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Important Note – These are descriptions to changes implemented in WoodWorks Shearwalls for version 9.2 and may not reflect current behavior.
The program now allows you to specify the direction for wind uplift loads, that is, the lateral direction of wind force with which the uplift load is associated. Therefore you can enter uplift loads that correspond to the uplift coefficients for the windward and the leeward surfaces in NBC Figure I-7 for low rise loads and Figure I-15 for all heights. Previously the one wind uplift load applied to a surface would be used for both the windward and the leeward cases. This involved the following program changes:
The Wind direction input is now enabled and allows you to choose either direction or Both, similar to a Wind shear load.
In the Plan View and Elevation View, the wind uplift force is only drawn if the direction of the uplift force matches the direction of load direction selected in the Show menu.
Different uplift forces are used to create combined hold-downs at the same location for different force directions. These appear in the Hold-down Design table.
A Direction column was added to the Uplift Loads table,
When self-weights were entered in stages for several levels of the structure, and building masses and loads generated at each stage, the loads due to the lower portion of the wall mass from the storey above were not included in the calculation if the loads were generated from top to bottom. Similarly, the loads due to the upper portion of the wall mass from the storey below were not included twice in the calculation if the loads were generated from bottom to top.
Furthermore, the calculation of total building mass used only the masses from floors that had already been generated, leading to a different result than if the loads had been generated all at once.
These problems lead to significantly non-conservative loading when the loads are generated in stages, particularly when it is done from top to bottom of the structure.
They have been corrected and the program now generates the correct seismic loads when building masses are generated in stages. Note that the seismic loads that are generated for a particular level after the entire structure is complete will be different than those at an intermediate stage, because of the difference in total building mass. The loads generated at the intermediate stages should not be used for design.
When walls were created using multiple blocks, then all but one of the roof blocks are deleted, the program considered it a single block building when deciding whether low-rise wind loads were allowed. The program used the walls created from only one of the original constituent blocks to determine the height to width ratio, and disallowed buildings that should be allowed. If the one block used had an allowable h/w ratio, then the program generated wind loads on only the walls on that block, and not on the rest of the building. Now, if multiple blocks are used to create the walls, wind loads cannot be generated for low-rise load design, and you are alerted with a message.
The value of Cu (Sd < 0.4) from ASCE 7-05 Table 12.8-1 was changed from the ASCE 98 value of 1.2 to 1.4 for ASCE 02, but Shearwalls still used the 1.2 value. This affected the upper limit of period T = Ta*Cu, that is imposed when you enter your own value of T rather than accepting the calculated Ta. This resulted in higher-than-expected forces and conservative design in this case.
In the shear results table, the shear force on each perforated wall is mistakenly divided by the perforation factor, so that the sum of the wall forces exceeds the total shear force on the shearline.
This problem affects only the display of these forces in the output report, and the incorrect values are not used for shearwall design, deflection analysis, hold-down force or drag strut force generation.
The checkbox that allows you to impose minimum loads to the structure now includes the ASCE 7 reference for these loads, 6.1.4.1.