Geometry

 

Commands in the Geometry group are used for defining the column's geometric features.

 

The Section Shape drop-down list can be accessed under the Geometry button, from where it is possible to select the desired section shape. To select a shape, simply click on the corresponding profile shape. The viewport will display the column with the selected section shape.

 

 

The Section Shape command

 

The Section Shape command

 

 

 

 

 

 

 

 

The Section shape can also be changed through the Geometry dialog box, from the Geometry group, by clicking the upper button of the command.

 

 

 

The characteristics may vary depending on the selected cross-section type.

 

 

 

 

The Geometry dialog box

 

The Geometry dialog box

 

 

 

 

 

 

Section Geometry

 

Shape: specify the desired cross-section type
Width: specify the width of the column cross-section
Height: specify the height of the column cross-section
Web thickness: specify the center thickness of the column cross-section. Available only for T and L column shape
Flange thickness: specify the flange thickness of the column cross-section
Provide chamfer: bevels the edges of the column cross-section. Available only for Rectangular and Square column shape
Chamfer length: specify the chamfer distance
Column height: clear height of the compression member between end restraints

 

 

 

 

 

 

 

The Upper Elements dialog box

 

The Upper Elements dialog box

 

 

 

 

 

 

Upper Column

 

Upper column: check this option to define the upper column

Height: define the height of the upper column

Eccentricity along x: define upper column eccentricity along the abscissa (x) in relation to the designed column

Eccentricity along y: define upper column eccentricity along the ordinate (y) in relation to the designed column

Identical section with main column: column above identical to considered column

Width: define the upper column cross-section width

Length: define the upper column cross-section width

Web thickness: specify the center thickness of the upper column cross-section. Available only for T and L column shape

Flange thickness: specify the flange thickness of the column cross-section

Provide chamfer: bevels the edges of the column cross-section. Available only for Rectangular and Square column shape

Chamfer length: specify the chamfer distance

 

Upper Beams

 

Upper beams: check this option to define the upper beams

Height: specify the beam height

Front/Back: separately define the beam for the front/back face of the column

Left/Right: separately define the beam for the left/right face of the column

 

 

 

Buckling length command opens a dialog box to select the desired buckling length calculating method of the column for both X and Y directions. The selected buckling type along X and Y can be previewed in the ribbon.

 

 

 

The Buckling length dialog box

 

The Buckling length dialog box

 

 

 

 

 

 

EC2 uses two methods to determine the buckling lengths:

 

1. In the case of isolated elements having a constant section in 5.8.3.2.(2), some examples of different buckling modes and corresponding effective lengths are given.

2. In the case of  compression members in regular frames in article 5.8.3.2.(3), two formulas for calculating the effective length are proposed:

 

 

 

Braced members

 

 

 

 

 

Unbraced members

 

 

 

 

 

 

where:

 

K1, k2 are the relative flexibilities of rotational restraints at ends 1 and 2, respectively:

 

k

 

 

 

θ is the rotation of restraining members for bending moment M

 

EI is the bending stiffness of compression member

 

l  is the clear height of compression member between end restraints

If an adjacent compression member (column) in a node is likely to contribute to the rotation at buckling, then (E Ι / l) in the definition of k should be replaced by [(E Ι / l)a+(E Ι / l)b], a and b representing the compression member (column) above and below the node. [EN 1992-1-1 §5.8.3.2.(4)]

 

Example of k calculation considering the article §5.8.3.2.(4) from EN 1992-1:

 

 

k calculations

 

 

 

 

The two methods suggested by EN 1992-1-1 are found in the dialog as the two options Standard and Auto.

 

This dialog is used for entering the column height, as well as for choosing conditions for column end supports along the X-axis and the Y-axis, to automatically calculate the buckling lengths and the slenderness ratio.

 

 

- Buckling Length (Lx): If an adjacent compression member (column) in a node is likely to contribute to the rotation at buckling, then (E Ι /l) in the definition of k should be replaced by [(E Ι / l) a + (E Ι / l)b], a and b representing the compression member (column) above and below the node. [EN 1992-1-1 §5.8.3.2.(4)] effective length about X-axis

- Slenderness (λX): slenderness ratio about X-axis

- Standard: select this option to use effective lengths for isolated members with constant cross-section, according to chapter 5.8.3.2(2) from EN 1992-1-1

- Auto: select this option for the evaluation of the buckling length of a column in a multi-story frame, with the contribution of members converging at the bottom and top ends

 

 

- Free at the top, fixed at the bottom

- Pinned at the top, pinned at the bottom

- Displacement at the top, fixed at the bottom

- Pinned at the top, fixed at the bottom

- Fixed at the top, fixed at the bottom

 

You can choose not to use any of the options available under Standard, and input stiffness at both ends. The software will calculate the corresponding buckling length using a structure calculation method with braced or unbraced nodes. For this, you must apply the option in the supports area (with Auto selected) to open the Buckling Length Calculation dialog box.

 

 

 

Buckling Length Calculation

 

 

 

 

 

 

 

In the Buckling Length Calculation dialog, the column considered is the column between A and B points.

 

For the buckling length to be automatically calculated, the user must enter the values for:

 

 

 

Manual stiffness method

 

The theoretical analysis uses idealized end restraints, whose translational and rotational stiffnesses are set to either zero (free end) or infinity (fixed end). In some instances, it may be acceptable for the designer to assume a column has these idealized end restraint conditions, especially for preliminary design purposes, when a more rigorous analysis is to follow.

 

The influence that end restraints have on the buckling capacity can be further analyzed by taking into account the fact that, for real structures, the rotational and translational stiffness of the end restraints is somewhere between rigid and free.

 

In Advance Design modules, the spring supports functionality can be found as the Manual stiffnesses option, which can be selected in the Buckling length dialog. When Manual stiffnesses are selected, FEM calculation is automatically activated and the effective length of the column is no longer calculated using simplified formulas.

 

Note: During FEM calculation, in the preliminary calculation of reinforcement (using one of the EN 1992-1-1 methods), the effective length is considered equal to the column height. The calculation starts from this assumption.

 

You can define nodal stiffnesses against displacement and rotation for both the top and bottom ends of the column, using the specific dialogs Nodal Stiffness along X and Nodal Stiffness along Y.

 

 

 

Manual stiffness method

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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