(1)
Except as required by Clause (2)(b), structures with a Type 6 irregularity, Discontinuity in Capacity - Weak Storey, as described in Table 4.1.8.6., are not permitted unless the Seismic Category is SC1 and the forces used for design of the SFRS are multiplied by Rd Ro.
(2)
Post-disaster buildings shall
(a)
not have Type 1, 3, 4, 5, 7, 9 or 10 irregularities as described in Table 4.1.8.6., where the Seismic Category is SC3 or SC4,
(b)
not have a Type 6 irregularity as described in Table 4.1.8.6.,
(c)
have an SFRS with an Rd of 2.0 or greater,
(d)
where they are constructed with concrete or masonry shear walls, have no storey with a lateral stiffness that is less than that of the storey above it, and
(e)
where they are constructed with other types of SFRS, have no storey for which the inter storey deflection under lateral earthquake forces divided by the inter storey height, hs, is greater than that of the storey above it.
(3)
High Importance Category buildings shall
(a)
not have Type 1, 3, 4, 5, 7, 9 or 10 irregularities as described in Table 4.1.8.6., where the Seismic Category is SC4,
(b)
not have a Type 6 irregularity as described in Table 4.1.8.6.,
(c)
have an SFRS with an Rd of at least
(i)
2.0 where the Seismic Category is SC4, and
(ii)
1.5 otherwise,
(d)
where they are constructed with concrete or masonry shear walls, have no storey with a lateral stiffness that is less than that of the storey above it, and
(e)
where they are constructed with other types of SFRS, have no storey for which the inter storey deflection under lateral earthquake forces divided by the inter storey height, hs, is greater than that of the storey above it.
(4)
Where the fundamental lateral period, Ta, is greater than or equal to 1.0 s and IE S(1.0) is greater than 0.25, shear walls that are other than wood-based and form part of the SFRS shall be continuous from their top to the foundation and shall not have Type 4 or 5 irregularities as described in Table 4.1.8.6.
(5)
For buildings in Seismic Category SC3 or SC4 that are constructed with more than 4 storeys of continuous wood construction, timber SFRSs consisting of shear walls with wood-based panels or of braced or moment-resisting frames as defined in Table 4.1.8.9. within the continuous wood construction shall not have Type 4 or 5 irregularities as described in Table 4.1.8.6. (See Note A-4.1.8.10.(5) and (6))
(6)
For buildings in Seismic Category SC3 or SC4 that are constructed with more than 4 storeys of continuous wood construction, timber SFRSs consisting of moderately ductile or limited ductility cross-laminated timber shear walls, platform-type construction, as defined in Table 4.1.8.9. within the continuous wood construction shall not have Type 4, 5, 6, 8, 9 or 10 irregularities as described in Table 4.1.8.6. (See Note A-4.1.8.10.(5) and (6))
(7)
The ratio α for a Type 9 irregularity as described in Table 4.1.8.6. shall be determined independently for each orthogonal direction using the following equation:
(8)
For buildings with a Type 9 irregularity as described in Table 4.1.8.6. and where IE S(0.2) is equal to or greater than 0.5, deflections determined in accordance with Article 4.1.8.13. shall be multiplied by 1.2.
(9)
For buildings where the value of α, as determined in accordance with Sentence (7), exceeds twice the appropriate limit specified in Table 4.1.8.6. for a Type 9 irregularity and where IE S(0.2) is equal to or greater than 0.5, a Non-linear Dynamic Analysis of the structure shall be carried out in accordance with Article 4.1.8.12. and the following criteria:
(a)
the analysis shall account for the effects of the vertical response of the building mass,
(b)
the analysis shall account for the effects of the vertical response of building components that undergo a vertical displacement when displaced laterally,
(c)
the analysis shall use vertical ground motion time histories that are compatible with horizontal ground motion time histories scaled to the target response spectrum and that are applied concurrently with the horizontal ground motion time histories,
(d)
the largest inter storey deflection at any level of the building as determined from the analysis shall not be greater than 60% of the appropriate limit stated in Sentence 4.1.8.13.(3), and
(e)
the results of an analysis using the ground motion time histories in Clause (c) multiplied by 1.5 shall satisfy the non-linear acceptance criteria. (See Note A-4.1.8.10.(9))
(10)
The design of buildings in Seismic Category SC3 or SC4 with a Type 10 irregularity as described in Table 4.1.8.6. shall satisfy the following requirements:
(a)
the structure shall be designed to resist the additional earthquake forces due to the vertical accelerations of the mass supported by inclined vertical members, and (See Note A-4.1.8.10.(10)(a))
(b)
the effects of the horizontal and vertical movements of inclined vertical members, while undergoing earthquake-induced deformations, on the floor systems they support shall be considered in the design of the building and accounted for in the application of Sentence 4.1.8.3.(5).