The Ontario Building Code | Dynamic Analysis Procedure
18.104.22.168. Dynamic Analysis Procedure
(1) The Dynamic Analysis Procedure shall be in accordance with one of the following methods:
(a) Linear Dynamic Analysis by either the Modal Response Spectrum Method or the Numerical Integration Linear Time History Method using a structural model that complies with the requirements of Sentence 22.214.171.124.(8), or
(b) Nonlinear Dynamic Analysis, in which case a special study shall be performed.
(2) The spectral acceleration values used in the Modal Response Spectrum Method shall be the design spectral acceleration values, S(T), defined in Sentence 126.96.36.199.(7).
(3) The ground motion histories used in the Numerical Integration Linear Time History Method shall be compatible with a response spectrum constructed from the design spectral acceleration values, S(T), defined in Sentence 188.8.131.52.(7).
(4) The effects of accidental torsional moments acting concurrently with the lateral earthquake forces that cause them shall be accounted for by the following methods:
(a) the static effects of torsional moments due to (± 0.10 Dnx)Fx at each level x, where Fxis either determined from the elastic dynamic analysis or determined from Sentence 184.108.40.206.(6) multiplied by RdRo/IE, shall be combined with the effects determined by dynamic analysis, or
(b) if B, as defined in Sentence 220.127.116.11.(9), is less than 1.7, it is permitted to use a three-dimensional dynamic analysis with the centres of mass shifted by a distance of – 0.05 Dnxand + 0.05 Dnx.
(5) Except as provided in Sentence (6), the design elastic base shear, Ved, is equal to the elastic base shear, Ve, obtained from a Linear Dynamic Analysis.
(6) For structures located on sites other than Class F that have an SFRS with Rd equal to or greater than 1.5, the elastic base shear obtained from a Linear Dynamic Analysis may be multiplied by the following factor to obtain the design elastic base shear, Ved:
(7) The design elastic base shear, Ved, shall be multiplied by the importance factor, IE, as determined in Article 18.104.22.168., and shall be divided by RdRo, as determined in Article 22.214.171.124., to obtain the design base shear, Vd.
(8) Except as required by Sentences (9) and (12), if the base shear, Vd, obtained in Sentence (7) is less than 80% of the lateral earthquake design force, V, of Article 126.96.36.199., Vd shall be taken as 0.8 V.
(9) For irregular structures requiring dynamic analysis in accordance with Article 188.8.131.52., Vdshall be taken as the larger of the Vd determined in Sentence (7) and 100% of V.
(10) Except as required by Sentence (11), the values of elastic storey shears,storey forces, member forces, and deflections obtained from the Linear Dynamic Analysis, including the effect of accidental torsion determined in Sentence (4), shall be multiplied by Vd/Veto determine their design values, where Vd is the base shear.
(11) For the purpose of calculating deflections, it is permitted to use a value for V based on the value for Ta determined in Clause 184.108.40.206.(3)(d) to obtain Vdin Sentences (8) and (9).
(12) buildings with more than 4 storeysof continuous wood construction and having a timber SFRS of shear walls with wood-based panels, braced frames or moment-resisting frames as defined in Table 220.127.116.11., having a fundamental lateral period, Ta, as determined in Clause 18.104.22.168.(3)(d), shall have the base shear, Vd, taken as the larger of the base shear obtained in Sentence (7) and 100% of the lateral earthquake design force, V, as determined in Article 22.214.171.124.