4.1.8.16.Foundation Provisions

(1) The increased displacements of the structure resulting from foundation movement shall be shown to be within acceptable limits for both the SFRS and the structural framing elements not considered to be part of the SFRS. (See Note A-4.1.8.16.(1).) (2) Except as provided in Sentences (3) and (4), foundations shall be designed to have factored shear and overturning resistances greater than the lateral load capacity of the SFRS. (See Note A-4.1.8.16.(2)) (3) The shear and overturning resistances of the foundation determined using a bearing stress equal to 1.5 times the factored bearing strength of the soil or rock and all other resistances equal to 1.3 times the factored resistances need not exceed the design forces determined in Sentence 4.1.8.7.(1) using RdRo = 1.0, except that the factor of 1.3 shall not apply to the portion of the resistance to uplift or overturning resulting from gravity loads. (4) A foundation is permitted to have a factored overturning resistance less than the lateral load overturning capacity of the supported SFRS, provided the following requirements are met: (a) neither the foundation nor the supported SFRS are constrained against rotation, and (b) the design overturning moment of the foundation is (i) not less than 75% of the overturning capacity of the supported SFRS, and (ii) not less than that determined in Sentence 4.1.8.7.(1) using RdRo = 2.0. (See Note A-4.1.8.16.(4)) (5) The design of foundations shall be such that they are capable of transferring earthquake loads and effects between the building and the ground without exceeding the capacities of the soil and rock. (6) Where the Seismic Category is SC3 or SC4, the following requirements shall be satisfied: (a) piles or pile caps, drilled piers, and caissons shall be interconnected by continuous ties in not less than two directions (See Note A-4.1.8.16.(6)(a)), (b) piles, drilled piers, and caissons shall be embedded a minimum of 100 mm into the pile cap or structure, and (c) piles, drilled piers, and caissons, other than wood piles, shall be connected to the pile cap or structure for a minimum tension force equal to 0.15 times the factored compression load on the pile. (7) Where the Seismic Category is SC3 or SC4, basement walls shall be designed to resist earthquake lateral pressures from backfill or natural ground. (See Note A-4.1.8.16.(7).) (8) Where the Seismic Category is SC4, the following requirements shall be satisfied: (a) piles, drilled piers, or caissons shall be designed and detailed to accommodate cyclic inelastic behaviour when the design moment in the element due to earthquake effects is greater than 75% of its moment capacity, and (See Note A-4.1.8.16.(8)(a)) (b) spread footings founded on soil designated as XV, where Vs30 is less than or equal to 180 m/s, XE or XF shall be interconnected by continuous ties in not less than two directions. e1 (9) Each segment of a tie between elements that is required by Clause (6)(a) or (8)(b) shall be designed to carry by tension or compression a horizontal force at least equal to the greatest factored pile cap or column vertical load in the elements it connects, multiplied by a factor of 0.1IES(0.2), unless it can be demonstrated that equivalent restraints can be provided by other means. (See Note A-4.1.8.16.(9)) (10) The potential for liquefaction of the soil and its consequences, such as significant ground displacement and loss of soil strength and stiffness, shall be evaluated based on the ground motion parameters referenced in Subsection 1.1.3., as modified by Article 4.1.8.4., and shall be taken into account in the design of the structure and its foundations. (See Note A-4.1.8.16.(10))