Mesh vs. Fibres in Composite Floors
Iftekhar Waseem, Structural Engineer for ComFlor® at Tata Steel Europe, discusses mesh vs. fibre reinforcement in composite flooring. He demonstrates that each method has its own merits in different scenarios.
Traditional mesh reinforcement in floor slabs has long been a key factor in maintaining structural integrity. However, given the current growth in popularity of fibre solutions, it is perhaps worth reflecting on exactly what both options offer: –
Mesh Reinforcement Advantages:
- Provides bending resistance at the supports in the fire condition.
- Aids distribution of the effects of localised point loads and line loads.
- Reduces and controls cracking at the supports. This occurs because of flexural tension and differential shrinkage effects.
- Contributes towards a fire resistance of up to 120 mins, without having additional rebars in troughs, depending upon the type of deck, span and loading.
- Act as transverse reinforcement for the composite beams.
- Fulfils the robustness requirement in accordance with BS5950, Part 1.
- Enough guidance/standards available to design/calculate a non-standard scenario.
- Potential health and safety issues, such as trip hazards, cuts & bruises etc.
- Mesh requires a lot of time and effort, an increase of deliveries to site, plant equipment, storage requirements and labour to hoist mesh into position, factors which may delay the construction programme.
- Nesting of mesh reinforcement may be required in slab construction, where a bigger size mesh is adopted in a shallower slab.
Fibre Reinforcement Advantages:
- FibreFlor® , a combination of Novocon FE1050 steel fibres and polypropylene Fibremesh 150, provides resistance to fire and controls shrinkage cracking during construction and when in use.
- Fibremesh also provides resistance to explosive spalling of concrete, due to the pressure generated in a fire.
- Fibre reinforcement provides resistance to plastic shrinkage, settlement cracking and toughness, but the performance is related to the specific system deployed.
- Like mesh reinforcement, fibres contribute to a fire resistance of up to 120 mins, depending upon the deck type, span and loading.
- The longitudinal shear reinforcement requirement in the form of bars can be dramatically reduced with the usage of fibres.
- The installation of the floor is easier and safer because there is less reinforcement to obstruct the floor working area.
- Reduction in labour, plant and transport costs and a saving on the construction programme by up to 20%.
- Additional rebars in troughs are required at supports for horizontal tying to fulfil the robustness requirement.
- Additional bars are required to meet the transverse shear requirement, when deck is running parallel to the beam.
- It is still good general practice to use U-bars on composite edge beams and bar reinforcement around the openings in the slab.