1613.4.3 Lateral Forces
Each structure shall be analyzed for the effects of static lateral forces applied independently in each of two orthogonal directions. n each direction, the static lateral forces at all levels shall be applied simultaneously. For purposes of analysis, the force at each level shall be determined using Equation 16-36a.
Fx = The design lateral force applied at level x.
Wx = The portion of the total dead load of the structure, D, located or assigned to level x.