How to maintain all laps staggered & not more than 50% bars to be
- Thread starter ashok
- Start date
Dnyan Deshmukh
Staff member
Do again cross check for LD, 50D is very high figure and i dont think any structural consultant will state it to 50D.
For staggered lapping.
Staggered lapping means - all bars should not be lapped at same level. You can have max 50% bars which can be lap one level.
Lapping should never fall in colum beam junction. In unavoidable situation you can show it to consultant, in that situation lapping need to be welded with cold welding rods and in stiches of length and numbers as specified by your consultant.
Lapping should be done at levels where forces are minimum.
I am considering the column have 16 nos vertical bars of dia 25mm.
Your floor to floor height is 3050mm
I m considering beam is of 600mm
So the free height is 2450mm
Half of it is 1225mm
Considering LD = 36D
As per ld lapping required is 36x 25 = 900mm
So there is a space of approx 325mm in which you can adjust 50% bars lapping below half height and above slab. 50 % bars lapping above half height of the column and below beam bottom.
So i can make my column bars to heights by cutting and adjusting heights of bars in alternate an staggered way.
Also will check for wastage of steel.
Bars comes in length of 12 meter + 50 to 150mm (you need to check the length of recieved steel as per brands, each manufacturer cuts and have + side tolerance as per their comfort levels)
Now my floor to floor height is 3050mm
If i cut bars of 3050 mm from 12meter long bar
I can get max 3 bars and a remaining peice of 2.85 meter.
We need to do all feasibility calculations and how much bars we can get, what to do with remaining cut bar of xyz length, can it be used anywhere.
Base on calculations, we can arrive at
We get xyz amount of direct waste if we cut columns and beam bars from the full bar.
We can reduce wastage if we get bars of length 12.2 meter etc.
Most of the designer consider those facts and generally design structures with floor to floor height of 2.95meter.
Your specs leads to huge amount of wastage and indicates designer is immature and dont have knowledge of practical issues.
Ok say now we got everything.
First thing is to adjust bars of column as per staggered lapping.
If slab is concreted - you can cut bars with extra height to required level by using cutting tool.
If you started new work, then the column reinforcement should be cut according to staggered lapping.
So if consider example of 3.050 meter and i need to staggered lap lengths.
I will ensure 50 % bars are at height 1 meter approx from slab top level. ( you can have it at any level and below center of free height and mostly away from center)
Remaining 50% bars at height 2.2 meter or any suitable height below beam bottom level.
So i will cut the existing bars say as below.
In one row
1m, 2.2m, 1m, 2.2m, 1m, 2.2m, 1m and 2.2m = 8 bars
In second row will cut in 2.2m, 1m and so on
Likewise all 16 rebars in columns are staggered.
I will finalize the cutting length of column rebar as 3.05 meter. - this ensure lapping always falls at same level and in staggered way.
This example gives you insight of practical problems and designing issues.
In cases where you cant do much with designing issues - you need to bare the wastage of steel.
For staggered lapping.
Staggered lapping means - all bars should not be lapped at same level. You can have max 50% bars which can be lap one level.
Lapping should never fall in colum beam junction. In unavoidable situation you can show it to consultant, in that situation lapping need to be welded with cold welding rods and in stiches of length and numbers as specified by your consultant.
Lapping should be done at levels where forces are minimum.
I am considering the column have 16 nos vertical bars of dia 25mm.
Your floor to floor height is 3050mm
I m considering beam is of 600mm
So the free height is 2450mm
Half of it is 1225mm
Considering LD = 36D
As per ld lapping required is 36x 25 = 900mm
So there is a space of approx 325mm in which you can adjust 50% bars lapping below half height and above slab. 50 % bars lapping above half height of the column and below beam bottom.
So i can make my column bars to heights by cutting and adjusting heights of bars in alternate an staggered way.
Also will check for wastage of steel.
Bars comes in length of 12 meter + 50 to 150mm (you need to check the length of recieved steel as per brands, each manufacturer cuts and have + side tolerance as per their comfort levels)
Now my floor to floor height is 3050mm
If i cut bars of 3050 mm from 12meter long bar
I can get max 3 bars and a remaining peice of 2.85 meter.
We need to do all feasibility calculations and how much bars we can get, what to do with remaining cut bar of xyz length, can it be used anywhere.
Base on calculations, we can arrive at
We get xyz amount of direct waste if we cut columns and beam bars from the full bar.
We can reduce wastage if we get bars of length 12.2 meter etc.
Most of the designer consider those facts and generally design structures with floor to floor height of 2.95meter.
Your specs leads to huge amount of wastage and indicates designer is immature and dont have knowledge of practical issues.
Ok say now we got everything.
First thing is to adjust bars of column as per staggered lapping.
If slab is concreted - you can cut bars with extra height to required level by using cutting tool.
If you started new work, then the column reinforcement should be cut according to staggered lapping.
So if consider example of 3.050 meter and i need to staggered lap lengths.
I will ensure 50 % bars are at height 1 meter approx from slab top level. ( you can have it at any level and below center of free height and mostly away from center)
Remaining 50% bars at height 2.2 meter or any suitable height below beam bottom level.
So i will cut the existing bars say as below.
In one row
1m, 2.2m, 1m, 2.2m, 1m, 2.2m, 1m and 2.2m = 8 bars
In second row will cut in 2.2m, 1m and so on
Likewise all 16 rebars in columns are staggered.
I will finalize the cutting length of column rebar as 3.05 meter. - this ensure lapping always falls at same level and in staggered way.
This example gives you insight of practical problems and designing issues.
In cases where you cant do much with designing issues - you need to bare the wastage of steel.
rameshchandrapatel
Active Member
For staggered reinforcement the the difference between two bars should be minimum 1.3 times Ld (development length) in the alternate bars of reinforcement.
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