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Important Note – These are descriptions to changes implemented in version 10 and may not reflect current program behaviour.
The program now includes component additive method from NBC 2015 Division B Appendix D-2.3 for fire design of wood and steel framed walls, floors and roofs.
It calculates the fire-resistance rating of a framed assembly by adding the time assigned for the membrane such as gypsum wallboard on the fire-exposed side to the time assigned for the framing members and the time assigned for additional protective measures such as insulation.
The implementation is limited to Beam and Column Mode and is not included in Concept mode.
The method is applied to walls, floors and roofs. Allowable materials are lumber, MSR, MEL and for floors, I-joists. SCL and glulam are not allowable materials.
Sizer’s Beam/Joist mode and Column/Wall mode include the below inputs when walls, roof joists, and/or floor joists are selected. There are numerous interdependencies in the inputs based on the combinations materials for which there are design values in Appendix D-2.3, and not all the choices listed below appear for each combination of inputs.
Unknown material means that the program selects the choice in the process of achieving a sufficient fire equal to or greater than the required duration.
Gypsum or Plaster. None indicates that CAM fire design is not to be performed.
½" (12.7 mm), 5/8" (15.9 mm), or (Unknown).
Unknown, and, for walls ½" (13 mm), 5/8" (16 mm), ¾" (19 mm); for floors and roofs, ¾" (19 mm), (7/8") 23 mm, 26 mm (1")
Unknown, none, Rock/slag fiber, Cellulose, Fibreglass.
Not used, 400, 600 mm
Unknown, Gypsum, Metal
A checkbox for floors.
Unknown, then several combinations of cement, lime, gypsum, sand, wood fibre, perlite, vermiculite.
A checkbox when gypsum lath is used.
A checkbox when gypsum lath is used.
A checkbox for walls
A checkbox for walls. When checked, load input is not available.
Given the input parameters, a fire resistance rating is determined primarily using NBC Tables D-2.2.4. A-G
When Unknown is selected for one or more inputs, a procedure cycles through the values to provide incremental increases in fire protection, giving preference to parameters with lower cost and/or commonly used materials, until the required duration is achieved.
The selected or designed fire protection parameters for the assemblage is shown in the Design Check output report in the section of the report that gives other details of the materials specification
In the Force vs. Resistance table, a line for Fire showing the required duration, the actual duration, and the ratio between them is shown. If the ratio is greater than one, the red failure warning message shows the design criterion Fire.
A design note appears giving the general NBC reference, and a reference to provision for upper membrane provisions for floors and roofs, and an explanation of exterior membrane requirements for walls.
The program now implements fire design using CSA O86 Annex B.
O86 fire resign is applied to Beam, Column and Concept mode.
The method is applied to solid beams and columns composed of sawn lumber in timber sizes, glulam, and SCL; and CLT floor, wall and roof panels.
Built-up beams and columns are not included.
For glulam members, there is a Design setting to allow you to choose between the existing NBC Appendix D-2.11 method and O86 Annex B method.
The following inputs have been added to the Fire Design data group of Beam view.
The fire exposure duration t in CSA O86 which determines the extent of charring of the member.
A beam or column can be exposed on 0, 3, or 4 sides, CLT panel on 0 or 1. 0 sides exposure means that fire design is not applied. 3 sides means it is exposed on the top or bottom and both sides.
Future versions of the program will allow for 1- and 2-side column or beam exposure and 2-side CLT exposure.
This input to allows you to select from the fire protection choices in O86 B.8.1, or no protection at all. The choices for beams and columns are 1- and 2-ply ½" and 1-ply 5/8" Type X gypsum wallboard. For CLT, 2-ply 5/8" wallboard is added.
Loads analysis is performed separately for fire design to generate forces and stresses from specified (unfactored) loads rather than the load combinations used for strength design.
Fire load combinations are generated from live, dead, and snow load types only. Wind and earthquake are excluded due to the low probability of fire occurring at the same time as a severe windstorm or seismic event.
As with ordinary design, load combinations are constructed with all subsets of the load types included
The program determines the reduced cross section for fire design by calculating the notional char depth from B.4.4 using the user input fire duration. Since this method is employed, corner rounding from B.4.5 will not be considered.
Sizer will apply the char depth to reduce the section size by considering the number of sides exposed. It is assumed that for 3-sided exposure, one of the member widths, or "b" surfaces, is not exposed, and for 4-sided members, all surfaces are exposed.
Fire duration is reduced by the values given in B.8.1 for the protection method chosen.
The additional reduction in cross section due to the zero-strength layer in B.5.1 is applied.
Sizer performs shear, axial, bending moment and combined axial and bending design on the fire-reduced section using the same provisions in CSA O86 as those for regular design.
As per B.3, the factors related to lateral support KL, CC, and KC are calculated using the fire reduced section, size factor KZ is calculated using the full section, duration factor KD factor is for short-term loads regardless of the loads on the member, system factor KH is 1.0, and the resistance factor φ is 1.0 rather than the usual 0.9.
The strength adjustment factor Kfi from B.3.9 will be applied to shear, bending, compression and tension strengths.
Under the specification of the beam or column materials, the program shows the user input fire endurance, the no. of exposed sides, and fire protection, if applicable.
In the table showing the design results for the various criteria, the program repeats the lines for shear, bending, axial, and axial + bending design under a subtitle "Fire", giving the analysis value using fire loads analysis, resistance using reduced cross section, and ratio between them.
The FACTORS table of the Design Results has lines for Fv, Fb, Fc and Ft with the word (fire) beside them.
The load combinations used for fire design will appear in the CRITICAL LOAD COMBINATIONS section if the Design Results, with the word (fire). These will just show 1.0 for all load factors.
The CALCULATIONS section of the Design Results will show the following values: residual section size, char rate, Kfi factor, resistance factor φ, fire protection duration.
In the list of load combinations in the Analysis Results, the symbol (f) is placed beside fire load combinations.