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).

Approach	Supported 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

Beam

Text

Hollowcore

Text

Core fillings

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

They are however considered with the β_f-factor.

Table 3.2 β_f-factor (FIB Bulletin 6)

Figure x. Distance h_c.

Joint concrete

Text

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 b_web, h_web, b_joint, h_hc, h_topping and b_support.

Topping on hollowcore

Text

References