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The Tragedy of Bridge Management in West Bengal

Partha Pratim Biswas (drppb@yahoo.in) is with the Department of Construction Engineering, Jadavpur University.

Recurrent bridge collapses in West Bengal point out to the lack of coordinated institutional arrangements in the governance of bridge infrastructures in the state. Accountability in designing and construction, and supervision and maintenance, which strengthen different tiers of bridge governance system, are missing. Given the dearth of skilled workforce and the physical infrastructure for supervision, bridge maintenance is reduced to patchworks of painting railings and girders, without persistent evaluation of structural health and resultant repair or rehabilitation of infrastructure.

Three fatal road overbridge (ROB) collapses in Kolkata within a span of five years have triggered serious concerns regarding the management of bridge infrastructures in West Bengal. Though one cannot overlook the “humanness” of engineering, the increasing number of fatal structural disasters presents a confusing image of technological advancements (Petroski 1992). On the other hand, bridges being state-owned assets, governments cannot shirk their accountability for management of such infrastructures. Thus, bridge failures are needed to be introspected from the perspectives of both engineering as well as policy failures.

Institutional Arrangement

Over time there has been a modal shift of freight traffic from rail to road in India, with 65% of the freight traffic being carried by the road sector now. Concurrently, a major change in vehicle configuration on Indian roads has taken place in the form of “containerisation.” Big containers as a trailer unit with multiple large axle load have become the need of the hour to make the road transport cost-effective and competitive with respect to other modes. For handling such higher axle loads at increasing frequency, the ROBs need to undergo specific structural changes in the form of “retrofitting” (Priestley 2007). Except for a small proportion of bridges that are maintained by the National highway Authority of India (NHAI), ROBs in India are not retrofitted in general. Though the repair of bridges is qualitatively different from that of roads in terms of both duration and costs, they are usually treated at par by most of the institutions responsible for bridge management in India. To increase the carrying capacity, existing roads are widened and strengthened without strengthening the ROBs, potentially to curtail expenditures, among other things, notwithstanding that the probability of casualty involved in bridge collapse is higher than that from the collapse of a road section.

In West Bengal, the supervision of various bridges is entrusted to different ministries and government departments. In Kolkata alone, for example, the Tallah bridge on the Barrackpore Trunk (BT) road is under the state Irrigation and Waterways Department; the recently collapsed Majherhat bridge is under the Public Works Department (PWD); the Vivekananda Setu (commonly, the Posta flyover), which collapsed in March 2016, is under the jurisdiction of the Urban Development and Municipal Affairs Department; the Kolkata Port Trust (KPT) looks after the Howrah bridge (Rabindra Setu); the Hooghly River Bridge Commissioners (HRBC) looks after the Vidyasagar Setu; the Kolkata Municipal Corporation is the custodian of few minor bridges and culverts in the city; while the bridges over railway tracks are generally under the Indian Railways.

Following the collapse of the Majerhat bridge in September 2018, two major changes were proposed for this fragmented organisational structure of bridge governance. First, the I&WD declared to transfer the responsibility of future maintenance of the bridges under its jurisdiction to PWD. Second, the chief minister announced to set up the “State Bridge Corporation” to supervise the design and construction of new bridges and monitor the rehabilitation of old bridges with comparatively smaller spans in the rural areas. But, these seem to be knee-jerk efforts for contingency management. It is not clear how changing the jurisdiction will resolve the governance crises, given that none of the aforesaid state government establishments have enough workforce, technical skills and financial resources for managing bridge infrastructure sustainably. In addition, the lack of coordination between different government departments is a major obstacle to efficient governance of bridge management system; and this issue remains largely unaddressed. Moreover, extant experiences with the Uttar Pradesh State Bridge Corporation found that setting up such bodies has not been effective in curbing the incidents of bridge collapse. Instead, the government and/or the nodal agencies need to adopt appropriate technological solutions and a professional mindset for the governance of bridges.

Structural Health

In this context, one must remember that bridge healthcare is comparable to human healthcare. Just as aged people need more frequent medical examination and care than the youth, so do older bridges. Again, just as diagnostic tests and treatments vary across patients and diseases, similarly bridges need to be treated differently depending upon the types of distress identified during structural monitoring. So, there is no blanket solution for bridge repairing and strengthening.

Structural health monitoring is nothing but a scientific approach to study the response of bridge components in real- life situations with advanced technology either in a continuous or discrete manner (Farrar 2007); and herein lies the need for planning by the nodal agencies. In this context, the remaining life assessment of bridges must be made to compare the cost of their repair and/or rebuilding at any point of time (Priestley 2007). It is to be noted that the cumulative burden of bridge maintenance cost is likely to be substantially higher than the cost of new construction, since the service life of bridges is expected to be markedly long. Similarly, rejection of a bridge, too, should be pre-planned based on its remaining life assessment data so that suitable alternatives can be formulated well in advance. Thus, the government budget must be prepared for not only the construction of new bridges, and/or repair/rehabilitation of old bridges, but also to accommodate the costs of rejecting a bridge infrastructure.

In India, the structures that were built in the post-independence era are identified to have higher hazard of maintenance, with maintenance costs increasing exponentially when timely repair is not done. This point needs to be asserted in the current context, when poor and untimely maintenance predominate as the cause of fatal bridge collapses. Unfortunately, a political blame game following every bridge collapse has been the trend in West Bengal’s state politics. Such blame game ultimately dilutes the process of introspection and the scope of learning from failures, with the latter being one of the most trusted paths to develop sustainable engineering design and forensic engineering.

Engineering Issues

Bridge collapses can be understood in terms of four broad issues: First, (faulty) bridge design; second, (poor) construction materials; third, choice of construction technology and supervision of construction work; and fourth, monitoring in post-construction period/during operation. For bridges that are in operation for a long period, such as the Majherhat bridge, fault in design and construction materials may be ruled out; while the lack of monitoring over the period of operation is a more potent cause of collapse. However, the local “syndicate” pressure often compels the contractors, even if selected on techno-commercial grounds, to compromise on the quality of construction material. The contractors/executing agencies are compelled to outsource the material contracts to the local suppliers, who are the potential source of dilution in the quality of construction materials. The Posta flyover collapse in 2016, for example, is reported to be partly due to faults in design and largely due to poor construction materials. The recent collapse of bridge girders in Fasideoa near Siliguri and in Kakdip in South 24 Parganas district, are classic examples of faulty construction practices adopted by the contractors. It is to be noted that faults during construction may not initiate an instantaneous collapse of bridge elements, but progressively reduce the service life of the bridges when these are functional. The recently identified faults in Dunlop bridge, Ultadanga bridge and Chingrighata ROB are examples in this category. Unfortunately, the government departments dealing with the governance of bridges do not pay adequate attention to any of these issues unless a disaster takes place.

Designing Urban ROBs

Bridge inspection entails components of both routine as well as detailed inspections, which are considered mandatory for the upkeep of the bridge inventory (IRC 2010). However, the government establishments in West Bengal do not adhere to these modules of inspection due to a shortage of skilled engineers and inspection infrastructures. There is no denying that the extant graduate courses in civil or construction engineering do not include “inspection” as a major topic in the bridge-engineering curriculum. Therefore, unless the in-service engineers are trained specially, these departments cannot overcome the limitations of professional bridge inspections. Simultaneously, the skills of contractors in erecting bridges by applying modern technologies are dubious. Moreover, the pressure of early completion of construction/repair projects with semi-skilled local labour is emerging as a growing threat. It will be relevant to mention here that the transfer of technology from technocrats to technicians is a time-consuming process, particularly in developing societies; and till such transitions occur, cautious steps should be taken while executing bridge engineering with the existing skill sets.

In Kolkata, there is little room for increasing road lengths, except by introducing elevated roads at selected locations of congestion and bottleneck. Due to land acquisition problems within the built-up areas of the city, the geometry of an elevated road is usually kept like that of the existing road at the ground level. Thus, the elevated roads are designed with a difficult geometry of a steep radius of horizontal curvature and vertical gradients. In this context, it is important that the policymakers dealing with urban infrastructure development should introspect the structural design guidelines of steel bridges with a small turning radius and steep vertical gradients. It is important to note that the probability of road accidents due to overspeeding is usually higher on elevated roads because of their difficult geometry with less traffic density. Against this backdrop, the sustainability of elevated roads in congested urban areas should be evaluated.

Climate Change

Ageing of bridge structure is not only associated with the load that it carries during its service period, but also with the climate/environment that it endures. Therefore, unanticipated factors associated with climate and/or environmental changes often adversely affect the service life of a bridge (Neumann et al 2015). In urban areas, the growing levels of chloride, sulphate, oxides of carbon, sulphur and nitrogen are found to damage the top skin cover of concrete bridge structures, making the concrete porous for moisture to reach the reinforced steel or prestressed cables forming the backbone of the concrete structure. Continuous moisture movement aggravates the corrosion of steel, resulting in drastic loss of strength of the concrete, and premature collapses. Corrosion usually exhibits through spalling of surface and surface cracks, which widen over time. Thus, surface cracks on concrete structures act as indicators of structural weaknesses, which can be identified even by the unskilled technicians. Similarly, the presence of rooted plants on bridge structure is also a major indication of water-filled cavity in concrete. More than three-fourths of Kolkata’s bridges suffer from such problems due to the lack of petty and/or routine maintenance. The lack of minor maintenance at required time cumulates to cause major distresses. It is high time for the policymakers to realise this.

In bridge structure, not only the metallic corrosion but also the non-metallic corrosion of bearing and the stress corrosion of different components are to be assessed periodically. Painting bridge railings and girders, in the name of bridge maintenance, has become a common practice in West Bengal. This is not only unscientific but also uneconomical. The paints used by the government departments do not have the porosity and quality to protect the bridge structures from ingress of water and corrosion. Moreover, a popular notion amongst the representatives is that colour washing and illumination are the most important tasks of bridge maintenance. Given this, the institutions/departments for bridge maintenance have started neglecting the more pressing issues of bridge safety. Herein lies the need for a professional mindset and a scientific understanding of the policymakers for making transport infrastructures safe and sustainable.

References

Farrar, C R and K Worden (2007): “An Introduction to Structural Health Monitoring,” Philosophical Transaction of the Royal Society A, Vol 365 (1851), 15 February.

IRC (2010): “Manual for Highway Bridge Maintenance and Inspection,” Indian Roads Congress, Special Publications 18, New Delhi.

Neumann, J E, J Price, P Chinowsky, L Wright, L Ludwig, R Streeter, R Jones, J B Smith, W Perkins, L Jantarasami and J Martinich (2015): “Climate Change Risks to US Infrastructure: Impacts on Roads, Bridges, Coastal Development, and Urban Drainage,” Climate Change, Vol 131, No 1, pp 97–109.

Petroski, H (1992): To Engineer Is Human: The Role of Failure in Successful Design, First Vintage Book Edition, April.

Priestley, M J N, F Seible and G M Calvi (2007): Seismic Design and Retrofit of Bridges, John Wiley & Sons, Inc.

Updated On : 4th Nov, 2018

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