Design (Concrete Column)

Last modified by Fredrik Lagerström on 2021/08/06 10:46

When Design has been activated a design of one or more load cases in Ultimate Limit State can be performed. Load cases in Serviceability Limit State can also be defined but will be ignored during the calculation. A calculation of these will be performed when Control is activated.

The Input data field

The input data field contains a number of tabs where the example is being defined. The field contains initially the tabs Section information and Load case.

Section information

This section applies for Section information in Control-mode as well.

In the Section information dialog the current cross-section is defined by using the Section database. The Section database contains the options Standard Eurocode concrete and Non standard concrete.

Standard Eurocode concrete

Standard Eurocode concrete consists of eight geometries where a number of pre-selected sections has been added.


Non standard concrete

Non standard concrete consists of eight geometries for which a name and the dimensions are to be given by the user. When the section has been defined it will be put in the Section name list where it will be available for the current program installation. New sections are stated by the Add button, removed from the list with the Delete button and are opened for changes with the Change button.


Load cases (Load combinations)

In the load case dialog box current section forces as well as limit state and type are defined.


A defined moment is assumed to act with a constant value along the structure.


For load combinations in the Ultimate Limit State also the initial bow imperfection should be defined. A value x is defined as shown below and a corresponding moment N * lc / x will be calculated in each direction. The default value for x is 400 according to EN 1992-1-1 5.2 (7). For Ultimate load cases also the type Accidental can be stated and for Serviceability load cases is chosen between short and long time. In program mode Design only load cases in the Ultimate Limit State can be calculated. Load cases in the Serviceability Limit State will be ignored but can be calculated in program mode Control.

When a load case has been defined the active section, as well as other active input data, will be tied to it. When one or several load cases have been stated the currently active load case will be stated in the status bar at the top of the program window. All input data and results belong to the active load case.


Thus selecting another load case in the table also changes section data. This means that sets of section forces simultaneously can be calculated with several different sections. A cross-section can, as an alternative, at a simultaneously calculation be designed for an arbitrary number of load cases.

This can be changed if Link load cases are chosen.

The input is made easier by load-directions that are shown for the section of the active load case on the drawing area.


Load cases can be edited in several ways using Add, Change, Delete and Copy. By pressing the Add button a new load case is added to the table provided that a new load case name (and forces) has been stated in the input field. The new load case will copy the current active section using default material but no reinforcement.

By pressing the Change button section forces in the selected load case are changed. By pressing the Delete button all data in the selected load case is deleted.


By pressing the Copy button a new dialog window is opened in which it is possible to select from which load case data shall be copied. Some or all input from a specified load case together with calculated or defined reinforcement can be copied.

When the section and the load cases have been defined the input data field is completed with the tabs: Material, Reinforcement details and Calculation settings. If one or more long time load cases are defined then also the tab Creep data is shown.

Link load cases

Load cases can also be linked to each other by pressing the Link load cases button.


At least two load cases has to be defined and this option means that all load cases will inherit all input except loads and creep values from the active load case.

The following message will be shown:


Simple mode means that all load cases will be connected to the same section, the same buckling lengths, the same material, the same reinforcement details and the same calculation settings. In simple mode only the button Change is available. All changed input except creep data and loads will affect all load cases. This mode is sometimes preferred for simplicity.


With the button above the program returns to the advanced mode.

Creep data

This section applies for Creep data in Control-mode as well.

In the Creep data dialog box effective creep coefficients for load cases in Ultimate Limit State and creep coefficients for long time loads in Serviceability Limit State are defined.


If creep values are not defined the following warning message will be displayed:


Note that an empty field is not the same as the value 0, for ultimate limit states. The empty field lacks the correct value in ultimate limit state, while 0 is a valid input.


For serviceability limit states a 0-value is invalid for longterm serviceability limit states.

Buckling data

This section applies for Buckling data in Control-mode as well.

In the Buckling data dialog box the actual column length and the buckling length in both directions for columns. For columns it is also possible to define one direction as laterally braced meaning that no flexural buckling is possible in that direction.


For walls only the buckling length in the weak direction is defined.


As default the structure is considered as slender meaning that 2nd order effects will be considered. If the user for some reason wishes to neglect such effects the option Short should be activated.


In the Material dialog box all material strength input is assembled. By pressing the grey button a dialog box to show the complete data of the selected material or to define a user defined material is opened.



Under the header General, conditions that affect the calculation are stated. Exposure class and life time class are defined and affect code checks where relevant. The options Quality control and reduced deviation and Reduced or measured geometrical data can be checked. The two latter options together with the option Low strength variation, see below, changes the partial factors for materials according to EN 1992-1-1 Annex A A2.1 and A2.2.


Concrete strength class can be defined by selecting from the list. Current design values are shown. If the option Low strength variation is checked together with one or both of the two options described above the partial factor for concrete will be changed according to EN 1992-1-1 Annex A A2.1 and A2.2.


By pressing the button beside strength class the options above are displayed. With Create new user defined materials can be defined. With Show the complete current data is being shown, as is a graphic presentation of the stress-strain diagram. The options Edit and Delete can only be used for user defined materials.


In the Reinforcement dialog boxes type of reinforcement for bottom- and top bars and stirrups as well as for longitudinal bars can be defined by selecting from lists. Longitudinal bars are only used to resist torsion and biaxial shear and are not used in this program. Current design values as well as current diameters are shown.


By pressing the button beside strength class the options above are displayed. With Create new user defined materials can be defined. With Show the complete current data is being shown, as is a graphic presentation of the stress-strain diagram. The options Edit and Delete can only be used for user defined materials.

92848_-_denmark_flag.png Danish Annex

In the Danish Annex environmental classes are defined instead of exposure classes.


The relations between these are the following:


For the Danish Annex also the Inspection Level should be defined which affects the partial factor for materials.


If the option Prefabricated elements is checked the partial factors for material is changed.
The options Reduced or measured geometrical data, Reduced or measured geometrical data and Low strength variation are not used in the Danish Annex.

92865 - finland flag.png Finnish Annex

For the Finnish Annex also the Construction class are defined which affects the required cover.

Reinforcement details

In the Reinforcement details dialog box bar diameters, cover of reinforcement, and input used to distribute calculated amounts of reinforcement, can be defined.


Main bar details

The diameter for bottom and top reinforcement are defined. If standard reinforcement is chosen the diameters are the ones available for that type. For non-standard reinforcement the available diameters are 1-99 mm.

Further on the covers at bottom, top and side are defined together with allowed distances between bars in the same layer and for different layers.

How the reinforcement is positioned is also influenced by the options Vibration space and Largest aggregate size.

The option Cover deviation represents the part of the total cover called Δcdev according to EN 1992-1-1

The option Use regular spacing in layer places the reinforcement evenly in the section instead of concentrated at the edges for relevant section types.

The program will choose minimum values (displayed with blue print) for the current diameter and code with the Code value button.

When the Code control option of input data has been activated the chosen values will be controlled, and compared with, existing rules for the current code.

Calculated main reinforcement is displayed on the continuously updated drawing area.

Secondary bar details

Stirrups are stated with current spacing, diameter and strength class. Defined stirrup reinforcements are displayed on the continuously updated drawing area. The stirrup reinforcement is removed (see section picture) if spacing is defined as zero.

Calculation settings

This section applies for Calculation settings in Control-mode as well.

In the Calculation settings dialog different options governing the calculation can be set.


Design settings

The option Use compression reinforcement is not active as compression reinforcement is always considered in this program.

The user can define if minimum bending reinforcement according to EN 1992- 1-1 or should be considered.

The option Consider current section cracked is only used for SLS load cases which are only calculated in Design mode.

Concrete section iteration settings

Input for the iterative section calculation can be adjusted here but is normally not needed.

SLS settings

The user can chose between two different crack criteria’s in the Serviceability Limit State.


According to EC2 7.1 (2) the value of the concrete tensile strength fct,eff may be taken as fctm or fctm,fl.

Normally fctm is used. fctm,fl is the criteria that normally result in the highest tension capacity and may be used for pure flexural stress. If tensile stresses, also those caused by shrinkage or thermal effects is present fctm should be used. As default fctm is used.

92997_-_flag_sweden.png Swedish annex


For the Swedish annex 7.3.2.(4) a third crack criterion can be used.

fct,eff = fctk / ζ

where ζ is a safety factor for cracking which depends on environment and age of structure table D-3.

Some guidance about which criteria is to be used will be displayed by pressing the info button and can be found in “Svenska Betongföreningens handbok till Eurokod 2” Volym I ch. 7.1.

2nd order moment calculation

The flexural buckling check is made according to one of two methods according to the user’s choice. The method based on nominal stiffness according to EN 1992-1-1 5.8.7 or the method based on nominal curvature according to EN 1992-1-1 5.8.8.
The two methods can sometimes result in rather different capacity for the structure but it is enough if one of them is sufficient.

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