4.1.8.6 — Structural Configuration

(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 IEFaSa(0.2) is less than 0.2 and the forces used for design of the SFRS are multiplied by RdRo. (2) Post-disaster buildings shall, (a) not have any irregularities conforming to Types 1, 3, 4, 5, 7 and 9 as described in Table 4.1.8.6., in cases where IEFaSa(0.2) is equal to or greater than 0.35, (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, and (d) have no storey with a lateral stiffness that is less than that of the storey above it. (3) For buildings having fundamental lateral periods, Ta, of 1.0 s or greater and where IEFvSa(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 irregularities of Type 4 or 5 as described in Table 4.1.8.6. (4) For buildings constructed with more than 4 storeys of continuous wood construction and where IEFaSa(0.2) is equal to or greater than 0.35, timber SFRS of shear walls with wood-based panels, braced frames or moment-resisting frames as defined in Table 4.1.8.9. within the continuous wood construction shall not have irregularities of Type 4 or 5 as described in Table 4.1.8.6. (4.1) For buildings where IEFaSa(0.2) is equal to or greater than 0.35 or IEFvSa(1.0) is equal to or greater than 0.2 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, or 9 irregularities as described in Table 4.1.8.6. (5) The ratio, α, for Type 9 irregularity as described in Table 4.1.8.6. shall be determined independently for each orthogonal direction using the following equation: 𝛼 = QG / Qy where, QG =gravity-induced lateral demand on the SFRS at the critical level of the yielding system, and Qy =the resistance of the yielding mechanism required to resist the minimum earthquake loads, which need not be taken less than Ro multiplied by the minimum lateral earthquake force as determined in Article 4.1.8.11. or 4.1.8.12, as appropriate. (6) For buildings with a Type 9 irregularity as described in Table 4.1.8.6. and where IEFaSa(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. (7) Structures where the value of α, as determined in accordance with Sentence (5), exceeds twice the limits in Table 4.1.8.6. for a Type 9 irregularity, and where IEFaSa(0.2) is equal to or greater than 0.5 are not permitted unless determined to be acceptable based on non-linear dynamic analysis studies.