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24. Heavy Loads Without Propping with INCO 70.4

Calculation example using INCO 70.4 Composite and REI 90 for high loads without propping. The analysed solution verifies an imposed load of 18.0 kN/m² over 3.20 m spans, while maintaining construction without propping.

The objective of this example is to analyse the behaviour of a composite floor subjected to high loads while maintaining a construction process without propping. The case makes it possible to assess how the load-bearing capacity of the slab, the structural depth and the fire-resistance requirements interact in a moderate-span solution.

Initial assumptions

The following initial conditions are considered:

Geometry and structural arrangement

  • Profile: INCO 70.4 Composite
  • Sheet thickness: 1.20 mm
  • Spans in the composite stage: 4 equal spans
  • Span: 3.20 m (V1 = V2 = V3 = V4)
  • Sheet layout during the formwork stage: 2 sheets (2+2 spans)
  • Construction: composite floor without propping
  • Required fire resistance: REI 90
  • Steel supports: 100 mm wide

Materials

  • Base steel: S320GD (resistance tables available for S280GD steel)
  • Structural concrete: HA-25

Loads

  • Additional permanent loads: 2.0 kN/m²
  • Imposed load: 18.0 kN/m²
  • Self-weight of the floor: considered internally by the calculation software

Verification criteria

  • Formwork stage: L/180 and an absolute limit of 20 mm, including ponding effect
  • Composite stage: L/350 (spans ≤ 3.50 m)
  • Verification in accordance with Eurocodes 3 and 4, with fire resistance verified in accordance with EN 1994-1-2

Resulting structural solution after verification

Applying the above criteria and verifying the formwork stage, composite stage and REI 90 fire resistance, the following configuration is obtained:

  • Total floor depth (H): 200 mm
  • Concrete compression layer (h): 130 mm
  • Upper reinforcement mesh (crack control and negative moments): 150×150×10
  • Lower fire reinforcement: Ø6 per trough, according to the specific verification

Verified imposed load: 18.0 kN/m² over four 3.20 m spans, with REI 90 fire resistance and construction without propping.

Structural interpretation

This example represents an application in which a moderate span allows the design to focus on the load-bearing capacity of the slab and the fire-resistance requirement, while maintaining construction without propping. Within these ranges, the design is governed by:

  • verification of the sheet during concrete pouring (formwork stage),
  • the total floor depth, due to its influence on stiffness and fire behaviour,
  • and the amount of lower reinforcement required to achieve REI 90 under high loads.

In practical terms, the case shows that a solution using 1.20 mm INCO 70.4 Composite can withstand an imposed load of 18.0 kN/m² over 3.20 m spans without propping, when a floor depth and reinforcement arrangement compatible with the structural and fire-resistance verifications are adopted.

Conclusion

For a composite floor using 1.20 mm INCO 70.4 Composite, H = 200 mm and REI 90 fire resistance, the example verifies an imposed load of 18.0 kN/m² over four 3.20 m spans, while maintaining construction without propping through a continuous 2+2 layout.

The case shows how, for moderate spans, the system can accommodate high loads through a combination of sheet thickness, slab depth and the required reinforcement. The final design must be carried out through a project-specific verification under the actual conditions of each project.

Composite Floor Calculation Report

The above example is for guidance purposes and is based on specific assumptions regarding loads, span, fire resistance and structural arrangement.

The final design of an unpropped composite floor must be formalised through a specific calculation report, documenting the verification of:

  • Ultimate limit states (bending and shear).
  • Serviceability limit states during the formwork and composite stages.
  • Fire resistance in accordance with EN 1994-1-2.
  • Construction conditions and the adopted structural arrangement.

The Incoperfil Technical Department issues supporting calculation reports adapted to the actual conditions of each project, in accordance with Eurocodes 3 and 4. Requests for calculation reports can be submitted through the technical form available on the website, providing span, load and fire-resistance requirements.

Request a composite floor calculation report through the corresponding technical form.

Related articles

  • Structural calculation of composite floors
  • Unpropped composite floors
  • Types of reinforcement for composite floors
  • Fire resistance of composite floors
  • Long spans without propping with INCO 100.3

Incoperfil Technical Manual

For the complete definition of the system, design criteria, calculation bases, resistance tables, construction details and installation procedures, please consult the Incoperfil Technical Manual for Composite Floors, available upon registration in the Documentation section.

Last updated: September 2026

© Incoperfil. All rights reserved.

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24. Heavy Loads Without Propping with INCO 70.4

Calculation example using INCO 70.4 Composite and REI 90 for high loads without propping. The analysed solution verifies an imposed load of 18.0 kN/m² over 3.20 m spans, while maintaining construction without propping.

The objective of this example is to analyse the behaviour of a composite floor subjected to high loads while maintaining a construction process without propping. The case makes it possible to assess how the load-bearing capacity of the slab, the structural depth and the fire-resistance requirements interact in a moderate-span solution.

Initial assumptions

The following initial conditions are considered:

Geometry and structural arrangement

  • Profile: INCO 70.4 Composite
  • Sheet thickness: 1.20 mm
  • Spans in the composite stage: 4 equal spans
  • Span: 3.20 m (V1 = V2 = V3 = V4)
  • Sheet layout during the formwork stage: 2 sheets (2+2 spans)
  • Construction: composite floor without propping
  • Required fire resistance: REI 90
  • Steel supports: 100 mm wide

Materials

  • Base steel: S320GD (resistance tables available for S280GD steel)
  • Structural concrete: HA-25

Loads

  • Additional permanent loads: 2.0 kN/m²
  • Imposed load: 18.0 kN/m²
  • Self-weight of the floor: considered internally by the calculation software

Verification criteria

  • Formwork stage: L/180 and an absolute limit of 20 mm, including ponding effect
  • Composite stage: L/350 (spans ≤ 3.50 m)
  • Verification in accordance with Eurocodes 3 and 4, with fire resistance verified in accordance with EN 1994-1-2

Resulting structural solution after verification

Applying the above criteria and verifying the formwork stage, composite stage and REI 90 fire resistance, the following configuration is obtained:
  • Total floor depth (H): 200 mm
  • Concrete compression layer (h): 130 mm
  • Upper reinforcement mesh (crack control and negative moments): 150×150×10
  • Lower fire reinforcement: Ø6 per trough, according to the specific verification

Verified imposed load: 18.0 kN/m² over four 3.20 m spans, with REI 90 fire resistance and construction without propping.

Structural interpretation

This example represents an application in which a moderate span allows the design to focus on the load-bearing capacity of the slab and the fire-resistance requirement, while maintaining construction without propping. Within these ranges, the design is governed by:
  • verification of the sheet during concrete pouring (formwork stage),
  • the total floor depth, due to its influence on stiffness and fire behaviour,
  • and the amount of lower reinforcement required to achieve REI 90 under high loads.

In practical terms, the case shows that a solution using 1.20 mm INCO 70.4 Composite can withstand an imposed load of 18.0 kN/m² over 3.20 m spans without propping, when a floor depth and reinforcement arrangement compatible with the structural and fire-resistance verifications are adopted.

Conclusion

For a composite floor using 1.20 mm INCO 70.4 Composite, H = 200 mm and REI 90 fire resistance, the example verifies an imposed load of 18.0 kN/m² over four 3.20 m spans, while maintaining construction without propping through a continuous 2+2 layout.The case shows how, for moderate spans, the system can accommodate high loads through a combination of sheet thickness, slab depth and the required reinforcement. The final design must be carried out through a project-specific verification under the actual conditions of each project.

Composite Floor Calculation Report

The above example is for guidance purposes and is based on specific assumptions regarding loads, span, fire resistance and structural arrangement.The final design of an unpropped composite floor must be formalised through a specific calculation report, documenting the verification of:
  • Ultimate limit states (bending and shear).
  • Serviceability limit states during the formwork and composite stages.
  • Fire resistance in accordance with EN 1994-1-2.
  • Construction conditions and the adopted structural arrangement.

The Incoperfil Technical Department issues supporting calculation reports adapted to the actual conditions of each project, in accordance with Eurocodes 3 and 4. Requests for calculation reports can be submitted through the technical form available on the website, providing span, load and fire-resistance requirements.Request a composite floor calculation report through the corresponding technical form.

Related articles

  • Structural calculation of composite floors
  • Unpropped composite floors
  • Types of reinforcement for composite floors
  • Fire resistance of composite floors
  • Long spans without propping with INCO 100.3

Incoperfil Technical Manual

For the complete definition of the system, design criteria, calculation bases, resistance tables, construction details and installation procedures, please consult the Incoperfil Technical Manual for Composite Floors, available upon registration in the Documentation section.Last updated: September 2026© Incoperfil. All rights reserved.