Bridges are normally designed for 60 years with a regular maintenance schedule. Most modern major bridges are designed and constructed for a service life of 100-120 years. However, their lifespan can be extended if maintained properly. In fact, many British era bridges in Mumbai and Delhi can safely be used in the years ahead with some minor repairs.
However, routine inspection is an imperative.
NHAI has prepared an elaborate inspection plan and made it a contractual responsibility of the contractor or concessionaire. To ensure better inspections, availability of mobile bridge inspection units has been made mandatory. In important bridges, instrumentation has also been done to keep a continuous watch on the behaviour of the bridge. Naini Bridge and Chambal Bridge are examples in this regard.
“Quality of construction and maintenance are definitely important factors that influence longevity,” says SV Desai, Executive Vice-President & Head - Heavy Civil Infrastructure IC, L&T Construction. “Quality of construction is ensured through operational and skill checks (by constructing a true prototype and conducting mock trials, etc, before actual construction), engineering checks (full-scale testing of critical components to ensure operational safety throughout design life), and administrative checks (authority audits as per systems and compliances, independent sampling and third-party testing) to ensure the bridge will serve its intended purpose for the defined duration.”
After construction, he adds, quality is maintained by installing IoT-based monitoring devices for real-time data and periodic replacing of components like bearings, joints and cables, wherever required. The Bridge Preventive Maintenance Plan (BPMP) aims to extend lifespan by identifying and performing maintenance activities approved by the concerned authorities, like deck treatments such as waterproofing, painting, deck asphalt replacement, and the like.
As for post-construction, NN Sinha, Chairman, National Highways Authority of India (NHAI), and Managing Director, National Highways & Infrastructure Development Corporation (NHIDCL), says, “For up to 10 years, the authority entrusts O&M work to the EPC contractor; after completion of the O&M period, the authority itself, or through an OMT contractor, maintains the bridge.”
In terms of safety, a separate chapter on SHE (safety, health and environment) is now a part of all major bridge contracts, informs Limaye. And Sinha shares that all structures are constructed based on the standards and specifications of the Indian Road Congress (IRC). Additionally, plans and drawings submitted by the contractor are reviewed by a safety consultant, both during tendering and after construction.