MrJB
Structural
- Oct 7, 2021
- 15
Is anyone able to clarify the link between the mew and Sp values and which values are relevant for designing footings to AS 1170.4 and AS 3600?
Section 11.2 of AS3600 asks for an analysis to be performed with mew of 1 and Sp of 1 to determine if there is any compression/tension in the structural walls. If the full earthquake load needs to be applied elastically does the standard imply the structural walls may need to take this full load? If so, should the footing loads be calculated with a mew of 1 and Sp of 1?
An EDCII building using the equivalent static analysis procedure with limited ductile structural walls results in a mew of 2 and Sp of 0.77. This results in 38% of the full earthquake load being applied elastically and the remainder being applied inelastically. Is the 62% of the load being applied inelastically just absorbed by the structure without the load path being resolved through the footings? If the base reactions can be adopted for footing design it seems that considerable economy and time savings during construction could be achieved by increasing the detailing to cover moderately ductile structural walls. Unless other load cases govern (ie wind or gravity), the footing loads could be reduced by nearly half which must be more efficient than adding in additional ligs in boundary elements and staggering splices etc as required by section 14 of AS3600. I would however need much more comfort before applying this methodology...
Section 11.2 of AS3600 asks for an analysis to be performed with mew of 1 and Sp of 1 to determine if there is any compression/tension in the structural walls. If the full earthquake load needs to be applied elastically does the standard imply the structural walls may need to take this full load? If so, should the footing loads be calculated with a mew of 1 and Sp of 1?
An EDCII building using the equivalent static analysis procedure with limited ductile structural walls results in a mew of 2 and Sp of 0.77. This results in 38% of the full earthquake load being applied elastically and the remainder being applied inelastically. Is the 62% of the load being applied inelastically just absorbed by the structure without the load path being resolved through the footings? If the base reactions can be adopted for footing design it seems that considerable economy and time savings during construction could be achieved by increasing the detailing to cover moderately ductile structural walls. Unless other load cases govern (ie wind or gravity), the footing loads could be reduced by nearly half which must be more efficient than adding in additional ligs in boundary elements and staggering splices etc as required by section 14 of AS3600. I would however need much more comfort before applying this methodology...