Waqar Saleem

how to design the basement walls fir the vertical loads? is it correct to take 1feet strip and check for stresses against vertical loads and provide the required reinforcement just like the slab is designed?

ask some experienced person who have site experience or a senior QS he would tell you hopefully or consult ESTIMATING AND COSTING in CIVIL ENGINEERING by B.N. Dutta,there are some examples given to select the time and hours for differnt works done.

i am afraid sir i disagree at the point then why we do not take the load of slab on beam as cantilever in more exact form that slab is projecting on the beam,then we should take triangular cantilever portion of slab on the beam on shrter side and trapezoidal cantilever portion on the other longer side.it makes more sense as slab is cantilever from the beam not on the top side of the beam. don't mind sir i am argueing to clarify myself.

sir my point of view is that triangular/trapezoidal loading comes from the slab but on beam we take it as uniform loading,the picture a shered above is not continouos beam it is the two sides of one span beams taking loading from shorter and longer side of slab.hope you got my point

sorry sir that fig was misunderstood by me check this attahed fig. it will clear what i need to say

there are moderators who haven't visited the forum for months .even visiting faculty members and visiting students visit classes once a week at least.

thanx RAna bro

@RANA thanx sir but this is not the triangular load on the beam in the sense you described here.load on the triangular area of slab of slab is distributed over the beam but it is not the triangular load in exact sense.this is the tributry area for the beam which is triangular or trapezoidal. Kindly consider the chapter 14 of Nilson 13e yieldline analysis for slabs fig 14.1 and fig 14.2

it means for noraml building where we are not considering seismic loads there is no need of defining "mass sorce"

@haroon there is no option for single span beam fixed at ends so i mentioned earliar that check the moment diagram for that and BMD for one beam would be same as the one for fig d.so we can use the coefficents of that option.

thanx Rana it is clear how loads are distributed in two way slab at 45 degrees as you have shown the fig.why do we multiply the loads with factors 1.33 and 1.30 what is the reason?any reference to these factors.as you said we multiply these factors for converting the loads to simple uniform loading on beams from slab,even then the laod on the shorter side will be different from the load on longer side.also why the factor for shorter span is 1.33 and greater than the factor for longer side.in actual sense shorter span beam takes lesser load.

what loadings are you applying on the slab?what is the live load and what is the dead included all finshes and insulations or if you have taken only dead,plz let me know.and how is it possible that with same loading on the slab a beam with span of 10' and other with 20' carrying same load.even if one is carrying triangular portion and other is taking trapezoidal.you yourself calculated it above "remember it will distribute load by 45 degree method you despite that your slab is 10x20 (1way and your short beams will carry nothing) but if you do it by 45 degree your short beams will also have 625lb/ft load for live loading... I did this in another way like this, 10x20=200 so ¼ of this 200ft^2 will be for shorter beams that is 50ft^2 so 25 for one shorter beam and 25 for other so our live load is 125 so for shorter end beam 125 x 25/10=312.5 lb/ft udl for shorter end beam. For longer beam xied it with 75ft^2.. 625 lb/ft will be triangular load so we have to convert it into udl then use it. The way I am doing is right?? If found it very easy so doing by this."

@Rana sir moment coefficients are not 1/12 and 1/24 here . @haroon , moments in the continous beam need to be caculated by coefficient method and where you are taking them wl^2/8 that is incorrect.for beam use Nilson pg#396,for shorter beams fig(a) use column option as support i.e 1/16,1/14/,1/10and for 2span longer beams fig ( also the column option 1/16,1/14.in case of yours only one beam fixed at both ends use the fig d coefficients look at the BMD of the d option you will get my point. @rana sir when slab is 10x20 then it can be considered one way or two way ,etabs take it two way and distributes the loads in that way on both side beams by yield line theory method of distributing loads at 45 degrees.you said that the loads on both shorter and longer span both be same 625lbs so that would not be possible. @haroon PLATE beahaves like a beam it resist by bending only no horizontal stresses are distributed,they can bend in two direction i.e up and down and twist. MEMBRANE take only horizontal stresses and can not bend.this is known as membrane action also SHELL have both the charactersistics of membrane and plate. this is the simplest difference among the three.the idea is hard to aplly in practical.

Salam waqac nominal shear strength is the sum of the two 1.shear strength by concrete,Vc and 2.shear strength by steel reinforcement, Vs. the expression for the Vc you mentioned is used for manual calculations and is a bit conservative and ACI put a limit on it for the sqrt(fc') should not be greater than 100.also this expression is based on the test results for concrete fc' 3000-5000psi,when we increase the fc' shear strength of concrete decreases further than 6000psi.at first there is shear is only resisted by concrete and there is no steel reinforcemnt is required at all but ACI requires a minimum shear reinforcement.so at first only small shear reinforcement adds greater than to Vc which might be greater than the expression you mentioned actullay.there is limit of Vc must not be greater than 3.5 sqrt(fc')bd,it can actually be greater than this but ACI have put the limitation.so this could be the reason for the difference in experimental and theoretical results. if you have mentioned the compressive strength of concrete you used in the tests and the the location of beam X-section where you have observed the shear crackes one can comment more easily.

@KHALID sir i dint ask for the shortcut, i love to study i was of the view about suggesting some good books or article about dome ...

http://www.nts.org.pk/ntsweb/SBP_30Dec2012/SBP.htm

i guess,segregation doesn't have types but it could have different reasons to be segregated on that basis we can say it have kinds. i found three types at http://www.aboutcivi...cting-them.html Segregation may be of three types Coarse aggregate separating out or settling down from the rest of the matrix. Paste separating away from coarse aggregate. Water separating out from the rest of the material being a material of lowest specific gravity.

i have a problem in RC book for the design of isolated footing but there is no bearing capacity given.in problem just mentioned that soil is sandy clay and i found bearing capacity for sandy clay 1500psf on the net and according to this have to take 17-ft square footing for the given 12-in square column,with D=150k and L=100k, depth of footing base is 5' .one engineer said that take more than 1tonne i took 1.3tsf=2.87psf,using this i get 10-ft square footing.plz suggest what wud be the bearing capacity for this problem.

please differentiate shell and membrane ?how do we say that one slab is membrane and other is shell or plate ?

@RANA when we say that uncracked section has more inertia and more stiffness and more moment taking but cracked section has less inertia and less stiffness and less moment taking,inertia is the geometric property moment taking is related to strength, uncracked concrete section has less strength than cracked section so sir Rana what do you say about that?also in case of concrete when section is cracked it means it has started taking loads otherwise its strength is not fully generated so what about the stiffness of cracked and uncracked section?

Respected Members, what is the main purpose of property modifiers in defining farme sections in etabs and how we can relate them to theoretical knowledge??

i request all seniors that in your profile please add your specialization on the profile or in some new thread so to help final year students to target you for guidance and discussion i make this request more precise that seniors who have experience in performance-based design or related to this topic ...

sir i need the email and contact number of your friend who had thesis on the performance based design if possible plz trace him out? who was his supervisor/guide if you know plz let me know i be thankful...

thanx...

thanx sir