# Ribs in Advance Design - Case Study

This case study focuses on using the **Ribs design** function for conducting analysis by considering linear elements as ribs.

## Example 1: When the ribs element has B1 ≠ B2 ≠ 0:

Ribs design option in Advance Design

In this scenario, the **Ribs design** option plays a significant role in determining whether beams should be treated as ribs of the slab. When the option is enabled, beams are considered ribs, while disabling the option excludes beams from being treated as ribs of the slab.

Effective flange width parameters

To begin, the distances **B1**(b1) and** B2**(b2) need to be manually inputted in the **Ribs-Effective width** dialog:

**B1** represents the distance in the 'Y-' direction of the local axis and can be calculated as (4.00m-0.30m)/2 = 1.85m
- Similarly,
**B2** represents the distance in the 'Y+' direction of the local axis and can be calculated as (6.00m-0.3m)/2 = 2.85m.

Effective width- Ribs dialog

Once the **FEM+RC design** is completed, open the **Effective Width** dialog to examine the values of Beff1 and Beff2.

Ribs characteristics

These values can be obtained using the following formula:

**NOTE:*** l0 refers to the distance that varies based on the span type. For rib elements with a single span, l0 is equal to the span between the two axes.*

Effective flange width parameters

In this case, the manual calculation is as follows:

Beff,1 = 0.2 x 1.85 + 0.1 x 6 = 0.97m ≤ 1.20m

0.97m ≤ 1.85m

Beff,2 = 0.2 x 2.85 + 0.1 x 6.0 = 1.17m

1.17m ≤ 2.85m

## Example 2: When the rib element has B1 ≠ 0 and B2 = 0:

In this case, the **Ribs design **option is still relevant, with B1 representing the distance in the 'Y-' direction and B2 being 0.

Ribs design - Properties

B1=(6.00m-0.30m)/2=2.85m

B2=0

Effective width- Ribs dialog

After completing the F**EM+RC design**, refer to the **Effective Width** dialog to observe the values of Beff1 and Beff2, obtained through the same calculation formula mentioned earlier.

Ribs characteristics

**For Span1:**

Beff,1 = 0.2 x 2.85m + 0.1 x (0.85 x 4m) = 0.91m ≤ 0.68m

0.68m ≤ 2.85m

**For Span2**:

Beff,1 = 0.2 x 2.85m + 0.1 x (0.85 x 6m) = 1.08m ≤ 1.02m

1.02m ≤ 2.85m

These calculations demonstrate the effective widths of the rib elements in each scenario.

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