Digital Uptake

New technologies for bridge design and construction

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.

Others

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.

Maintaining bridges

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.

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