DHANALAKSHMI COLLEGE OF ENGINEERING, CHENNAI DEPARTMENT OF CIVIL ENGINEERING CE6601 DESIGN OF REINFORCED CONCRETE AND BRICK MASONRY STRUCTURES

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1 DHANALAKSHMI COLLEGE OF ENGINEERING, CHENNAI DEPARTMENT OF CIVIL ENGINEERING CE6601 DESIGN OF REINFORCED CONCRETE AND BRICK MASONRY STRUCTURES UNIT I : RETAINING WALLS PART A (2 Marks) 1. Define - Retaining wall Retaining walls are generally used to retain earth or such materials to maintain unequal levels on its two faces. The soil on the back face is at a higher level and is called back fill. Retaining walls are extensively used in the construction of basements below ground level, wing walls of bridge and to retain slopes in hilly terrain roads. 2. State the difference between cantilever and counter fort retaining wall (N/D-13) In cantilever type, vertical stem resisting earth pressure on one side and the slab bends like a cantilever. In counter-fort type, the vertical stem is designed as a continuous slab spanning between counter-forts. 3. Name the different types of retaining walls (N/D-14) Gravity retaining wall Cantilever retaining wall Counter-fort retaining wall Buttressed retaining wall Anchored retaining wall 4. What is a cantilever retaining wall? The most common and widely used retaining wall is of cantilever type. Vertical stem resisting earth pressure one side and the slab bends like a cantilever. The thickness of the vertical slab is large at the bottom and decreases towards the top in proportion to the varying soil pressure. 5. What is a counter fort retaining wall? Counter fort retaining walls are used for large heights exceeding 5 m of earth fill. In counterfort retaining wall the vertical stem is designed as a continuous slab spanning between the counterforts. Counter forts are designed as cantilever beams from the base slab. 6. When do you prefer counter-fort type retaining wall? (N/D-13, M/J-13) For larger heights exceeding 6m Bending moment developed in the stem, heel and toe slab are very large resulting in larger thickness of structural elements tending to be uneconomical. 7. State the necessity of providing shear key in retaining wall. (N/D-13) In case of backfill with surcharge, the active pressures are relatively high and consequently the required factor of safety against sliding by the frictional forces above will not be sufficient. In such cases, it is advantageous to provide shear key below base slab. 8. What are the assumptions made in the design of toe slab of a cantilever retaining wall? (N/D-12) Neglect the weight of soil above it The toe slab will bend upwards as a cantilever due to upward soil reaction. Hence reinforcement is placed at the bottom face. Thickness of both toe slab and heel slab is kept same.

2 9. How the development of tension in a base slab is checked? In order to avoid development of tension in the base slab, the resultant of various forces acting on the wall should cut the base in the middle third of width of base. Further maximum pressure on the base slab should not exceed the allowable soil pressure. 10. What is the function of counter-forts in a retaining wall? (A/M-15) The stem of the counter-fort retaining wall acts as a continuous slab supported on counter-forts. The counter-forts take reactions both from the stem as well as the heel slab. Since the active earth pressure on stem acts outwards and net pressure heel slab acts downwards, the counter-forts are subjected to tensile stresses along the outer face of the counter-forts. 11. What factors govern the spacing of counter-forts? Spacing of counter-forts depends on various factors such as height of retaining wall, cost of steel and concrete, allowable soil pressure and cost of framework. 12. How the vertical slab for the counter-fort retaining wall is designed? (A/M-10) The vertical slab or stem is designed as a continuous slab with span equal to spacing of counter-forts. The spacing of counter-forts may vary from 2.5m to 4m. Maximum negative moment at the end supports and intermediate supports are taken as (PL 2 /10) and (PL 2 /12) where L is span between the support and P is intensity of earth pressure. 13. Define Active Earth pressure. (N/D-14) If the soil exerts a push against the wall by virtue of its tendency to slip laterally and seek its natural slope (angle of repose) thus making the wall to move slightly away from the back filled soil mass. This kind of pressure is known as AEP. 14. Define Passive earth pressure. (N/D-14) The pressure or resistance which soil develops in response to movement of the structure towards it is called the Passive Earth Pressure. 15. How a toe slab of a counter-fort retaining wall is designed? Toe slab is designed as a cantilever bending upwards due to earth pressure from the bottom. Incase front counterforts are provided, the slab is designed as a continuous slab supported on counter-forts. 16. What is a buttressed retaining wall? It is similar to counter-fort retaining wall except that the transverse stem supports called buttress are located in the front side instead on the backfill side. Here the buttress interconnects the stem with the toe slab. 17. List the conditions that demand the provision of temperature steel in the stem slab of a retaining wall. (N/D-12) Temperature reinforcement is provided transverse to main reinforcement should be provided in the vertical and horizontal directions near the front face, which is exposed to the atmosphere. 18. What are the stability conditions should be checked for the retaining walls? (N/D-12) The stability of retaining walls should be checked against the following conditions. The wall should be stable against sliding The wall should be stable against Overturning The wall should be stable against bearing capacity failure. 19. What is a shear key? (N/D-14) Shear key increases the resistance against sliding as the passive earth pressure developed on the shear key provides additional resistance against sliding.

3 20. What do you mean by backfill of a retaining wall? (N/D-07) The material retained or supported by a retaining wall is called backfill. 21. What is meant by surcharge? The position of the backfill lying above the horizontal plane at the elevation of the top of a wall is called the surcharge. 22. What is a gravity retaining wall? (N/D-12) A gravity retaining wall is the one in which the earth pressure exerted by the backfill is resisted by dead weight of the wall, which is either made of masonry or mass concrete. 23. What is meant by submerged backfill? The sand fill behind the retaining wall saturated with water is called submerged backfill. 24. What is meant by back anchoring of retaining wall? When the height of retaining wall is much more, it becomes uneconomical to provide counterforts. In order to reduce the section of stem etc. in the high retaining walls, the stem may be anchored at its back. The anchor practically takes all the earth pressure and B.M and S.F. in the stem are greatly reduced. 25. Write expressions of Rankine s theory of earth pressure for the following: (M/J-14) a) When the earth is level b) When the earth is surcharged at an angle α Lateral earth pressure = KɤH Earth pressure coefficient For horizontal backfill 1 sin K a 1 sin K p 1 sin 1 sin For sloping backfill K a cos cos cos cos 2 2 cos cos 2 2 cos K p cos cos cos cos 2 2 cos cos 2 2

4 PART B (16 Marks) 1. Describe briefly about the design procedure of cantilever retaining wall 2. Describe briefly about the design procedure of counterfort retaining wall 3. Design a cantilever retaining wall to retain earth embankment 3m high above ground level. The unit weight of earth is 18kN/m 2 and its angle of repose is 30 ο. The embankment is horizontal at its top. The SBC of soil is 100kN/m 2 and the co-eff. of friction between soil and concrete is 0.5. Adopt M20 concrete and Fe 415 steel. Take factor of safety against overturning and sliding as 1:40 (N/D-15) 4. Design a counterfort retaining wall to suit the following data: a. Height of the wall above ground level = 6m b. Safe bearing capacity of soil at site = 160kN/m 2 c. Angle of repose of soil = 30 ο d. Spacing of counterforts = 3m c/c e. Unit weight of soil = 16kN/m 3 f. Grade of concrete = M20 g. Grade of steel = Fe 415 (N/D-14) 5. Design a Cantilever retaining wall to retain 5m of horizontal backfill. The Density of the soil is 17kN/m 2 Safe Bearing Capacity of the Soil=165kN/m 2 Angle of internal Friction of Soil=250 The Coefficient of friction between base slab and concrete=0.55 Factor safety against sliding and over turning is 1.45 Use M20 concrete and Fe415 Steel. (A/M-15) 6. Estimate the reinforcement and design the main bars of 12mm diaand distribution bars of 8mm dia required at the bottom section of the stem of a counterfort retaining wall to retain a horizontal backfill level with its top for the following data. Height of the stem = 6.5m. Thickness of stem at top and bottom: 250mm and 450mm respectively. Density of soil is 18kN/m³ and angle of repose is 30.

5 Centre to Centre spacing of counterforts = 3m Materials used in the construction are M25 grade of concrete and Fe415 steel reinforcement. 7. A cantilever retaining wall has 4.5m high wall from the top of the base slab and retains earth with an inclined fill (20 o to the horizontal). Density of the soil retained is 15kN/m3 and its angle of repose is 30 o. Estimate the reinforcement and design the base section of the wall for flexure. (N/D-12) 8. a) Explain under what circumstances counterforts are preferred. b) Explain the methods of designing shear key in a retaining wall

6 UNIT II : WATER TANKS PART A (2 Marks) 1. What is the concept of rectangular tank based on L/B ratio? (N/D-13) L/B ratio < 2 Walls are designed as continuous frame subjected to pressure varying from zero at top to maximum at H/4 or 1m whichever is more. The bottom portion is designed as cantilever. Wall is subjected to direct tension and bending, L/B ratio > 2 Long walls are designed as cantilever and short walls as slabs supported on long walls. 2. What are the types and forces acting on domes? Types: Spherical dome Conical dome Elliptical dome Types of forces: Meridional thrust Hoop compression (M/J-11) 3. Name the types of reinforced concrete water tanks (N/D-11) Tanks resting on ground Underground tanks Elevated water tanks According to shape: Circular water tank Rectangular Spherical Intz tank 4. Mention the loads considered for the design of water tank (N/D-11) For underground tank: Self weight Soil weight For elevated tank: Water pressure Live load Self weight 5. What are the loads to be considered in design of staging of a water tank? (N/D-12) Wind force Seismic force 6. What is the minimum reinforcement to be provided in domes? (N/D-11) 0.3% of total gross sectional area for mild steel 0.24% of total gross sectional area for ribbed steel 7. Define the term: Dome: (N/D-13) A Dome is defined as a thin shell generated by the revolution of a regular curve about one of its axes.

7 8. What are the three types of joints in water tank? i. Movement joints Contraction Expansion Sliding ii. Construction joints iii. Temporary open joints 9. For what conditions underground water tanks are designed and checked? (N/D-14) Tank full with water, with no earth fill outside. Tank empty, with full earth pressure due to saturated earth fill. Check the underground tank for uplift pressure 10. What is the function of bracing in the staging of water tank? (N/D-09) Overhead tanks are supported on columns. As columns are very long they are susceptible for buckling due to wind pressure. Hence to reduce the effect of long column and convert as short columns braces are provided. Braces are designed for bending moment and shear. 11. What are the stresses acting on spherical dome? (M/J-11) Domes are designed for meridinal and hoop stresses, Domes are usually subjected to uniformly distributed load. 12. State the reason for not using rectangular underground tanks for large capacity. (N/D-13) Rectangular tanks are used for smaller capacity as they are uneconomical for large capacities. Vertical walls are subjected to bending moment and tension. 13. What are the forces experienced by ring beam of a dome? (N/D-12) Hoop tension Hoop compression 14. What are the essential requirements of an impervious water tank? (N/D-14) The concrete used must be of well graded mix of low w/c ratio and it should be fully compacted The concrete must be free from cracks. 15. Mention the thickness and steel requirement of dome. A minimum thickness of 7.5cm is provided to protect steel. Minimum steel requirementis 0.15% for mild steel bars and 0.12% for HYSD bars of the sectional area in each direction meridionally as well as along the latitudes. 16. What is the foundation specification for small capacity tanks? For small capacity tanks individual footings for columns can be provided. Infact, the type of footing will depend upon the nature of soil and type of staging. In case of low lying areas of low safe bearing capacity with high ground water table, pile footings are provided. In any case of foundation slab, lean mix of 1:4:8, 150mm thick may be provided as levelling course. 17. What are the methods available for the analysis of circular tank? IS code method Reissner s method Carpenter s method Approximate method

8 18. What are movement joints in water tanks? (N/D-10) These joints require the incorporation of special materials in order to maintain water-tightness while accommodating relative movement between the sides of the joints. All movement joints are essentially flexible joints. 19. How the overhead tank is supported? Overhead tanks may be supported on roof top for domestic purposes. For large public use it is supported on staging. If columns are provided in staging they are braced by number of ring beams. 20. Give the advantages and disadvantages of approximate analysis in water tank design (N/D-14) Advantages Ready to use Saves lot of time Design method is simple Disadvantages It does not reflect the exact behavior 21. What is meant by expansion joint in water tanks? (N/D-10) It is a movement joint with complete discontinuity in both reinforcement and concrete, and is intended to accommodate either expansion or contraction of the structure. 22. What are underground water tanks? Underground water tanks are used for storage of water received from water supply mains operating at low pressures, or received from other source. 23. What are the four components of design of underground water tanks? (i) Design of long walls (ii) Design of short walls (iii) Design of roof slab (iv) Design of base slab 24. What are two methods of analysis of rectangular tanks? Approximate analysis Exact analysis based on elastic theory 25. Where are domes used? Roof of circular areas Circular tanks Hangers Exhibition halls, auditoriums Bottoms of tanks, bins and bunkers

9 PART B (16 Marks) 1. Design a circular water tank with a flexible base for a capacity of litres. The depth of water is to be 5m. Free board = 200 mm. Use M20 grade concrete and grade- I mild steel. Permissible direct tensile stress in concrete is 1.2 N/mm 2. Permissible stress in steel in direct tension = 100 N/mm 2. (N/D-11) 2. Design an underground water tank 3m x 8m x 3 m for the following data. The weight of subsoil is 16kN/m 2. Angle of friction of soil = 30 ο. The water table can rise up to ground level. Design the side walls of the tank. Use M20 and Fe 415 combinations (M/J-12) 3. Design side walls of a square RCC tank of capacity litres of water depth of water tank is 3.8 m and free board is 0.2 m. Adopt M20 concrete and grade I mild steel. Tensile stress in steel is limited to 100 N/mm 2 of water face and 125 N/mm 2 away from face. 4. Design the side wall of a circular tank of capacity 1.5 lakhs litres of water. The depth of the tank is limited to 2.5 m. The joint between the wall and base is flexible. The base slab rests on the ground. Use M20 grade concrete 5. A circular slab of dia 3m is subjected to a super imposed load of 4kN/m 2. It may be considered as simply supported. Use M20 grade concrete and Fe 415 grade steel. Design the slab. Take poison s ratio as zero 6. A rectangular RCC water tank with an open top is required to store 1 lakh liters of water. The inside dimensions of the tank are 6 x 4m. The tank rests on wall on all four sides. Design the side walls of the tank using M20 grade concrete and Fe500 HYSD bars. (N/D-14) 7. Design a circular water tank for a capacity of 400 Kiloliters with flexible base. Adopt M20 concrete and Fe 415 steel. Also sketch the reinforcement details

10 8. Estimate the reinforcement and design the side wall of a circular tank of capacity1.5 lakh litres of water. The sub soil consists of silt having angle of repose of 30 o and saturated unit weight of 18kN/m 3. The water is likely to rise up to ground level. Use M20 grade concrete Fe415 grade steel. 9. Write down the radial moment and circumferential moment for the 6 various cases of support conditions with near sketch. 10. A circular slab is to be provided for 6m diameter circular hall. The live load on the slab is 3500N/mm 2. Calculate the reinforcement and design the slab. Assume partially fixity at the support. Use M20 grade concrete and Fe415 grade of steel. (M/J-13)

11 UNIT III : SELECTED TOPICS 1. Define - stair case A staircase consists of a number of steps arranged in a series, with landings at appropriate locations, for the purposes of giving access to different floors of a building. 2. Mention the three components of stair Flight Tread Riser 3. What are the types of staircases? (N/D-11) They are broadly classified as i. Straight stair Ii Quarter turn stair ii. Half turn stair iii. Dog legged stair iv. Open newer stair with quarter space landing v. Geometrical stairs such as circular stair, spiral stair, etc. 4. How the load is distributed in case of open well stair? In case of open well stair, the load on areas common to any two such spans may be taken as one half in each direction. 5. What are the limitations in direct design method for flat slab? (N/D-14) There shall be minimum three continuous spans in each direction The panel should be rectangular and L/B should not be > than 2 The design live load shall not > 3 DL 6. What is meant by Flat slab? (M/J-13) A flat slab is a typical type of construction in which a reinforced slab is built monolithically with the supporting columns and is reinforced in two or more directions, without any provision of beams. 7. What are all the components of flat slab? i. Drop of flat slab ii. Capital or column head iii. Panel 8. How will you calculate the load effects on a stairs waist slab spanning in the longitudinal direction? (N/D-14) Live load: Stair liable for overcrowding = 5kN/m 2 Stair not liable for crowding = 3kN/m 2 Dead load: Self weight of steps Self weight of waist slab

12 9. Define capital or column head. Sometimes the diameter of a supporting column is increased below the slab. This part of column with increased diameter is called column head. 10. Write the different types of flat slabs? i. Slabs without drops and column heads ii. Slabs without drops iii. Slab with drops and column with column head (M/J-13) 11. What is the minimum rise and tread in residential buildings? In residential buildings, the rise may vary between 150mm to 180mm tread between200mm to 250mm. 12. What is the minimum rise and tread in public buildings? In public buildings, the rise may vary between 120mm to 150mm tread between200mm to 300mm. 13. Mention the places where the following staircase can be used Single flight staircase is used in cellars or attics where the height between floors is small and the frequency of its use is less. Quarter turn staircase flight generally runs adjoining the walls and provides uninterrupted space at the centre of the room. Generally used in domestic houses where floor heights are limited to 3m. Dog legged staircase is generally adopted in economical utilization of available space. Open well staircases are provided in public buildings where large spaces are available. In congested locations, where space availability is small, Spiral stairs are provided. 14. Define drop of flat slab. Drop is that part of the slab around the column, which is of greater thickness than the rest of the slab. 15. Define panel of flat slab. It is the area enclosed between the centre lines connecting adjacent columns in two direction sand the outline of the column heads. 16. What are the methods of analysis of flat slab? (i) The direct design method (ii) The equivalent frame method 17. What are all the assumptions made in equivalent frame method? i. The structure is considered to be made of equivalent frames longitudinally and transversely. ii. Each frame is analysed by any established method like moment distribution method. Iii The relative stiffness is computed by assuming gross cross section of the concrete alone in the Calculation of the moment of inertia iv. Any variation of moment of inertia along the axis of the slab on account of provision of drops should be considered. 18. What are all the assumptions made in direct design method? (N/D-12) (i) There shall be minimum of three continuous spans in each direction. (ii) The panel shall be rectangular, and the ratio of the longer span to the shorter span within a panel shall not be greater than 2.0.

13 19. Explain about box culvert shortly. (N/D-12) A box culvert is continuous rigid frame of rectangular section in which the abutment and the top and bottom slabs are cast monolithic. A box culvert is used where a small drain crosses a high embankment of a road or a railway or a canal- especially when bearing capacity of soil is low. 20. Give the names of various types of bridges. i. Solid slab bridge or deck slab bridge. ii. Deck girder bridge or T-beam bridge. iii. Balanced cantilever bridge iv. Rigid frame culvert.

14 PART B (16 Marks) 1. Design a interior panel of a flat slab with drops for an office floor to suit the following data:(m/j-13) a. Size of floor = 20 x 20 m b. Size of panels = 5m x 5m c. Loading class = 4kN/m 2 d. Grade of concrete = M20 e. Grade of steel = Fe Explain the methods of design of Mat foundation 3. Design a dog legged stair for a building in which the vertical distance between the floor is 3.6 m. The stair hall measures 2.4 x 5 m inner dimensions. The live load on the stair is 3000 N/m 2. Use M20 and Fe 415 combinations (N/D-11) 4. Explain the design principles of box culvert 5. Explain the components of bridge in detail 6. An intermediate flight of a staircase is supported only at the edges of landing support Perpendicular to the direction of the flight). Height between landings is 1.5m. The Flight has steps consisting of 10 risers (each rise=150mm) and a treads (each tread=250mm). The steps are supported on a waist slab. Landing is 1 m width. Support width is 300 mm each. Calculate the reinforcement and design the waist slab and landing for bending moment alone. Use M20 concrete and Fe 415 steel. Live load on stair is 3.0kN/m2. Width of flight = 1.5 m. 7. Design a dog-legged stair for a building in which the vertical distance between floors is 3.6 m. The stair hall measures 2.5 m x 2.5 m. The live load may be taken as 2.5kN/m 2. Adopt M20 concrete and Fe 415 steel. (N/D-11)

15 8. A flight of a dog-legged staircase has the following details: Going =2.25 m Landing width = 1.25 m Raise of a flight = 1.5 m Support width = 300 mm Choosing appropriate dimensions for rise and tread, and taking the flight to span longitudinally between the supports, Determine the reinforcement of the flight. Assume live load as 3kN/m 2 (M/J-13) 9. Design a dog-legged stair for a building in which the vertical distance between the floors is 3.5m. The Stair hall measures 3.5m x 5.5m (inner dimensions). The live load on the stair is 3000N/m 2.Adopt M20 Grade concrete and Fe415Grade Steel. (N/D-14) 10. Design a RC slab culvert for class AA loading for the following data: Clear span = 6m; clear width of roadway = 6.8m; thickness of wearing coat = 80mm; width of kerbs = 600mm. Grade of concrete M20 and grade of steel id Fe500. (N/D-14)

16 UNIT IV : YIELD LINE THEORY PART A (2 Marks) 1. What is meant by yield lines? (N/D-13) The failure of reinforced concrete slabs of different shapes such as square, rectangular, circular with different types of edge conditions is preceded by a characteristic pattern of cracks, which are generally referred to as yield lines. 2. What are the characteristic features of yield lines? (N/D-14) i. Yield lines end at the supporting edges of the slab ii. Yield lines are straight iii. A yield line or yield line produced passes through the intersection of the axes of rotation of adjacent slab elements. iv. Axes of rotation generally lie along lines of supports and pass over any columns. 3. State the principle of virtual work. (M/J-14) If a deformable structure in equilibrium under the action of a system of external forces is subjected to a virtual deformation compatible with its condition of support, the work done by these forces on the displacements associated with the virtual deformation is equal to the work done by the internal stresses on the strains associated with this deformation. 4. What are the two methods of determining the ultimate load capacity of reinforced concrete slabs? (i) Virtual work method (ii) Equilibrium method 5. What is the direction of yield line in one way slab? In one way slab, the direction of yield line is perpendicular to the direction of steel. 6. What is the direction of yield line in two way slab? In two way slab, the direction of yield line is not perpendicular to the direction of steel. 7. What is the concept of yield line method? (M/J-13) In the yield line method, the computation of ultimate load is based on the pattern of yield lines that are developed in the slabs under conditions approaching collapse. 8. Who innovated yield line theory? This method was innovated by Ingerslav (1923) and was greatly extended and advanced by Johanssen 9. What is a yield line? (N/D-13) A yield line is defined as a line in the plane of the slab across which reinforcing bars have yielded and about which excessive deformation under constant limit moment continues to yield leading to failure. 10. What is meant by an orthotropically reinforced slab? (N/D-12) If the reinforcement in the two directions is not the same, it is said to be orthotropically reinforced slab. 11. What is meant by an isotropically reinforced slab? (N/D-12) The ultimate moment of resistance in an isotropically reinforced slab, in any direction, is the same.

17 12. Define static indeterminacy of a structure. If the conditions of statics i.e., ΣH=0,ΣV=0 and ΣM=0 alone are not sufficient to find either external reactions or internal forces in a structure, the structure is called a statically indeterminate structure. 13. Define: Unit load method. The external load is removed and the unit load is applied at the point, where the deflection or rotation is to found. 14 What is the absolute maximum bending moment due to a moving udl longer than the span of a simply supported beam? When a simply supported beam is subjected to a moving udl longer than the span, the absolute maximum bending moment occurs when the whole span is loaded. Mmax = wl / State the location of maximum shear force in a simple beam with any kind of loading. In a simple beam with any kind of load, the maximum positive shear force occurs at the left hand support and maximum negative shear force occurs at right hand support. 16. What is meant by maximum shear force diagram? Due to a given system of rolling loads the maximum shear force for every section of the girder can be worked out by placing the loads in appropriate positions. When these are plotted for all the sections of the girder, the diagram that we obtain is the maximum shear force diagram. This diagram yields the design shear for each cross section. 17. What do you understand by the term reversal of stresses? (M/J-13) In certain long trusses the web members can develop either tension or compression depending upon the position of live loads. This tendency to change the nature of stresses is called reversal of stresses 18. What is the moment at a hinged end of a simple beam? Moment at the hinged ends of a simple beam is zero. 19. Define similitude. Similitude means similarity between two objects namely the model and the prototype with regard to their physical characteristics: Geometric similitude is similarity of form Kinematic similitude is similarity of motion Dynamic and/or mechanical similitude is similarity of masses and/or forces

18 PART B (16 Marks) 1. Explain the guidelines to draw the possible yield patterns and locate the axes of rotations. (N/D-14) 2. A square interior panel of an intermediate floor is of effective dimension 5mx5m. The live load on the floor is 2.5 kn/m 2 Finishes is 1 kn/m 2. Analyse the slab using yield line approach and design the slab. Use M20 concrete and Fe 415 steel. (M/J-11) 3. (i) Write any four characteristics of yield line? (ii) Find the ultimate load of the isotropically reinforced square slab simply supported on its all edges and uniformly loaded. Use virtual work method. 4. Design a rectangular slab 6m x 4m simply supported on its all edges. The live load is 5kN/m 2.The coefficient of orthotropy may be assumed as Use M25 concrete and Fe415 steel. (N/D-14) 5. Derive the expression for calculating the ultimate moment (Virtual work method) for a simply supported square slab. 6. Design a circular slab of 3 meter diameter, simply supported along the edges, to carry a service load of 4 KN/m 2. Adopt M20 Grade concrete and Fe 415 Grade steel. Use equilibrium method for analysis. (M/J-13) 7. Derive from principles the ultimate design moments for a rectangular simply supported slab panel using yield line approach. Hence determine the design moments for a simply supported rectangular slab 3 m x 4 m effective, subjected to a live load (working) of 2.5 kn/m 2 and finish of 1 kn/m 2. Assume suitable load factor. 8. A square interior panel of an intermediate floor is of effective dimension 5 m x 5 m. The live load on the floor is 2.5kN/m 2. Finishes is 1kN/m 2. Analyze the slab using yield line approach and design the slab. Use M20 concrete and Fe 415 steel. (N/D-11) 9. Derive an expression for calculating the ultimate moment of resistance for a simply supported rectangular slab. 10. A rectangular slab 3.5 m x 5 m in size simply supported at the edges. The slab is expected to carry a service load of 3kN/m 2 and a floor finishing load of 1kN/m 2. Design the slab if (i) It is isotropically reinforced and (ii) It is orthotropically reinforced with μ = Find the ultimate load carrying capacity of a 4 m x 6 m slab continuous on all edges if yield moments are 25kN m/m for positive and negative moments respectively, they being uniformly loaded.

19 12. Find the ultimate load for isotropic of the following profiles simply supported on all edges carrying distributed load throughout the slab. (M/J-12) Square slab and

20 UNIT V : BRICK MASONRY PART A (2 Marks) 1. What is reinforced brick work? (N/D-14) Reinforced brickwork is a typical type of construction in which the compressive strength of bricks is utilized to bear the compressive stress and steel bars are used to bear the tensile stresses in the slab. 2. What is cross sectional area of Masonry unit? Net cross sectional area of a masonry unit shall be taken as the gross cross sectional area minus the area of cellular space. Gross cross sectional area of cored units shall be determined to the outside of the coring but cross sectional area of groves shall not be deducted from the gross cross sectional area to obtain the net cross sectional area. 3. What is bond in brick masonry? Arrangements of masonry units in successive courses to tie the masonry together both longitudinally and transversely; the arrangement is usually worked out to ensure that no vertical joint of one course is exactly over the one in the next course above or below it, and there is maximum possible amount of lap. 4. How will you calculating effective length, effective height and effective thickness? (M/J-10) The height of a wall to be column to be considered slenderness ratio. The length of a wall to be column to be considered slenderness ratio. The thickness of a wall or column to be considered for calculating slenderness ratio. 5. What meant by lateral support? A support which enables a masonry element to resist lateral and/or restrains lateral deflection of a masonry element at the point of support. 6. What is the slenderness ratio for walls? (N/D-13) For a wall, Slenderness ration shall be effective height divided by effective thickness or effective length divided by the effective thickness is less. 7. What is the slenderness ratio for walls and columns? For column slenderness ration shall be taken to be the greater of the ratios of effective heights to the respective effective thickness in the two principal directions. Slenderness ratio for a load-bearing column shall not exceed What is slenderness ratio in brick masonry structures? (N/D-12) In brick masonry structures, For a wall slenderness ratio shall be the effective height divided by the effective thickness or effective length divided by the effective thickness whichever is less. 9. What is slenderness ratio in brick column masonry structures? For a column slenderness ratio shall be taken to be the greater of the ratios of effective height s to the respective effective thickness in the two principal directions. Slenderness ratio of a load-bearing column shall not exceed 12.

21 10. What is the purpose of providing a lateral support in a masonry structures? (N/D-11) Masonry structures gain stability from support offered by cross walls, floors and roofs. Lateral support for loadbearing walls limit the slenderness of the structure. Further the lateral support reduces the possibility of buckling of member due to vertical loads and to resist horizontal forces. 11. List out the factors which affect the permissible stress of masonry. (N/D-08) Type and strength of bricks Slenderness ratio Shape and size of bricks Strength of mortar Eccentricity of loading Cross-sectional area of the masonry 12. List the factors which contribute for eccentricity on brick walls. (N/D-11) Long floor edges Magnitude of loads Relative stiffness of slab or beam and the wall Flexibility of the support Unequal spans Geometry of the support 13. What is an equivalent eccentricity? (N/D-13) In an eccentricity loaded wall, there is an axial load and a bending moment. These two may be combined into single resultant load acting at a distance. This is known as equivalent eccentricity. 14. Define middle third rule. (M/J-11) Middle third rule which states that for no tension on the section, the resultant thrust should lie within the middle third of the axes. 15. What is cross sectional area of masonry unit? Net cross sectional area of a masonry unit shall be taken as the gross cross sectional area minus the area of cellular space. Gross cross sectional area of cored units shall be determined to the outside of the coring but cross sectional area of groves shall not be deducted from the gross cross sectional area to obtain the net cross sectional area. 16. What is bond in brick masonry? Arrangements of masonry units in successive courses to tie the masonry together both longitudinally and transversely; the arrangement is usually worked out to ensure that no vertical joint on one course is exactly over the one in the next course above or below it, and there is maximum possible amount of lap. 17. Enumerate the factors governing the design of brick masonry. (N/D-14) The strength of individual units. The strength of mortar The thickness of mortar joint and The layout and orientation of bricks. 18. What is Reinforced brick work? (N/D-14) Reinforced brickwork is a typical type of construction in which the compressive strength of bricks is utilized to bear the compressive stress and steel bars are used to bear the tensile stresses in the slab.

22 19. What is the slenderness ratio for walls and columns? For a wall, slenderness ratio shall be effective height divided by effective thickness or effective length divided by the effective thickness is less. For a column, slenderness ratio shall be taken to be the greater of the ratios of effective height to the respective effective thickness in the two principal directions. Slenderness ratio for a load bearing column shall not exceed 12.

23 PART B (16 Marks) 1. Calculate the allowable axial load on column 200mm x 200mm constructed in first class brick work in CM 1:3to a height of 3m. The compressive strength of units may be assumed as 7.5MPa. (M/J-12) 2. Design a interior load bearing wall of a two storied building to carry 150mm thick R.C.C slab with 3m ceiling height. The wall is unstiffened and supports 4m wide span. Take Live load on floor and floor is 2kN/m 2 Weight of floor finish=1kn/m 2 Weight of Terrace=1.8kN/m 2 Unit Weight of Masonry=19.2kN/m 3 3. Design a solid wall of a single storey Mill building that is 3000mm in height, securely tied with roof and floor units and supporting two beams on either side of it that exert reactions of 30kN and 20kN. The thickness of the wall is 230mm. the beam bears on the wall is 115mm. Assume uniform bearing stress. Neglect the load due self-weight. 4. Calculate and design a solid square masonry column of height 2000mm to carry an axial load of 150kN. The column is tied at the top and bottom. Include the self-weight of the column for the design. (N/D-12) 5. A single room building 3mx7m is provided with a brick masonry wall supporting a RC roof 150mm thick. The slab supports a live load of 1.5kN/m 2 along with a finish of 2kN/m 2. A parapet 750mm in height and 230mm thick is provided all around. Height of wall from basement to the underside of the roof is 3m. Assuming that there are no openings in the walls calculate and design the thickness of long wall. Brick strength of 5 N/mm2 and 1:5 mortar mixes are to be used. Nominal sized bricks are to be used. 6. A masonry wall is subjected to an axial load of 180kN and the height of the wall is 3.6m. Determine the reinforcement of walls. 7. A masonry wall is subjected to an axial load of 150kN and bending moment of 30kNm. The height of the wall is 4m.design the walls. (N/D-12) 8. Explain brief note on: (N/D-11) (i) Classification of walls. (ii) Effective length and effective height of walls (iii) Permissible stress in brick masonry.

24 9. What are the factors to be considered while designing the brick masonry with respect to stability and lateral supports on the structure? Explain in detail. (N/D-14) 10. Determine the reinforcement of an interior cross wall of a two storied building to carry 100mm thick RC slab with 3 m ceiling height. The wall is unstiffened and it supports 2.65m wide slab. (M/J-13) Live load on roof: 1.5kN/m 2 Live load on floor: 2.0kN/m 2 Weight of floor finish: 0.2kN/m 2 Weight of terrace: 2.0kN/m 2