Setting-out Works
Setting-out of a building marking of a
building position, size and shape in terrain.
Vedprakash marlapalle
Setting out of Load bearing Structure
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In this method , the rectangle ABCD formed by the center lines of
the outsides of the walls of buildings is set out accurately with tape.
The corner of the building are then located by measuring there
distances with reference to these rectangle. As the excavation
proceeds ABCD will get disturbed & hence they will no longer
available for reference. To over come this difficulty reference stakes
1 to 8 on the prolongation of the sides..
In uneven ground the required reference points, may be transferred
on the ground by using plumb bob.
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Setting out of culvert
Fix a peg at O
Set up theodolite over O
Bisect the point B. and fix the a number of points along OB.
Transits the telescope and fix a number of points along OA.
Set out the line CD at right angle to AB and fix a number of points
necessary to define the line CD .
Set off the distance O1,O2,O3,O4 etc along CD. On side of O and
1a,2b,3c,4d, etc along AB on either side of O. fix arrow at these
points.
In similar manner other corner of the wing walls and abutments may
be marked by their co-ordinates and pegs are driven.
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Setting out sewer
Fix stakes on the ground at the center line of the proposed sewer at 20m
intervals.
Set out a parallel line to the proposed center line of the sewer on one side
at a distance apart so that it may not get disturbed during excavation.
Excavate the sewer trench of desired width and depth.
Erect cross heads at 30meter apart and each change of gradient and
direction.
Set the top edge of each sight rail truly horizontal with help of a spirit level.
Drive in a nail on the top edge at the centre of the sight rail to define the
centre line of the sewer.
Establish the gradient of the line joining top edge of two consecutive sight
rails as that of the invert of the sewer.
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Setting out of bridge pier
Locating pier position
Lay one base line on each bank exactly at right angle to center line
AB , extending on either side of the centre line.
Measure the accurate length of centre line AB by triangulation.
Locate the position of the piers on the centered line a under.
Calculate the distance BP1, P1P2,P2A between the abutment and
piers.
Measure distances B1,B2 equal to BP1 and BP2 respectively on the
base line perpendicular at B on either side.
Similarly measure distances A2, A1 equal to AP2 and AP1 on the
base line perpendicular at A on either side. The interacting line 1-1&
2-2 make angle of 45 with base lines on opposite banks and also
with the centre line AB
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The position of pier 1 may be located by simultaneously sighting at
the interesting of the two intersecting lines 1-1
Similarly the position of pier 2 may be located by simultaneously
sighting at the intersection of the two intersecting lines 2-2
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Transfer of center line inside
tunnel
A theodolite is set up on top of the hill at a suitable position to
maintain the center line of the shaft.
With the help of leveling instrument, the RL of both ends of the shaft
are determined. Since the bottom level of the tunnel is already
determined, the exact depth of the shaft is calculated with reference
to the top RL.
Then the excavation of the shaft is started and verticality is
maintained by plumb bob suspended from wire. Excavation is
continued until the calculated bottom level is reached.
the center line inside the tunnel should be maintained by a precise
theodolite.
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Checking verticality of high rise structures.
its very easy. first set the total station, that is, you put on
tripod and level the bubbles. the place you set it should not
be very far from the buildings you are checking for
verticality. switch on the total station. you need not to set
anything. bisect the bottom of one corner of the building
and clamp the alidade of the total station. turn the telescope
upwards as you sight through it. if the cross hairs move
along the edge of the wall all along to top, then the building
is vertical. but there may be small variations which are
negligible e.g deviations to left and right as you go up. but
if there is a constant deviation to one side, then there is a
problem with verticality.
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