Jamuna Bridge
Photo: AFP
My attention has been drawn to the piece on Jamuna Bridge published in your daily on March 5 by Engr. Saikh Wazir. Apparently, his technical analysis of bridge construction contains valuable suggestions. It is presumed that he has visited the site and made visual inspection before making such detailed technical advice on the physical aspects of this mammoth construction. The design and structural detail of such construction is always based on load factor and tolerance level. Jamuna Bridge was originally planned as road link between two parts of the country i.e. East and West. The bridge has provided enormous possibilities and has revived the hopes and aspirations of the neglected monga people as well as the most deprived part of the country. When the design and structural details of the road bridge were at the final stage, the then govt decided to include provision for railway. The inclusion of railway on a road bridge changed the technical criteria and design parameter of the road bridge, that is, railway to run both broad gauge and meter gauge on a single section & four-lane road. This means load bearing capacity of the bridge had to be increased substantially as it would include thousands of concrete sleepers plus three heavy rails for broad gauge and meter gauge besides the rolling stock which includes passenger train, cargo rake and fully loaded tank wagon. It is hoped that Bangladesh Railway, Roads & Highways and communications ministry have provided correct data for maximum load bearing capacity of the bridge to accommodate the railway traffic. It is evident that the Korean construction company under the guidance of the engineering consultants and the government agencies involved possibly did not change the basic design required to accommodate extra load for the railway, rather they modified the design. At present the railway track rolls over the cantilever from the shoulder of the main construction, that is, the road bridge. One would like to know what is the load bearing capacity of the cantilever and what is the actual load that has rolled over the cantilever from time to time. There are mainly two weight factors i.e. weight of the thousand concrete sleepers plus the weight of three heavy rails and the total load when a passenger or goods train or fully loaded tank wagon rolls over the cantilever of the bridge. Thus what is the design load and the actual load, that is, rolling over the cantilever at present? Further, the vibration tolerance limit at critical point and whether this limit has been ignored and crossed. Clippings in TV showed that the bridge has tilted towards railway side. Thus the bridge has been destabilized which resulted in tearing off from the holding anchors which has also caused the cracks both horizontally and widened the gap between sections which will ultimately give in. During the period of the last government when oil tanker could not reach Bagabari (North Bengal) oil terminal due to navigability problems, the government decided to use the Jamuna Bridge to transport oil to North Bengal, though railway ferry could have been used between Bahadurabad and Tistamukh ghat and also Jagannathgonj and Serajgonj ghat to ferry tank wagons. Thus the than government violated/ignored the permissible load code parameters of the bridge and allowed fully laden tank wagons with petroleum products each weighing around 50 to 60 ton, that is, weight of tank wagon + petroleum product. If the rake contains 20 such tank wagon plus 60 ton locomotive total weight comes to more than 1200 tons. It can be summarised that actual load beyond the permissible load on the cantilever railway track has destabilised, tilted the structure and caused gap in the sections vertically as well as slicing of the horizontal sections by tearing apart all the holding structural mechanism. It may be noted here that the high-tension inter-connector pylon stands on the edge of the shoulder of the main structure on this side of the bridge. On the other side of the bridge, only the East-West gas pipe line has passed below the similar cantilever. The bridge has not been damaged as expressed by Engr. Saikh Wazir, rather it has been damaged beyond repair.
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