Technical data · Tests and calculation
StarModul joint strength: data for structural design
This page gathers the data we send with our quotes for the structural design of a bolted steel structure with the StarModul system: materials, reference loads, the strength of the bolted joints of the 1010 series (tension, compression, shear and bending moments), the reinforcing fasteners, indicative spans, bracing and the failure tests.
1 · General aspects and materials
Structural design of a StarModul steel structure
The structure is analysed as a single 3D model. Secondary door and window sub-frames are left out of the global model (on the safe side) unless they are needed to place bracing such as X-bracing. The building is designed to meet the Spanish Building Code (CTE) and the structural and concrete standards in force.
Materials used in the calculation
| Element | Material | fy (N/mm²) | fu (N/mm²) | Standard |
|---|---|---|---|---|
| Hollow sections 100×2 and 100×3 | S250GD+Z | 250 | 330 | UNE-EN 10346 |
| Cold-formed omega sections | S350GD+Z | 350 | 420 | UNE-EN 10346 |
| Hot-rolled sections, bracing and plates | S275JR | 275 | 430 | UNE-EN 10025-2 |
| Ordinary bolts | Grade 8.8 | 640 | 800 | UNE-EN ISO 898-1 |
Partial factors: 1.00; 1.00; 1.25. Data from the document “Basic data for structural design with the StarModul system”. In recent projects the tube is also modelled as S280 or S355 depending on the batch certificate.
Certificates of the 100×100 mm structural tube
| Tube | Steel and coating | Standard | Certificate | Re (MPa) | Rm (MPa) |
|---|---|---|---|---|---|
| 100×100×2 mm, 12 m | S350GD + ZM310 (zinc-magnesium) | EN 10219-1/-2 | 3.1 EN 10204 (2026) | 487–549 | 511–615 |
| 100×100×3 mm, 12 m | S350GD + ZM310 (zinc-magnesium) | EN 10219-1/-2 | 3.1 EN 10204 (2026) | 467–549 | 516–615 |
| 100×100×4 mm, 12 m | Galvanised Z275 | EN 10305-5 | 2.2 EN 10204 (2026) | 279–318 | 371–399 |
Minimum and maximum values of the certified heats. According to the certificate, S350GD+ZM310 meets grade S355JR of EN 10219.
Joints
3 mm steel sheet (DD11, EN 10111; 3.1 certificate: Re 246 MPa, Rm 356 MPa) with electrolytic zinc plating and trivalent passivation, free of chromium VI. CE marking to harmonised standard EN 1090-1 (system 2+, EXC2), factory production control certificate 0370-CPR-2637. Reaction to fire A1.
2 · Reference loads
Permanent loads considered
Self-weights: reinforced concrete 25.00 kN/m³; steel 78.50 kN/m³. The system’s reference permanent loads are:
| Load | Value | Breakdown (kN/m²) |
|---|---|---|
| G1 · Upper floor slab | 2.50 kN/m² | 100 mm panel 0.125 · 10 mm cement board 0.120 · flooring 0.305 · underfloor-heating screed 0.950 · partitions 1.000 · omegas (in the software) |
| G2 · Terrace | 2.50 kN/m² | 100 mm panel 0.125 · cement board 0.120 · flooring 0.305 · sloping screed 1.950 |
| G3 · Light roof | 0.40 kN/m² | 100 mm panel 0.125 · 35 mm panel 0.100 · secondary slope structure 0.125 · suspended ceiling 0.050 |
| G4 · Façade | 0.35 kN/m² | 100 mm panel 0.125 · external finish 0.225 |
Imposed, snow, wind and seismic loads depend on the site and are set by the engineer for each project.
3 · 1010 series joints (100×100 tube)
Bolted joint strength: load table
Summary strength values for each joint type, obtained in failure tests at the LERMA laboratory (UPC) with 2 mm tube. Forces in kN; bending moments in kN·m.
| Joint | Node type | Tension (kN) | Compression (kN) | Shear (kN) | My (kN·m) | Mz (kN·m) |
|---|---|---|---|---|---|---|
| 1010-01 | Corner node, 3 arms at 90° | 17.90 | 34.63 | 24.75 | 2.30 | 2.15 |
| 1010-02 | L node, 2 arms at 90° | 25.00 | – | – | 3.00 | 1.70 |
| 1010-03 | 2 arms at 90° + 1 hinged | 19.46 | – | – | – | – |
| 1010-05 | T node | 20.26 | – | 28.97 | 1.45 | 4.20 |
| 1010-06 | 4-arm node at 90° | 21.10 | – | 23.11 | 1.07 | 2.98 |
| 1010-07 | 3 arms at 90° + 1 hinged | 21.99 | – | – | – | – |
| 1010-11 | Cross node, 4 arms | – | – | 22.18 | 2.88 | 3.73 |
| 1010-13 | Column base anchor to a surface | 20.00 | – | – | 4.00 | 1.20 |
| 1010-14 | Hinged anchor to a surface | 25.00 | – | – | – | – |
| 1010-15 | Tube fixing to a parallel surface | – | – | – | 2.00 | 2.80 |
| 1010-16 | Hinged crossing of two tubes | 30.00 | – | – | – | – |
| 1010-17 | Hinged T joint (bracing) | 35.00 | – | – | – | – |
| 1010-19 | 120° node (ridge) | 45.00 | – | – | 2.50 | 4.40 |
| 1010-21 | 180° splice of 2 tubes | 65.00 | – | – | 3.20 | – |
“–”: not tested. Indicative laboratory values; they are not design resistances. In many tests failure occurred in the tube (local buckling or tearing), not in the joint. With 3 or 4 mm tube the capacity of the assembly increases, but each case is checked in the calculation.
Failure load of each specimen (2017–2018 tests)
| Joint | Test | Specimen 1 | Specimen 2 | Failure mode |
|---|---|---|---|---|
| 1010-01 | Tension | 19.42 kN | 17.90 kN | deformation of the joint |
| 1010-01 | Compression | 34.63 kN | 35.30 kN | local buckling of the tube |
| 1010-01 | Bending My | 2.43 kN·m | 2.29 kN·m | deformation of the joint |
| 1010-01 | Bending Mz | 2.60 kN·m | 2.14 kN·m | deformation of the joint |
| 1010-01 | Shear Ty / Tz | 32.29 / 24.75 kN | 27.14 / 26.56 kN | local buckling of the tube |
| 1010-02 | Tension | 28.61 kN | 30.98 kN | deformation of the tube |
| 1010-02 | Bending My | 2.03 kN·m | 2.27 kN·m | bolt and deformation |
| 1010-02 | Bending Mz+ / Mz− | 3.95 / 3.42 kN·m | 3.95 / 3.77 kN·m | deformation of the node |
| 1010-03 | Tension (hinged arm) | 19.46 kN | 20.73 kN | deformation of the joint |
| 1010-05 | Tension | 20.26 kN | 22.81 kN | deformation of the joint |
| 1010-05 | Bending My (2017 / 2018) | 1.45 / 3.06 kN·m | 1.61 / 2.89 kN·m | deformation of the joint |
| 1010-05 | Bending Mz | 4.24 kN·m | 4.20 kN·m | deformation of the joint |
| 1010-05 | Shear Ty / Tz | 30.31 / 34.10 kN | 28.97 / 34.06 kN | local buckling of the tube |
| 1010-06 | Tension | 23.55 kN | 21.10 kN | deformation of the joint |
| 1010-06 | Bending My (2017 / 2018) | 1.19 / 0.86 kN·m | 1.07 / 1.13 kN·m | deformation |
| 1010-06 | Bending Mz | 2.99 kN·m | 3.59 kN·m | deformation |
| 1010-06 | Shear Ty / Tz | 23.11 / 25.55 kN | 24.35 / 34.04 kN | local buckling of the tube |
| 1010-07 | Tension (hinged arm) | 24.22 kN | 21.99 kN | deformation of the joint |
| 1010-11 | Bending My / Mz | 2.89 / 3.73 kN·m | 2.98 / 4.29 kN·m | deformation |
| 1010-11 | Shear Ty | 23.12 kN | 22.18 kN | local buckling of the tube |
| 1010-13 | Tension | 57.12 kN | 52.32 kN | deformation of the plate |
| 1010-13 | Bending My / Mz | 4.92 / 1.41 kN·m | 4.67 / 2.36 kN·m | deformation of the plate |
| 1010-14 | Tension | 31.36 kN | 29.78 kN | tearing of the tube |
| 1010-15 | Bending My / Mz | 2.14 / 3.30 kN·m | 2.56 / 3.24 kN·m | deformation |
| 1010-16 | Tension | 30.49 kN | 34.41 kN | tearing of the tube |
| 1010-17 | Tension | 49.33 kN | 40.42 kN | tearing of the tube |
| 1010-19 | Tension | 49.99 kN | 53.14 kN | deformation of the tube |
| 1010-19 | Bending My / Mz | 4.07 / 4.89 kN·m | 2.93 / 4.68 kN·m | deformation |
| 1010-21 | Tension | 72.75 kN | 71.88 kN | shear of the fasteners |
| 1010-21 | Bending My | 3.59 kN·m | 3.65 kN·m | deformation of the tube |
4 · Fasteners and bracing
Self-drilling screws, flat bars and tensioners
6.3×25 reinforcing self-drilling screw
The joints are reinforced with 6.3×25 self-drilling screws, which stop the members from separating under tension. Each screw provides 3.40 kN in shear with an additional safety factor of 3. Every joint has at least 2 fasteners on two of its faces, and most have 6 or more.
| Diameter (mm) | Tension (kN) | Shear (kN) |
|---|---|---|
| 4.8 | 9.34 | 6.58 |
| 5.5 | 12.50 | 8.95 |
| 6.3 | 14.45 | 9.40 |
Mechanical strength of the screw (core hardness 390 HV; surface 560 HV).
| 6.3 screw: sheet thickness (mm) | Pull-out resistance (kN) | Drilling time (s) |
|---|---|---|
| 4 | 9.85 | 2.8 |
| 5 | 12.30 | 3.4 |
| 6 | 14.50 | 3.7 |
Flat-bar bracing
Bracing is treated as tension-only ties: X-bracing with 40×4 flat bar or rigid tube members, placed in the façades where openings allow.
- 40×4 flat bar, S275JR steel: NRd = 30.0 kN in tension.
- Double flat bar 2 × 40×4: NRd = 62.0 kN.
- The piece joining the tensioners is the 1010-17, with 35.00 kN in tension in the tests, above what the flat bar can take.
- The bracing piece is fixed to the structure with grade 8.8 M12 bolts.
Bracing tensioners
| Tensioner | M6 | M8 | M10 | M12 | M16 | M20 | M24 | M30 | M36 |
|---|---|---|---|---|---|---|---|---|---|
| Guaranteed tensile strength (kN) | 2.35 | 3.20 | 5.35 | 6.65 | 16.65 | 25.35 | 36.65 | 53.35 | 71.65 |
5 · Indicative spans
Indicative maximum spans with tube and omega sections
Reference spans of the StarModul system with 100×100 tube and 200 mm omega section. They are indicative: every project is calculated.
| Element | Max. span (m) | Spacing (m) |
|---|---|---|
| Roof, tube at one level | 4.50 | 1.90 |
| Roof, tube at one level | 5.27 | 1.39 |
| Roof, tube at 2 levels | 3.00 | 3.00 |
| Roof, tube at 2 levels | 3.70 | 2.15 |
| Roof, tube at 2 levels | 5.30 | 1.50 |
| Roof, omega 200 | 5.36 | 1.65 |
| Interior floor, double tube | 5.27 | 1.00 |
| Floor, omega 200 | 6.50 | 0.50 |
For industrial buildings the tube-and-joint system reaches about 12 m span; for larger spans, up to about 20 m, we use bolted IPE steel buildings.
6 · Finite element design (2026)
Bracing and splice joints: IDEA StatiCa check (Eurocode 3)
In 2026 two system joints with SHS 100×100×3 mm tube were checked by calculation with IDEA StatiCa Connection (component-based finite element method, EN 1993-1-8, 1-3, 1-1 and 1-5).
Hinged bracing joint
Two SHS 100×100×3 sections (S250) at 45° or 90°, with grade 8.8 fasteners. Maximum resistance for each action on its own (not combined, no moments):
| Configuration | M10 8.8 bolts: axial (kN) | Horizontal V (kN) | Vertical V (kN) | 5.5 self-drilling screws: axial (kN) | Horizontal V (kN) | Vertical V (kN) |
|---|---|---|---|---|---|---|
| 45°, 3 bolts per line | 38.0 | 11.0 | 15.0 | 30.0 | 9.2 | 12.0 |
| 45°, 2 bolts | 33.0 | 10.5 | 12.5 | 20.0 | 8.5 | 9.2 |
| 45°, 1 bolt | 18.0 | 10.5 | 9.2 | 10.0 | 10.0 | 9.2 |
| 90°, 3 bolts | 77.0 | 9.2 | 11.7 | 52.0 | 8.5 | 11.4 |
| 90°, 2 bolts | 68.0 | 9.0 | 11.7 | 35.0 | 8.2 | 11.0 |
| 90°, 1 bolt | 33.0 | 8.5 | 10.0 | 11.0 | – | 7.9 |
The reports study 4, 8 and 12 bolts in total per joint (1, 2 or 3 per line). Values valid only for the geometry, materials and layout studied.
Tube splice joint
Splice of two SHS 100×100×3 (S280) with an external 110×110×4 tube sleeve (S235) and 12 grade 8.8 M12 through-bolts (6 per side). Hinged joint (transfers axial and shear forces, not moments).
- Check under the loads of a real project (industrial building): design load of ±75 kN in tension and compression, with 21.6 % bolt utilisation.
- Ultimate resistance analysis: load factor of 300 %, i.e. about 225 kN axial in tension or compression.
7 · Failure tests
Joint failure load: tests at the LERMA laboratory (UPC)
The 1010 series joints were tested to failure at the Laboratori d’Elasticitat i Resistència de Materials (LERMA) of the Universitat Politècnica de Catalunya in two campaigns: May 2017 (reports 46009) and October 2018 (reports 47008). Each test used two 100×100×2 mm tube specimens loaded to failure with a 100 kN load cell.
Each test has its load-displacement curve (tension and compression) or moment-rotation curve (bending about the y and z axes). These are the curves for each joint (click to enlarge).
8 · Examples and documents
Structural calculation examples and documents
With every quote we send the document “Basic data for structural design with the StarModul system”. For projects that need a calculation (houses, industrial buildings, other buildings), our engineer prepares the calculation report and structural drawings, quoted separately.
Basic data for structural design
The document we include with every quote: materials, reference loads and test values of the 1010 series joints.
- Download “Basic data for structural design” (in Spanish) (PDF · 9 pages · 0.8 MB)
Single-storey detached house (Alicante, 2024)
StarModul structure in SHS 100×100×3 and 100×100×2 tube with 1010 series joints, flat roof with omega sections and façade bracing. Floor area of about 113 m² and 4.26 m height to the first roof.
Contents: calculation report (codes, actions, combinations, 3D model, member, joint and omega checks, reactions) and structural drawings (plan, roof, sections and 3D views).
- Download the calculation report (in Spanish) (PDF · 118 pages · 2.6 MB)
- Download the structural drawings (in Spanish) (PDF · 7 sheets · 0.6 MB)
Real documents: client, site and engineer details have been removed.
IPE steel buildings (Torre-serona and Gabon)
Calculation drawings of two bolted IPE buildings: on the IPE buildings page.