CUTTING AND BENDING OF REINFORCEMENT
Cold worked bars and hot rolled high yield bars shall not be straightened or bent again once having been bent. Where it is necessary to bend mild steel reinforcement projecting from the concrete, the internal radius of bend shall be not less than twice the diameter of the bar. Heating of bars is not permitted. All bending shall be done cold by the use of an approved bending machine. Only experienced steel benders and fixers shall be employed.
WELDING OF REINFORCEMENT
When fabricating reinforced steel frame and netting, if there is no specific requirements for designing to follow, theses standards will govern:
• For round and plain steel, welding is at all joint point
• For edged steel, welding is at all joint points on the two circumference lines. The other rest points will be welded at the middle on the line which skipped one line by one line alternately.
• For reinforced steel beam frame, welding is at all the joint points.
The welding points should meet these requirements:
• The surfaces shall be smooth without burns, interruption points, partial shrinkage and foam.
• Ensure all the welding height and length as the designing standard.
The welding joints shall be inspected by types and plots. Each plots consisted of 100 joints or 100 reinforced steel frame and netting. These plots will be checked as the followings principles:
• Each plot, 5% of the products but not less than 5 samples for checking the dimensions and 3 samples for checking pulling and 3 samples for checking bending.
The quantity, sizes, form, positions and spacing of all steel reinforcement bars shall be in accordance with the Drawings. All cutting and trimming of bars and wires shall be done cold with the used of approved manual or power operated cutters. Welding of reinforcement shall not be permitted except in special circumstances where approved by the Engineer. Reinforcement projecting from work already concreted shall not be bent out of its correct position for any reason, unless permitted by the Engineers, and shall be protected from deformation or other damage.
Spacer blocks shall be placed at regulars’ intervals to support first layers of reinforcement off the concrete blinding or bottom formwork. Spacers shall be securely fixed to the reinforcement at the time of placing. The number of spacers shall be the minimum necessary to maintain the reinforcement in its correct position. Spacers blocks shall be of standard cement mortar or such other composition as previously approved by the
Engineer. In slabs provided with two or more layers of reinforcement, the upper layers of steel shall be supported in position by the use of steel chairs.
LAP LENGTH FOR REINFORCED BAR
Binding works (two ends overlapped together) for reinforcement will follow the designing requirements. There is no binding points at the high-pressured or bending points. In the cross section of structure, the binding points will not exceed 25% of the total area of cross section for round bar and not exceed 50% for deformed bar.