# Flexible Support Theory Handbook

The Theory handbook collects all the information used to be able to use and understand the underlying calculations with regards to Flexible Support.

Figure 1. Excessive schematic representation of a floor slab supported on flexible beams. (F. Lagerström, 2016)

# Calculation of stresses in hollowcore cross sections

The aim with calculating these stresses is to avoid any cracking within the hollowcore cross sections. There are several different approaches to this, explained in FIB Bulletin 6 and the Finnish Code Card 18. There is also another approach described by T. Roggendorf in his PhD Thesis Zum Tragverhalten von Spannbeton-Fertigdecken bei biegeweicher Lagerung, Aachen Technische Hochschule (2010).

ApproachSupported by StruSoft Flexible Support
FIB Bulletin 6
Code Card 18
Roggendorf, 2010

## Calculation principles

The calculation uses stiffnesses of the beam, hollowcore, joint concrete, and screed to calculate the deflection of the beam, causing the stresses within the concrete cross section of the hollowcore.

Figure 2. Picture of the shear flow and shear force of the hollowcore cross section (FIB Bulletin 6)

## Properties of different regions

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### Core fillings

Core fillings are ignored in the calculation of the stiffness of the composite beam.

They are however considered with the βf-factor.

 Slab thickness [mm] 200 265 320 400 Filling length < 50 mm 1 1 1 1 Filling length at least equal to the depth of the void (hc). All voids filled 0.7 0.7 0.5 0.5

Table 3.2 βf-factor (FIB Bulletin 6)

Figure x. Distance hc.

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### Topping on beam

 Case Visualization Properties Beam web is lower than hollowcore Beam web is higher than hollowcore, but not higher than hollowcore and topping Beam web is higher than hollowcore and topping

Table x. Properties of different cases of topping

Figure x. Definition of bweb, hweb, bjoint, hhc, htopping and bsupport.

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# References

Created by Fredrik Lagerström on 2021/02/09 14:53