Reinforcement is a main part of the concrete structures. Therefore it is need to have a good attention about the workmanship of the reinforcement. Therefore each and every element of the building needs to check carefully by the consultant engineer. So also engineers of the contractor need to give their attention for the reinforcement.
In the project 10mm, 12mm, 13mm, 16mm, 20mm, 25mm, 32mm and 40mm deformed type 2 bars are used for construction. Structural designer was used 13mm diameter tor steel bars instead of 12mm diameter bars. Therefore in the initial stages of the building the contractor imports 13mm diameter bars from Malaysia and use it. But June onwards the stocks were finished and the contractor convert 13mm diameter bars to 12mm diameter tor steel. Due to that structural drawings were changed in the construction. Major part of the bar bending is doing in the contractor's head office and bar bending at the site is only doing at the special cases. When new steel load came to the site, those are checked to conform whether it is corroded or not.
Checking of the reinforcement is very important in the concreting work. Therefore Engineers of the consultant team checking the reinforcement before the concreting of any element. First of all, main reinforcement bars should be checked with the drawings. In this check the size of the reinforcement, number of reinforcement and spacing of the reinforcement were checked. Then the lap length, the location of lapping and are checked. Then tension anchorage, compression anchorage, tension lap and compression lap were checked. After the main reinforcement; shear links sizes, spacing of the shear links and correct bar bend according to the drawing were checked. Finally covering for the reinforcement from both top, bottom and sides were checked. In the walls and columns verticality of reinforcement also checked before the concreting.
Reinforcement for RC Walls and Columns
In the erection of the reinforcement of columns and wall it is need to make the starter bars at their correct positions with correct cover and spacing. Then required amount of shear links were placed on the column or wall. After that vertical bars attached to the starter bars and bind it with correct spacing. In some cases shear links are no need to take before the vertical bars and it can bind as requirement. However the requirement is bind the reinforcement as shown in the structural drawing.
In the project some RC walls are ended in the 29th floor and sizes of some RC walls and columns are reduced. Therefore the reinforcements that are coming from the below floor levels were need to bend and anchor it to the slab. Due to the change of the columns and RC walls their reinforcement also changed. Due to that overlapping the reinforcement was happened. Therefore the contractor places the reinforcement as shown in the following figure.
RC wall detail 21st – 29th floor (above) and 29th floor onwards (below)
Placement of the changed reinforcement
Reinforcement for Slabs and Beams
Reinforcement of the slabs and beams are important in the concrete construction work. Therefor laying reinforcement should be more accurate. Reinforcement bar sizes, no. of bars, shear links, link spacing, anchorages and lap lengths are important. If any one of followings will changed it can cause a large damage. As the consultants of the project we had a great responsibility to check all the reinforcement works before concrete it.
Typical detail to tension and compression anchorages of a beam
The arrangement of the apartment of the building was changed 29th floor onwards. Therefore the reinforcement details also changed in the 29th floor onwards. Therefore it is need to bit of time to change to those for contractors and they can do wrong things at that stage. Therefore it is need to very alert for condition like those.
After finishing the formwork of the slab and beams it is need to start the reinforcement works of the beams first and finish it before the start of slab reinforcement. Binding of the beam reinforcement was done as follows.
- Put few main bars with sufficient cover blocks to the bottom
- Insert required amount of links to the main bars
- Put remaining main bars and tie them with links
- Put cover blocks to the bottom and sides.
After finishing the beam reinforcement, slab reinforcement can start and it is done in following steps.
· Laying bottom reinforcement with required spacing and bind it
- Provide cover blocks for bottom reinforcement
- Laying top reinforcement with required spacing and bind it
- Provide spacer or chairs to take the required cover
After laying the reinforcement, slab and beam should be cleaned and it should be free from unnecessary materials and equipment.