Detailed Torsional Analysis Output

Detailed intermediate calculations for torsional analysis are accessed via the Torsional Analysis Details button. It is possible to edit this output in the Shearwalls viewer with insertions and deletions, and to copy information with Ctrl-C,

The bulk of this file consists of blocks of data showing the calculations and results for torsional analysis leading to shear line forces for combinations of

• building levels
• rigid or flexible diaphragm
• wind or seismic design.
• load direction ( E->W or W->E; N->S or S->N)
• low rise wind load cases

Levels

The first level organization is for building levels - all blocks of data for the load cases uppermost level are shown first, and the cases for lower levels are show in sequence.

Rigid or Flexible Diaphragm

The first case shown is for seismic design for flexible diaphragms according to NBC structural commentary J 178. There is no requirement for wind design for torsional analysis for flexible diaphragms. .

The flexible diaphragm case contains just one block of data. All the other blocks are for rigid diaphragm analysis.

Seismic and Wind Cases

The blocks of data for seismic and wind design are interspersed in a seemingly random fashion, and it can require some patience to find the case you are interested in.

Two cases are shown for seismic or all-heights wind design - for one for E->W and S->N design, the other for S->N and W->E design. These can differ because of differing arrangements of hold-downs on the shear lines. or for wind design, for asymmetric roof ridge lines. Loads are not applied in orthogonal directions simultaneously; they are output together for convenience.

For low-rise wind loads, 4 cases are shown, one for each windward corner shown in Figure 4.1.7.6-A. Within each block of data, there are sections for Load Case A and Load Case B. For low-rise wind loads, loads from both orthogonal directions are applied simultaneously.

Structural Characteristics

Within each block of data, the first section shows the expressions for the following characteristics of the structure along with their values in each orthogonal direction

• Center of rigidity
• Building dimension perpendicular to the force
• Total Rigidity
• Torsional Rigidity J

Loads and Forces

For each force direction, the program outputs the following data related to loading on the building level, along with the expressions for these values from Torsional Analysis Calculations.

• Total load F, split into forces from upper levels and load on current level
• Center of load
• Inherent eccentricity (center of load - center of rigidity)
• Accidental eccentricity, and design code reference for the required accidental eccentricity

Shearline Forces

For each force direction, the program outputs a table showing data for each shearline. Before the table it outputs expressions for these values from Torsional Analysis Calculations. The following columns are in the table:

• Rigidity of shearline
• Location from edge of structure
• Distance from center of rigidity
• Total force on the line
• Direct force on line
• Torsional force for both positive and negative accidental eccentricity eccentricities, and the one used to calculate the total force.

Torsional Sensitivity Calculations

At the end of the file, there is a table showing the intermediate results to determine the torsional sensitivity ratio B_x from NBC 4.1.8.11.(10). On each level and in each of the four cardinal directions, and for each case of positive and negative eccentricity, the program shows

• the force on the extreme right and left shear lines
• the storey drift on the extreme right and left shear lines
• the average of the drift on the extreme left and right lines
• B_x = (maximum of left and right) / (average of left and right)

Notes below the table explain the meaning of the values shown and the significance of the results..