Direct Analysis Method (DAM)

The Direct Analysis Method for steel frame structures was introduced in the 2005 AISC Specification. The primary benefit of this approach is the possibility to check the section capacity during the design phase, without using effective lengths or amplified moments.

Requirements

The Direct Analysis Method is available for space frames, trusses, shells, and buildings for which Ultimate Limit State (ULS) combinations have been defined.

In order to be able to run an analysis following the Direct Analysis Method (DAM), results must be available for the main model. If results are not available, then the program runs standard calculations on the main model before running the analysis.

Note: The DAM analysis is not compatible with a phase structure analysis. Because of this restriction, you cannot run a DAM analysis if you have defined phases on your structure.

Static seismic approach

The Direct Analysis Method currently supports the use of the static seismic approach as defined in the following codes: ASCE 7-10, IBC 2012, NBCC 2010, AS 1170-4:2007, EC 8 1998-1:2005.

Note: The current version does not support nonstatic load cases such as the ones used in spectral seismic analyses, and will not consider them during the generation of load cases.

DAM model

When the DAM analysis is run, the program creates a DAM model. This DAM model is an altered copy of the original model including all its properties, supports, and load cases. In the DAM model, all load cases pertaining to the main model are inactive because the Direct Analysis Method considers adequately modified load combinations only.

The DAM model differs from the original model in three ways:

• Additional notional loads are generated for the load combinations.
• The element stiffness of the sections is reduced.
• The P-DELTA analysis is enabled.