If you use load combinations for ALLOWABLE STRESS DESIGN, the code permits allowable stress increase
factor of 1.2.
The relevant para. of ASCE 7;
Where allowable stress design methodologies are used with
the seismic load effect defined in Section 12.4.3 or 12.14.3.2
and applied in load combinations 8, 9, or 10, allowable stresses
are permitted to be determined using an allowable stress increase
factor of 1.2. This increase shall not be combined with increases
in allowable stresses or load combination reductions otherwise
permitted by this standard...
However , AFAIK ,the code is silent for sliding resistance increase.
My suggestion would be , use strength design combinations and follow Table 12.13-1.
Use Sliding friction coefficient at base of footing 0.67 Tan ø for the coefficient of sliding resistance.
And multiply with Resistance factor, Phi = 0.85 per Table 12.13-1 of the Standard.
You may provide more detail to get better responds. E..G. Is this a storage tank , vessel etc ?
