Create Support dialog

Used to define support (boundary) conditions of the structure to nodes. The dialog consists of a series of tabs, each of which are used to assign a different support condition. Each tab includes options for the specified support condition.

Note: The Supports - Whole Structure dialog also opens simultaneously so that some of the other options available from that dialog box may be utilized.

If the support is not assigned as it is created, it can be assigned later from the Support dialog. However, note that if it is not assigned to at least one spring support when is closed, then the definition will not be saved in the STD file.

Fixed tab

Used to create a fixed support tag and (optionally) to assign that to selected nodes. A Fixed support is restrained in all six degrees of freedom.

Refer to TR.27.1 Global Support Specification for additional information on global supports.

Opens when Add Support > Fixed is selected from the Specification ribbon tab Supports group.

There are no settings for assigning a Fixed support.

Pinned tab

Used to create a pinned support tag and (optionally) to assign it to selected nodes. A Pinned support is restrained in all three translational degrees of freedom and free in the 3 rotational degrees of freedom.

Refer to TR.27.1 Global Support Specification for additional information on global supports.

Opens when Add Support > Pinned is selected from the Specification ribbon tab Supports group.

There are no settings for assigning a Pinned support.

Fixed But tab

Used to create various types of roller, hinge and spring supports with specified restrained degrees of freedom and to assign them to selected nodes.

Refer to TR.27.1 Global Support Specification for additional information on global supports.

Opens when Add Support > Fixed But/Spring is selected from the Specification ribbon tab Supports group.

Setting	Description
Release	Select the degrees of freedom you want to release.
Define Spring	To specify a spring support, the spring constant in the appropriate edit box.

Enforced tab

Used to create a fixed-condition support definition. The Enforced support is the same as a Fixed support except that the restrained degrees of freedom are defined in terms of being stiff springs. The real advantage of using the Enforced type lies in the fact that it enables STAAD.Pro to accept loads such as support displacement loads in the case of plates and solids. Support displacement loads are not permitted for plates and solids if the FIXED support type is used. So, for structures without these characteristics, the Fixed type of support offers the same level of functionality as the Enforced support type.

Refer to TR.27.1 Global Support Specification for additional information on global supports.

There are no settings for assigning an Enforced support.

Enforced But tab

Used to create a fixed-condition support defined in terms of being stiff springs with the option to release selected degrees of freedom. The Enforced But support type is the same as the Enforced support except that we have a choice on the degrees of freedom we wish to restrain. For example, you can select Enforced But and restrain just the FX, FY, and FZ degrees of freedom, and let the remaining three free to deform.

Refer to TR.27.1 Global Support Specification for additional information on global supports.

Setting	Description
Release	Select the degrees of freedom you want to release.

Inclined tab

Used to create supports that offer restraints in an axis system that is inclined with respect to the global axis system.

Refer to TR.27.2 Inclined Support Specification for additional details on specifying inclined supports.

Setting	Description
Incline Reference Point	Specify a point in space to define the incline.
Support Type	Select to use one of the standard STAAD.Pro support types: Pinned, Fixed, Fixed But, Enforced, or Enforced But.
Release	(Fixed But or Enforced But options only) Select the forces and moments to release by checking the respective box.
Spring	(Fixed But option only) To specify a spring support, the spring constant in the appropriate edit box.

Foundation tab

Used to create spring supports for independent footings and mat foundations and to assign them to selected nodes.

Refer to TR.27.3 Automatic Spring Support Generator for Foundations for additional details on Foundation supports.

Setting	Description
Foundation	Footing - Select this option to define a spring support for an isolated footing. Provide the Length (L) and Width (W) dimensions of the footing in current units. In generating spring supports for mat foundations, there are two methods available in STAAD.Pro. Both those options require the program to calculate the influence area of the nodes which define the surface, and then multiply that area by the subgrade modulus of the medium. The difference between these two options lies in the way the influence area is calculated. Elastic Mat - In this method, the area is calculated using a Delaunay triangle principle. Hence, the candidates for this option are the nodes which define the mat. To achieve best results, one needs to ensure that the contour formed by the nodes form a convex hull. Plate Mat - If the foundation slab is modeled using plate elements, the spring supports can be generated using an influence area calculated using the principles used in determining the tributary area of nodes from the finite element modeling standpoint. Hence, the candidates for this option are the plates which define the mat. When the mat is modeled using plates, this produces superior results than the ELASTIC MAT type.
Direction	The X,Y, Z, XONLY, YONLY, and ZONLY indicate the direction of resistance of the spring supports. If X ,Y or Z is selected, then a spring support is generated in that direction only whereas the associated rotational degree of freedom and the other two translational d.o.f receive a fixed support. For example, if Y is selected, then FY is supported by a spring support, where as MY, FX and FZ are fixed supports; and MX and MZ are free. If XONLY, YONLY, or ZONLY is selected, then a spring support in that direction alone is generated, and every other d.o.f is set to be free to deform.
Subgrade	Type a value for the subgrade modulus of the soil.
Print Influence Area of Each Joint	(For Mat footing options only) Select this option to have the influence area of each support included in the output. The are used in the calculation of the spring stiffness of each joint used when defining a Plate Mat or Elastic Mat command will be included.
Generate Compression Only/Multi-linear Spring	(For Mat footing options only) When the Compression Only option is set, then if after any of the cycles of analysis, the force at a node included in the command range (in the elastic mat range or used to define a plate in the plate mat range) is found to be tensile (i.e. negative reaction), then the load case is marked for a re-analysis with that support removed.

Multilinear Spring tab

Used to enter displacement and spring stiffness data pairs for a multilinear spring definition, which is then used for a Fixed But support type.

The Multi Linear support type allows the user to model the support type for which the resistance offered to external loads varies with the extent of deformation of the support node. For example, when its behavior in tension differs from its behavior in compression, as in the case of soil springs, this facility can be utilized. Another example is a partial roller support where translation can occur without any resistance for a certain amount of displacement, after which it becomes fully restrained. The problem is solved iteratively using cycles of analysis and convergence checks. Hence, only on static load case can be specified per analysis command. It cannot be used with dynamic load cases.

Refer to TR.27.4 Multilinear Spring Support Specification manual for additional information.

Setting	Description
Multilinear Spring table	Values are entered in order from least to greatest displacement (including negative displacements, which are then ordered first) and their corresponding spring stiffness values.

Tension/Compression Only Spring tab

Used for support types which are capable of unidirectional action only, such as soil under a foundation slab.

Refer to TR.27.5 Spring Tension/Compression Specification for additional details on Tension/Compression Only Spring supports.

Setting

Description

Reaction Type

Select whether the support degree(s) of freedom (d.o.f) are tension only or compression only. Indicates that if, after any of the cycles of analysis, the direction of the force in the spring is of the wrong ‘type’, then the support will be removed from that direction and a new analysis performed.

Reaction Type	Support will be active if the reaction is…	Support will be made inactive and a new analysis will be performed if the reaction is…
Tension Only	- ve	+ ve
Compression Only	+ ve	- ve

Spring Direction

Select the degree(s) of freedom to set as unidirectional. More than one d.o.f may be set at a time.

Parent topic: Specification tab

Related concepts	Related tasks
G.13 Supports EX. US-23 Spring Support Generation for a Slab on Grade EX. UK-23 Spring Support Generation for a Slab on Grade EX. US-24 Analysis of a Concrete Block Using Solid Elements EX. UK-24 Analysis of a Concrete Block Using Solid Elements EX. US-19 Inclined Supports EX. UK-19 Inclined Supports EX. US-3 Soil Springs for Portal Frame EX. UK-3 Soil Springs for Portal Frame	M. To assign a fixed or pinned support M. To assign a foundation support M. To assign an enforced support M. To assign an inclined support M. To assign a spring support M. To assign support springs as a one-way