Anchor configuration for base plate design for considering supplementary reinforcement as per Euro code. 1

[M_U]

Hi,
I am designing a base plate. The shear force is around 2200 kn. I am unable to use the anchor configuration given in EN 1992-4. I want to use some other configuration. my question - can we use supplementary reinforcements to prevent the breakout failure as per the code if we go with some other configuration? I am using HILTI profis. As soon as my configuration is changed from the standard the software does not show the option for supplementary rebars.

 

[BridgeEngineer21]

I think this is between you and your client/reviewer. If you can design it and detail it in a way you're comfortable with, and you can convince the reviewer of it, then you're good to good. The limitation in Eurocode 1992-4 I believe is a limitation based on the maximum size of connections they did testing on. You can maybe gain some confidence that other codes based on the same body of research, such as ACI 318, don't have such a limitation.

One thing to note is if you have such a large anchorage configuration and large shear force, it is most likely impractical to apply all the shear force on your front row of bolts as required in Eurocode. Assuming you're close to an edge, you'll probably never get the required anchorage length in the failure cone. I would instead consider to apply the resultant shear at the middle of the group as in the clause from fib design guide 58 below, with the justification that for such a large anchor group, the hole tolerances will never all be in the same direction, presumably the fixture is reasonably stiff, so the shear force should distribute well to the whole group of anchors before a concrete failure plane forms



But again, these are just some thoughts/suggestions to consider without knowing much about your situation. I think the main point here is that you have to be comfortable with this detail on fundamental level and ready to convince whoever is reviewing your work. It sounds like a situation outside the scope of HILTI software so you'll have to develop your own calculations.

 

[HTURKAK]

The shear force is around 2200 kn. I am unable to use the anchor configuration given in EN 1992-4

Your first picture is Figure 1.2 — Configuration of headed and post-installed fastenings covered by this EN. The second picture ( a lot of anchors with 20 anchors ) shows that this is column base . What about the axial load and moment ? What is the reason for using 20 anchors ?

 

[M_U]

I think this is between you and your client/reviewer. If you can design it and detail it in a way you're comfortable with, and you can convince the reviewer of it, then you're good to good. The limitation in Eurocode 1992-4 I believe is a limitation based on the maximum size of connections they did testing on. You can maybe gain some confidence that other codes based on the same body of research, such as ACI 318, don't have such a limitation.

One thing to note is if you have such a large anchorage configuration and large shear force, it is most likely impractical to apply all the shear force on your front row of bolts as required in Eurocode. Assuming you're close to an edge, you'll probably never get the required anchorage length in the failure cone. I would instead consider to apply the resultant shear at the middle of the group as in the clause from fib design guide 58 below, with the justification that for such a large anchor group, the hole tolerances will never all be in the same direction, presumably the fixture is reasonably stiff, so the shear force should distribute well to the whole group of anchors before a concrete failure plane forms

View attachment 15251

But again, these are just some thoughts/suggestions to consider without knowing much about your situation. I think the main point here is that you have to be comfortable with this detail on fundamental level and ready to convince whoever is reviewing your work. It sounds like a situation outside the scope of HILTI software so you'll have to develop your own calculations.

Thank you very much for the insights.

 

[M_U]

Your first picture is Figure 1.2 — Configuration of headed and post-installed fastenings covered by this EN. The second picture ( a lot of anchors with 20 anchors ) shows that this is column base . What about the axial load and moment ? What is the reason for using 20 anchors ?

The shear is around 2200 kN and axial force is 1000 kN. It is the base of a chiller platform. The designer has assumed pinned support at the base. I am still deciding the numbers of anchors. Your suggestion will be very helpful.

 

[HTURKAK]

I am still deciding the numbers of anchors. Your suggestion will be very helpful.

In this case the use of post installed anchors is not a good idea. ( the Figure 1.2 in EN 1992-4 shows applicable configurations for post installed anchors). In your case , IMO the use of conventional cast -in anchors having bigger diameter ( say 50-80 mm dia ) and without hole clearance the way to go.

I attached the column base doc. as per EC.

Final say ; ( Don’t force it…Use a bigger hammer
ANONYMOUS ).