Beam, Slabs, Lintels: Reinforcement and details

Reinforcement and details for lintels and projections.
Reinforcement and details of R.C.C. beams: simply supported, rigid, continuous
and cantilevered. Reinforcement and details for one-way and two-way slabs with
fixed continuous and cantilever end conditions.

1. Beam, Slabs, Lintels: Reinforcement and details Lecture seris.9 Prepared by Snr.Lctr.D.Mubarak Osman

2. 1.0

3. Lintel Beam Followings are the general loads that should be considered for lintel beam design : Self-weight of the lintel. Self-weight is a kind of dead load. Load of the wall above the lintel beam. It is also a dead load . Loads transferred from the floor or the roof supported by the wall over the lintel. Both live and dead load from the roof should be considered.

4. 2.0 Beam and its reinforcement details Reinforced concrete beams are structural members that support the transverse load which usually rest on supports at its end. Girder is a type of beam that supports one or more smaller beam . Types of Concrete Beams Beams are classified as Simple Beam Continuous Beam Semi-Continuous Beam cantilever beam T- beam Girder The girder is basically a beam that supports other small beams and serves as the main horizontal supports of a structure. Unlike beams, the girder is designed to support major concentric loads such as columns or beam reactions, and their load carrying capacity is much higher than that of beams.

5. 1. Simple Concrete Beams Simple concrete beam refers to the beam having a single span supported at its end without a restraint at the support. Simple beam is sometimes called as simply supported beam. Restraint means a rigid connection or anchorage at the support . Fig: Simply supported beam

6. 2. Continuous Beam It is a beam that rest on more than two supports. It can be a single beam provided for long span between columns or walls with intermediate supports of smaller beams or a single continuous beam for entire length of the structure with intermediate column or wall supports . Fig: Continuous beam with reinforcement details

7. 3. Semi-Continuous Beam Refers to a beam with two spans with or without restraint at the two extreme ends . Fig: Semi-continuous beam

8. 4. Cantilever Beam Cantilever beams are supported on one end and the other end projecting beyond the support or wall . Fig: RCC Cantilever beam reinforcement details

9. 5. T - Beam Fig: RCC T-beam When floor slabs and beams are poured simultaneously producing a monolithic structure where the portion of the slab at both sides of the beam serves as flanges of the T-Beam. The beam below the slab serves as the web member and is sometime called stem.

10. how a simply supported reinforced concrete beam is reinforced in order to evenly distribute any load that acting on it. When a vertical load is placed on a beam or slab that rests on upright supports, the beam or slab tends to sag in the center between the supports (see the following figure). • During this bending action, a squeezing force created on the top of the beam. • At the same time, a stretching force is exerted on the lower side. • Where the beam passes over the supported column a sheer (cutting) force is present. • Where the beam rest on the column, the forces are reversed. • Tension force is on the top and compression force is underneath. • In order to equalize these forces, the main steel bars are placed in the beam as shown in the below drawing. • Steel reinforcement is mainly placed wherever the tension occurs. • The steel bars are then bent accordingly. Others are added to these bars for equalizing other pressures that the building may be subjected like earthquake and • wind pressure.

11. Figure show load distribution methods in simply supported beam

12. Slab reinforcement details The slab is the horizontal structural component that provides a flat and purposive surface. Such a surface may be floor, roof, or ceiling. One-way slab & Two-way slab are the types of the slab. Slab carries the loads imposed on it and duly transfers the forces either in a one-way or in a two-way mechanism. Thus , the slab serves both as a load-bearing surface as well as a walking surface. Depending upon the requirement and the design of the structure, different types of slabs such as concrete slabs, flat slabs, waffle slabs, etc can be used . The major functions of the slab can be listed as follows: a . Slab serves as a flat surface or a walking surface. b . Slab provides support to the loads imposed on the structure. c . It acts as a means of sound, heat as well as fire insulator. d . It also serves as a divider between the consecutive floors thereby providing privacy to the occupants.

13. One way and two way slab

14. 2. One Way Slab and Two Way Slab A. One Way Slab The one-way slab can be defined as the type of slab in which the ratio of the longer span to the shorter span is greater than two. Mathematically ; Longer Span / Shorter Span ≥ 2 In other words, the one-way slab is supported by beams in such a way that the load is carried along one direction. The shorter span of the one-way slab is provided with the main reinforcement while the longer span is provided with the distribution reinforcement. Some of the prominent examples of one-way slabs are the cantilever slabs and verandahs .

15. Points to Remember a. Every two edge supported slabs are always one way. b. All cantilever slabs are one way. c. Slab containing supports on less than 4 sides can be designed as a one-way slab .

16. a. Reinforcement Details of One Way Slab

17. 1. Minimum Slab Thickness According to it, the specified thickness values are as follows: a . For simply supported one-way solid slabs, Minimum Slab Thickness = l/ 20 b . For one end continuous one-way solid slabs, Minimum Slab Thickness = l /24 c . For both end continuous one-way solid slabs, Minimum Slab Thickness = l / 28 d . For cantilever one-way solid slabs, Minimum Slab Thickness = l /10

18. 2. Span The span requirement for the slabs is given by according to design standard: According to it, if a slab rests on its support freely, the span length may be taken as equal to the clear span plus the depth of the slab but need not exceed the distance between the centers of supports.

19. B. Two Way Slab In two way slab, the ratio of the longer span to the shorter span is less than two i.e. Longer Span/Shorter Span <2 The load is carried in both directions in a two-way slab. So, the main bars are provided in both directions. Two-way slabs are extensively used in multi-story and commercial buildings.

20. a. Types of Two Way Slab There are 3 types of two-way slabs. They are: 1 . Two Way Solid Slab ( with beams) This slab can be used for a wide variety of loading systems. It is suitable for small to large-scale constructions. 2 . Two Way Waffle Slab (with beams) This slab system is used for office buildings (low rise), warehouses, parking structures, etc. 3 . Two Way Waffle Slab (with Integral Beams) This slab system is provided with a greater span as compared to the solid slab. It is suitable for modular constructions.

21. b. Reinforcement Detailing of Two Way Slab Figure: Reinforcement Detailing of Two Way Slab The reinforcement detailing of a two-way slab is shown in the figure above. As shown, the ratio of longer to shorter span is less than two, and main anchored bars are provided in both directions.

22. C. Advantages of Two Way Slab a. Availability of flat ceiling because of the absence of beam in the middle of the cell. b . More availability of the height of the room. c . Increase in the aesthetic beauty of the room. d . Reflection of light is not obstructed . D. Disadvantages of Two Way Slab a . Less economical as compared to one-way slab. b . More complex to design and construct. c . The requirement of skilled workers for construction.

23. difference between one-way and two-way slab One way slab Two way slab If L/b the ratio is greater than or equal to 2 then it is considered a one-way slab. If L/b the ratio is less than 2 then it is considered a two-way slab. In one way, slab bending moment occurs only in a shorter span direction. While in two-way slab bending moment occurs in both directions that are shorter and longer span. In a one-way slab, the main reinforcement is provided in a short span and distribution reinforcement is provided in a long span. In a two-way slab, the main reinforcement is provided in both directions.

24. One way slab Two way slab In a one-way slab, the crank is provided in two directions. In a two-way slab, the crank is provided in four directions. The one-way slab is supported by a   beam   on two opposite sides only. The two-way slab is supported by the beam on all four sides. In a one-way slab, the load is carried in one direction perpendicular to the supporting beam. In a two-way slab, the load is carried in both directions. In a one-way slab, bending is only in one direction i.e. in a shorter span. In a two-way slab, bending is in both directions. The deflected shape of the one-way slab is cylindrical. Whereas the deflected shape of the two-way slab is a dish shape.

25. WAFFLE OR RIBBED SLAB CONSTRUCTION PROCESS.

26. Construction Procedure Of Waffle Slab 1. Design and Planning Effective design and planning are essential for successful waffling installations. Structural engineers and architects collaborate to determine the appropriate grid pattern, slab thickness, and reinforcement requirements based on the load-bearing needs. 2 . Formwork and Shoring The formwork is set up to create the grid pattern for the waffling system. Shoring is used to support the formwork and ensure that it remains in place during the concrete pour. 3 . Reinforcement Reinforcement involves placing steel rebar or mesh within the formwork to provide additional strength to the waffle slab. The reinforcement is positioned according to the design specifications to ensure optimal performance .

27. Continue 4 . Concrete Pouring Concrete is poured into the formwork, filling the grid pattern and surrounding the reinforcement. Proper compaction is essential to remove air pockets and ensure a solid bond between the concrete and reinforcement. 5 . Curing and Finishing After pouring, the concrete is allowed to cure for a specified period to achieve its full strength. During the curing process, the surface is finished to achieve the desired texture and appearance.

28. ADVANTAGES OF WAFFLE SLAB. 1. Larger span of slab and floor with less number of columns. 2 . load carrying capacity is greater than the other types of slab . 3. Savings on weight and materials. 4 . Good vibration control capacity. 5 . Attractive soffit appearance when exposed. 6 . Lightweight. 7 . Vertical penetrations between ribs are easy. 8 . Economical when reusable formwork is used. 9 . Fast and speedy construction.

29. DISADVANTAGES OF WAFFLE SLAS. 1. The framework required for the waffle slab's production is quite expensive. 2 . The waffle slab needed expert craftsmanship to produce. 3 . High wind loads cannot be supported by waffle slab construction. 4 . Because the waffle slab has a higher floor height than a standard slab, the number of floors in the structures is lowered. 5 . The sloped slopes are not suitable for the construction of waffle slabs. 6 . Waffle slab maintenance is both costly and complicated.