Specify the material for general slab types

General slab types can have steel plate, timber, or general deck types. The material grade properties for each deck type can either be selected from the material database or they can be user-defined.

Choosing the grade from the material database

If the Deck type is set to:

Steel plate - the Grade lists all the available Steel materials in the Materials database under the current head code.
Timber - the Grade lists all the available Timber materials in the Materials database under the current head code.

Note: When using a timber deck type, the program will initially default to a material override option rather than displaying a Grade. This is because the Poisson’s ratio in the timber materials database is generally invalid for isotropic elastic analysis (of 2D elements), for which it must be > 0 and < 0.5. You can disable the override to select a timber grade, but you must then enable it again to enter a valid Poisson’s ratio (other grade properties such as density and modulus of elasticity will be retained).
General - the Grade lists all the available General materials in the Materials database under the current head code.

If the general material grade you want to use is not listed, you can open the Materials dialog and add the grade to the database, taking care to first select the General material type as shown below.

Override material properties option

Unlike other slab types, general slab types each have an option to override material properties. This option is provided primarily to allow the existing properties of steel or timber deck slabs created in older versions of Tekla Structural Designer (pre 2020 SP5) to be retained, but it can also be used to enter the material properties directly if required.

Note: When creating new timber decks, the program will default to the override option. This is because the Poisson’s ratio in the timber materials database is generally invalid for isotropic elastic analysis (of 2D elements), for which it must be > 0 and < 0.5. You can disable the override to select a timber grade, but you must then enable it again to enter a valid Poisson’s ratio (other grade properties such as density and modulus of elasticity will be retained).