## Composite action in slab of timber and concrete, deflection

## Composite action in slab of timber and concrete, deflection

(OP)

I have modelled a composite floor slab of 200 mm timber with 120 mm concrete on top (also called a TCC). I am trying to verify the deflection given by Abaqus with the analytical solution given by the "gamma method". My problem is i can not get close enough results. My Abaqus result show a midspan deflection of 6 mm while the gamma method shows a deflection of 3.3 mm. Any guidance will be very appreciated!

I first want to study 100% composite action. In the gamma method i use gamma equals to 1 and in Abaqus i set the connection between the concrete and timber surface to "tie".

Concrete: 8x2.4x0.12 m

Timber: 8x2.4x0.2 m

Concrete

E-modulus: 33 Gpa

Poisson: 0.2

Timber

E1: 12GPa

E2: 0.5 GPa

E3 0.9 GPa

Nu: 0.3

G12: 600 MPa

G13: 600 MPa

G23: 60 MPa

Load: 3500 N/m2

BC: Pinned in one end and locked in Z in one end (simply supported).

I first want to study 100% composite action. In the gamma method i use gamma equals to 1 and in Abaqus i set the connection between the concrete and timber surface to "tie".

**Dimensions:**Concrete: 8x2.4x0.12 m

Timber: 8x2.4x0.2 m

**Material data:**Concrete

E-modulus: 33 Gpa

Poisson: 0.2

Timber

E1: 12GPa

E2: 0.5 GPa

E3 0.9 GPa

Nu: 0.3

G12: 600 MPa

G13: 600 MPa

G23: 60 MPa

**Load and BC:**Load: 3500 N/m2

BC: Pinned in one end and locked in Z in one end (simply supported).

## RE: Composite action in slab of timber and concrete, deflection

## RE: Composite action in slab of timber and concrete, deflection

## RE: Composite action in slab of timber and concrete, deflection

Edit: That assumes that the timber and concrete actually make a composite section, i.e. there is a rigid connection between the two with enough shear capacity for them to act as a single piece. Otherwise, you just calculate the bending stiffness using Ic*Ec and It*Et and sum them.