4. Arbitrary section designer - Nous

Nous is an autonomous program for check and design of arbitrary sections. It provides the option of geometrically defining a new arbitrary section with the option of adding a jacket* and can edit all the simple sections originating from the section design (rectangular, T-, L-, U- and circular sections) as well as the RC and masonry wall sections (.wal and .mas) that were created in the relevant editor (see section Σφάλμα! Το αρχείο προέλευσης της αναφοράς δεν βρέθηκε.). Moreover, it includes the computational algorithm for check and design of arbitrary sections in biaxial bending with axial force. It collaborates interactively with the design application (described in section Σφάλμα! Το αρχείο προέλευσης της αναφοράς δεν βρέθηκε.) and formulates a reliability auditing tool for the program results.

* Requires the Strengthening license to be activated.

The program includes 6 tabs (to the left of the window). The top two are identical and concern the geometric description of the core and the jacket8 of the section.

The corner point co-ordinates for the core and the jacket and the centreline co-ordinates for the reinforcing bars are entered at the left side of the window. Data manipulation is accomplished by using the following buttons :
Add new point (corner point for the section or centre point for the reinforcing bar) using the co-ordinates that are input in the corresponding fields below.
Edit selected point (corner point for the section or centre point for the reinforcing bar) in the table by pasting the co-ordinates input in the corresponding fields below.
Delete selected point (corner point for the section or centre point for the reinforcing bar) from the table.
Delete all points (corner point for the section or centre point for the reinforcing bar) from the table. If the core or jacket points are deleted, then the respective reinforcement bars are also deleted.

Note: The geometric description of the section core must be in an anti-clockwise manner, whilst that of the jacket in an anti-clockwise manner for the external face and a clockwise manner for the internal face (in contact with the core).

The following additional options are activated when Nous is run via the design procedure during editing of rectangular and T-sections :

Reinforce core as beam (top-bottom) with Ø12 bars.

Reinforce core as column (perimeter reinforcement) with Ø12 bars.

In the above options it is taken into consideration the value of the field Reinforcement Cover (mm).

The third tab of the program includes the automatic jacket* creation for an arbitrary, rectangular or T- core section. The jacket reinforcing bars are distributed around the perimeter and to the centre of the jacket thickness with an initial bar diameter Ø12, which can be altered later. Data manipulation is accomplished by using the following buttons :

  Perimetric jacket. Can be applied to all cases.

One-sided jacket. Can only be applied to rectangular sections when Nous is run via the design process.

Two-sided jacket. Can only be applied to rectangular sections when Nous is run via the design process.

  Three-sided jacket. Can only be applied to rectangular sections when Nous is run via the design process.

  T-section jacket. Can only be applied to T-sections when Nous is run via the design process.

Jacket thickness : Defined in m in the corresponding field.

*Requires the Strengthening license to be activated.

Additional options for three-sided jackets (only when Nous is run through the design procedure for rectangular sections) :

In the fourth tab, the fields for the material properties for the core and the jacket are displayed in the following form :

e.g. for C20/25 concrete : (ΜPa)

e.g. for B500C steel : (ΜPa)

The fifth tab includes the areas and the corresponding diameters for the core and jacket reinforcement, as these have been defined in the first two tabs. Data manipulation is accomplished by using the following buttons :

Edits the area (in cm²) or the diameter (in mm) of the selected reinforcement in the table that has been defined in the corresponding field. When the area is altered in this field, then the corresponding diameter is calculated automatically and vice-versa.
Redistributes the areas/diameters of all the reinforcement according to the percentage (% times the concrete area of the section) that is input in the adjacent field, whilst simultaneously it equates all the areas/diameters for all the reinforcement.
Redistributes the areas/diameters of all the reinforcement according to the percentage (% times the concrete area of the section) that is input in the adjacent field, whilst the current ratio of areas/diameters is retained among the reinforcement.

The total reinforcement areas for the core and the jacket is always displayed under the respective reinforcement tables.

In the sixth tab the applied forces to the section are input, more specifically, the axial force N (in KN, negative sign for compression) and the moments M2 and M3 (in KNm) that correspond to the local axes 2 and 3 (displayed at the top left corner of the section shape). The correlation between the moments and axes is vectorial and follows the rule of thumb.   

The various program functions are displayed on the toolbar. These are the following :

New section  button : Begins input of a new section, deleting any previous section data. A warning message appears if the previous section has not been saved.

Open... button : Opens a prepared section (file with .sd or .wal or .mas extension) from the hard drive.

Save   button : Saves on the hard drive the current section (file with .sd extension) under the name displayed in the relevant field (above the tabs).

Save as...  button : Saves on the hard drive a previously saved section under a different name.

Clone sections  button : The .sd files for cloning are initially chosen and then the user is prompted for the floor names for which the selected sections are to be cloned to. This function is particularly useful if it is required to provide identical jackets to identical sections at different floors of the model.

Background color switch or button : Switches the background colour in the graphics window from black to white and vice-versa, as well as the graphic colours of the section according to the user preferences.

Labels or button : Displays the numbering of the section corner points and of the reinforcement positions.

Information or button : Displays various information in the graphics window of the section :- Number of iterations

• Number of reinforcement changes during design
• External forces (Ν, Μx, My)
• Internal forces (Ν_i, Mx_i, My_i)
• Neutral axis transitions for every iteration (dx, dy, dφ)
• Difference between external and internal forces (dN, dMx, dMy)
• Neutral axis location (x_p, y_p, φ_p) from ultimate limit state design
• Safety and capacity ratios from ultimate limit state design
• Safety and capacity ratios from linear elastic design (if there is no solution in ultimate limit state design, e.g. in cases of very high axial forces – small bending moments – unusual forms of cross-section)
• Centre of gravity for the section (x_o, y_o)
• Elastic neutral axis location (x_n­, y_n)
• Core and jacket concrete area
• Core and jacket reinforcement areas and percentages

Stresses button : Displays the internal stresses of the section and the corresponding values at the corner points and reinforcement locations. Moreover, the outline of the concrete compression zones for parabolic and rectangular stress distribution are displayed.

Deformations button : Displays the internal section deformations and the corresponding values at the corner points and reinforcement locations.

Safety factor button : Calculates the section safety factor (SF) under ultimate limit state design (failure for SF < 1, adequacy for SF ≥ 1). The safety factor is displayed in the graphics window of the section (if the display information button  has been selected) as well as in the sixth tab, under applied forces. Additionally, the section capacity ratio (λ) is displayed, which is the invert of the safety factor (failure for λ > 1, adequacy for λ ≤ 1).

Required reinforcement button : Designs the section, calculating by iterative process the required reinforcement so that the safety factor is equal to 1. Should a jacket be present, the design is with respect to the jacket’s reinforcement.

Next iteration button : Displays the next iteration of the safety factor calculating process under ultimate limit state design.

Previous iteration button : Displays the previous iteration of the safety factor calculating process under ultimate limit state design.

Restart button : Cancels the safety factor calculation process and returns to the inintial elastic state. If the design has been performed, the program returns to the initial reinforcement solution.