Question

Though steel have high tensile strength, detailing is necessary not only for the steel structures but also for the RCC members as it is the translation of all the mathematical expression’s result. For that matter, coin a comprehensive definition for detailing of reinforcement bar (steel).

Answer 1

First we have to look at what is RCC and why the steel reinforcement is used in it.As we all know concrete is good at resisting the compression but it is weak in resisting tension force and steel is good in resisting both compression and tension.That is why these two materials are combined together to form a material which is more versatile that is called reinforced cement concrete or RCC which is good in resisting both tensile and compressive forces without failure.It is due to this property RCC is used for constructing large spans and also for constructing columns taking vertical or actual loads.Steel is a material that is widely used in construction industry and it is used in various forms.Steel reinforcement used in RCC is in the form of steel bars which is called as 'Rebars'.Two types of steel bars are mainly used in steel reinforcement they are mild steel bars and High yield strength bars(HYSD bars).Mild steel bars has a smoothsurface and has relatively lesser strength as compared to HYSD bars so it is no longer used after the invention of HYSD bars.HYSD bars has a rough surface with ribs which make it more stronger and durable.

Detailing of this reinforcement steel bars assumes greater significance in the design of a structure because poor detailing makes an elaborate analysis of a structure worthless whereas good detailing of the steel reinforcement of a structure ensures that the reinforcement behaves as designed and the structure becomes strong and durable.Good detailing makes the RCC strong,durable and free from defects such as honey combing and cracks.It ensures sufficient horizontal distance between the rods so that the biggest size of the aggregate in the concrete can pass through it.Let's have a look at the important points relaed to the steel reinforcement detailing of beams and columns.

Minimum gap between the rods shall be 5mm more than the maximum size of the aggregates.Avoid congestion of the rods at the beam column junction.The distance between the parallel bars in a beam shall not be less than 25mm.Stirrups or rings in beams are very important.The number of rings ,position and spacing shall be as required by the engineering design.The main reinforcement as well as the stirrups should be checked thoroughly by a proffessional engineer so that to avoid the failure of the structure.The same importance should be given to the number,position and spacing of steel reinforcement bars in the slabs also.The location of bending up the bars and proper tieing as well as provision of cover blocks and chairs for top rods shall be inspected by a professional engineer before concreting.Lapping of main reinforcement in slabs and beams shall be avoided at the midspan.The size of the columns shall not be less than 12mm diameter and their should a minimum of 4 rods in a rectangular column and 6 rods in a circular columns.The horizontal distance between vertical rods in a column shall not exceed 300mm.Make it ensure that the column reinforcement cage remain in its vertical position till concreting of its foundation.The diameter and spacing of the lateral tie bars which is commonly called as stirrups should be kept as per the drawing and should be checked at all the stages.The stirrups at the location where vertical rods are lapped should be kept at closer spacing.Lapping of the longitudinal bars in a column should be staggered and not more than 50% of the bars shall be lapped at any locations.Lapping can be done when the vertical rods with lap length as per the design or two rods can be welded to save the lap length.In columns and beams the length of lap is provided as per the design.The end of the longitudinal bars of a column that goes into the footing shall be bent to a minimum length of 300mm to enable the stability till the foundation is concreted.