WR1

modular ratio is used in cracking analysis. Its used in stress strain compatibility because reinforced concrete is not just 1 material. Its concrete and the bars. Anyway, composite construction means where concrete is used with structural steel. For example concrete topping and steel metal deck. So in such cases modular ratio is often increased.

yeah in all cases in beams, footings and slabs but mind you this is a research-type thing. You dont have to involve in this unless you are really doing some hifi task. Anyway thanks for your deep interest. I personally like your questions because they are different and to me sometimes difficult to answer. But i love to reply them. You have got a curious mind and i love those people. lets b friends

dead load is redcued for uplift ..this is actually the load factor like 1.2d and 1.6L but in case of uplift we reduce it bcz the only thing resisting the uplift is dead load..so we reduce it (means the concept is same as in 1.2d + 1.6L) its actually a stability issue even 0.6D is used in wind combos

I have used modular ratio of 15 in composite concrete. Its normal

yeah it is true for deep beams the shear strength decreases with increase in size. Its called sizing effects. Its been proven from concrete research. Deep beams provisions shear is different from normal beams. there are many factors involved for example the increase in sizes of concrete members and compressive strength the ductility is reduced. but for normal deep beams the code quation with factor 2 holds good unless you are doing research or desiging a critical member having high shear force. http://www.ias.ac.in/sadhana/Pdf2012Feb/89.pdf

i think the large continous sway was because of the resonance...although it the ductility of the steel was remarkable

its not necessary that you put in 45 degree you can also add this amount in the x and y direction rebars...usually the required area at the discontinous ends will be less and it can easliy be accounted for. If you are designing in SAFE it will automatically include everything in rebar areas or moment contours of M11 and M22 but just remember to add M12 in both M11 and M22 conservatively

i didnt find that text under the same topic in 14th edition of nilson book which i have..

usually if your edge beams have significant torsion stiffness the positive moments in edge panel will be reduced but negative moments in edge panel will be increased...

pls quote the referenced section of the book!

check the units and make sure you applied correct loads...may be the load u apply is 100psf but you didnt select the proper units. check the stability of the model joint shear is not necessary unless its in a high seismic zone similarly beam column ratio check the story height and material properties

and what about seismic drift....what combination to use..i believe its only static load case that is only EQx, EQy etc..no combination....

but those combinations are strength combination using 50 year return period. In ASCE commentary the equation is D+0.5L+0.7W

k also tell me what is the load combination to check drift on both seismic and wind?

So it means for wind drifts one must use! Ig for beams = 0.5 and for columns =1.0 If seismic then use according to chapter 10?

thanks baz, another confusion In ACI R8.8 it states two options for use of stiffness modifers... option a & b Option a is what we use in ETABS And in commentary it states that its intended for strength design but at the same time the deflections or drifts from wind or quake can also be read from the same model. So no need to make another model or to use another set of modifiers...Is my interpretation right?

as a whole we dont go in tiny details like adjusting cardinal points....remember that there are 100 ways to pass a failed member but just dont do it..its not practical to adjust each and every beam and column by selecting appropriate cardinal points..just do center to center...struc analsyis is based on center to center..there are ways and means to be on the safer side.. I mean you should limit your interaction reatio for columns upto 0.8 not more than that instead of 0.99...So put more attention on the results rather being lost in model making perfection (like what i used to be in past )

First of all you should refer to ACI 318 by year too. I mean the clause you mentioned is from ACI 2005 or 2008. Because numbering of the clauses has been changed. So 8.2.1.6 in 2005 is different from 8.2.1.6 rather there is no such 8.2.16 in 2008 version. Anyway, Regarding your question of minimum reinforcement. Always remember that reversal of moments or forces takes place for example in wind or eartquake. So your positive moment becomes negative and vice versa. For example in a blast loading your slab may crack because in middle span the top reinforcement you provided was insufficient. That is the region where you can ignore the reinforcement generally. Thats why ACI has some limits for minimum reinforcement, although the minimum reinfocement will still not be enough for blast loading but thats another issue. Minimum reinforcement is different than the temperature and shrinkage reinforcement. For example Temp reinforcement (0.0018bh) is the total area of steel you have to put in slab or footing. Put half at top and half at bottom or total at mid..whatever..ok! But 0.0018bh if you talk about min flexural reinf you have to put full at top and and full at bottom.

May be my questions seem stupid but just for the sake of disucssion today I have posted this to Mr. Arshad Khan, Civilea forum and SEFP forum. Looking forward to arrange all the answers by you guyz and write a tutorial Dear all, I have following question regarding slenderness in ETABS 1) Why moment magnification method and 2nd order elastic method both are used by ETABS. I mean in ACI there are 3 methods to do (any of them) then why we put modifiers and then ETABS calculates internally the moment magnification factors. 2) If structure is braced then how to stop etabs from calculating moment magnification? 3) If drift limits are defined for example in ASCE H/400 then why is the need to perform P-delta. If we control the drifts to be H/400 still we need to perform p-delta? 4) We take wind drifts for 10 year return period. that is multiplying 0.7 to W of 50 year year..to convert this into service level....What type of modifiers are required to be put in ETABS to take drift or deflections on this 10 year Wind.. Serive modifiers Beam=0.5 & Column=1.0 or Ultimate modfiers Beam=0.35 & Column=1.0 I mean as per ACI we can multipy the deflections from ETABS to 1.43 if we use strength level modifiers?

kam kam aur kam!

about 14 hrs and 45 minutes... what abt ya!

Where are my guyz! cmon! post something!

due to high load on foundation lean is converted into fine powder...(crushing) simple....permissible settlement varies..but generally its 1 inch or 25mm!

Dear jammer! The angle theta you are talking about is the angle of bank of the backfill with the horizontal. But the question Waqar asked is about the angle of the face of the wall...such that there is additional wedge of soil Waqar, If the wall is inclined towards backfill, then there is passive earthpressure If wall is moving away from backfill then its called Active earthpressure. There are many theories...to calculate it...most famous are the one mentioned above by Baz You have to keep in mind about the notation of different angles Phi is the angle of internal friction of backfill....Tanget of which is the angle of repose of that material (approx.) angle of repose is the angle by which that material is retained..in stable form.. Delta (or theta according to jammer) is the angle of backfill bank with horizontal Many books and authors use sometimes different notations for each angle..so be careful Now i would recommend you a book called REINFORCED CONCRETE DESIGN 11th edition by REYNOLD Read its chapter about RETAINED MATERIAL...for you i have attached the snapshots for calculating the active and passive pressure

YEAH ITS OBVIOUS...