My question relating to Concrete Design in RCC framed structure:
1. Effective length factor for column is automatically calculated by STAAD pro based on analysis or it to be entered manually? If it to be entered manually then any data for same is available in STAAD analysis?
2. If I use analysis from STAAD pro and Column designs by RCDC then Effective length factor for column is automatically calculated by STAAD pro based on analysis or it to be entered manually? If it to be entered manually then any data for same is available in STAAD analysis?
In addition to above response, please note the following,
if you use analysis from STAAD and design from RCDC, then RCDC auto calculate the effective length factor based on the analysis result. The effective length factor is based on the Axial loads, story drift, column height and the lateral load. Calculation of effective length factor is part of column design, thus it is calculated in RCDC itself. Based on the analysis results it identifies the type of story as sway or Non-sway and effective length factor is calculated. for sample calculation please click on below link.
it also allow user to override these value if required. Based on the final values RCDC will perform the design.
I downloaded files effective length comparison.pdf and Column C1-16.258 level.html from link given by you. In these files design calculations done by RCDC shows calculation for sway and also for calculation of effective length factor. But when I design column with RCDC (version 184.108.40.206) here is no such calculations found. Here in code reference it says "Multiplying factor to Beam Stiffness for effective length calculation : SP 24 1983 APPENDIX D". Why?
Version 6 is very old. RCDC has been updated a lot. I would request you to upgrade to version 9.2.00.32 and check the issue. The validation is related to latest versions.
RCDC does provide the detailed calculation for calculation of effective length factor. the report has been enhanced over the period to give more details to users. Please click on below link for detailed design calculation report for column design for your reference.
As per SP 24-1978, it has suggested to apply the modification factor to the stiffness calculation of beams which is used for the Beta computation. these factors are based on the type of frame. i.e. sway and Non-sway. the modification factor for the beam stiffness was based on the deflection pattern of the beams. it was assumed that the Under Non-sway frame, beams will bend in single curvature thus the stiffness has been reduced to 50 percent. similarly for Sway frame, beams will bend in double curvature thus stiffness of the beam can be increased.We were using these factors for the Beta calculation however presently we are not using same. The reason the ignoring is that now days we get more accurate results with effect of planner elements like rigid slab.
Answer Verified By: Abhijeet Gundaye
Why does RCDC and Etabs have different effective length factor? I can see this for most of the columns. This is why reinforcement in RCDC is more as compared to Etabs.
Hi VineeethThe validation document for effective length calculation is available above. Also, detailed calculation of effective length factor is available in design calculation report of RCDC.I would request you to go through the same and raise the query if you have any issues.Regarding the E-tabs, i would request you to connect to the their technical person to get the clarification.