UmarMakhzumi

Hello Sohaib, Can you share more details. This would make an interesting discussion. What is the scope of project and what are you building. Why are choosing to go with base isolation for your structure? Thanks.

The same way the you would design a slab.

Hilti has a software called Profis. Its free and if you use it, it will tell you the minimum embedment or capacity based on available embedment. There is development length and there is bond strength b/w the epoxy and rebar. The software would check all limit states based on concrete cracked, uncracked, submerged etc conditions considering concrete breakout and rebar failure (Same checks as that of anchor bolts). Also FYI, concrete breakout might govern failure for tension or shear load. Thanks.

You can use moment release to model hinged or pinned ends (depending on what you call rotation unrestrained boundary condition).

Welcome aboard Serguei. Glad to have you.

This is standard practise for manual design.

As long as you have designed your pile to transfer the tension from the pile to adjacent soil, the concern related to concrete cracking just because a tensile load to a concrete member has been applied is minimal. You can also refer to a text book to see "things to be aware of" while designing a concrete member subjected to tension load. Pile is like a column with lateral support. Thanks.

Strain compatibility means C=T equation for reinforced concrete design. The other end is in tension. Bending of wall will create compression at one face and tension on another. You can assign Tension forces at different bar levels as T1, T2, T3 and so on and use C=T to find the value of small 'c'. Hope that helps.

Welcome aboard Sadia.

Hi Zohaib. The following thread has a very rigorous discussion on time period and what values should be used. Please check it out. Also, generally speaking if the computed time period is greater than 2*Cu*Ta then you should check your model for errors. Thanks.

This is great. Thanks so much for the update.

Dear Uzair Sb, The error is in slab element 22836. You can find that element by looking at respective story level. For that, you will need to turn on the Area Labels and use the X, Y and Z Coordinates provided in the error log. Solution to the problem is to either re-mesh the area manually for that part or to do the load distribution manually and directly apply load at beams and just delete the slab. Please let us know if the problem has been fixed or otherwise. Thanks.

The intent here is to evaluate and analyse the statement that why modelling columns at the end of shear wall in an incorrect approach. This approach is used widely in Pakistan by design consultants that are too lazy to model a proper boundary element where boundary elements are thicker than the wall and in some cases in all situations just to pass the models. One way to prove that this approach is incorrect is to show that modelling columns is not as same as having boundary elements. To prove that, you can check the stiffness in both cases to establish that both modelling approaches are not apples to apples and in fact by modelling columns at ends of walls you are doing stuff to pass the model that doesn't make sense. The numbers answer your original question asked in the first post that "Can I model a wall with columns on it's ends and is it the same as the wall with boundary elements defined in section designer????". The answer as you can see yourself is no. Modelling columns is not same as having boundary elements defined in section designer. For the case where you have columns at the end of shear walls, your stiffness is 140.5 kip/inch. For the case where you don't, your stiffness is its 110.3 kip/inch. Adding columns results in an increase of 27% stiffness. The increase in stiffness due to modelling columns is not justified. Stiffness comes out of E and I and what you should be getting is same as modelling a single wall where end regions are assigned as boundary in section designer. Generally FEA software work from node to node so I doubt if the software would consider visual overlaps. Well that should be the expected results. If you move columns farther out, the are not connected to wall. To summarize, use section designer to define boundary elements. I hope this exercise provided you with some insight about the issue. Thanks.

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It could be. All depends upon relative stiffness. Their are buildings where column configuration changes after X number of stories. The floor at that specific level is very very thick to allow for new columns arrangements (and satisfy other limit states requirements) but this happens all the time in high rises in Dubai.

I have seen some people model 2 columns at wall ends but I don't agree with that approach. The only way to find this out if the approach of modelling columns at the ends of wall is correct or not is to make two models. The first model should contain a wall with boundary elements using section designer and the second model without boundary element and 2 columns at the end. Apply a 1 kN load at the top of wall. Calculate the stiffness for both cases. If stiffness is same, both approaches are the same. If not, then they aren't. Calculating stiffness is easy. You can apply see the displacement for each model and divide the 1kN by that displacement. Stiffness is the force required for unit displacement. Let us know, we are waiting. Thanks.

Hi Shamas, Please check this out: https://ocw.mit.edu/courses/civil-and-environmental-engineering/1-561-motion-based-design-fall-2003/ Thanks.

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There is also another point in this discussion. The assumption of a fixed based for isolated foundations is not valid because these foundations are susceptible to rotation. That would mean no moment (there would be some as foundation has rotational stiffness) at column foundation interface and more moment at beam column interface - plastic hinging in beams column joint. Although the original discussion is about developing plastic hinge at foundation column interface but I think the fact that isolated foundations rotate makes these two conditions mutually exclusive (some degree). If the foundation rotates then it is a pinned end and the only forces there would be shear and axial.

I found another thread on the forum where isolated foundation rotation was discussed. The author (posted excerpt from Pauley and Priestley ) recommends modelling isolated foundation using a rotational spring to avoid unexpected column hinging at top of lower story columns. FYI, Thanks.

Thanks Rana. This would be applicable for all foundations. @BAZ, Sir when you mentioned isolated foundations only, is there any specific item other than what Rana has described that you would were thinking. I don't have any idea about this topic other than that isolated foundations can rotate but don't know how that would be related to this discussions. Thanks.

WSalaam Hali, The following topic discusses how to resolve forces in lb-in/in or any other format for plates, shells etc. The discussion is for SAP2K but I would assume the same would be applicable for Staad (you can check its manual). Thanks.

Thanks for the great reply. I will just add that modulus of different soil layers is different so the pile to be divided either equally within each layer. Thanks

Thanks for the great reply Yasir. I will just add that the member nodes should be continuous (able to transfer moment + shear) once they are broken or else the model would be unstable. Thanks.

Hello Rahim, I have lost the document while changing laptops. Sorry. Thanks.