• Registered: 2016-04-22
  • Posts: 12

Topic: Stirrup

Hi,

I have modelled RCC column. I have placed steel plate of the same size of column section on top for loadings and at bottom for support. Load has been applied as point load under deformation control. During analysis I identified few issues:

1. The load has not been transferred (can be seen from real time view) to longitudinal bar (LB), although I have modelled as perfect connection. Column had cover of 10 mm all around and at end as well. My colleague suggested me to increase the vertical length of reinforcing bar to the end of column (no cover at the end of vertical bar) as such it will be in contact with loading plate. Is it a viable solution? What may be other problem?

2. The stirrups near the column end were stressed and yielded, but load has not been transferred to LB. Ideally the column should fail around mid-section. However, the concrete and stirrups were deformed near support and it failed locally there. My colleague suggested me that there is no connection between stirrups and longitudinal bars. It seems to be so.

Here, how I modelled the stirrups: The diameters of LB and stirrups are 16 mm and 6 mm, respectively. While I drew the stirrups, I put the joints at (8+3)=11 mm away from the centre of LB. The 6 mm stirrups should automatically be in contact on the surface of LB.

In ATENA reinforcements are drawn in line, in geometry we can see gap between LB and stirrups. My colleague suggested to draw the stirrups on the same level of LB so that stirrups line pass through the LB. Should we not keep the gap for bar diameter as I read in other post in Forum?

I would appreciate your responses.

Quote Post 1

  • dpryl
  • CC software developer
  • Offline
  • Registered: 2007-07-13
  • Posts: 1,107

Re: Stirrup

Dear ahsanparvez,
first of all, if you need help/advice regarding your model, please send us the model etc. following Troubleshooting, 2.1.1. Without that, guessing the problem source(s) is problematic/impossible.

Ad 1.: What is the real setup like - are the bars welded to the loading plate? If so, you should end them inside the plate = extend them a little outside of the concrete (e.g., a few mm or 1/5 of the plate thickness or similar).

Ad 2.:
1. As the 1D bars only have axial stiffness, connections of perpendicular segments only have limited influence.
2. All reinforcement nodes inside a single finite element of the surrounding material get automatically connected to the same nodes (although not with identical weights), which effectively connects them. If they are located inside 2 neighbouring finite elements, they are still linked to about 1/2 of the same Master nodes.
If your mesh in the concrete is so fine that a whole element falls between the 2 reinforcement nodes (i.e., edges length <11mm), you might indeed get unrealistic cracking between the bar and the stirrup, however, in that case modelling concrete as a homogeneous continuum is probably already questionable...

You may also be interested in reading ATENA Troubleshooting, 2.2.10 How can I take the bending and/or shear contribution of reinforcement bars into account?

dpryl's Website

Quote Post 2

  • Registered: 2016-04-22
  • Posts: 12

Re: Stirrup

Thank you very much. Your suggestions were helpful.

Quote Post 3