RCDC -Column Design as per IS 13920

Question

Hi, 
 I am unable to use joint check option in ductile column design in RCDC. The option is greyed out. Refer to screenshot below. What could be the possible reason for it. 
 Note: I already have run and designed all the beams in the model. 
 /resized-image/__size/320x240/__key/communityserver-discussions-components-files/5932/Screenshot-_2800_1037_2900_.png

ARPIT CHAWLA · Answer

But I did found some issues listed below: 
 1) When the column dimension is less than 300mm for ductile design, no warning has been observed to be given by RCDC. This violates the IS 13920:2016, Cl.7.1.1. Although its mentioned in HELP that it i will give warning, but none is seen and the design is shown as SAFE. Can you please share how and where the warning is shown? 
 2) IS 13920:2016, Cl.7.5 directs to compute shear forces in column based on the beams moment capacities framing into that column. Now, in column design module, RCDC doesn't take any input for the reinforcement of beam. What it is doing is, based on the end moments it calculates the required Ast and then as per that it selects appropriate bar dia and Ast provided. This might not always match with what actually is provided. May be if the beam is governed by crackwidth or deflection, Ast actually provided is more. Then in that case, beam moment capacity will be under estimated and consequently design shear force in column will also be under-estimated. Moreover, this under estimation of moment capacity of beam when compared with moment capacity of column (for weak beam and strong column concept to maintain capacity ratios of column to beam strength as 1.4) will yield incorrect results. Is there any way to take care of this? 
 3) this is a very minor issue. While giving user defined effective depth factors to column, it round offs the value to upto 2 decimal places if we give it separately for each column. But if we assign same value to all the columns using the assign to all option at the bottom of the table, then it take as much decimal places as is required. This leads to minor errors in the design calculations.

Nidhi Valia · Answer

Hi 
 Reply to pt.no. 1 -- 
 There is a print mistake in RCDC Help content. 
 For minimum size of column, RCDC will not report &lsquo;warning&rsquo; if any of the dimensions is less than 300 mm. 
 It is expected that User is aware of the clause requirement as well as the design criteria whether Ductile / Non-ductile for which the column will be designed. So, the Column size needs to be decided by user while modelling itself as User can control it. 
 As design software, RCDC will take the dimensions available from analysis and design for same. 
 Reply to pt.no. 2 -- 
 RCDC performs steps same as mentioned by you but Criteria like Crack Width effect in beams is not taken into consideration because both Beams and Columns are designed in different module in RCDC. Further to import the complete which will be a huge Design data from beams at all the levels and then designing the column for actual shear from beam is currently not handled in RCDC. We will be implementing it once we consider design of all elements in single module. 
 Reply to pt.no. 3 -- 
 It is been rounded on higher side up to 2 digits which has nearly no impact on the final slender moment and is anyway on a BIT higher side.

RCDC -Column Design as per IS 13920

Top Replies