How ETABS computes the Global Force Balance Relative Error which is reported in ETABS .LOG and .OUT files?
For each Analysis Case, the sum of all joint forces and moments acting on the structure should be in equilibrium. The program computes and prints a global force balance for the following types of Analysis Cases: Loads, Modes, Specs, and Combos; no global force balance is computed for Histories, or Combos that contain Histories. You should always review the global force balance as a check on the validity of the structural model and the analysis. For each Analysis Case, the program computes the resultants at the global origin for all joint forces and moments acting on the structure. Separate resultants are computed for each type of joint force: • Applied loads • Inertial loads • Spring forces • Link forces • Restraint Forces (Reactions) • Constraint forces • P-Delta forces Each force resultant is computed as the sum of the forces acting on all joints in the structure. Each moment resultant is computed as the sum of the moments acting on all joints in the structure, plus the moments about
