# SCIA Engineer against StruCla: concrete frame with columns and beams

Check sheet of the validation on https://strucla.com/validation/concrete-frame.html (2026-11-01). Machine-readable version: concrete-frame-checksheet.json (same items).

Use this sheet with the SCIA output (https://strucla.com/validation/scia-output-concrete-frame.html) and the StruCla report (https://strucla.com/validation/strucla-report-concrete-frame.html).

## Result
- section force: 166 equal, 13 small difference, 1 differs
- support reaction: 18 equal, 0 small difference, 0 differs
- capacity response check: 9 equal, 2 small difference, 1 differs
- provided reinforcement: 8 equal, 0 small difference, 0 differs
- Total: 218 values: 201 equal, 15 small difference, 2 differs.

Equal: |difference| <= max(1 % of the SCIA value; 0.06). Small difference: <= 5 % or <= 0.3 absolute. Section forces other than N are compared as magnitudes (different local axes and signs).

## Model
16 members, 24 nodes, C16/20, E = 28 600 N/mm2, B400B. Supports: K5 and K72: five degrees of freedom fixed, rotation about X free. BG3 contains a line load of 0.62 kN/m on the columns S3 and S60 that is in the SCIA file but not in the printed output; it is included in StruCla.

## Not compared
- Reinforcement of S55, S59, S61, S65 is not entered in StruCla (not shown in the SCIA output); S59 has the same provided areas as S3 on SCIA sheet 21.
- SCIA deformations at selected points (sheets 18-19): StruCla gives the maximum displacement per combination and the member deflections.
- SCIA steel check (sheet 20) was not calculated (error E-C04); no steel members.

## Known differences
- 10 of 30 section-force rows differ in at least one value by more than 1 %: weak-axis moment M_z of the columns (1.1 to 3.9 % for values above 5) and shear force and moment of S68 and S69 (1.3 to 2.4 %). The cause is not found; the largest relative difference for values above 5 is 3.9 %.
- Capacity check of S69-type steel stresses: SCIA divides by 373 N/mm2 (inclined top branch), StruCla by f_yd (horizontal branch); both allowed by NEN-EN 1992-1-1 3.2.7(2). Not present in the three SCIA rows above.

## Capacity response check (SCIA sheet 22)
| Member, position | SCIA UC | StruCla UC | x SCIA / StruCla (mm) | sigma_c SCIA / StruCla | sigma_s SCIA / StruCla |
|---|---|---|---|---|---|
| S3 dx 0.383, /1 = 0.90 BG1 + 1.50 BG2 + 1.50 BG4 | 0.04 | 0.04 | 716 / 681 | 0.41 / 0.42 | 0.7 / 0.6 |
| S60 dx 6.125, /2 = 1.35 BG1 + 1.50 BG2 + 1.50 BG4 | 0.05 | 0.05 | 832 / 1741 | 0.49 / 0.49 | 0 / 0.0 |
| S57 dx 1.500-, /2 = 1.35 BG1 + 1.50 BG2 + 1.50 BG4 | 0.71 | 0.72 | 185 / 185 | 4.04 / 4.05 | 155.4 / 155.6 |

For S57 the unity check is governed by the compression zone limit of NEN-EN 1992-1-1+NB 6.1(9) (UC x_u 0.72); the strength check (3-D interaction) is 0.33.

## Items
- F-S3-3.833+-a61-M_z: SCIA 18.91, StruCla 19.151 kNm (small difference, 1.27 %)
- F-S60-3.833+-a61-M_z: SCIA 21.87, StruCla 22.112 kNm (small difference, 1.11 %)
- F-S61-0-a74-M_z: SCIA 1.88, StruCla 2.193 kNm (differs, 16.65 %)
- F-S55-0-a61-M_z: SCIA 1.22, StruCla 0.977 kNm (small difference, -19.92 %)
- F-S59-0-a61-M_z: SCIA 2.27, StruCla 2.142 kNm (small difference, -5.64 %)
- F-S61-2-a61-M_z: SCIA 7.65, StruCla 7.353 kNm (small difference, -3.88 %)
- F-S68-0-a61-V_z: SCIA 6.07, StruCla 5.993 kN (small difference, -1.27 %)
- F-S68-0-a61-M_y: SCIA 5.1, StruCla 4.983 kNm (small difference, -2.29 %)
- F-S69-0-a61-V_z: SCIA 7.48, StruCla 7.374 kN (small difference, -1.42 %)
- F-S69-0-a61-M_y: SCIA 7.33, StruCla 7.179 kNm (small difference, -2.06 %)
- F-S69-3-a116-V_z: SCIA 0.72, StruCla 0.616 kN (small difference, -14.44 %)
- F-S69-3-a116-M_y: SCIA 4, StruCla 3.832 kNm (small difference, -4.2 %)
- F-S68-3-a61-V_z: SCIA 1.65, StruCla 1.73 kN (small difference, 4.85 %)
- F-S68-3-a61-M_y: SCIA 1.54, StruCla 1.409 kNm (small difference, -8.51 %)
- C-S3-x: SCIA 716, StruCla 681 mm (small difference, -4.89 %)
- C-S3-sigma_s: SCIA 0.7, StruCla 0.6 N/mm2 (small difference, -14.29 %)
- C-S60-x: SCIA 832, StruCla 1741 mm (differs, 109.25 %)

All other items in the JSON file are equal.

## Prompt for another AI
"Compare the SCIA Engineer output (scia-output-concrete-frame.html, values also as text on that page) with the StruCla report (strucla-report-concrete-frame.html) and with this check sheet. Check that the model input is the same (sections, loads, supports, combinations), that the combinations are applied as printed, and recalculate a few values by hand: the self weight of S3 (0.45 x 0.70 x 25 kN/m x 9.5 m), a support reaction and the compression zone limit x_u/d <= 500/(500 + f_yd) = 0.59. List every difference, however small, and say which differences are explained by the stated conventions."