Error Percentage in Finite Element Analysis and Solutions

No structural element should have its length, thickness, or modulus of elasticity set to zero. Zero values for these parameters cause infinite displacement demand in the element.

If the mass of elements is set to zero, the system cannot be solved in modal analysis with finite elements using the mass matrix, or mode values become undefined.

If there are walls on the upper floor resting on the slab, drawing beams on the lower floor ceiling with height equal to slab thickness and width equal to the wall width above, or solving with irregular triangular mesh as described in the related articles, increases the accuracy of the analysis.

If a wall penetrates into the middle section of another wall (not at the endpoints), it is not necessary to split the penetrated wall. StatiCAD automatically makes corrections during analysis.

Small wall segments of 1-2 cm remaining between doors and windows (as in misaligned openings) should be deleted (or the window should be widened). Very short elements produce unrealistic results with very high stiffness and strength.

The finite element analysis verifies the accuracy of the solution by comparing the sum of earthquake forces applied to the building with the sum of base shear forces. If the error percentage is more than 1-2%, a modeling issue should be suspected. Elements with errors are marked in the error list and should be reviewed. The causes listed above are the most common sources of errors.

If walls that appear to be a single wall are actually modeled as overlapping separate wall segments, these should be merged into a single wall. Overlapping walls cause artificial stiffness increases and lead to incorrect analysis results.

In buildings with very rigid systems (such as thick shear walls), the finite element mesh density may need to be increased for more accurate results.