New technologies, designs and construction methods are being increasingly deployed in order to mitigate the challenges in bridge construction. At the recent InfraBuild India conference, industry experts shared their views on the needs and requirements for bridge construction, experience so far, the key challenges faced, emerging technologies and upcoming opportunities in this space. Excerpts…
Historically, Indian Railways (IR) has been a frontrunner in bridge construction. On IR bridges are categorised as minor, major and important. Currently, there are more than 0.15 million bridges on IR’s network. Dedicated freight corridors also include a variety of bridges with innovative designs and methods of construction. Important bridges that are under construction in hill areas are bridges on river Anji and Chenab on Kashmir rail project. IR has its own codes and manuals for the bridges, which prescribe stringent inspection and maintenance schedules. These well-designed inspection and maintenance schedules for the bridges are laid down in various codes and manuals. Numerical Rating System is used for condition monitoring of bridges. IR has its own Geo-Portal where all assets including bridges are mapped. In addition, there is IR’s Bridge Management System (IR-BMS) a web-enabled IT Application for management of bridge assets, which has all the construction details, design drawings, inspection, condition details, etc. The application provides a single source of data being used from field level.
The construction industry is consuming about 50 per cent of materials all over the world. In the near future, the net zero emissions and sustainability benefit will become central to project outcome. We can achieve this outcome by using advanced material, optimized design, reduced construction time, stress on refurbishment, maintenance, etc. Digital transformation across all sectors is an emerging trend. Building Information Modelling (BIM) will play a key role in the future. There are various construction projects being implemented using digital twin technology by which the monitoring progress and asset management are becoming very efficient. 3D printing of modular buildings are becoming quite popular and being used extensively in China and some other parts of Asia. Construction procurement is also changing and the new trend is emerging where revenue based on the economic, social and environmental outcomes in asset life cycle is becoming key to the procurement process. Diverse workforce, inclusion, staff motivation and retention, using resources away from traditional civil engineering background are some of the key trends that is likely to shape the future of civil engineering.
Lt Gen. Ravi Shankar (Retired)
New Generation Modular Bridges – a Gap in National Capability: Modular Steel Bridges have not received the attention they deserve in India. The concept is however not new. One of the three most important technological developments of the Second World War, the Bailey Bridge is still being used in India as a quick fix during an emergency. They are also used by the Border Roads Organization to speed up road construction in the mountains. With the axle loads of vehicles increasing, the Bailey bridges are prone to over loading, making them unsafe. Other problems are that their life is relatively short; they are single lane and thus choke traffic on double lane National Highways. The new generation modular bridges used all over the world have overcome this. They can be constructed as permanent bridges, as fast as the Bailey Bridge and can take the required loading as per IRC codes.
A major gap thus exists in our national capability to respond to emergency needs, as we are still limited to the use of Bailey Bridges. We must shift to new generation bridges, which can be of single, double or three-lanes. These have standard members for trusses that can be stocked in bulk. It can be delivered on site at short notice, ready to be assembled and launched, all in three to four weeks, as against conventional bridges, which can take up to 18 months. This is beneficial for infrastructure that needs to be refurbished on busy routes as the traffic needs to be stopped or diverted for less time. This can be extremely cost effective if you allow for the value derived by the speed of launch, lesser maintenance and commercial savings because of minimum down time due to construction.
Orthotropic steel decks used in these modular bridges are designed to distribute the loads better, and are much lighter than concrete decking. These designs create a reduction of 400-500 tonnes of Dead Load in a two lane bridge of about 60 metres. We have started using this decking selectively in India, in some projects to keep the sub-structure light. Together with modular trusses, the applications include replacing super structure for old bridges where traffic is high and down-time critical or in emergencies when important road-communications have to be restored urgently. The communications along our borders can considerably be enhanced with this.
Geospatial technology for monitoring the condition of bridges remotely is another area that needs focus, especially for bridges in difficult areas including railway bridges.