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These settings pertain to the interpretation and application of provisions from the National Building Code (NBC).
Importance Category
This input appears in both Beam and Column mode Load Input view and in the Concept mode toolbar.
It allows you to input the importance category for the structure and applies the appropriate ultimate limit states and serviceability states factors to live, wind, snow, and earthquake loads. The dropdown shows the Ultimate limit state factor for the load currently selected, however the category applies to all loads input, and in Concept Mode, to all members in the structure.
This selection can be saved as default for new member files and is saved for each member file. It can be applied to Concept Mode The default value is Normal.
Part 9 Snow Loads
For structures meeting the requirements of Part 9 of the NBC, many users design using Part 4 but with snow loads specified using Part 9, In this case, the importance factor is 1.0 for serviceability (deflection) rather than the 0.9 Part 4 importance factor shown in O86 Table 5.2.3.2. For this reason there is an Importance category called Normal, Part 9 snow. When this is selected, the factors are the same as for the Normal importance category, except that for snow loads are selected the serviceability limit state (SLS) factor is rather than 0.9.
Live and Snow Loads on Exterior Surface
To comply with NBC 4.1.5.5, a setting allows you to specify that a live load is on an exterior surface, so that is is not included in load combinations with snow loads. This is used to model a member supporting a surface such as a roof terrace or parking area, that can be expected to have direct live and snow loading.
To model a situation such as a member supporting a balcony with both live loads or snow loads, and an interior space with occupancy live loads, you place separate live loads on the interior space and balcony, and activate this option for the balcony load.
When the setting is checked for all live loads on a member, the program will omit those combinations that have both live (L, Ls or Lf) loads and snow (S) loads. If the program would ordinarily create combinations with L + S together but not separately, then the L-only or S-only combination is created.
Refer to the sections under Canadian Load Combinations for the precise load combinations created when this setting is checked.
In Concept Mode, those members on the roof level of the structure have this property set to “true”. For those on other levels of the building, it is “false”.
This option can be saved as default for new member files and is saved for each member file. The default value is that it is not checked.
Sustained Live Load
This input appears in both Beam and Column mode Load Input view and in the Concept mode toolbar.
A load with the sustained live load type means that Sizer will use the load factors given in NBC 4.1.3.2.(5) for controlled fluids and NBC 4.1.3.2.(6) for storage and equipment, and a load duration factor typical of permanent loads such as dead loads (0.65).
You choose which application via the Sustained Live load due to... dropdown. This selection applies to all loads on the member, it is not possible to create storage loads and fluid loads on the same member. In Concept mode, all sustained loads on the structure are either controlled fluid loads or storage loads, according to the setting when the Design button is pressed.
This option can be saved as default for new member files and is saved for each member file.
Refer to Sustained Load Combinations for more information.