Rak Production Technology of Concrete Structures (2015) Concrete Reinforcement

Transcription

1 Rak Production Technology of Concrete Structures (2015) Concrete Reinforcement

2 Learning Outcomes To acquaint the student with concrete reinforcement 2

3 Reinforcement The of concrete app. 10 times lower than its compressive strength. The reinforcement usually 25 to 30% of the overall cost of normal strength concrete. 3

4 Type of steel reinforcement Plain bars Ribbed bars (in general 80% of the total amount) Flat bars Wires, Tendons (prestressed reinforcement) Cold-rolled deformed bars Hot-rolled deformed bars 4

5 Preparation of the reinforcement General rules for preparation of hooks, according to BY50 Bending of reinforcement bars 5

6 Preparation of the reinforcement Internal bending radius of re-bars, according to BY50 Longitudinal connection of main reinforcement bars; a) by welding, b) by wire 6

7 Preparation of the reinforcement Minimum overlapping length for elongation of reinforcement bars. Spacing of reinforcement bars, S h (ø; 1.2 x size of aggregates; 25mm) 7

8 Preparation of the reinforcement Environment classes, BY50 Minimum concrete cover according to the exposure classes, according to BY50 8

9 Preparation of the reinforcement at the building site Bending of reinforcement bars and mesh Bonding of reinforcement bars by wire. Bar Wire 9

10 Preparation of the reinforcement at the building site Manual bonding or reinforcement by welding 10

11 Standardized reinforcement components 11

12 Montage of reinforcement 12

13 Slabs Bottom reinforcement Bottom reinforcement plastic spacer Upper reinforcement Upper reinforcement, support (in the case of bended steel bar at least 40mm protection against corrosion at both ends) Examples of spacer for reinforcement 13

14 Pre- and Post- tensioned reinforcement Pre-stressing tendons are made of wire or rods. The bars and rods were prestretched beyond yield Delivered in spirals The most common is 7-wire strand Pre-tensioning, the strands embedded in concrete anchorage bind Post-tensioning headed wires anchored into anchorage plates 14

15 Pre-tensioning of reinforcement Montage of formworks with reaction frames Montage of hydraulic jacks Montage of strands and additional reinforcement and accessories Stretching of strands Concreting Curing Release of tensioning forces 15 nknp_800_800/aaeaaqaaaaaaaa KUAAAAJDI1YzJkYTYzLTEwN2EtN GYzNy04MTY4LTFjMDJmNjNmZGIx NA.jpg

16 Post-tensioning of reinforcement Montage of formworks Montage of regular reinforcement, accessories and ducts Concreting Curing Transportation to the montage spot Tensioning Injection of cement grout into the duct 16

17 Post-tensioning of reinforcement Example of anchorage head 17

18 Un-bonded Post-tensioning of reinforcement As de-bonding means were used; paper, grease and at present plastic shielding Typical 7 wire strands used for un-bonded posttensioning Example of post tensioned bridge girder 18

19 Learning Summary Type of steel reinforcement Preparation of the reinforcement in general Preparation of the reinforcement at the building site /resources/images/cdn/cms/bentsha pes-web.jpg 19