A CULVERT
is defined as a structure having a total length of 6.0 M or less between the inner faces of Dirt walls(Backing wall) A CAUSEWAY
is a structure constructed across a stream which allows the normal flow of water through its vents and allows the Flood waters at MFL CONDITION above it. Normally Causeways are designed to take 30% of Flood water through vents and
balance to overflow during MFL Condition
A MINOR BRIDGE
is a structure having a total length of 60.0m or less
between the inner faces of Dirt walls (BACKING WALLS) i.e. more than 6.0M and less than 60.0M
A Major Bridge
is a structure having a total length of more than 60.0 M Between the inner faces of Dirt walls (Backing
walls)
ROB Means a Road Over Bridge
constructed across a Railway line over the Rails. This means the road traffic passes over the Railway line.
RUB Means a Road Under Bridge Constructed across a Railway line under the Rails. This means the road traffic passes under the Railway line. This is less costlier, but causes stagnation of water in rainy season and may cause submersion during y rains.
WATER
The properties of Water plays very important roll in achieving the required strength of concrete
(1) The PH of Water should be more than 6
(2) The Sulphate content should be less than 400mg/Litre.
(3) The Chloride content should be less than 500mg/Litre for R.C.C and less than 2000 mg/Litre for P.C.C
Curing of water is very important and must be continued for 28 days irrespective of grade of cement.
Water used for mixing and curing should be of same source and of good quality. It is a wrong notion that Water used for Curing need not be of good quality
In case of Structures near Sea coast Potable water may not be available. In such cases Extra water lead may be included in Estimate and insisted during Execution.
Adequate number of COVER BLOCKS with Binding wire fixed may be casted and cured well in advance not less than 15 days and CURED under water before laying
PIPE CULVERTS
(1) The Depth of Foundation for Pipe culvert should be 0.90M Below sill level as per IRC SP-13, WITH Bed protection. It may be increased to 1.20M Below sill level WITHOUT Bed protection.
(2) The Sill level may be fixed at 0.15M Below existing Bed Level.
(3) The Width of Body wall at bottom may be fixed as (0.40H+0.30) where H IS HEIGHT OF WALL in Meters
(4) In case of multiple row Pipe Culvert the distance between the pipes should be not less than ½ the Outer diameter of pipe subject to a minimum of 450mm.
SLAB CULVERTS
(1) Slab Culverts are effective in discharging flood waters compared to Pipe culverts even though the construction takes little more time. The Pipe Culverts are likely to get choked due to Debris, Jungle etc in vents during floods.
(2) IRC SP-13 gives the sections of Abutments, Wing walls for different heights, sections of Deck slab and Reinforcement for Spans ranging from 1.0M to 6.0M (3) The Sections in IRC SP-13 are applicable for soils with a S.B.C. of not less than 16.50 T/M2. For lower S.B.C. Values of foundation soils Raft foundation may be adopted.
FOUNDATIONS
SHALLOW FOUNDATION(< 4M) DEEP FOUNDATIONS(>4M)
RAFT INDIVIDUAL
(1) Raft Foundation is adopted when the S.B.C. of Foundation soil is less than or equal to 10T/M2 like Black cotton soils, marshy soils with small span arrangement.
(2) Individual Footings are adopted when the S.B.C of the Foundation soil is more than 16.50T/M2.
(3) This type of foundations are suitable when HARD soils are met at shallow depths and in case of ROB/ RUB where there will not be any scour likely to
occur as there will not be any flow.
(4) Suitably designed Aprons are to be provided both on Upstream side and on Downstream side to Protect the Bridge structure.
Earth work excavation for open foundations in sandy soils. As it is difficult to excavate individual foundation trenches, the excavation was done continuously like a canal. As it is in the heart of town limits shoring and shuttering adopted to avoid sliding of sand and damage to adjoining railway quarters as they demanded total cost of structures on the plea that there quarts will be collapsed.
LAYING OF CEMENT CONCRETE BED 100 MM THICK UNDER PIER FOOTING
Reinforcement completed for pier footings. A beam connecting the three circular piers can be seen above the footing reinforcement. The center to center distance of piers should be verified carefully and main reinforcement of pier should be
A trapezoidal section was
adopted for pier footing.
Hence the top reinforcement was to be bent accordingly to suit the concrete section with a cover of 50 mm
Laying of plain concrete for Abutment foundations in V.C.C. M15 using 40 mm graded metal. Each layer should not exceed 200 mm for proper vibration of each layer. Shear keys in the form of holes may be provided by keeping concrete blocks in each layer of concrete and removing the same after one hour to leave holes and to act as key.
Concrete completed for pier footing. A trapezium section with a beam connecting 3 circular piers of 1.0 m dia. can be seen. The shutters should be thoroughly checked for maintaining three piers in one line and at exact distance to avoid variation in span.
Circular piers of 1.0 m dia. completed by laying concrete in each stage of 2.50 m inside face of sloped face of Abutment can be seen with weep holes.
PHOTO SHOWING TREMIE PIPE FOR BOTTOM PLUGGING OF WELL.
Filter media using 50% of 150 mm HBG stone and 50% of 40 mm HBG metal were placed behind Retaining walls to allow seepage water to drain off easily in to weep holes. As the formation is to be filled with sandy soils, 0.60 m thick Gravel Backing adjoining the filter media is provided to avoid scooping out of sand with seepage water from pavement, other wise Gravel Backing adjoining filter media is not necessary
STRIP SEAL EXPANSION JOINT FOR LARGER MOVEMENTS ELASTOMER SEAL I .S ANGLES ANCHOR RODS ANCHOR RODS
Fixing of strip seal joint with main reinforcement of superstructure in the recess of concrete
Close view of fixing of strip seal joint with main reinforcement of super structure
Camber should be provided in joints itself at RCL and should
The top level of strip seal joint shall be kept equal to top level of wearing coat and care must be taken that no jerk is observed at joints.
PIER
WELL AFTER SCOUR
WELL AFTER SCOUR
DECK SLABS COLLAPSED PIER
The load is to be accommodated in the span which gives maximum bending moment. For 10m clear span the critical load works out to 68.0 MT (4x17.0 MT). For other spans this will be different. This critical load is to be increased by 25% as per is 456-2000
LOADING FOR CLASS 70R LOAD AS PER APPENDIX I OF IRC 6-2000
TRACKED VEHICLE :70.0M.T WHEELED VEHICLE :100.0 M.T
LOAD TEST FOR BRIDGE 70R LOADING
THE LOADING SHALL BE DONE AT 30%,50%,70%, 80%,90%,100% 0F TOTAL LOAD.
THE MAXIMUM DEFLECTION PERMISSIBLE IS 40L2/D (WHERE L IS THE EFFECTIVE SPAN),AS PER CLAUSE 17.6.3.1 OF IS 456-2000 WHICH WORKS OUT TO 5.33mm FOR 10.76M C/C SPAN. THE STRUCTURE SHOULD HAVE A RECOVERY OF NOT LESS
THAN 75% OF MAXIMUM DEFLECTION DUE TO SUPERIMPOSED LOAD ON REMOVAL, AS PER CLAUSE 17.6.3 OF IS 456-2000. THE SUPERIMPOSED LOAD SHALL BE KEPT FOR 24 HOURS AND
LOAD TEST ON R.O.B. MARKAPUR WITH STEEL PLATES OF 610X410X25 MM EACH TAKING A LOAD OF 10.625 M.T
LOADING WITH SAND BAGS EACH WEIGHING 35 KG
CLOSE UP VIEW OF LOADED PLATES 610X410 MM, IS BEAMS, PLOTFORM
CLOSE UP VIEW OF LOADED PLOTFORM, CHANNELS, IS ANGLES,PLATES
SIDE VIEW OF PLOTFORM WITH SAND BAGS EACH WEIGHING 35 KG
LOADED PLOTFORMS 2 NO. EACH WITH 4 SETS OF PLATES. LOAD ON EACH SET OF PLATES IS 10.625 M.T
LOADED PLATFORMS 2 NO, EACH WITH 4 SETS OF PLATES. LOAD ON EACH PLATE IS 10.625 M.T .
LOADING PLOTFORMS EACH CARRYING 42.5 M.T TOTALLING TO 85.0 M.T FOR 10 M CLEAR SPAN`
DIAL GUAGES UNDER SLAB FOR MEASURING DEFLECTIONS 3 NO. ALONG SPAN+ 2 NO. TRANSVERSE DIRECTION
CLOSE UP VIEW OF DIAL GUAGES FOR MEASURING DEFLECTIONS, PLOTFORMS
DEFLECTO
METER
IDENTIFIC
ATION
MEMBE R LOCATI ON DEFLECTI ON AFTER 24 HOURS LOADING (MM) DEFLECTIO N DUE TO TEMPERAT URE DURING LOAD PERIOD (7 AM TO 6PM) IN MM COR RECT ED DEFL ECTI ON (MM) LIMITIN G DEFLECT ION (MM) MAX VAL UE AS PER ANA LYSI S (MM ) % RECOVER Y AFTER 24 HOURS OF LOADING D1 R/S END 1.17 0.92 UPWARD 2.09 5.33 mm 6.90 85.6% D2 CENTRE OF DECK 0.84 1.15UPWARD 1.99 -do- -do 89.4%
D3 L/S END 0.46 0.77 UPWARD 1.23 -do- -do- 86.2%
D4 ¼ SPAN 0.94 0.77UPWARD 1.71 -do- -do- 87.1%
D5 ¼ SPAN 0.73 0.73 UPWARD 1.46 -do- -do- 80.1%
RESULTS OF LOAD TEST
1) From the results of load test ,the maximum deflection recorded is 2.09 mm ,against the limiting deflection of 5.33mm,as per clause 17.6.3 of IS 456-2000.
2) The deflection recovery of the Deck slab was found to be more than Stipulated minimum % of recovery of 75% after removal of test load.
3) Hence it can be concluded that the deflection behavior of the Deck slab of the bridge is within the permissible limits.
