Help Needed Regarding Concrete Structure Designed In Etabs

[haro0n]

Assalam o alaikum

I am attaching a model which I have made in etabs. This was the assignment which teacher gave us to design it. I have designed it in etabs this is my first model and need your guidence I want to know whether its acceptable or not??? If I need to revise it what things I should change.??

Also after designing we can see longitudinal steel, shear reinforcement etc.. this is different for each section so how I can use these to select the bar reqirement, spacing e.t.c as we have one section plan for beam and column etc. but this is different for all sections so how I select this for column, beam et.c what about slab?? Its reinforcement etc.. I used property modifiers and other tips also which I found on this site so kindly guide me.

Details of the building r as follows.

4-story building

X-direction spacing = 6 @10 feet

Y-direction spacing =2 @20 feet

One way slab

Load is assigned using Shell/area loads ( I selected all panels of one story then applied the shell/area load dead, live et.c then for next story) but the load is not fully transferred to column etc, why? After analyzing the stress diagram looks odd to me.

Rcc wall is used in basement. Auto meshing is done 4x4

Seismic effect is not taken into account so only one load combo is used. I deleted the others but after analysis they were shown why??

How I will know that any member is failing and I need to change it??

In final design we show the bar, spacing, etc but as I mentioned it is change for every sections so how I should finalize this for column beam and what for rcc wall?? After analysis it looks like that no load is transferred to it..

Kindly check this model by performing manual checks on it. Waiting for ur response.

want to learn from ur experience

thanks in advance

assignment.rar

[WR1]

Assalam o alaikum

I am attaching a model which I have made in etabs. This was the assignment which teacher gave us to design it. I have designed it in etabs this is my first model and need your guidence I want to know whether its acceptable or not??? If I need to revise it what things I should change.?

In which semester you are? You should design manually..not in etabs at this stage..this is just my personal opinion. well from your question, you reminded me my undergrad period 3 yrs ago when i was asking more or less same questions from sir umar makhzumi..lolz...but its good to ask...keep it up! at this stage you cannot develope a full understanding of the concepts but atleast you started...so just stick it to it..and have patience...dont lost it...remember...

Also after designing we can see longitudinal steel, shear reinforcement etc.. this is different for each section so how I can use these to select the bar reqirement, spacing e.t.c as we have one section plan for beam and column etc. but this is different for all sections so how I select this for column, beam et.c

even if a building is very regular like in ur example, you need to design for 2 sections; one for internal (beam, col & foundation) and another for external. Now all the internal beams having same span and loading etc shall have same moments and reinforcement. if not then something is wrong. But in ur example you have different spans in x and y so yes you each beam will have different reinforcement. but for simplicity you can use the reinforcement of the beam having maximum values and apply for all beams provided if it can be accomodated in all beams (after checking min and max reinf)

what about slab?? Its reinforcement etc..

Slabs are designed in SAFE not in etabs..but if the slab is shell you can check the moments and calculate reinf manually but this can be done only for SHELL areas not membrane.

I used property modifiers and other tips also which I found on this site so kindly guide me.

First of all you used modifiers in section properties..i would not recommend you to follow this approach...what i do is to select all beams before running my model and goto ASSIGN>FRAME>MODIFIERS and apply it...second you didnt apply torsion modifiers...

Details of the building r as follows.

4-story building

X-direction spacing = 6 @10 feet

Y-direction spacing =2 @20 feet

One way slab

Load is assigned using Shell/area loads ( I selected all panels of one story then applied the shell/area load dead, live et.c then for next story) but the load is not fully transferred to column etc, why? After analyzing the stress diagram looks odd to me.

you need to understand here the basic concepts of shell and membrane..how they behave in etabs...your system is one way slab supported by beams all around..so why you are using shell assignment in slabs? You should use membrane so the load is transferred to beams by tributary area...(as you do manually..thats why i told you to do it manual before doing it on etabs)...anyway...you can still design beams with shell slabs with a fine meshing..but at this stage you shoud have considered membrane slabs...it will be more realsitic to your manual calculations. You applied shell slabs so the load is transfered to four corners points and going to columns in form of axial loads...if you goto DISPLAY>SHOW LOADS>FRAME you will see that the options are disabled because etabs is unable to show you transferred loading...because you didnt apply membrane..

Rcc wall is used in basement. Auto meshing is done 4x4

I dont know why you applied wall modifiers equal to 0.1..this is too much cracked section...apply only m11 and m22 = 0.7 here in your example...try to get concept about cracking of various structural elements...

Seismic effect is not taken into account so only one load combo is used. I deleted the others but after analysis they were shown why??

Dont worry about other load combinations they are automatically generated...but you should check what combinations you are including in your design...it will design only on the combinations which you have slected in DESIGN>CONCRETE FRAME>SELECT DESIGN COMBOS....

How I will know that any member is failing and I need to change it??

Your members are having green color after designing..it means they are all passed..if any member fails it shows RED color...for that you need to change the sections or investigate other matters with that beam or col etc...

In final design we show the bar, spacing, etc but as I mentioned it is change for every sections so how I should finalize this for column beam and what for rcc wall?? After analysis it looks like that no load is transferred to it..

Like for slabs...walls moments shall be read manually on specific load combinations...and designed for reinforcement..or you can assign it pier labels...

Kindly check this model by performing manual checks on it. Waiting for ur response.

I have applied corrections to your model..please download this and use it..but as i said....design this simple case your self manually...and compare...

want to learn from ur experience

thanks in advance

You are always welcome...

some more comments:-

dont apply raft in your etabs model..export the reactions to SAFE and model raft there...or if you want to model it in etabs..then dont apply fixed supports..apply area springs according to your soil properties...in your model i have removed the raft...

you applied PLATE option for RAFT..but you should be familiar with the differences between MEMBRANE, PLATE and SHELL...

This time i have applied modifiers according to your approach...( inside frame section properties..) now you should not select the beams or cols and goto ASSING>FRAME>MODIFIERS...dont apply it again..otherwise it will be duplicated and etabs will multiply both values...i mean if you applied inside 0.25 and then from menu again 0.25 so it will consider 0.25x0.25

remember i have changed your slabs to MEMBRANE..so no need to apply meshing to MEMBRANE...also before designing your sections select sway ordinary as in your case the frame is not sway frame...

still i didnt applied manual checks..you should do it your self...calculate the tributary area of any column and multiply by load..and see if your base reaction for that column is okay or not? check the loading of a beam manually and compare with etabs...

calculate the moments of any frame on a grid by ACI 8.3 approx coefficients method and compare...or you can moment redistribution methid,,,

now u must be thinking how hard struc engg...makes the life...

my version is 9.7.4 so im attaching only text file..import it in your etabs model...

good luck

assignment_checked.zip

[WR1]

check different etabs topics in this forum and other internet sources...

check answers by arshad khan here:

http://en.allexperts.com/q/Civil-Engineering-1357/indexExp_18389.htm

[haro0n]

sir first of all thnks for replying in that much detail. and yes i have started this so inshALLAH it will keep this going. and i am in my final year 7th smstr. i am also doing this manually and i want to compare it with etabs for that reason i am doing it in etabs but i can compare it when i will do it correctly in etabs so thats why i shared it here so that i came to know how to do it correctly as if i dont do it correclty then results will not match.

u pointed alot of things and i have started working on it but its really very difficult after reading about different thing here on SEFP i came to know that i knows nothing about structurl engrg its very tought..

one of our teacher taught us about this so i did it in that way plus other help taken from differnt soucres and i am combining that all so thats why there r mistakes about applying modifiers, assigng slab as shell etc .

sir i have noted these all and also doing it manually nd will return back after that with more questions

thnks again 4 ur time

[kHURRAM ALI]

for distribution of steel in beam of etabs
PLEASE DOWNLOADTHIS IMAGE