WR1

From the information in tables above, I dont think your building is irregular (torsional) and if the overall sway is within limits, you dont need more walls.

Yes you have to select areas separately and assign it a different name for diaphragm to have two diaphragms at same level.

Autocad. Hint: Google 'lisp' files.

What happens if, supports in your example are very flexible as compared to slab or beam, so it behaves as simply supported. If the support stiffness is huge (rotational restraint) as compared to the member, it will be a continuous frame. Yes you can do separate analyses and combined together as long as you respect the equilibrium, comparability of deformations, constitutive relations.

First-off, I am not sure about your system, is it a moment resting frame, dual frame or shear wall frame interaction? I assume it is a building frame system where lateral loads (all) are taken by shear walls (in-plane) and all gravity (mostly ~ 90%) is taken by columns. The above assumption can be checked by checking reactions after applying 0.7,0.35 modifiers to walls and 0.7 modifiers to columns. This is your routine design..Right? Now comes the question of temperature loading, for that please update what is the temperature magnitude you are using? What is the use of building? It is heated/un-heated structure? For example if its a parking structure where under-sides of beams also have temperature loading, slab stresses will be minimal (almost zero if equal values). Also for parking structure, the first slab will have huge stresses due to fixity of base. And as @UmarMakhzumi pointed out, you also need to check bending under temperature gradient (manually by using C and T approach for a single reinforced section or by computer using complex analysis). Anyway, In my view, I hope that authorities would not go for that. But for normal temperature analysis, I would recommend you to make a 1 page A4 calculation, stating the design philosophy for temperature loads and put it as appendix or part of your report. In that report you would mention, 1. use of semi-rigid option 2. use of reduced modifiers for tension cracking for walls (even for columns if they are showing tension). You can use 0.25 and if it not working reduced further. It would be nAs/Ag for the members where you havee tension. 3. show formula for modulus of rupture for restrained slabs and subtract that capacity from ETABS values. 4. Assign piers or average manually the axial force over whole length of wall piers to reduce magnitude further. Make sure that reinforcement provided for temperature is same on both sides for slabs/walls and same on all sides for beams/columns. Now next question is regarding lateral load RE-distribution. If you reduced the stiffness of walls and columns both by same amount, that would not affect re-distribution of lateral forces. But if you just reduced stiffness of walls, columns will start taking more lateral loads (depends on relative stiffness of wall/columns, I do not know the dimensions) so As @UmarMakhzumi pointed out, you should this design too. Because axial stiffness of walls/shells = in-plane stiffness of walls/shells so changing axial stiffness will also change the bending stiffness for lateral loads and re-distribution will happen. So check for this condition too, you might need to increase some columns that again depend on dimensions and framing system. In that case, read Tranath book on tall buildings chapter 3 on lateral loads to see what you actually need to increase, columns or beams? Please update us what happens.

Ofcourse, you should use semi-rigid diaphragm for temperature analysis or other axial loads.

1. I forgot to mention and as is Rummann understood correctly, that reason for using reduced stiffness for axial tension is that we will get less tension from analysis (due to less stiffness/restraint). 2. Negative temperature will produce tension near restraint (like slab supported on heavy walls). 3. What is the use of building? Is it a car park where you need to apply temperature to all the structure? Otherwise as Umar and you already pointed out, its the top slab where you need to consider differential temperature between top and bottom slab and thats not possible with ETABS 9 atleast. 4. Yes, tension should be checked on appropriate combination with other loads and that is 1.2D+1.6L+1.2T plus other loads if you have. If still you are getting tension that means it will be carried by modulus of rupture + steel only. 5. I would recommend you to use reduced stiffness of 0.25 and then also subtract the tension capacity of concrete (equal to half of 0.62(f'c^0.5)xthicknes in Mpa), half because slabs are restrained as per ACI. 6. For compression, cracking modifier should be increased but walls are quite stronger in compression. So just use 0.25. This is your separate model for temperature analysis. Keep it separate from lateral analysis where you might be using 0.7 or 0.35 modifiers for shear walls. Or it will affect the distribution of lateral forces to columns as you pointed out. But keep in mind, that is the real situation, if temperature cracks walls before earthquake hits, walls would be very weak transferring lateral forces to columns. Others can shed light on this more.

You should not get moment from temperature load in ETABS. Because temperature is applied as axial load not as gradient like in SAP. Yes walls will fail in F11, F22 (axial force, tension mostly). But remember for tension, walls will be cracked and to account for cracking you have to apply a very low value of axial stiffness. I would say to start with F22 and F11 as 0.25 and if it still fails you can even reduce it to like 0.10 (tension will be carried only by steel) plus some portion by tensile capacity of concrete. This is true if cracks are not your concern like in water tanks etc. Imagine what is the goal of your calculations? failure mode? service or ultimate? Ultimate right? Ok, now at ultimate stage what is the predicted cracking mode? How much cracking do you expect? For axial tension, I expect fully cracked concrete with section capacity only equal to n.As. So nAs/Ag is the modifier you should use for f11 and f22 in tension. For compression, i dont expect cracks so section is mostly less cracked (only from shear or flexure).

Yes spec x and spec y are not shown in load cases but in load combination.

Naseem, SE Pakistan does not support plagiarism, violation of copyrights, intellectual property theft or pirated material. You can buy the document from ACI store.

No, scaling is for dynamic base shear. Scaling will not increase mass participation. If 90% is not achieved you have to include more mass, that means increase the number of modes.

Abid, T can be calculated from both the methods and can be used in static analysis. Thanks.

Dear Abid, this is not a platform where others can review your project in detail. If you have a specific question please bring forward and we would be delighted to help you for that.

No wait. Im sorry i was wrong. Tb can be used in static analysis as well.

When you right click for governing combination, make sure you are not checking flexural governing combo. Max shear combo might be from another combination. 2nd point is, when more than 1 load combinations govern (for example when column has 1% reinf from all cases), right click might not give you the "governing" combos. You have to check it; manually or by telling ETABS to check instead of design (for columns) and check utilization ratios or by other mean.

Yes, Tb is calculated by computer based on stiffness of building. The book you are referring to clearly explains what are you are asking. 1. Choose method of analysis: Static or Dynamic? A. Static Calculate Ta Calculate base shear V based on Ta Calculate Drifts based on Ta 2. Dynamic Calculate Ta Calculate Tb For base shear V, use Tb but Tb should not be more than 1.4Ta (or 1.3) For drifts disregard the upper limit and just use Tb without 1.3/1.4 limit. Hope that clarifies.

In reality, load/moment transfer depends on relative stiffness of columns and beams. When you model a whole building, the software takes care of relative stiffness automatically. For manual calculations, there are various methods. For example in above image, replace the pin supports with actual columns and try solving this Moment Distribution Method by hand and compare the results. Or make a computer example of above frame in elevation with actual columns and try reducing/increasing column sizes to see what are the effects.

First-off could you please phrase your question (typing) properly? Secondly, As in UBC, Ta = Ct(hn)^0.75 And Tb comes from dynamic analysis (see UBC-97 Chapter 16) For drift you dont need to satisfy limit of 1.4 or 1.3 times Ta. Is this you are referring to?

It should be relative deflection. For example a beam in X supporting on girders in Y direction. You need to take the net deflection of supports and mid-span (for s.s. case) to compute deflections.

As I understand the question, he is not allowed to increase depth of floor system.

ILYAS, even ETABS 9 had the similar options but that did not work.

1 Astounding observation. Just to add my 2 cents that in exterior columns, minimum e does not govern. For interior columns it is always good idea to design columns for minimum eccentricity. Yes this is conservative and depends on the choice of designer. 2 Even if the structure is braced, magnification factors will be so small that they will not matter much. 3 See discussion below

Inter-story drift limitation is intended to limit the damage. Abs disp of max point of upper stories wrt to base is to check for seismic separation. Both checks are must.

Dear Ahmad, I am not able to review your model. But if increasing reinforcement does not help you sure, you need to think about step 5 in my previous post.

Yes you should calculate it from ultimate load combination including E. If the building has no sway under gravity loads, load case E and load combos including E will give same lateral sway.