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The program includes an implementation of CSA O86 11.8.8 and Table 11.6 for seismic design, which specifies the maximum gypsum contribution on any level of the structure, in each direction.
Design Checks
Check for Total Capacity vs. Force
The program checks on each level and in each direction, that the total capacity of all walls on that level is at least as great as the total force. In this case, at least some of the shear walls will have failed, and the program does not go on to check for minimum wood capacity or maximum gypsum capacity as indicated in the following sections.
Check for Minimum Wood Capacity
After shear wall design, the program checks that there is sufficient capacity from wood panels in the designed shear walls to satisfy the requirements of CSA O86 Table 11.8.8 if all force were to be distributed to those wood panels. It does so independently on each level and for each force direction, for both wind and seismic design.
If the wood capacity is not at least 100% minus the allowable GWB percentage, the program regards this as a design failure and indicates so via a message box on the screen, and via failure notes under the Shear Design table and the Gypsum Wallboard Percentage table, via “FAILED” showing on the walls of that level on elevation view, and via a note in the Design Summary.
Check for Maximum Gypsum Capacity
After shear wall design, the program checks if the percentage of total shear force taken by gypsum wallboard exceeds the maximum in CSA O86 Table 11.8.8. In determining the shear force taken by GWB, it assumes that the force into composite wood/gypsum shear walls is distributed proportionally to material capacity. It does so independently on each level and for each force direction, for both wind and seismic design.
If there is greater than the maximum allowable gypsum contribution, the program offers you the choice of ignoring gypsum wallboard contribution in design and redesigning, or proceeding with the design anyway. For seismic design, it also offers you the opportunity to regenerate loads on the structure with the revised response modification R value appropriate to all-wood systems.
If you choose not to redesign, the program presents a warning under the Shear Design table and the Gypsum Wallboard Percentage table indicating that you must ensure that sufficient shear force is distributed to wooden panels to avoid excess gypsum contribution.
Ignore Gypsum Wallboard in Design
If you have selected the “Ignore gypsum wallboard design setting for either or both of wind and seismic design, the program does not do the above mentioned Check for Minimum Wood Capacity or Check for Maximum Gypsum Capacity for that design case, instead putting a note explaining this in place of the Gypsum Wallboard Percentage table. ‘
Five- and Six-storey Structures
For five- and six-storey structures, all gypsum contribution to seismic shear resistance is automatically ignored in load distribution and design, on all levels of the structure, as per CSA O86 11.8.8. The program indicates in the notes to the Shear Results table and in a note that appears in place of the Gypsum Wallboard Percentage table that GWB has been ignored for this reason.
Gypsum Wallboard Table
Separate tables are output for each design case (rigid, flexible, wind, seismic) giving the relevant data to implement the restrictions on gypsum wallboard contribution in CSA O8 Table 11.8.8
The table outputs the following data for each storey and each direction of force:
Insufficient Total Resistance Failure
If there is insufficient total resistance on a particular storey and direction to resist the total force, then two exclamation marks (!!) appear in the % gypsum column in place of the data, and a red failure note starting with !! appears below the table. In this case, at least some of the walls on the shear line will have failed, and there is little point in checking the % gypsum contribution.
Insufficient Wood Capacity Failure
If there is insufficient capacity from wood panels available to resist the remaining storey force after the maximum gypsum contribution from Table 11.8.8 is taken away, then one exclamation mark (!) appears beside the Wood Capacity % data for that storey and direction. A red failure note starting with ! appears below the table.
Excessive Gypsum Wallboard Contribution Warning
Wherever the percentage of storey shear resisted by gypsum wallboard on a particular storey and direction is greater than the maximum allowed by Table 11.8.8, an asterisk (*) appears beside the %GWB value, indicating a warning note at the bottom of the table saying that you must modify the design to ensure sufficient shear force is redistributed to wooden panels to avoid excess gypsum contribution.
Shear Design Table
In order to alert you that there may be failures or concerns arising from CSA O86 11.8.8 and Table 11.8.8, the program includes warnings under the Shear Design tables. It does so separately for the wind design and shear design tables, as follows:
Design Summary
If either of the red failure or warning messages appears in the Shear Design table, a message in the Design Summary alerts you to that fact and refers you to the Shear Design table.