. Fortunately ASDIP STEEL has a feature called Design Manager which will do exactly this, quick and easily, as shown below.
How do you optimize the design in ASDIP STEEL?
Go to Design > Design Manager in the menu bar. This will open the Design Manager window as shown below. After setting up the beam type and depth limitations, click on the Find Sections button. ASDIP STEEL will run every steel section in the specified depth range and it will populate the table with the sections that pass all the design checks (winners). This may take a few seconds to complete.
Depending on the depth range, you may end up with many winners in the table, so it may not be straightforward to decide what winner to pick. Note that the table can be sorted by weight or by design ratio. For example, if you sort the table by weight, the lightest section will show up at the top. If you sort the table by ratio, the most efficient section will show up at the top. In the sorted table pick the desired selection. Finally click the Select button to accept the selection and update the results with the new section. Clean and easy.
ASDIP STEEL includes the design of continuous beams, either composite or non-composite. It has a feature called Design Manager, which lets you find all structural sections that pass the design checks, and then pick the winner section to be used in your design.
For engineering background, please read the blog post Steel and Composite Beams: A Design Overview. For software usage, please read the blog post Steel and Composite Beam Design Using ASDIP STEEL. For our collection of blog posts about steel design please visit Structural Steel Design.
Javier Encinas, PE
ASDIP Structural Software