- Monday, 01 September 2014

### 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 2.3). Moreover, it includes the computational algorithm for check and design of arbitrary sections in biaxial bending with axial force. It collaborates interactively with design application (described in section 2.5) and formulates a reliability auditing tool for the program results.

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.

Additional options for three-sided jackets (only when Nous is run via 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.

Several aspects of the view window can be changed and extra design information can be also be displayed.

View -> Background color switch or button : Switches the background color in the graphics window from black to white and vice-versthe reinforcement positions.

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

View -> 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 (Νi, Mxi, Myi)
- Neutral axis transitions for every iteration (dx, dy, dφ)
- Difference between external and internal forces (dN, dMx, dMy)
- Neutral axis location (xp, yp, φp) 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 froms of cross-section)
- Centre of gravity for the section (xo, yo)
- Elastic neutral axis location (xn¬, yn)
- Core and jacket concrete area
- Core and jacket reinforcement areas and percentages

View -> Stresses or 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.

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

Solve -> Safety factor or 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).

Solve -> Required reinforcement or 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.

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

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

Solve -> Restart or 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.