General operation

This page has been superseded by Introduction and for the Mac and PC by Introduction and for the Android phone and iPhone  by Introduction.

General operation

Number input and editing

A text edit box is provided for each number to be input, or that may be changed by the user. Each such edit box can be given the focus by a “left click” of a pointing device when the pointer is on it. While such an edit box has the focus text characters can be made to appear in it by such as a keyboard. The focus is removed from such an edit box when the focus is given to another feature on the screen. Other features include other text edit boxes and buttons.

Any action by the user that would remove the focus from an edit box causes an automatic check on the validity of the contents of that box. If that contents does not represent a valid number an error condition is created. The background color of the edit box is changed to yellow and all the other edit boxes, buttons etc are disabled. In this error condition only the content of the offending yellow edit box can be changed. However, one changed in this offending yellow edit box will cause all the other edit boxes and buttons etc to be enabled again.

Some number edit boxes have an exponent immediately to the right. Generally there is “x10” on the same background color as the general background color outside the edit box and an exponent such as “-3″ or ” 6″ on a rectangular background the same color as the background inside the edit box. A left click on the exponent will lead to a dropdown list of alternatives that may be selected as the exponent.

In instances where the exponent happens to be zero the “x10” is not visible and the rectangle for the exponent is blank. Nevertheless this rectangle is visible being of a different color from the general background. A left click on this rectangle will lead to the dropdown list of alternative exponents. This list includes blank that means a zero exponent.

Where metric units are in use the “x10” and the exponent are replace by the metric prefixes “k”, “M”, etc. on a rectangle of that different color, and similar facilities for a dropdown list of the alternatives.

Table edit dialogs

The component edit dialogs and the material edit dialog (with Properties as described selected) have a button labeled “…. table” that leads to a table edit dialog. The table consists of lines of cells. Generally one cell has the focus indicated by a blue colour.

The focus can be moved to another cell by a click of a pointing device, or the arrow keys on a keyboard.

The cell that has the focus will change to an edit mode:

  • By a click of a pointing device on the focused cell
  • By the Enter key.
  • By any key on a key board representing a printable character. However, the character will replace the whole content of the cell.

In this mode the content of the cell can be edited by a keyboard; the horizontal arrow keys moving a cursor within the cell.

A cell will be taken out of the edit mode:

  • By a click of a pointing device on any other cell or a button on the dialog.
  • By the Enter key.
  • By either the up or down arrow keys.

Any of these actions will provoke a check on the validity of the contents. If it is not valid an error condition is created. A text edit box with the invalid contents appears above the table along with an OK and a Cancel button. Also everything on the dialog is disabled except that text edit box, the associated Cancel button and the main Cancel button below the table. If the content of the text edit box is changed to be valid the associated OK button is also enabled. That OK button will cause a return to the normal table mode with the new value in the offending cell.

Near the bottom of the dialog are buttons labeled “Insert new line” and “Delete line”. The “Insert new line” button will cause a new line to appear below the line with the focused cell and the focus moves to a cell in the new line.

The “Delete line” button deletes the line with the focused cell. The focus moves to a cell in the line above.

The top line cannot be deleted and it is not possible to insert a new line above the top line.


The meaning of some words

Some words have a specific meaning.

Component” means a part of a structural member. The ACI 318 uses the word “element” to mean a part of a structural member. In that context what is referred to as an element is called a component in the context of this application. However, in this context the word “component” also means a number of steel bars that are all of the same grade of steel and all of the same size.

strain” means a slight change in a dimension of a body. See Distortion for an elaboration on this.

other” is used in two contexts; in the expression “other distortions” and in the expression “other axis”.

other distortions” means distortions from causes other than stress. (See Distortion – Stage, Other, Stress and Load-case distortion defined.)

other axis” means an axis other than the axis of interest. The orthogonal axes in the plane of the cross-section used to describe the cross-section are referred to as “the x, y axes”. The axis of interest in a particular analysis may be anywhere on the plane of the cross-section. To accommodate this, this application uses a second set of orthogonal axes. The axis of interest is referred to as the “reference axis” and the axis at right angles to that axis as the “other axis”. (See Load Cases)

restrained” and

unrestrained” relate to the circumstances of the structural member being analyzed. It indicates whether or not curvature about the “other” axis is restrained. Usually the expression “biaxial analysis” refers to an unrestrained case. (See Load cases)

Curvature deviation” means the angle between the axis of a bending moment and the axis of the curvature caused by that bending moment. (See Load cases – Methods that provide automatic trial and adjustment)


The application can display a graphical representation of the cross-section and of the stress-strain relationship of each material. These displays can not be changed: they simply represent the data at the time a “Display” menu item is clicked. The dialogs for these displays are non-modal so that other facilities in the application can be used while the display remains on the screen. However the displays are not updated if the data they represented is changed.

Main menu Load cases includes a Display item that leads to a dialog that displays the whole cross-section. Note that this is disabled unless there is at least one load case. The reference axis of the current load case is shown in blue. All the points in the point components are shown as black circles of a size consistent with the cross sectional area in the point component description.

Main menu Materials includes a Display item that leads to a dialog that displays the stress-strain relationship of a material. If the material is of material kind “concrete” the display has negatively increasing stresses up and negatively increasing strains left to right and the ultimate compressive strain is indicated in blue. If the material is of material kind “steel that yield” the yield tensile strain is indicated in blue.

 “Display as text” button

The edit dialogs for each entity kind includes a button labeled “Display as text”. This leads to a further dialog that displays a complete description of the entity as one text document. This display is not editable. It is text limited to ASCII characters 10, 13 and 32 to 126.

There is a “save as” button that leads to a standard save as dialog. The saved file is text intend to be read by a text editor application. A text editor application that is able to use a hard-copy printer is envisaged so that a hard copy of the cross-section details can be produced.

If the type font used with these files has a fixed character width then tables of numbers will appear in columns. Also in tables there is a comma on each line between each column. These commas are intended to assist in the use of the table facilities that are provided in some text editor applications.

Unfortunately a fixed character width type font is not available within this application so that columns are not well presented in the dialog on the computer screen.

The xseckeep.txt file

The Windows version makes minimal use of the registry.

The application uses the home path of the application’s writable scratch directory or storage where it puts a file called “xseckeep.txt”. On startup it looks for this file and if it does not find such a file it continues the session using default values for the information the user might expect it to remember from a previous session. On closing a session it writes such a file.

This is completely automatic and the user need not be aware of the xseckeep.txt file.

On the Windows computers used for testing so far, one running Windows 7 and two running Windows 8 the home path was:


On an Apple MacBook running OS X 10.10 the home path was:

<Macintosh HD/Users/user>