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The floor tie is used in the analysis by staging the loads into two stages, pre and post floor tie. The analysis is run with the pre-floor tie loads, selected based on a user input, using all boundary conditions besides the floor tie. Then the analysis is run with the remaining loads, including self weight, using the deflected shape from the initial stage. These results are summed together for the final analysis results. When a floor tie is defined, the user can determine at what stage the floor tie is installed. When dividing loads to pre and post floor tie, earth surcharge is considered a live load and will be applied after the floor tie installation.

Structural Model

The method of analysis is the displacement or stiffness method.  The structure is represented by a matrix consisting of member stiffnesses.  These are derived for three possible movements at the ends of members:  vertical, horizontal, and rotational.  The following boundary conditions are then applied to the matrix: 

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