 last class we have finished last two class design of this counter four retaining walls we are continuing with this design of counter four retaining walls in this part we have finished this for a particular counter four retaining wall the height was given we have finished for this first step one your dimensions step two stability analysis step three structural design part of your toe slab heel slab upright slab as well as counter four walls now we are going to do this connection between this counter four and the upright slabs if this is my counter four walls this is your retaining wall and in this retaining wall counter four these are the counter fours counter four has been connected between your upright slab if this called upright slab between upright slabs and counter four and heel slab and counter fours now how this connection has to be made that design part we left it and as well as your drawings so now connection between counter four and upright slab so consider the bottom of one meter deep strip of upright slab the consider the bottom one meter deep of the strip so the pressure on the strip on strip we have calculated earlier three three six thousand Newton per meter square lateral earth pressure transferred to the counter four for one meter height lateral earth pressure transferred to counter four for one meter height which is equal to thirty three thousand six hundred into three minus zero point four two it comes out to be eight six six eight eight Newton so steel required per meter height steel required per meter height per meter height is about eight six six eight eight by stress in steel is your hundred forty it comes about six twenty mm square so you can take eight mm five bars five bars at a spacing at a spacing you can take it as a eighty mm center to center now similarly connection between counter four and heel slab counter four and heel slab so tension transferred in one meter width of the counter four near the heel slab and how much tension transferred in one meter width of counter four near the heel slab it comes about to be transferred it comes about to be five zero one zero three three minus zero point four two which is equal to one two nine two six six Newton so steel required steel required which is equal to one two nine two six six by hundred forty this about nine twenty three mm square we can consider eight mm five two leg it is a two leg bar two leg bar in this case also eight mm five two leg bar at a spacing of hundred mm center to center now the question was once the structural design part is over how this counter four has been connected to your upright slab as well as how the counter four has been connected to your heel slab the connection the steel required for the connection that means your tie bars about eight mm five bars in case of counter four and upright slab eighty mm center to center it is a two leg similarly eight mm five bar for counter four and heel slab spacing hundred mm center to center it is again a two leg bar if I draw simple now if I draw this how this drawing looks like if you look at these bars to be connected now this way this drawing has to be provided so this comes out to be this dimension your this dimension your like the same dimension this is your this center dimension for this this is your four twenty mm and this about your zero point four meter so now if I am writing it you have to show this which is main bar which is your reinforcement bars this is your sixteen mm five at the rate hundred mm center to center and this part is your twelve mm five at the rate hundred forty mm center to center and this your eight mm five at the rate hundred twenty mm center to center and this also all the bars means which is your main which is your shear reinforcement you have to show it very clearly eight mm five bar at the rate hundred twenty mm center to center and these two are these two are main reinforcement that means this is your sixteen mm five at the rate hundred sixty mm center to center and these also these are all your shear reinforcement eight mm five at the rate two twenty mm center to center this is your cross sectional elevation midway between the counter four if this will continue this retaining wall will continue in this way if it will continue in this way like this it is every you can say that every three meter interval your counter four is there this cross sectional has been taken where this counter four wall is there and this reinforcement bar has been shown if you look at here in this case these two are is your main reinforcement this is your sixteen mm five bars at the rate hundred sixty mm center to center these are all your shear distribution this is your eight mm five bars at the rate two twenty mm center to center we have also calculated in this case this one is your main reinforcement because it deflect like this the pressure will be more at this and pressure will be less in this case the pressure in the vertical will be more and it will be deflected in this way that is why this is the this is the main reinforcement in this case in this case this part is your main reinforcement at it can be extended it can be extended at the both the ends. So, this main reinforcement for tow slab it is about sixteen mm five at the rate hundred mm center to center for heel slab this is about twelve mm five bar at the rate hundred forty mm center to center rest is your these are all your shear reinforcement these are all your shear reinforcement then this bars alternative bars has been extended here it can be put it as a as a additional bars both the sides. So, that monetarily or may be additional instead of providing additional bars this bar may be extended here and here. So, that it can be adjust now if I take cross sectional elevation how it looks I just put it this bars then I can show this how this curtailment has can be made curtailment can be made if you look at here as I have calculated I said earlier how this curtailment has been made I can say that up to three point one meter three point one meter. So, it will be two bars eighteen mm five this is for counter four then up to four point four meter up to four point four point four meter this will be four bars at the four four bars of eighteen mm five eighteen mm five diameter then up to your six point you can say that five point five meter five point five meter this will be six bars six bars eighteen mm five. So, at this case this will be your eight bars eighteen mm five if you look at this two parts one is your cross sectional view of cross sectional elevation view of this where this counter four is passing then you make it this counter four. So, from there we say that this is my main reinforcement these are my shear reinforcement for tow slab this is my main reinforcement this is the shear reinforcement similarly this is the main reinforcement this is the shear reinforcement. Now, if I come back to counter four there are total eight bars required in this case if you look at the here every section there is a curtailment of bars. So, here we have already calculated in three point one meter there are only two bars at the top then at four point four meter there are only four bars of eighteen mm five at five point five meter at five point five meter there are only six bars of eighteen mm five at the bottom that means six point one there are eight eight bars of eighteen mm five. So, once you show these two diagrams after the design this field engineer they can understand that that means whatever bar they are going to provide how they are going to curtail and how many number of bars they are supposed to cut it will be clearly spelled out. So, this completes your complete design of your counter four retaining wall as well as cantilever retaining wall. So, we have followed this design into three steps just for a quick review we have followed into into three steps. So, first one is your dimension first one is your dimension tentative dimensions you start with this tentative dimensions then with this tentative dimension check this stability analysis check this stability analysis stability analysis there are four one is your overturning second is your sliding third is your tension crack bearing capacity then third part is your structural design. So, there are three part three steps we follow generally in design of cantilever as well as counter four retaining wall first one is your tentative dimensions. So, there are set of dimensions with this tentative dimensions then you check your stability analysis stability analysis there are four four parts of stability analysis one is your overturning movement second is your sliding tension crack and bearing capacity if stability analysis is that means if it is stable that means this stable with respect to your assumed value of tentative dimensions that means there is no change in tentative dimensions. If this stability value is not coming then maybe you can change your tentative dimensions or maybe try to put your key if sliding value is less than 1.5 one step one and step two has been satisfied then we go for a structural design basic structural design. So, we provide shear reinforcement main reinforcement also we can say that in this structural design we show that main reinforcement main reinforcement then shear reinforcement shear reinforcement main reinforcement as well as your curtailment of curtailment of bars curtailment of bars. So, main reinforcement shear reinforcement and curtailment of bars and once this structural design is over this completes your complete design of cantilever as well as counter four retaining walls. So, once the design is over we will have to show this sectional view how this steels are going where is your main reinforcement where is your shear reinforcement as well as I said in the earlier also previous diagram you can show that curtailment of bars at what distance from the top and what are the number of bars to be curtailed it may be alternative bar it may be quarterly bars what are the bars to be curtailed then this finish your complete design of your cantilever as well as counter four retaining walls. Now start with one more thing most important part in this cantilever and counter four that is a new thing. So, sometimes this counter four walls we provide counter four walls with relief platform with relief platforms or it called sleeves or sleeves counter four walls with relief platforms. So, sometimes what happen in this counter four retaining wall this stability analysis may not satisfy even if within this permissible values of your tentative dimensions. So, the moment you provide your relief platform or sleeves this it becomes more stable it become more stable if I draw it how it looks the cross sectional part of this how this counter four retaining wall with relief sleeves how it looks with this is my you can say this is the I can make it this is a typical counter four retaining wall with this counter four retaining wall generally every cross section every cross section every in the sectional view at regular intervals we provide relief walls relief slab or relief self we provide this this is the relief sleeve what is the use of the relief sleeve this relief platforms or sleeves once you provide it says that it will be more stable how far it is going to change your earth pressure distribution diagram we will see it now let me draw a bigger picture of your counter four retaining wall. So, if I see this that means relief platforms or sleeves has to be provided at regular interval these are all your relief sleeves or relief platform has been provided. So, what exactly going to happen. So, this suppose this length is l 1 and this is l 2. So, if I draw here this will retain the soil mass of gamma 1 gamma h 1 and this will retain the soil mass of gamma h 2 and let us say above this there are also surcharge acting on this surcharge if I make the extension of this let it be rho. So, l 2 comes out to be h 3 cos rho cos rho then you can find it out l 1 l 2 all the value you can find it out this also comes out to be rho this also comes out to be rho. Now if I draw the pressure distribution diagram earth pressure distribution diagram without providing relief shelves for cantilever retaining walls a counter four retaining walls this is my earth pressure distribution diagram. The moment you provide your relief walls relief walls what will happen or relief this is the value of e 1 this is the value of e 2 this is the value of e 3 and this is the value of e 4 and let us say this part is your h 1 and this to be h 2 this should be h 3 this should be h 4 height h 4. So, if you look at this complete picture this figure without any relief platforms or sleeves how without any relief platforms this is my relief platforms or sleeves at alternate means at regular interval we provided if there is no relief platform or sleeves what will happen what is your pressure distribution diagram the pressure distribution diagram will be complete triangular. So, it will come there the moment you apply relief platforms or sleeves sleeves your pressure distribution diagram it will be like this you see this is this is how much pressure how much pressure has been reduced earth pressure coming to this retaining wall has been reduced without relief platforms or sleeves the pressure distribution diagram is your triangular the moment you provide your sleeves or relief platforms that means up to this height up to this height say h 1 this height is your h 1 and this height is your h 2 this is your h 3 this is your h 4 for h 1 entire soil mass entire soil mass whatever the weight coming it will be taken by your relief sleeves or relief platforms. So, that means your earth pressure for this case is your e 1 below this relief platform from here to here this part of only soil will take. So, earth pressure instead of starting from here it will start from this l 1 and it will go there this is your reduction of earth pressure distribution diagram in this case because of your relief platforms or sleeves. So, then what will happen for then you take individual cases like height h 1 what is your earth pressure height h 2 what is your earth pressure height h 3 what is your earth pressure height h 4 what is your earth pressure for all together for 4 heights you find it out your earth pressure. So, this part of the earth pressure will be reduced in this case. So, the height you can increase by providing relief platforms or sleeves the height of this counter for retaining wall can be increased. So, you can also go for whatever height for counter for retaining wall without relief sleeves it will be 1.5 times more than providing your relief sleeves or relief platforms or sleeves. So, this is a new new development generally earlier days try for cantilever wall if it is not stable then go for counter for wall if it is not stable then go for counter for retaining wall with relief platform. And this design is same design is same this relief platform only provided to reduce your earth pressure, but rest design is same you can check this stability analysis by taking your tentative dimensions then once the dimension has to be satisfied stability analysis has to be satisfied that means the dimension is ok. Then after the dimension is ok then you can go for your structural design while doing this structural design you consider for your modified value even if for overturning moment modified value of your earth pressure earlier this earth pressure is complete triangular in this case earth pressure will be reduced. So, modified value of earth pressure will have to consider for subsequent design point of view. Other part of this stability analysis about your tentative dimensions structural design is same this relief sleeves or self or the relief platforms it is only to provide to reduce your earth pressure nothing else it will only to reduce your earth pressure. So, that you can increase this height of the wall or may be counter for retaining walls are more stable I will stop it here I can start my next lecture in a new topic there thanks a lot.