Notes to Figure 4.1.7.6.H.:
4.1.8.1. Analysis (1) Except as permitted in Sentence (2), the deflections and specified loading due to earthquake motions shall be determined according to the requirements of Articles 4.1.8.2. to 4.1.8.22. (2) Where IEFsSa(0.2) and IEFsSa(2.0) are less than 0.16 and 0.03 respectively, the deflections and specified loading due to earthquake motions are permitted to be determined in accordance with Sentences (3) to (15), where, (a) IE is the earthquake importance factor and has a value of 0.8, 1.0, 1.3 and 1.5 for buildings of Low, Normal, High and Post-Disaster importance respectively, (b) Fs is the site coefficient based on the average  or su, as defined in Article 4.1.8.2., for the top 30 m of soil below the footings, pile caps or mat foundations and has a value of, (i) 1.0 for rock sites or when  or su > 100 kPa, (ii) 1.6 when  or 50 kPa ≤ su ≤ 100 kPa, and (iii) 2.8 for all other cases, and (c) Sa(T) is the 5% damped spectral response acceleration value for period T, determined in accordance with Subsection 1.1.2. (3) The structure shall have a clearly defined, (a) SFRS, as defined in Article 4.1.8.2., to resist the earthquake loads and their effects, and (b) load path or paths that will transfer the inertial forces generated by the earthquake to the foundations and supporting ground. (4) An unreinforced masonry SFRS shall not be permitted where, (a) IE is greater than 1.0, or (b) the height above grade is greater than or equal to 30 m. (5) The height above grade of SFRS designed in accordance with CSA S136, “North American Specification for the Design of Cold-Formed Steel Structural Members”, shall be less than 15 m. (6) Earthquake forces shall be assumed to act horizontally and independently about any two orthogonal axes. (7) The minimum lateral earthquake design force, Vs, at the base of the structure in the direction under consideration shall be calculated as follows: Vs = Fs Sa(Ts) IE Wt / RS where, Sa(Ts) =  value of Sa at Ts determined by linear interpolation between the value of Sa at 0.2 s, 0.5 s and 1.0 s, and = Sa(0.2) for Ts
≤ 0.2 s, Wt = sum of Wi
over the height of the building, where Wi
is defined in Article 4.1.8.2., and Rs = 1.5 except Rs
= 1.0 for structures where the storey strength is less than that in the storey above and for an unreinforced masonry SFRS, where, Ts = fundamental lateral period of vibration of the building, as defined in Article 4.1.8.2., = 0.085(hn)¾
for steel moment frames, = 0.075(hn)¾
for concrete moment frames, = 0.1 N for other moment frames, = 0.025hn
for braced frames, and = 0.05(hn)¾
for shear walls and other structures, where, hn = height above the base, in m, as defined in Article 4.1.8.2., except that Vs shall not be less than FsSa(1.0)IEWt/Rs
and, in cases where Rs = 1.5, Vs need not be greater than FsSa(0.5)IEWt/Rs. (8) The total lateral earthquake design force, Vs, shall be distributed over the height of the building in accordance with the following formula:  where, Fx = force applied through the centre of mass at level x, Wx,Wi = portion of W that is located at or is assigned to level x or level i respectively, and hx, hi = height, in m, above the base of level x and level i as described in Article 4.1.8.2. (9) Accidental torsional effects applied concurrently with Fx shall be considered by applying torsional moments about the vertical axis at each level for each of the following cases considered separately: (a) +0.1DnxFx, and (b) –0.1DnxFx. (10) Deflections obtained from a linear analysis shall include the effects of torsion and be multiplied by Rs/IE to get realistic values of expected deflections. (11) The deflections described in Sentence (10) shall be used to calculate the largest interstorey deflection, which shall not exceed, (a) 0.01hs for post-disaster buildings, (b) 0.02hs for High Importance Category buildings, and (c) 0.025hs for all other buildings, where hs is the interstorey height as defined in Article 4.1.8.2. (12) When earthquake forces are calculated using Rs = 1.5, the following elements in the SFRS shall have their design forces due to earthquake effects increased by 33%: (a) diaphragms and their chords, connections, struts and collectors, (b) tie downs in wood or drywall shear walls, (c) connections and anchor bolts in steel- and wood-braced frames, (d) connections in precast concrete, and (e) connections in steel moment frames. (13) Except as provided in Sentence (14), where cantilever parapet walls, other cantilever walls, exterior ornamentation and appendages, towers, chimneys or penthouses are connected to or form part of a building, they shall be designed, along with their connections, for a lateral force, Vsp, distributed according to the distribution of mass of the element and acting in the lateral direction that results in the most critical loading for design using the following equation: Vsp = 0.1FsIEWp where Wp is the weight of a portion of a structure as defined in Article 4.1.8.2. (14) The value of Vsp shall be doubled for unreinforced masonry elements. (15) Structures designed in accordance with this Article need not comply with the seismic requirements stated in the applicable design standard referenced in Section 4.3.