Initial Bow

The initial bow is used to determine the initial shape of the member for the analysis. Because of this when the initial bow is not equal to zero secondary moments will be generated even if the analysis type is not P-Delta. The total initial bow is the sum of the prestressing camber and the additional bow the user inputs (positive being towards the exterior).

Floor Tie

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.

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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