Shingurabi Village Suspension Bridge Technical Specification
Technical
specification
For Suspension Bridge
Technical Specification and Guide Lines for Site Engineer
Clearing of site
DESCRIPTION OF WORK
Clearing of vegetation shall consist of cutting back all trees, bushes, other
vegetation, rubbish, fences and all other objectionable material including the
disposal of all material resulting from the clearing operations.
Cleaning out existing drainage paths will consist of removing all soil,
stones/boulders and vegetation from existing drains, ditches and culverts. Any
reinstatement works will be measured and paid for in accordance with relevant
sections of these specifications, provided that such reinstatement has not arisen
out of the actions of the contractor.
EXECUTION OF WORK
The portions of the bridge to be cleared shall extend for a distance of at least 5m
from the edge of the existing bridge ‘shoulders’. All grass, weeds, and bushes
shall be cut back to as close as practicable to ground level ensuring that the root
structure remains. Branches of large trees,
The sections where drainage paths are required to be cleaned will be instructed
by the Engineer. Cleaning of existing drainage paths will include removal of all
materials that block or cover the drains and/or culverts and shall include all small,
localized slips/slumps etc.
Construction materials
All materials used in the work shall be best quality available. The final
acceptance of materials lies with implementation engineer. Implementation
engineers are responsible for the produced under their control!
Particular care shall be taken in the storage of material before use so they are
not damaged and to prevent any contamination.
Sand for mortar, plaster and concrete:
Sand for use in mortar, plaster and for concrete shall be clean natural material
graded from fine to coarse. It has to be free from organic matter, free from lumps,
clay and other rubbish.
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(Implementation engineer note): sand shall not contain more than 10% of
material finer than 0.1 mm and not more than 5% remaining on 2.3 mm sieve. All
material shall pass through a 10mm screen and shall be substantially non plastic.
If doubt the sand should be tested prior to start of work.
We have considered the following strength of the materials for this bridge:
Concrete: 20 MPa, and 15 MPa
Concrete slump: 50mm to 100mm
Steel bars: 280 MPa
Structural steel: 250 MPa.
Grout strength : 14 MPa
Mortar for stone masonry: 13 MPa
Soil bearing capacity : 1.5 kg/cm2 =15 Ton/m2
Grout slump shall be 200 mm to 250mm
1.2
Aggregate for concrete:
fine aggregate is sand as described above.
Course aggregate shall consist of quarried or crushed hard stone or a
combination of these. It shall be clean, well shaped, and free from soft matter.
Coarse aggregate has to comply with following grading.
Sieve size (mm)
25
20
12.6
10
5
1.18
Percentage of dry weight passing
100
75-100
40-80
20-60
0-20
Nothing to pass this sieve!
The right coarse aggregate will seem to consist of approximately even parts
smallish rocks up to 10mm and over 10-25mm. All material has to pass through a
25mm screen. If in doubt the coarse aggregate should be tested prior to start of
work.)
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1.3
Cement:
Cement shall be Portland cement. All cement must be fresh and dry. The bags
shall be stored in dry conditions protected from rain.
1.4
Water for mortar, plaster and concrete
Water used in mortar plaster and for concrete shall be clean and fresh. Water
has to be approved by the Implementation Engineer. Water from excavations.
Surface drains or irrigation canals must not be used unless approved by the
Implementation Engineer.
Reinforcing steel
Reinforcement bars shall be deformed cold worked ribbed steel bars of the sized
and dimensions shown on the drawings reinforcing steel shall be free from
pitting, rust, mill scale, paint, oil, grease, adhering earth or any other dirt. Such
materials will prevent the bond between the concrete and reinforcement, cause
corrosion of the reinforcement and cause the breaking of the concrete.
Stone for masonry work
Stone shall be procured from and approved source and shall be hard, tough,
compact and durable. Free from faults and openings, In general individual stones
for masonry work shall weigh between 5kg to 40kg and be of various sizes
Measurement of materials for concrete:
Fine and coarse aggregate and cement shall be mixed in the proportions shown
on the drawings or as otherwise directed by the Implementation Engineer.
As a guideline for the production of concrete intended for compaction by hand,
The quantities of water and aggregates per 50kg of cement shall be
approximately as follows:
One 50kg
Concrete Bag
of
Mix
by cement by
Volume
volume
(Liters)
1:2:4
35
(15Mpa)
1:1,5:3
35
(20Mpa)
Total
Aggregate
by volume
(Liters)
Fine
Aggregates
by volume
(Liters)
Coarse
Aggregates Water/Cement
by volume Ratio
(Liters)
210
70
140
158
53
105
0.45
0.45
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If it is found on site that measuring in liters is difficult then any other measure can
be used. This measure could be ghee tin, a wheel barrow, a bucket or a drum
made up by a community member. The only requirement is for the
Implementation Engineer to measure the item as follows:
Using a known container with known volume, such as is a 1.5 liter plastic Coca
Cola bottle, establish how many liters fit into the measure which will be used.
For the specified mix of concrete divide the required volumes (refer table above)
by the volume which fits into the container.
The number resulting from this calculation is the correct mixing ratio for the
specified mix.
Example in 4 simple steps:
A 1:2:4 concrete is to be prepared. Available on site are 16 Liter ghee tins.
16Liters of material will fit into these tins. From the table above it can be seen the
1:2:4 concrete requires 35 liter cement + 140 liter coarse aggregate + 70 liter fine
aggregate + 22.5 liter water. Small variations are allowed.
The mix in liters is the same as 35/16=2.19 tins cement +140/16=8.75 tins of
coarse aggregate + 70/16 = 4.38tins of fine aggregate + 22.5/16 = 1.41 tins water.
The total volume of this mix is only 267.5 liter.
Because it is only a very small quantity the Implementation Engineer decides to
make up a bigger batch of 3 times the volume. All quantities have to be multiplied
by 3 (three). The mix then becomes 6.5 tins cement +26.25 tins of coarse
aggregate +13.11 tins of fine aggregate + 4.23 tins water.
To make things easy the Implementation Engineer says that the mix for each
batch of 1:2:4 is to be made up of: 6.5tins cement + 26tins of coarse aggregate
+13 tins of fine aggregate + 4 tins water. This is simple for the masons and will be
as specified on the drawings.
If it is necessary, as may be for a bigger job, the Implementation Engineer can
have a better quality measure made up in the community or even use different
kinds of measures. He may use a smaller one for cement and water and a bigger
one for aggregate. The result, accurately measured volumes, will remain the
same.
How to mix and place the concrete
The aggregates and cement shall be mixed together before adding water until
the dry mix is of an even color and consistency throughout. Water (as described
in this manual) shall be added in just sufficient quantity to produce a workable
mix. Refer to the mixing table above. The Implementation Engineer will always
determine the exact amount of water to be added to the mix.
Concrete must be mixed on clean ground for a duration required for uniform
distribution of the ingredients to produce a homogeneous mass of consistent
color but for not less than 10 (ten) minutes. The mixing shall be done by trained
laborers who have been previous instructed by the Implementation Engineer.
Mixing times and material quantities must be supervised by a competent person
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on site or the Implementation Engineer himself. At the conclusion of mixing, the
area shall be thoroughly cleaned out before the concrete remaining in them has
had time to set. The mixed concrete shall be placed while fresh and in any event
not later than thirty (30) minuts after being mixed.
Compaction of concrete
Particular attention shall be paid to proper compaction of the concrete. The
intention is to produce a dense, uniform and water tight concrete of maximum
strength. Compaction of the placed shall be carried out by mechanical vibration if
this is available. If this is unavailable then hand tamping (using short lengths of
steel reinforcing) is required. Move the steel rods until the concrete becomes
homogenous and some water appears on the top surface. It is not allowed to
compact the concrete until all the sands come to the surface and coarse
aggregate is at the bottom. This is called segregation and results in poor quality
concrete. The Implementation Engineer will decide when the concrete is well
enough compacted.
Curing of concrete
Particular attention shall be given to “curing” the concrete to allow the slow
chemical hardening process to be completed. Concrete requires all exposed
surfaces to be kept continuously damp for at least 6 (six) days. The surface shall
never be allowed to become dry during this period. Concrete blinding shall be
cured for a minimum of 1 (one) day. Curing shall start immediately after laying of
the concrete and shall be maintained uninterrupted. The Implementation
Engineer will develop a method of curing.
Great care shall be taken to keep the temperature of concrete as low as possible
during hot weather so as to prevent cracking or crazing of the concrete. In hot
weather consideration shall be given to carrying out concreting operations in the
very early morning or late evening. The Implementation Engineer will decide the
best time for concreting and advise the PM.
Mortar for stone masonry:
Quantity of cement and dry sand required for 1m3 of cement mortar 1:4 for stone
masonry is cement=380 kg,
sand=1.05m3
Pointing on stone masonry wall (100m2):
Cement mortar 1:3
Cement=306 kg,
sand=0.63 m3
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Suspension Bridge
This work shall consist of all work such as fixing of cable , steel deck, tower and
anchorage which shown in drawing.
Construction Material:
As is mentioned above
Cable:
The cable property as follows:
Dia
mm
13
Weight
kg/m
0.64
Approx.Load Breaking Load Allowble Load
Kn/m
KN
KN
0.0064
103
34
26
2.61
0.0251
386
129
32
3.80
0.038
585
195
36
4.81
0.0481
740
247
40
5.94
0.0594
914
305
The cable which is used should have the above property and should be hot dip
galvanized. The complete specifications are shown in page 15.
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Bulldog Grip: The bridges of bulldog grips must be drop forged and suitable
scored to grip a round strand rope of right – hand ordinary lay having six strands.
Bridges, U – bolts and nuts must be galvanized.
How to construct a Suspension Bridge?
Step 1: Sitting out of the bridge according to drawing, all point and elevation
should be transfer to the proper site, and after that the excavation of the main
tower should be started, once the excavation is completed re check the elevation
and alignment.
The excavation should be approved by supervisor or responsible man.
Step 2. Carpentry work and steel work should be started. all materials should be
purchased according to drawing , specification and approved by supervisor..
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Step 3 : Main anchorage excavation should start and the cable laying will be
started after the casting of anchorage is completed.
Step 4 : wind cable anchorage excavation and casting of concrete should be
finished.
Step 5 : fitting of suspender with main cable see page 23 and 24 for operation.
All U bolt and other adjuster should be spaced according page 25, 26.
Step 6: lay cable for wind cable.
Step 7: After the bridge fitting is completed all U bolt and grip must be checked
and adjusted again until the bridge camber take place or bridge return to the
position.
Step 8: wing wall and Approach work. Should be done according to drawing.
Some of necessary instruction is available in the following pictures.
..
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How to lying the cable? See following pictures for more care
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How to find the length of the cable for required span? and the required length
should be calculated by following formula and after that cable should cut as per
requirement. if don’t apply this formula may be the cut cable will not use.
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HOW TO CARRY MAIN CABLE ACROSS THE RIVER?
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FITING OF THE SUSPENDER
Before to start the fitting of the cable the contractor must be read the following
instruction and after that the fitting will start.
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