Godavari Arch Bridge

The Godavari Arch Bridge is synonymously known as the Kovvur-Rajahmundry Bridge. It is a relatively new bridge which has been built on river Godavari in Rajahmundry, a small town in Andhra Pradesh, India. This bridge is considered to be the third bridge in the series of bridges that criss-crosses the river in the state.

Old Godavari Bridge is a stone bridge, which is also referred to as the Havelock Bridge, was built by Sir Arthur Cotton in 1897 and the second railway bridge. It is a truss bridge which functions as a rail-cum-Road Bridge and is also known as the Godavari Bridge. Both of these bridges are located upstream of the new bridge and run laterally to the Godavari Arch Bridge.

Geography

The Godavari Arch Bridge has been built across the river Godavari which is considered to be South India’s largest river at 1,000 kilometers in length. The bridge has been built in the region with the river entering the reach of the deltaic before discharging itself into the sea 60 kilometers downstream of the bridge. The bridge has been built in a cyclonic area where the wind speed touches 200 kilometers (120 mi) per hour.

There are two channels to the bridge, the Rajahmundry channel and the Kovvur channel. This is one of the major reasons as to why the bridge is also referred to as the Kovvur-Rajahmundry Bridge.

A rocky bed which is also deep can be found at the Rajahmundry channel where the water level is 18–20 meters (59–66 ft). On the other hand the Kovur channel is shallow. It has a water depth of about 8–10 meters. Clay deposits are what make up the riverbed.

Description

Specifications

Pre-stressed concrete has been used to make the box girders, twin arches and also the struts.

28 corresponding spans of arches in twin mode of parabolic likeness are spaced at 5.6 meters each of the 97 meters spans. The total length of these spans is f 2.7 meters.

The effective span from centre to centre of the bearings is 94 meters (308 ft).

Every girder is 95.552 meters long.

There are 28 piers in the substructure of the bridge.

Design aspects

A girder in the shape of a bow-string is what makes the framework of the bridge. When it was initially designed, the bridge was built to accommodate the speed of the trains at 160 km per hour.

The cyclonic conditions of the state led the builders of the bridge to build it without live load at 200 kilometers (120 mi) per hour. The designers have also undertaken the dead load at 158 kilometers (98 mi) per hour. Being in the Seismic Zone I, the seismic load of the bridge has not been taken into account in the bridge’s design.

The Godavari Arch Bridge has been built in such a way that trains on it could run at a speed of 160 miles (260 km) per hour. It has also been designed in such a way so that they are able tolerate wind speeds of 200 miles per hour whenever a cyclonic storm occurs. This storm usually occurs in the region of Rajahmundry.

Arches

The arches of the bridge have been designed in such a way so that they are able to withstand 80% of the live load as well as the dead load is transferred from the hangers. These arches thus play an important role of discharging the flexure and shear stresses on the girder. Each hanger location which connects the bridge has twelve sinking supports which connect it with the girder.

Hangers

There are 24 hangers in each and every span of the bridge. These hangers have been further categorized into six types. Each one of them depends on their length. Every one of the Dina Hangar has been constructed from 49 high tensile steel wires which are of 7 millimeters (0.28 in) diameter each. These entire wires can been running laterally to each other. What’s more they have all been wrapped in a pipe which is of high tensile and is also cement grouted.

Girders

Grade concrete of M42 type is what was used to build these box girders. Each and every girder has been pre-stressed with 16 longitudinal cables. All of these cables were in turn pre-stressed each having a force of 2950 kN.

The responsibility of the box girder is to function as the deck of the bridge. It also has to carry the live load in which the end diaphragm is of 1,000 millimeters (39 in) thick) with inspection windows.

The design of the girder has been made in such a way so that it is able to withstand all sorts of train loads. Attempt has also been made to design the bridge in such a way so that it is able to withstand the temperature variation of ±10 °C (50 °F). Seven stages of casting were undertaken in the construction and design of each girder from removal of work forces to girder stressing in the arch section. The designers have also undertaken to look into the matter to see that no types of cracks appear in the arches at any stage.

Bearings

Pot bearings have been provided in the bridge of 1050 tonnes capacity. The girder takes its support from four pot bearings.

The role of the bearing which is PNa is to facilitate free sliding in both the directions which means that it functions in on one pier whereas the PNe type slides in only one direction and in the remaining pier the PN type is fixed.

It was from Switzerland that sets of three bearings were imported while the remaining bearings were made in India.

So, this is the grandeur of the Godavari Arch Bridge.

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