4.1.7.8.Dynamic Procedure

(1) For the application of the Dynamic Procedure, the provisions of Article 4.1.7.3. shall be followed, except that the
   exposure factor, Ce, shall be as prescribed in Sentences (2) and (3), and the gust effect factor, Cg, shall be as prescribed
   in Sentence (4), when determining the wind loads on the main structural system.

   (2) For buildings in open terrain, as defined in Clause 4.1.7.3.(5)(a), the value of Ce for the design of the main structural
   system shall be calculated as follows:

                                                             h 0.28
                                                    Ce = ( )               , but 1.0 ≤ Ce ≤ 2.5

   (See Note A-4.1.7.8.(2) and (3))

   (3) For buildings in rough terrain, as defined in Clause 4.1.7.3.(5)(b), the value of Ce for the design of the main structural
   system shall be calculated as follows:

                                                                 h        0.50
                                                 Ce = 0.5 (           )          , but 0.5 ≤ Ce ≤ 2.5
                                                              12.7

   (See Note A-4.1.7.8.(2) and (3))

   (4) For the design of the main structural system, Cg shall be calculated as follows:

                                                                                     σ
                                                              Cg = 1 + g p
                                                                                     μ

         where
                                                                      0.577
           gp = peak factor calculated as √2 ln(𝑣T) +                              , and
                                                                     √2 ln(𝑣T)

                      K         sF
          σ /μ = √         (B + ) ,
                     CeH        β

     where
                                                                     sF
           𝑣 = average fluctuation rate calculated as fnD √                ,
                                                                  sF+ βB

           T = 3 600 s,
           K = 0.08 for open terrain and 0.10 for rough terrain,
       CeH = exposure factor evaluated at reference height h = H,
           B = background turbulence factor, a function of w/H determined from Figure 4.1.7.8.,
                                                      π          1                 1
            s = size reduction factor calculated as       [               ][             ]
                                                                                  10fnD W ,
                                                      3 1+ 8fnD H              1+
                                                                  3VH               VH
                                                      x20
           F = gust energy ratio calculated as                4/3 , where x0 = (1 220fnD/VH), and
                                                 (1+x20 )

           β = damping ratio, which shall be determined by a rational method or may be taken to be 0.01 for steel
               structures, 0.02 for concrete structures and 0.015 for composite structures,
     where
       fnD = natural frequency of vibration of the building in the along-wind direction, in Hz,
           fn = lowest natural frequency of the building, in Hz, as described in Sentences 4.1.7.2.(2) and (3),
           H = height of the building,
                                                                             ∑hw
           w = effective width of windward face of the building calculated as ∑ i i , where wi = width normal to wind
                                                                                              hi
                direction at height hi, and

       VH = mean wind speed at the top of the structure, in m/s, calculated as V√CeH ,
     where,
                                                                                              2IW q
           V = reference wind speed at a height of 10 m, in m/s, calculated as √                      ,
                                                                                               ρ

      where
           Iw = importance factor for wind load, as provided in Table 4.1.7.3.,
           q = reference velocity pressure, in Pa, and
           ρ = air density = 1.2929 kg/m3.

       (See Note A-4.1.7.8.(4))

                                                      Figure 4.1.7.8.
                                             Background Turbulence Factor, B
                                             Forming Part of Sentence 4.1.7.8.(4)

This provision includes a table — formatting is preserved from the source; refer to the official code for the authoritative layout.

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Code text is reproduced for reference from the Ontario Building Code (O. Reg. 163/24, 2024 Building Code Compendium). This page is provided for general information and is not an official copy. Always verify requirements against the official Ontario Building Code and confirm with your local building department.