 So, let us discuss about design of dog leg distal, learning outcomes. At the end of session, the learners will be able to explain the procedure for determining the effective horizontal span and effective thickness of waist slab for each flight of a dog leg distal and also to determine the reinforcement required for each flight and sketch the reinforcement detailing arrangement. Introduction, staircase is a means of giving access to two different floors of or levels of a building and are used to in almost all buildings. It consists of number of steps arranged in a way that the person can move from one level to another level. The arrangement of steps is as per the convenience and as per the standards and the space availability. The common stairs used are as follow is straight straights, quarter turn stairs, open well stairs, dog leg stairs, circular and spiral stairs. So, further we have folded stairs also. So, figure one shows the different types of stairs. So, this is straight stair. In a straight stair if the number of steps are more than 15, then we go for with a mid landing in a straight stair also. Then next this is quarter turn stair and this is quarter turn stair with winders and this is a open well stair with half landing and this is open well stair with a quarter landing and this is the dog leg stair which we are going to discuss today and this is a circular stair and this is a spiral stair which is usually used for water tanks. So, this figure shows the elements of stairs. So, figure two shows the elements of stairs. So, in the elements of stairs we are having trade, then we are having rise. Rise is the height of each particular step and the portion which is horizontal that is called going and here any projection of this upper one upper flooring that is called as nosing. So, this is the waist slab at the bottom this is thickness of waist slab and this is landing portion. Now, let us discuss each rise. Rise is the vertical distance between the two successive steps is termed as riser or rise. Trade the horizontal top portion of the step where foot rest is known as a tread. The nosing it comes it in some cases trade is having projected is projected outward to increase the space. So, this projection is designated as nosing waist. The thickness of waist slab on which the steps are made to known as the waist slab that is made to rest are known as a waist slab then going. Going is the horizontal portion between the first and the last risers on an inclined flight. Inclined flight is inclined waist slab it is landing. A landing is the area of the floor near the top or bottom step of a stair and in and intermediate landing is a small platform that is built as a part of the uh allow stair to hang projections directions to change the directions or to allow the user to rest his feet dog leg stair. So, this is the most commonly used stair since the succeeding flight rise raise in opposite direction and occupies minimum plan area. A landing is provided corresponding to the level at which the direction of flight changes. A plan of the dog leg stair is shown in figure number 3. This is figure number 3. This shows the plan of a dog leg stair here you will find. So, this is up and far from the beginning then up this is mid landing. So, mid landing again there will be a change in direction. For design of dog leg stair vertical distance between the floors that is H is to be given. The assume the width of the stair shall be minimum 1 meter for residential building and 1.2 meter for public building. So, the rise are usually 170 mm for residential building and 150 mm for public buildings and trade T it is 250 mm for residential building and 300 mm for public building. So, depending upon the nature of building and availability of space we have to assume the width of the stair rise and trade then this is a plan. Now, the design of dog leg stair dog leg stair always consists of 2 flights. So, height of each flight the floor to floor height divided by 2 that is H by 2. So, no risers in each flight sorry number of risers in each flight is equal to the height of each flight divided by rise. So, the number of trades in each flight is number of risers minus 1. So, if we get number of risers some real number then we have to round it to the next one. Effective span the stair slab spanning longitudinally depending upon the supports the effective span is the horizontal distance between center to center of the supports load calculations. To determine the dead load of the waste slab it is necessary to assume the effective thickness of the waste slab which is 128 to 125th of the effective span. The total thickness T is effective thickness plus the effective cover to find the total load per meter horizontal width of stair weight of waste slab is equal to T into square root of 1 plus R by T square into density of concrete. Weight of steps half R into T into T divided by T that is to bring it to horizontal portion into density of concrete. Dead load ongoing portion is weight of waste slab plus weight of steps plus weight of finishing. Dead load on loading portion landing portion is weight of slab plus waste slab plus weight of finishing. Assuming the weight of finishing assume the weight of finishing as maximum 1 kilo Newton per meter square. The live load is to be taken as per IS 875 part 2 the total load is dead load plus live total factor load is 1.5 times the total load. The projected loading diagram for a total factored load is shown in figure 4. The loading on the loading loading on the going portion as is landing and going portion are same or not. Can you guess whether the loading will be same on and on the landing portion and going portion? The loading on the landing and going portion are different. So, here we have only the dead weight of the waste slab and live load and here in the going portion we have dead weight of the waste slab then the live load and dead weight of steps also. So, that is why there is a difference between the loading on the landing and loading on the going steps or going portion. So, then determination of maximum design bending moment. The maximum bending moment will be at the center of the flight because loading is symmetrical and find the support reactions first then afterwards find emu limit it is 0.36 fck b into x u limit into d minus 0.4 to x u limit x u limit is equal to 0.48 for fe 405 0.46 d for fe 500 and 0.53 d for mild steel. Compare emu limit with emu if emu is less than emu limit it is under reinforced section find the area of longitudinal steel. Find the area of longitudinal steel by this particular expression est is equal to 0.5 fck bd upon fy into 1 minus square root of 1 minus 4.6 emu upon fck bd square. Find the spacing from the below formula sv is equal to 0.87 fy svd divided by v us. So, find the low find area of distribution steel it is 0.12 percent of bd and spacing using ABO formula. Draw neat sketch and detailed sketch shows the stairs showing the reinforcement arrangement as shown in figure number six sorry figure number six shows the sketch of reinforcement arrangement. So, here we find this is landing slab this is waste slab which is inclined this is again upper landing slab. So, in the landing portion we find only the dead weight of landing slab as well as the dead weight of the finishing portion and a live load and in the going portion this is going portion from first riser to last riser it is going portion. So, in the going portion we have the weight of waste slab plus weight of steps therefore, the load is more here and at the end again on the landing slab same as the this one. So, now here we are having sagging bending moment at central therefore, the main steel is provided at the bottom side and this is the main steel which is at the bottom side and here it is taken up as the upper steel because of fixity we have negative bending moment also here and again to take the negative bending moment out of partial facility there is a top steel here also and perpendicular to this particular slide you find the dots. So, these dots are distribution steel. So, the bottom one is main steel and upper dots are distribution steel. So, this is how the reinforcement arrangement is to be made for a the dog-legged stair. So, each flight is similar therefore, similar portion and here if you find this particular portion you find the reinforcement arrangement is just like a scissor. So, therefore, it is also very famously known as kaichi jena on the field. So, these are the references used. So, advanced RCCU Bhavikatti and then other authors also and IS 456 2000 and thank you one end all.