Ahmed Waqar

On 7/30/2018 at 9:40 AM, Hamza Ahmad said:

AOA..

In foundation (Isolated) why we use reinforcement in the compression zone...?? 

Top reinforcement is provided when thickness is huge there are chances of shrinkage otherwise no steel required. In cases where water table is high top steel is also provided like Faisalabad Sargodga NIP

How you computed the modulus of subgrade for settlements and bearing capacity checks. Not for structural design

Have you checked the settlements. What is modulus of sub grade that you have taken. If you computed modulus of subgrade then multiply by FOS then you are using ultimate capacity of soil. For geotechnical design that's not workable. Check settlements if they are in range then ok. These are my view only...

Earth quake loads consider in foundation designs as well in its sizing as well as in its structural design. If someone omits, it purely his own choice

Send me link to download limcon please. You may check the result at RISA connection and STAAD RAM connection

Bo at the edge and corner is different moreover there are 2 more formulas if punching for corner and edge columns. If you consider this then see result

Dear Mr Iqbal

Correct me if I am wrong.

Suggestions

G+5 is not too much load we are not talking about. And bearing capacity is reasonably fine considering the magnitude of building. You can easily do the foundation with mat type. Its 44' span that must be govern as it will become one way;. In the you will get too much top moment. Moreover as most of load is concentrated on the edges it is recommended to cantilver your foundation as much as you can, 

Slabs

For slab just go for one way slab with main beams are 44' in length. Please make sure that one way spans shall be around 10 to 14ft. as this will drastic reduces your deflections. Make sure to remain one way slab, otherwise cross beams will create too much torsional moments.

These are suggestions only,

14 hours ago, UmarMakhzumi said:

Ahmed,

So you will have to enter modifier shear modulus manually.

For the above mode, you need to define at least 3 materiel properties. One for Beams (0.5*E), one for slabs(0.25*E) and one for columns and shear walls (0.7*E). I totally agree with Rana that tweaking modulus of elasticity is not a wise thing to do, but you can at least give it a shot and do a quick comparison with ETABS to see how off your results are.

Your understanding is not correct. When you change E, everything for that material would be based on modified E, not original E.

Thanks.

 

Thanks for the feedback. 

Frame elements like line elements and plate elements stiffness modifier will easily work. Now we left with shear walls. What i am saying is create new material profile for shear wall concrete. its stiffness for flexural desformations are 3EI/L (cube) and varies to 12EI/L(cube). Greater the shear walls greater is the trend towards cantilever nature of wall.Now we remain ourselves is elastic analysis of first and second order. As far as material is elastic its properties are well defined as per established principles of mechanics. Now we just change I to 0.7 of I which is stiffness modifier. In staad we cannot achieve this with ease like other elements (as per my knowledge of staad) So my proposal is just to change E to 0.7 of E instead of I. You will get the same results. Its simple mathematics. But this E is of shear wall only and precisely in flexural deformations only. Which is primarily over concern,

Thanks for the above feedback. I dont know of other softwares but in STAAD Pro, You have to give all the properties of the material if there is any change. Now, E of shear wall is the change material. And we know the pupose of shear wall is to reduce lateral displacements and to take lateral load as per his stiffness and that will be the fuction of EI. So only E will be change and all other parameters will be on E original characteristics. Correct me if I am wrong.

Agreed, @engruzair

YUP. Its an indirect way. As stiffness is the function of EI/L, Instead of changing I, just change E to 0.7 results will be same. 

Respected All,

Am doing shear wall analysis and design. Property reduction factors are easily incorporated in Frame elements. but for shear walls property modifiers i didnt find any. Please guide me that how can i change the property reduction factors of shear walls in STAAD Pro 

Agreed With Engr Uzair. Strap beam width is generally larger than to column dimension just to avoid massive congestion. Otherwise it has nothing to do with design.

Thanks Mr Umar.

There is book low price edition by an indian author "Design of folded plates and domes" By Prentice Hall of India can easily be purchased by paramount book stores. Domes and shells can easily be designed by STAAD pro as well

Correct I am wrong. As per UBC # of modes shall be such that it incorporates 90% of participating mass. If participating mass is 90% in first two modes then no need of other modes. If 90% is acheiving in first 6 modes then first 6 modes are sufficient. If 90% is not acheiving then you have to scale your spectrum. In STAAD add missing mass value.

Also, I have worked on STAAD mostly. If you require STAAD model then i can attach it as well.

Thanks to above all for your prompt response.

Thanks Mr Uzair.

But if we dont divide it by "R" then base shear becomes almost twice. which is too much. Means we are designing our building ir-respective of the detailing and any structural system as stated in UBC we are giving full earthquake to the structure. Which make no sense to me. Can you please guide me further. If you have any expereince with response spectrum analysis in projects then please share. 

Dear Mr Umar Makhzumi

Thanks for the feedback!

Artcle # 1631.2 Ground Motion of UBC

It is stated as "The ground motion shall not be reduced by quantity R" so code saying you have to apply full non linear earthquake not being divided by R. Please guide me if i put something wrong.

Respected Sir

May you please guide me that how to perform P Delta analysis on STAAD Pro in Concrete Building.

Dear All

If we doing response spectrum analysis as per UBC. do we need to lower our base shear because in UBC it is stated that direct result from spectrum shall be used to design for eerthquakes. If we do so then where is R value.