RCDC Beam design - effective depth Calculation

RE: RCDC Beam design - effective depth Calculation

Nidhi Valia — Mon, 31 Jul 2023 12:44:47 GMT

Hi,

The clear cover that is considered in RCDC is the clear cover to the main Longitudinal Bar and not the Link.

So, in the above example, the Deff for column would be calculated as:

Deff = 500 - 40 - 25/2 = 447mm.

Hope this clarifies.

Thanks

RE: RCDC Beam design - effective depth Calculation

Bryant Joel Macaraeg — Mon, 31 Jul 2023 07:51:59 GMT

Hello, In reinforced Concrete, how will you compute for the effective depth if the column has different rebar, like in this pic. And also for the d'.

The column has 4-25mm corner rebar and 8-20mm side rebar. It is also symmetrical and the size is 500×500mm. With 10mm lateral tie and 40mm as its concrete cover.

RE: RCDC Beam design - effective depth Calculation

Abhisek M — Fri, 09 Sep 2022 06:54:06 GMT

Please refer the explanation and the excel sheet available in below link.

https://communities.bentley.com/products/ram-staad/w/structural_analysis_and_design__wiki/59381/how-the-effective-depth-is-calculated-in-beam-design-and-what-is-the-impact-of-maximum-aggregate-2-size-on-effective-depth

RE: RCDC Beam design - effective depth Calculation

Abhisek M — Fri, 09 Sep 2022 06:54:00 GMT

Please refer the explanation and the excel sheet available in below link.

RE: RCDC Beam design - effective depth Calculation

Nidhi Valia — Fri, 09 Sep 2022 06:49:18 GMT

Hello Mr. Paresh,

Sharing the attached sheet for your reference and clarification.

Thanks

communities.bentley.com/.../Deff-and-Ast-calculation.xlsx

RE: RCDC Beam design - effective depth Calculation

paresh — Fri, 09 Sep 2022 06:32:55 GMT

Hi Nidhi,

Could you please share the effective depth calculation of RCDC.

Beam Size 230 x 300mm

Clear Cover -20mm

Bottom R/F dia - 16mm

Stirrups dia - 8mm

As per your above calculation methodology, eff depth should be

300 - 20 - 16 - 8/2 = 300 -40mm = 260mm

But as per RCDC , eff depth is coming as 250mm

RE: RCDC Beam design - effective depth Calculation

ARPIT CHAWLA — Mon, 17 Jan 2022 09:21:23 GMT

Hi,

Request you to please check and confirm.

RE: RCDC Beam design - effective depth Calculation

ARPIT CHAWLA — Mon, 17 Jan 2022 04:13:13 GMT

Hi,

Request you to please check and confirm.

RE: RCDC Beam design - effective depth Calculation

ARPIT CHAWLA — Wed, 12 Jan 2022 11:25:04 GMT

Hi,

I have attached a sample file. If you refer Beam B5, top right is provided with 3 layers of rebar. In that case how is the effective depth being calculated? Based on the solution given by Abhisek M I presume that it is calculated as below:

Effective depth, d = 450 (Overall Depth) - 30 (Clear cover) - 16 (for layer 1) - 25 (spacer bar between layer 1 and layer 2) - 16/2 (upto centre of layer 2) => d = 371mm = 370mm (rounded off).

But actual provision is 3 layers of 12 dia bar as per design, as per which calculation should be as follows,

Effective depth, d = 450 (Overall Depth) - 30 (Clear cover) - 12 (for layer 1) - 13.33 (Two third of aggregate size or bar dia, whichever is higher) - 12/2 (upto centre of layer 2) => d = 388.67mm = 385mm (rounded off).

So RCDC is basically calculating lesser effective depth than required. Is that correct?

Also confirm if my assumptions are correct.

communities.bentley.com/.../Plinth-Beam-B5_2C00_-B6-_2D00_-RCDC-Output-_2D00_-3-layers.pdf

RE: RCDC Beam design - effective depth Calculation

Nidhi Valia — Wed, 12 Jan 2022 10:32:53 GMT

Hi,

It would be useful if we can have an example based in which we can take this further.

You can provide us with a live example which you are doing manually and we will help you with validation oh how RCDC is doing it. You can share your own manual calculation by taking an example into consideration.

Thanks.

RE: RCDC Beam design - effective depth Calculation

ARPIT CHAWLA — Wed, 12 Jan 2022 09:01:41 GMT

Hi,

Agree of the part on how RCDC takes no. of layers into account during auto design. But what I observed is the following. Say my beam depth is 550mm as per which 2 layer will be assumed by RCDC. So effective depth is calculated based on 2 layers of rebar that is,

d = 550 (overall depth) - 30 (clear cover) - 16 (bar dia) -12.5 (spacer bar dia/2) = 491.5 = 490 (rounded off)

But as per design (auto-design), only 1 layer of reinforcement is provided consisting of 3 no. of 12 dia bars. But still effective depth corresponding to 2 layers is being used for design.

Also the usage of 16mm and 12.5mm is doubtful as provided is only 12mm bars.

If you can again refer to my previous reply and provide solutions issue-wise, it will be highly appreciated. Thank you.

RE: RCDC Beam design - effective depth Calculation

Nidhi Valia — Wed, 12 Jan 2022 07:37:46 GMT

Request you to kindly note following:

All cover is assumed to be cover to longitudinal reinforcement.
Assumption of number of layers of reinforcement:

At design time the number of layers of reinforcement is assumed as under to arrive at the effective depth, d:

D < 400 mm 1 layer
400 mm >= D <=1200 mm 2 layers
1200mm > D <= 1350 mm 3 layers
1350 mm > D <= 1800 mm 4 layers
1800 mm > D <= 2250 mm 5 layers
2250 mm > D <= 2700 mm 6 layers
2700 mm > D <= 3250 mm 7 layers
D > 3250 mm 8 layers

Detailing Philosophy:

The reinforcement required is computed as per the effective depth for the number of layer of reinforcementas per table above.
Rebars will be arranged in multiple layers if requiredand the style of detailing selected. The maximum number of layers usedwill be limited to thoseassumed when computing the effective depth.
In case it is not possible to provide the required reinforcement using the largest rebar arranged in the maximum possible layers the number of layers will be automatically increased. With the increase in number of layers the effective depth and the reinforcement required will be computed again.
When providing rebars across the section of the beam, the minimum and the maximum spacing criteria and the preferred number of rebars will be considered. The rebars wil be symmetrically arranged across the section.
In case the number of bars are varying across the section, the auto detailing will ensure that the symmetry will be maintained.eg. 6 bars will reduce to 4 and not 5 bars OR 5 bars will reduce to 3 and 4 bars.

RE: RCDC Beam design - effective depth Calculation

ARPIT CHAWLA — Wed, 12 Jan 2022 05:36:23 GMT

[quote userid="850250" url="~/products/ram-staad/f/ram-staad-forum/224428/rcdc-beam-design---effective-depth-calculation/691126"]d = D - Clear Cover - 16mm -12.5mm
d= D- Clear Cover -28.5mm[/quote]

Issue 1 : Does it take 16mm and 12.5mm (as quoted above) as the fixed values or these are based on User Input?

Also, referring to the link below, Q30 which says the assumed diameter of the bar, d1 as 20mm. how is it assumed.

https://communities.bentley.com/products/ram-staad/w/structural_analysis_and_design__wiki/41953/rcdc-beam

Issue 2 : Can you please tell how the effective depth is calculated for say 3 number of layers.

Issue 3 : Can you confirm, if RCDC does or does not calculate effective depth based on the rebars and layers actually provided?

Issue 4 : Also, at beam different locations (say top left and top right) different rebars in different layers may be provided, say at top left one layer is provided and at top right 2 layers are provided. But RCDC is giving only one effective depth for entire beam. How is that being considered?

RE: RCDC Beam design - effective depth Calculation

Abhisek M — Wed, 12 Jan 2022 04:56:18 GMT

Hello,

In RCDC the effective depth of a beam is calculated in the fllowing manner.
If D is the total depth and d is the effective depth, then
d = D - Clear Cover - 16mm -12.5mm
d= D- Clear Cover -28.5mm

Here, clear cover thickness includes stirrup dia. For effective depth calculation it is assummed that 2 layers of reinforcement is present and effective depth is calculated from the top most fibre to the mid depth of spacer bar. Though it is conservative in some cases, but we are in safer side. Considering this fact, a value of 16mm is considered as the bar dia of bottom most layer reinforcement. Then 25mm spacer bar is considered for which we take half the depth in claculation as 25/2=12.5mm.

After getting the d value it is again rounded down to nearest 5mm interval, which in turn make the aforementioned 28.5mm value, 30mm.

Can you please check and let me know if this matches with your calculation?