Bi-material cross section:
For determination of the neutral axis position of the composite bi-material cross section (NAC) following general equation is used:
where:
- EB and ET is representing elasticity modulus of the bottom and top layer of the composite cross section;
- AB and AT is representing area of the bottom and top layer of the composite cross section;
- ZB and ZT is representing distances from the neutral axis of the composite cross section to the centroid of the bottom and top layer in particular.
The reduced area AC of the composite bi-material cross section is calculated using following formula:
The reduction of the second moment of inertia IC of the composite cross section is performed as following:
The material properties of the composite bi-material cross section are reduced as following:
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Reduction of the composite cross section area and the second moment of area is done relative to the bottom layer of the composite cross section
The elasticity modulus of the reduced composite bi-material cross section is taken from the bottom part of the composite cross section
Second moment of area for the top and bottom layer of the composite cross section is calculated by referencing to the neutral axis of the composite cross section geometry, without taking in to account its bi-material nature
Using the standard composite prefabricated cross section, the bottom part of the cross section is prefabricated, where the top part of the cross section has meaning of the finishing/cover:
