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ASCE 7 and IBC now have an Allowable Stress Design (ASD) wind load factor of 0.6, rather than the previous 1.0; see ASCE 7 2.4.1 and IBC 2012 1605.3.1. This change is in conjunction with new wind speed maps with higher wind speeds intended for strength-level design.
For all load combinations with a wind load component, that component is now factored by 0.6, in addition to the 0.75 factor for multiple non-dead load types that may be in the combination.
The format for the load combination as it appears anywhere in the program is similar to the corresponding earthquake combination:
.6D+.7E -> .6D+.7W
D+.75(L+.7E) -> D+.75(L+.6W)
You can indicate in the Load Input view that the wind load is a Component and Cladding (C&C) load and that you wish to take advantage of IBC 1604.3 Note f, which applies an additional factor for deflection design. Because of the new 0.6 load factor, the program now factors the wind load by 0.42 = 0.6 x 0.7, whereas it used to factor by 0.7 only. The load combination used for deflection design is now shown as, e.g., D+.75(L + .42W).
Load combination 6 from ASCE 7 2.4.2, which includes a wind or earthquake load in combination with other loads, has been split up into 6a and 6b such that earthquake loads are not combined with live roof loads. All load combinations generated by Sizer which include earthquake and live roof have thus been removed. These are
D+.75(L+Lr+.7E)
D+.75(Lr+.7E)
D+.75(Lr+I+.7E)
D+.75(L+Lr+I+.7E)
Sizer implements this change in generating any load combinations which include a wind factor.
Sizer now allows you to apply an eccentricity proportional to the width or depth of the column, rather than an absolute value, to deal with uncertainty as to where the load will actually bear on the column.
This applies to both columns and wall studs, with the eccentricity for wall studs restricted to the wall depth direction only.
A setting has been added to the Design Settings for the percentage of the member width or depth to apply as axial load eccentricity to those columns that use auto-eccentricity, with a default of 16.7% = 1/6 of member dept, an amount commonly used.
A checkbox indicates whether this eccentricity is to be applied to all axial loads in the direction of the load face selection. If checked, the word “Auto” shows up in the eccentricity input, which is disabled. “Auto” also shows up in the loads list.
For a known section size, the program applies an eccentricity of the percentage entered in the setting of the member width or depth, according to the Load Face selected in Column Loads view.
When cycling through sections for unknown design, the program re-analyses the member to determine the new bending stress and combined combined axial and bending results based on the eccentricity for each new section width or depth.
In the Design Summary, for unknown section size, the program shows Auto in the Eccentricity column of the load list. For known section size it shows the calculated eccentricity.
In the Design Check output, where the section size is known, the program shows the calculated eccentricity using the proportion input in the settings.
Live roof loads are now restricted to 20 psf by IBC 1602.1 the remainder of the live load on the roof should be entered as an ordinary live load. Note that this limitation is not in ASCE 7-10, but so as to comply with IBC 2012, Sizer has implemented this limitation.
If a live roof load is entered greater than 20 lbs, it is automatically changed to 20 lbs and a message appears prompting you to enter the remainder as an ordinary live load. .
Note that if you insisted on following ASCE 7-10 rather than IBC 2012, you could enter more than one live roof load. The intention of this feature is to alert users to the IBC requirement.
In Column Loads view, the input for Use L + 0.5D indicates that it is for Note d of IBC Table 1604.3, similar to Beam Loads view. Previously the note letter was missing.