With rapid development of new technologies and evolving construction techniques, there have been major changes in how bridges are constructed across the globe. Artificial intelligence, virtual reality, drones, site robots, and other smart construction techniques and concepts are now being applied in almost all construction sites. Another frequently implemented smart construction technology used in bridge design is drones with light detection and ranging sensors and global positioning system tracking. By using drones, bridge engineers are able to pinpoint the location on which the bridge will stand, significantly minimising errors.
Precast segmental construction technology
Precast segmental construction technology has gained popularity in recent times. It is used for achieving accelerated bridge construction, better quality control and low life cycle cost, as well as for handling elements with difficult shapes and congested reinforcement at the ground level. This technology demands no formwork at site and therefore there is minimal disruption to existing traffic during construction. With only erection work at site, this leads to a reduction in noise and dust pollution. By using this technology for large projects, bridge construction can be standardised, which will help in saving cost. The Bandra-Worli Sea link is one of the major precast segmental concrete bridges in India. The brid-ge comprises parallel precast concrete box girder structures, which also include single tower two-span cable-stayed main span.
Building Information Modelling
Building information modelling (BIM) is a set of technologies and processes that are used to create a three-dimensional virtual model of a project. The virtual model contains all project information. As the BIM model is being developed with voluntary and non-binding industry foundation classes data schema and exchange file format, the bridge design and construction industry is recognising the benefits of digital bridge project delivery. Industry foundation classes is a particular data format that allows inter-exchange of an information model without loss or distortion of data. The model, thus, provides a graphical and functional representation of a bridge and its design which results in improving design quality, constructability and collaboration.
For the Chenab Bridge, which is part of the ambitious Udhampur-Srinagar-Baramulla rail link project, Tekla software is being used for structural detailing. In addition, all structures, temporary cables and related anchoring towers have been designed using BIM. With Tekla Structures, users can create a constructible, parametric model, which means each object holds its own data. This data can then be used for fabrication, erection, construction on-site and asset management during the maintenance of the bridge. Using BIM and Tekla Structures
software on the Chenab Bridge has made information assessment at every stage of the design project possible, while improving efficiency and productivity, and minimising the need for rework. The bridge is likely to be commissioned by December 2022.
High performance concrete
The use of high performance concrete with reduced permeability is the topmost mitigation strategy with respect to corrosion management. Epoxy-coated reinforced steel has been the most popular choice among transportation agencies to deal with the problem of premature bridge corrosion. Stainless steel is also a popular option for reinforcement in extremely harsh environments.
A 111 metre long bridge was constructed in Masalga of Latur with ultra high performance fibre reinforced concrete. Commissioned in November 2021, it is the first-of-its-kind bridge in the country. The steel fibre girders give it additional strength. This has resulted in saving 15-25 per cent of the total cost of the bridge.
Parametric modelling is another highly effective tool for putting together a bridge design draft, which then facilitates the creation of a detailed design. With parametric modelling, parameters are set by the engineer and then used for developing a design that meets the specific needs of bridge design. Changes to the design are also less time-consuming, as a parameter can be modified and the software can calculate how the change will affect the entire model, updating the model while ensuring that all the parameters are still met. Further, there is no need to rework the entire model, thus saving time.
Reinforced earth technology is being used for abutments instead of conventional retaining walls, which are built to support lateral pressure of an arch or span at the ends of a bridge. This is useful even in ground not suitable to construct foundation for retaining walls. Further, reinforced earth wall is compatible with a variety of facing systems, including large-sized discrete concrete panels, segmental panels, small-sized modular concrete blocks, vegetative facing with wrap around or with stones filled gabion, etc.
Bridge asset management system
Information technology has a key role in any bridge asset management system. Asset management software applications can be categorised into data collection software and web-based data analysis software. Data collection software is loaded on a tablet for field usage. The data input would be of inventory, condition survey, inspection, testing, repair, rehabilitation including costing. Field data is transmitted to standalone or cloud server of the bridge management centre. The centre has a web-based software to analyse the field data for generating output in the form of reports for user intervention at various stages of operation.
The Ministry of Road Transport and Highways has prepared the Indian Bridge Management System in order to collect information about all the bridges in the country. The purpose is to identify the distressed bridges which need immediate attention and to sensitise the concerned implementation agency for taking corrective measures such as repair, rehabilitation reconstruction/new construction, etc. During inventory creation, each bridge is assigned a unique identification number or national identity number based on the state, regional transport office zone and whether it is situated on a national highway, state highway or a district road. Then the precise location of the bridge in terms of latitude-longitude is collected through the global positioning system and the bridge is assigned a bridge location number. Thereafter, engineering characteristics, which include design, materials, type of bridge, loading, traffic lane, length and width of carriageway, are collected. These are used to assign a bridge classification number to the structure and also for doing a structural rating of the structure, after which each bridge is assigned a structural rating number. Further, the bridges are assigned a socio-economic bridge rating number, which decides the importance of the structure in relation to its contribution to the daily socio-economic activity of the area in its vicinity.
Many bridges need to be repaired, redesigned and renovated based on changing weather conditions, the age factor of the bridge, etc.
Bridge health can be determined depending upon the age, traffic count, construction material and structural form. Thereby expected loss of service life due to corrosion and expected balance service life of bridge can be evaluated. As the bridge ages, its strength decreases, which is a major threat to safety during hurricanes and cyclones. Therefore, it is mandatory to renew these bridges. Laser scanning is a great solution for the renovation process of any building or civil structure. The bridge can be scanned using laser scans after which a scan conversion can be performed.
Maintaining bridges to prevent incidents can also be made a lot simpler, safer and secured with a photonic monitoring system. Structural audit will not be sufficient for longer duration as any impact caused by overloaded vehicle or a sudden rise in the pressure of water on piers overnight are not recorded. Real-time data sets are persistently required related to strain, deflection, etc.
Thus, monitoring safety and health conditions of bridges remains important. For this purpose, a structure health monitoring process to find the accurate conditions and performance of the bridge structures has been initiated. The process provides permanent continuous, periodic or periodically continuous recording. For instance, most parameters to monitor the Naini bridge were based on traffic loads in order to assess the frequency of overload, settlement measures of the pylons and movements of pylons for design verification of creep assumptions for the bridge.
The way ahead
Going forward, as bridge design becomes more complicated, powerful, all-in-one computer-aided software programs will be needed. Further, these software programs must be able to process complex modelling challenges and also process complicated structural analysis including finite element analysis, time history analysis, etc. Fast evolving digital technology will continue to be adopted in the design and construction of bridges across the world. Although structural health monitoring has become a norm in bridge engineering, wireless technology will enhance monitoring of bridges further. In addition, drones will enable more focused inspection and maintenance to be carried out.