Slab item properties


General
Name	The automatically generated name for the slab item.
User Name	Can be used to override the automatically generated name if required.
Rotation angle (one-way slabs) or X direction (two way slabs)	This property is used for the following where appropriate: Span direction for 1-way load decomposition To determine the 2D solver element local axes in the solver model Bar direction for Slab on Beam and Flat Slabs. Different angles can be specified for different panels within the slab. Note: When SpanDirection is switched on in Scene Content, the rotation angle/X direction is represented by a blue arrow. See: Rotation angle for slab items and panels and Modify slab/panel span direction
Include in diaphragm	If this option is cleared, the slab item does not participate in diaphragm action. All nodes linked to the mat item will be able to displace independently of the diaphragm.
Override slab depth	By default all panels in a slab adopt the same depth. Checking this option allows the selected panel to have a different depth and vertical offset.
Vertical offset	Only available when ‘Override slab depth’ is checked. A positive offset raises the slab panel surface, a negative offset drops it. Note: Vertical offsets are not structurally significant
Auto-design	For panels in Auto-design mode, As,prov is increased until either a pass is achieved or the limiting reinforcement parameter limits have been exceeded. For panels not in Autodesign mode, the result will be a pass or fail.
Select bars starting from	This option controls the starting point for auto-design procedures.
Plane	Indicates the level at which the slab is placed.


Slab general
Name	The automatically generated name for the mat item.
User Name	Can be used to override the automatically generated name if required.
Slab type	Precast Steel deck Timber deck Composite slab Foundation mat
Deck type	The deck type depends on the slab type as follows: Precast concrete planks: Precast, Steel plate: Steel deck, Timber: Timber deck, Profiled metal decking: Composite slab, Reinforced concrete: Slab on beams, Flat slab, Foundation mat Post tension: Slab on beams, Flat slab, Foundation mat Note: Design of post tensioned slabs is beyond scope in the current release.
Decomposition	Decomposition choices depend on the slab type as follows: One-way only: Precast, Timber deck, Composite slab One-way or two way: Steel deck, Slab on beams Two-way only: Flat slab, Foundation mat


Slab parameters
Slab properties (general)
Overall depth	Specifies the slab thickness.
Diaphragm option	Sets the default diaphragm action for all slab items within the parent slab. Rigid Semi-rigid None
Slab properties (concrete slabs)
Concrete type	• Normal • Lightweight
Grade/Concrete class	Specifies the concrete grade.
Concrete aggregate type	Specifies the aggregate type.
Concrete density class	For normal weight concrete only, specifies the density class.
Dry density	Specifies the dry concrete density
Wet density	Specifies the wet concrete density
Long term elastic modulus = Ecm divided by... composite slab and precast only)	Factor by which the short term elastic modulus is divided to obtain the long term modulus .
Ponding allowance option, Ponding allowance value (composite slab only)	If required, choose either value or percentage and then specify actual ponding allowance accordingly.
Apply ponding to construction stage (composite slab only)	On = ponding allowance applied at construction stage
Apply ponding to composite stage (composite slab only)	On = ponding allowance applied at composite stage
Decking properties (where applicable)
Country, Manufacturer, Reference, Gauge	Defines properties of decking (where applicable).
Reinforcement in slab for crack control or fire requirements (composite slab, and precast with topping specified only)
Type, Rib type, Mesh type Class, Bar size	Defines reinforcement for crack control or fire requirements
Topping details (precast only)
Topping	None Non-structural Structural
Depth	Depth of topping when topping other than 'None' is selected.
Analysis parameters (two-way slabs)
Orthotropic	By default, the slab item is treated as having isotropic material properties. Checking this option allows assigning orthotropic material properties.
Calculate properties	Only available when ‘Orthotropic’ is checked. Allows setting material properties in two in-plane directions automatically based on the stiffness modification X and Y factors below. Note: For a detailed explanation of how the parameters are calculated, please refer to Orthotropic slab implementation
X factor and Y factor	Only available when ‘Calculate properties’ is checked. Applies stiffness modification factors in the local X and Y directions Note: Applying the same stiffness modification factors in both directions is an alternative way of specifying stiffness adjustments of isotropic slab items.
Ex, Ey, Gxy, Gxz \| Gyz, 𝜈x, and 𝜈y	Allows manually setting material properties, such as Young’s moduli, shear moduli, and the Poisson’s ratio. The fields become editable when ‘Calculate properties’ is unchecked (except 𝜈y, which remains read-only). Note: No distinction is made between Gxz and Gyz out-of-plane shear moduli.
Apply modification factors	By default, the modification factors are applied. Unchecking this option ignores the modification factors for the slab item. See: Use of modification factors and Analysis Settings
Design parameters (Head Code Eurocode)
Permanent load ratio	You are required to supply a value for the permanent load ratio parameter. A default of 0.65 has been assumed, but you are advised to consider if this is appropriate and adjust as necessary.
Maximum crack width	• 0.2 • 0.3 • 0.4
Deflection parameters
Restraint constant (ACI only)	See: Restraint constant (ACI)
Restraint type (Eurocode only)	See: Restraint type (EC2)
Cement class (Eurocode only)	See: Concrete Properties (Eurocode)
Material properties
Modulus of elasticity, Poisson's ratio, Shear moduls, Coefficient of thermal expansion	Properties specific to timber and steel decks.


Design parameters
Adjustment ratio direction X ,Adjustment ratio direction Y (slab on beam only)	These factors are applied to the enclosing lengths in X and Y in order to manually adjust the X and Y direction span in the span-effective depth check. See Slab on beam idealized panels
Enclosing length X, Enclosing length Y (slab on beam only)	The automatically calculated span length in the X direction, and Y direction. See Slab on beam idealized panels
Adjusted length X, Adjusted length X (slab on beam only)	The adjusted span lengths in the X and Y directions. See Slab on beam idealized panels
Edge category start X, Edge category start Y (slab on beam only)	The assumed support condition at the start of the span in the X direction, and Y direction. See Slab on beam idealized panels
Edge category end X, Edge category end Y (slab on beam only)	The assumed support condition at the end of the span in the X direction, and Y direction. See Slab on beam idealized panels
Average stiffness ratio (Slab on beam ACI/AISC only)	In the current release of Tekla Structural Designerr the average stiffness ratio is a user defined value. (Default value = 1.0). The way in which the minimum thickness is calculated directly depends on this value.


Live/Imposed load reduction
Reduce live/imposed loads by	This property is applicable for the design of transfer slabs and mats. Although the percentage of live load reduction is not determined automatically, this property allows you to specify the percentage manually. It can be applied to an individual slab item - you don't have to apply a single value throughout a slab or mat (this can be important if you have discrete transfer panels within a large slab area). • reducible loadcases are reduced • combinations incorporating reducible loadcases are reduced • The reduced results are used in slab design. Note: For mats, the bearing pressures are reduced as well.


Reinforcement
	Slabs panels can potentially have 4 layers of background reinforcement, (however any of the layers/directions can be set to “none” if required). Select/clear Outside layer in X direction as appropriate to indicate if the outside layer is in the X or Y direction. (The outside layer can be set differently for the top and bottom bars if required.)


Utilization ratio
Apply (to autodesign)	On When an Autodesign is performed, the design will be incremented to achieve a utilization ratio less than the ratio limit. Off When an Autodesign is performed, the design will be incremented to achieve a utilization ratio less than 1.0. See: Apply user defined utilization ratios
Apply (to check)	On When a Check is performed, the check will pass provided the utilization ratio is less than the ratio limit. Off When a Check is performed, the check will pass provided the utilization ratio is less than 1.0.
Ratio limit	The utilization ratio against which the autodesign or check is performed (when applied above).


All edges, Edge 1, Edge 2 etc.
Linear	Uncheck in order to specify curved edges.
Curvature	Defines the amount of curvature to all edges. Only displayed when Linear is cleared.


UDA
Name Finish Class Phase Note File	A customizable list of the attributes that can be applied to individual members and panels. See: Create and manage user-defined attributes