Rigid Column Bases

The Rigid Column Bases mode enables to design and check the load-bearing capacity of joints of the column bases which provide a rigid column-to-foundation connection. This mode comprises a wide range of designs for this type of joints, such as:

• column bases with a milled end (Fig. 1);
• column bases with wing plates and cantilever stiffeners (Fig. 2);
• column bases with external wing plates (Fig. 3).
• This mode performs the following checks in compliance with the selected building code:
• resistance of the structural members of the column base joint (base plate, anchor bolts, anchor plates, wing plates and cantilever stiffeners, foundation concrete in local bearing);
• resistance of welded connections (between the column and the base plate, between the wing plate and column flanges, between the wing plate and the base plate, between the cantilever stiffener and column flanges, between the cantilever stiffener and the wing plate);
• a number of structural and assortment constraints.

The Rigid Column Bases dialog box contains four tabs: Configuration, Forces, Structure, and Drawing.

First you have to select the type of the column section by clicking the respective button: Rolled I-section or Welded I-section in the Configuration tab. The interface of this tab depends on this choice. If a rolled I-section is selected as the column cross-section type, you then have to select an assortment and the profile number in this assortment in the Select profile dialog box, which can be invoked by clicking the Select the column section button.

When a welded I-section is selected as the column cross-section type, you have to specify the sizes of the column cross-section: the height, h_w, and the thickness, t_w, of the web; the width, b_f, and the thickness, t_f, of the flanges. The sizes of the column cross-section should be entered in the table in millimeters. It should be noted that the thickness of the flanges and of the web can be either entered manually or selected from the drop-down lists, which contain the set of thickness values according to the assortment of sheet and plate steel. The column cross-section can be checked in the Preview window, which can be invoked by clicking the Preview button ().

When the analysis and design are performed according to EN 1993-1-1:2005 and EN 1993-1-8:2005, the Configuration tab of the Rigid Column Bases mode also contains the Grout type drop-down list and the Grout thickness field, which are used to enter the respective information about the grout under the base plate of the column base joint.

Materials used for design and analysis of a rigid column base joint can be selected from the Steel and Concrete drop-down lists, which suggest the steel grades for steel members of the column base joint and concrete classes for the foundation (Fig. 4, 5). When the analysis and design are performed according to EN 1993-1-1:2005 and EN 1993-1-8:2005, the materials of the members of the rigid column base joint are specified using the Concrete drop-down list and the Column steel and Plate steel buttons. The Concrete drop-down list suggests concrete classes for the foundation of the column base according to EN 1992-1-1:2004. Clicking the Column steel and Plate steel buttons invokes the Steel information mode, where you can select a steel grade for the column and for the support base plate respectively.

Clicking the Stamp button opens a Stamp dialog box, which enables to fill in the stamp of the drawing used in the draft of the design of the rigid column base joint. The Save template button enables to save the entered data as a template of the stamp for the current session of the application. The saved template can be used both in the current and in other modes of the application by clicking the Load template button.

You can enter the service factor for the connected members in the respective text field, or it can be selected in the Service Factor dialog box after clicking the nearby button (). When the analysis and design are performed according to EN 1993-1-1:2005 and EN 1993-1-8:2005, you do not have to specify the service factor. The value of the coefficient taking account of long term effects and of unfavourable effects according to EN 1992-1-1:2004, which is by default taken as one, has to be specified in the respective text field instead.

When the analysis and design are performed according to EN 1993-1-1:2005 and EN 1993-1-8:2005, the Rigid Column Bases dialog box contains an additional tab, Connections, which is used to specify information on the peculiarities of welded and bolted connections of the joints of rigid column bases. In particular, the class of bolts and the type of bolt hole are selected from Class of bolts and Hole type drop-down lists respectively. The type of washer for bolted connections is specified using the respective radio buttons (plain or chamfered). You can also take into account the peculiarities of bolted connections with countersunk bolts by checking the Countersunk bolts checkbox and specifying the height of the bolt head in the respective text field. The partial penetration of butt welds can be taken into account for welded connections of the joints of rigid column bases by checking the Partial penetration butt welds checkbox and specifying the depth of penetration in the respective text field. The deep penetration of fillet welds can be also taken into account for welded connections of the joints of rigid column bases by checking the Deep penetration fillet welds checkbox and specifying the additional throat thickness in the respective text field. Checkboxes of the Peculiarities group enable to specify the peculiarities of steels of the joint members, in particular in those cases when the steel is taken according to EN 10025-5 or is exposed to the weather or other corrosive influences. You can also take into account the peculiarities of bolted connections in the following cases: when the threads of bolts do not comply with EN 1090-1:2009, or when the coated fasteners are used in the bolted connection, or when the bolted connections are made in the structures of towers and masts.

The Forces tab is used to specify the internal forces acting in the joint of the column base: an axial force, N; bending moments in two planes, M_y and M_x; their respective shear forces, Q_x and Q_y¹. The drawing next to the table of internal forces defines the positive directions of internal forces in the sections of the column base members. Clicking the Add button adds a new row to the table of internal forces, where you have to enter the values of internal forces for the current combination of loads. There can be any number of design combinations of loads. Units of measurement for the internal forces acting in the joint are defined in the Units of Measurement tab of the Application Settings dialog box. The default units of measurement for axial and shear forces are tonnes, and for bending moments – tonne×meter.

When the analysis and design are performed according to EN 1993-1-1:2005 and EN 1993-1-8:2005, the table in the Forces tab used for specifying the design values of forces for one or several combinations of loads has an additional column, Limit state, where you have to select the limit state for the current combination of loads (ultimate or serviceability).

The table can be also filled by importing the data from SCAD which describe the design combinations of forces (DCF). A file with the .rsu2 extension is created in the Element Information mode of the SCAD software and then can be imported by clicking the button . It should be noted that when creating an .rsu2 file in SCAD, the table of design combinations should include only those combinations that correspond to the section of the bar element adjacent to the node.

The Structure tab contains a group of buttons to select a design for the joint of the rigid column base.

To perform a check (i.e. check the load-bearing capacity according to SNiP, SP, DBN or EN (EC3)) of a known structural design of the column base, you have to specify all design parameters of the joint. The parameters include the sizes and thickness of structural members of the joint, diameters of anchor bolts, sizes which determine the mutual arrangement of members, leg lengths of welds, the number of bolts, the number of bolt rows, etc. The parameters of the joint are entered in the table on the right. The diameter, the steel grade, and the number of anchor bolts (for some types of bases) are selected from the special drop-down lists of the Anchor bolts group. The default units of linear measurement are millimeters.

Clicking the Design button drops down a menu. If the first item, All parameters are not specified, is selected, the automatic selection of all parameters of the joint design is performed and it is assumed that the parameters of the joint design are not specified (are equal to zero), and their previously specified values are ignored. If the Some parameters are specified menu item is selected, the program will automatically determine the values of the undefined (are equal to zero) parameters from the conditions of the adequate resistance and structural constraints defined by the standards with fixed values of the specified parameters. 

Moreover, this mode calculates the value of maximum factor K_max (a utilization factor of restrictions), indicates the type of the check in which this maximum took place, and generates the drawing of the joint design of the MS (metal structures) stage.

Clicking the Calculate button will perform the check of the load-bearing capacity of the specified joint members and of the connections between them according to SNiP, SP, DBN, or EN (EC3).  The result will include the value of maximum factor K_max (a utilization factor of restrictions) and the type of the check in which this maximum took place. A complete list of checks and values of the respective utilization factors of restrictions can be obtained by clicking the Factors button.

Clicking the Factors button invokes the Factors Diagram dialog box, where you can browse the values of all other utilization factors of restrictions. The list of the load-bearing capacity checks of the members and connections of the joints of the rigid column bases performed by the application is given in Table 1 and Table 2.

Clicking the Report button generates a report document which contains the initial data and the results of analysis.

Table 1. A list of the load-bearing capacity checks of the members and connections of the joints of the rigid column bases

Table  2. A list of the load-bearing capacity checks of the members and connections of the joints of the rigid column bases according to EN 1993-1-1:2005 [30] and EN 1993-1-8:2005 [22]

Once you switch to the Drawing tab, the application performs a check and design of the joint, similarly to the Calculate mode. If the results of analysis of the parameters of the joint members do not contradict the structural and standard requirements, a drawing of the joint design of the MS stage will be generated.

The upper part of the Drawing tab contains a toolbar with buttons (), which enable to zoom the image in or out, save the drawing as DWG (DXF) for AutoCAD, or print it out.

¹ To set a proper orientation of the specified internal forces with respect to the principal axes of inertia of the cross-sections that meet in a joint, each bar of the joint is referred to a local coordinate system, xyz. The application implements the following orientation of the local coordinate systems of bars: the x – x axis goes from the beginning of a bar (its start node) to its end (its end node), the y – y and z – z axes (the principal central axes of inertia of the bar cross-section) make up a right-hand Cartesian coordinate system together with the x – x axis. The y – y axis is parallel to the XOY plane of the global coordinate system, and the z – z axis goes to the upper half-space.