reinforcing steel reinforcing steereinforcing stee.pptx

reinforcing stee

1. Reinforcing Steel Prepared by: Suhayb Hazim Nma Farhan Superviced by: Dr. Danar Hassan 2023-2024

2. Introduction The implementation of reinforcing steel works in construction is one of the most important and dangerous works that the supervising engineer must be familiar with and know the methods of implementation and methods of receiving them according to the specifications . Any error in the process of reinforcing the building may lead to a lot of trouble in the safety of the structure.

3. Supply (provide) A table of quantities is prepared, after which the necessary number of each diameter of steel bar is supplied, according to the quantity in the table of quantities. The reinforcing process stages The map of the roof, bridges and columns is reviewed according to the approved drawings, then the supervising engineer starts calculating the necessary lengths of steel so that there is no damage left estimation 01 02 03 04 The steel bar is transported to the workplace, it is stored in a place where away from moisture and rain , and it must be covered so that it does not rust, and it must be close to the workplace so that it does not hinder the movement of workers or the transportation of supplies. preparation preparation and reinforcing the necessary quantities of steel bar are withdrawn first and cut by section according to demand. The reinforcing steel of the columns, then the bridges and then ceiling reinforced and linked according to the design . the ceiling is reinforced by placing two layers which connected together with (steel bar chair).

4. Important Notes on How to Use Rebar Due to the variety of steel sources available in the market, tests must be conducted on the steel used in construction laboratories to know the type of steel and its conformity with the required specifications, The need to use reinforcing steel from a single source . Install the steel bar in its positions according to the plan and prevent it from moving during the casting process. The steel bar must be clean and its surface should not be covered by any material that separates the steel from the concrete (such as asphalt, fat , rust and mud ).

5. Important Notes on How to Use Rebar Ensure that there is a distance of not less than (2 cm) between the lower reinforcing steel and the wooden template, using special plastic pieces (Plastic Cover - Spacer) or pieces of mosaic or alabaster tiles . The thickness of the concrete cover layer should not be less than (2.5 cm) for the roof, (3 cm) for the bridges and columns , and (5 cm) for the foundations. Concrete spacers produced by three basic materials: plastics, cement, and steel wires or rebars .

6. Important Notes on How to Use Rebar When the required length of rebar is not available, the rebar is connected in three methods: First simple lap splice, there are over lap, so that the distance of the rebar riding over each other is equal to : Over Lap = 50 * diameter of bar For example, if we use 10 mm steel bar in the project, over lap= 50*10 =500 mm=50 cm

7. Important Notes on How to Use Rebar Second welded lap splice , This method of splicing is done by welding so that the stresses are transferred by weld. Welded splicing is used for special conditions splicing of rebars with a diameter greater than 36mm.

8. Important Notes on How to Use Rebar Third Mechanical lap splice , the bars in direct contact are mechanically connected through sleeves or other similar devices. Mechanical splices join rebar end-to-end, providing many of the advantages of a continuous piece of rebar.

9. Important Notes on How to Use Rebar Bent or damaged steel is not allowed . When there are large quantities of rust (patina) on the reinforcing shutters, two methods used for cleaning, First an steel brush is used for cleaning, and then the reinforcing rollers are passed inside a pile of natural sand , and this process continues until the shutters are cleaned. Second using the Sand Blast (Air Compressor) pump, where the sand is pressurized through a special tube, and the reinforcing bars are hit with grains of sand at a high speed, which leads to flaking of the rust pieces. Reinforcing steel is usually of different diameters and is measured in millimeters. There is a local designation called the unit ( Ninah ), which is equal to ( 1/8) inch.

10. Important Notes on How to Use Rebar The main reinforcement of the balcony or trace (Cantilever) is from the top layer (as opposed to the roof) when its support is from one side only.

11. Important Notes on How to Use Rebar It is preferable that the cages (Stirrups) in the bridges be at closer distances at the ends near the supports (Near Supports), as well as in the areas where the bridges intersect with each other in order to prevent problems arising from shear force.

12. Important Notes on How to Use Rebar Corners are reinforced for non-continuous ceilings as follows: A- In the lower layer, the reinforcing shutters are placed perpendicular to the diameter of the ceiling, with a distance of (1/5) of the length of the room . B- In the upper layer, the reinforcing bars are placed in a parallel manner.

13. Important Notes on How to Use Rebar When there are openings within the ceiling, beams must be implemented on the sides of the opening if this opening is large, but if the opening is small, these bridges can be dispensed with by placing additional reinforcing bars in addition to diagonal bars reinforcement in the corners to prevent cracks.

14. Calculation of reinforcing steel quantities Calculate the weights of reinforcing steel according to the diameter per meter of length, the following equation is used:  

15. Calculation of reinforcing steel quantities Example: Calculating quantities of reinforcing steel in the ceiling, if we have (one way slab) and its dimensions are (30*20)m and the ceiling reinforced with two layers, spacing between two main bars and distribution bars are (0.2)m, and in each (0.8)m we have an steel bar chair , used steel bar dimeter is (12)mm . 0.2m 0.2m

16. Calculation of reinforcing steel quantities If we have (0.02)m concrete cover in each direction, as it showed. Now, total length of the ceiling = 30-(2*0.02) = 29.96 m And total width of the ceiling = 20-(2*0.02) = 19.96 m If we use (12)m steel bars, now along length of ceiling we have (2) over laps, and along it’s width we have one overlap. As we mentioned before, over Lap = 50 * diameter of bar. Length = 29.96 + (2*(50*0.012)) = 31.16 m Width = 19.96 + (50*0.012) = 20.56 m

17. Number of main bars = (30/0.2)+1 = 151 main bars 151 main bars of (31.16) m length. Number of distribution bars = (20/0.2)+1 = 101 distribution bars 101 distribution bars of (20.56) m length . Calculating steel weight with this formula Weight of main bars = 151*31.16*0.888 = 4,178.18208 kg Because we have two layers so we multiply weight of main bars by (2) Total weight of main bars = 4,178.18208*2 = 8,356.36416 kg   Calculation of reinforcing steel quantities

18. Weight of distribution bars = 101*20.56*0.888 = 1,843.98528 kg Because we have two layers so we multiply weight of distribution bars by (2) Total weight of distribution bars = 1,843.98528 * 2 = 3,687.97056 kg Calculating steel bar chair is same but it’s depends on the depth of ceiling. If the ceiling depth equal to (0.2)m ,then Height of chair = 0.2-(2*0.02)-(4*0.012) = 0.112 m Leg and Head of chairs must not less than (0.2)m, we use (0.2)m Total length for a chair = (2*0.112)+(2*0.2)+(0.2) = 0.824 m Number of chairs = (20*30)/(0.8*0.8) = 938 chairs Calculation of reinforcing steel quantities

19. Weight of chairs = 938*0.824*0.888 = 686.345856 kg Total weight of steel bars = 8,356.36416+3,687.97056+686.345856 = 12,730.680576 kg We take 5% more due to wastes. Final weight = 12,730.680576 +( 12,730.680576*0.05) = 13,367.2146048 kg = 13.5 ton Number of (12)m steel bars  X*12*0.888 = 13500  X = 1267 Number of (12)m steel bars = 1267 bars Calculation of reinforcing steel quantities

20. Disadvantages of Increasing or Decreasing the Quantities of Reinforcing Steel in Buildings A compressive force and at the bottom a tensile force , and on both sides the forces are reflected so that the tension is at the top and the pressure is at the bottom, and because the concrete bears the pressure and does not bear the tension, so the reinforcing steel is placed in places subject to tension - at the bottom of the bridge, for example - and the steel bar is (bent) to the top at the two ends to resist the force tension moved upwards . The Shear Force, for which cages ( Stirrups) are placed to resist it, with two steel bars on top to stabilize it. Sometimes steel bars are added at the top if the pressure force on the concrete is higher than its bearing, and the reinforcement in this case is double.

21. calculation of the amount of steel begins 1 - Determine the expected loads on the building, which are standard loads for each type of building. 2 - Additional loads are calculated for safety. 3 - After that, the compression force, tension force, shear force, and moment (if any) caused by the loads within the structural structure are calculated . 4- By dividing the tensile strength by the steel strength, the number of steel rods and their diameters required to resist these forces is determined .

22. calculation of the amount of steel begins Due to the presence of several types of reinforcing steel in terms of strength , regardless of its sizes, some of it is soft and does not bear more than (1200 kg / ) of the steel section after which it begins to elongate , and some of it is hard closer to steel that bears up to ( 4500 kg / ) The second reason for the increase in steel is the cheap schemes, as the budget does not allow the use of a structural engineer to design the reinforcement scheme. Therefore, the foreman sets the sizes of steel bar based on his experience in implementation, and to ensure the safety of the building, he will not be stingy with an additional amount, and therefore what the owner saves from the cheap plan he loses in the excess steel bar in addition to obtaining a cheap building.  

23. calculation of the amount of steel begins The third reason for the increase in steel is the strength of concrete, which leads to an increase in the depth of the bridges, the thickness of the ceilings and the width of the columns, in addition to that the design with weak concrete causes an increase in the reinforcing steel.

24. Disadvantages of Increasing Reinforcing Steel 1. Cost: Adding more reinforcing steel to a building comes with a number of drawbacks, chief among them being the increased expense. Because steel is expensive, adding more will result in higher costs. This may increase the cost of construction and have an effect on the project's budget. 2. Construction Time: The amount of reinforcing steel added can also affect how long a project takes to complete. More steel means more time to bend, cut, and install. Longer construction periods may result from this, which may have additional effects on the project's budget and schedule. 3. Transportation : Adding more reinforcing steel to a structure may also present logistical difficulties. To get more steel to the construction site, more trucks are needed, Additionally, this may raise the project's carbon footprint, which could worry some stakeholders .

25. Disadvantages of Increasing Reinforcing Steel 4 . Maintenance: Adding more steel to a structure can strengthen it, but it can also lead to maintenance problems. Greater steel indicates more places where corrosion may occur, which over time could erode the structure. Future expensive maintenance and repairs may result from this. 5. Sustainability: Increasing the amount of steel reinforcement may also have an effect on the project's sustainability. The manufacture of steel can have a substantial carbon footprint and requires a lot of resources. Overuse of steel can have a negative influence on sustainability and the environment.

26. Disadvantages of Decreasing Reinforcing Steel 1 . Safety : Reduced reinforcing steel in a building can compromise its safety, as it provides strength and stability. Removing steel can increase the building's vulnerability to collapse during natural disasters, potentially leading to severe harm or fatalities. 2 . Structural Integrity : Reduced reinforcing steel in a building can weaken concrete, leading to cracking and requiring costly repairs and maintenance, as it reinforces the concrete. 3 . Legal Issues : Reduced reinforcing steel in buildings can lead to legal issues, fines, and legal action, affecting the project's reputation and potentially causing negative publicity, as building codes and regulations mandate certain steel levels. 4 . Reputation : Reduced reinforcing steel in buildings can harm a company's reputation, create negative publicity, and negatively impact future business opportunities, potentially leading to revenue loss.

27. Limitations of Rebar Space due to Casting Concrete 1 . Structural Integrity : Insufficient space for reinforcing steel can compromise a building's structural integrity, leading to failures like cracks or collapse during extreme loads or natural disasters, potentially causing significant injury or loss. 2 . Structural Stability: Properly spaced rebar can affect structure stability, leading to tilting, sinking, or leaning, making the building unsafe for occupancy and negatively impacting the project's reputation and publicity. 3 . Repair and Retrofitting : Limited rebar space during construction can hinder future retrofitting or repair, potentially leading to costly repairs and structural modifications, affecting the project's budget and timeline.

28. THANK YOU…