Railway bridge construction involves a multitude of challenges and risks. In this article we explore the many ways that 3D virtual models can simplify railway bridge development and planning, fast-track approval timeframes, improve return on investment (ROI), and foster more human-centric designs. Featuring examples from modern railway bridge projects throughout Australia and beyond, we illustrate the tremendous advantages that CGI simulations bring to the construction of railway over bridges, flyover pedestrian bridges, underpasses, overpasses, and more.
CONTENTS: Railway bridge design | Engineering and pre-construction | Railway bridge construction processes | Segmental bridge construction | Dynamic simulation of moving parts | Total station survey equipment | Overpass and underpass connectivity | Risk management | Guard rails and barriers | Signs and signals | Disaster-proofing railway bridges | Maintenance and repair | Sustainability | Cost | Urban CGI Digital Twins
Railway bridge design – exploring and refining concepts in real-time
Designing railway bridges requires careful analysis of the dynamic forces exerted by moving trains and environmental conditions, as well as consideration of the long-term durability of the structure. The bridge design must incorporate appropriate safety margins and clearances – derived from the dynamic kinematic envelope of rolling stock (the maximum area a train is expected to occupy while moving down the track), ensuring that railway vehicles can pass unimpeded.
Railroad bridge design must also respect the visual character of the site and fit into the landscape in an aesthetically pleasing manner. If a design is visually intrusive, hinders visibility, or fails to meet public approval, this can lead to delays in the consent process and may require costly modifications.
Given these complexities, and the necessity of adhering to rigorous engineering safety and design standards, using a realistic 3D virtual model of the project in the planning – known as a ‘digital twin’ – can offer significant advantages. Digital twins allow you to accurately and realistically visualise a new train bridge design within the surrounding landscape. Digital simulations facilitate rapid optioneering and testing of concepts, simplifying design development and reducing uncertainties.
Rail bridge engineering and pre-construction planning
Strength, fatigue endurance, and robustness are fundamental to railroad bridge construction. Multiple stressors can impact the stability of a bridge, such as wind loads, water pressure, seismic activity, and cargo loads, which may result in structural deformation, deflection, or even collapse. These considerations are particularly complex in railway bridges that span large bodies of water or cross wide ravines at significant heights.
Built using precise geospatial survey data, digital twins are unrivalled in their ability to assist engineers in predicting and simulating these scenarios, aiding decision-making, and helping to optimise the resilience of the bridge structure.
Precise simulation of structural elements and construction processes
Digital twins offer a comprehensive model of a project, right down to the accurate representation of individual railway bridge components – such as waterproofing details, foundations, pipelines, structural steel bearings and sheets, anchor bolts, precast and prestressed concrete beams, track slabs, wingwalls, and crucial structural elements like railway bridge arches, piers, and abutments. These simulations help to ensure that the design can withstand real-world conditions and maintain structural integrity under load.
Digital twins are particularly useful for visualising and planning complex construction processes involving large precast elements, ensuring that work sequences are feasible in a given environment. Virtual representation of construction methods allows for the prediction of potential challenges, aiding construction crews in understanding complex procedures before actual work begins.
Simulation of segmental bridge construction
Many railway bridges are built in stages, with large structural segments fabricated in factories and then transported to the site. Launching girders are used to position these in a process called incremental launching, whereby bridge segments are assembled at one end of the bridge and then gradually pushed out over the piers using hydraulic jacks. Temporary support structures, often in the form of pylons or cantilever arms, are used to support the bridge as it is extended.
Once the segments are in place, the structure is secured with post-tensioning cables and the temporary supports are removed. (The tension places the concrete in compression, increasing the overall strength and durability of the bridge, helping it to resist dynamic loads like those from traffic or wind.)
The use of precast segments in railway bridges has a number of benefits. Firstly, it allows for faster construction. Secondly, the controlled environment in which segments are fabricated ensures a higher quality and uniformity of materials. Thirdly, the absence of cranes involved in span-by-span segmental bridge construction allows for the creation of railway bridges in tight spaces. This method can be particularly beneficial when constructing train bridges high above obstacles like rivers or difficult-to-access terrains, as it minimises the need for extensive scaffolding and heavy lifting equipment, reduces ground-level impact, and enhances worker safety.
Digital simulation is very helpful in planning this process. The motion of precast segments can be accurately simulated, including the machinations of launching girders, making it possible to plan and monitor the installation of bridge segments more efficiently without the enormous, dangerous, and costly errors were this process to go wrong.
Dynamic simulation of moving parts
Bridge structures can be highly dynamic. Suspension bridges, for example, are flexible in the face of wind loads. Other bridges include expansion joints to accommodate movement without causing damage to the bridge structure. These joints absorb the movement of bridges caused by thermal expansion and contraction, as well as seismic activity, wind, or other forces. Railway bridge expansion joints play an important role in preventing train tracks from buckling or becoming misaligned with each small movement of the bridge, and allow for the smooth operation of railway traffic.
As well as being able to model the movement of individual bridge components, digital twins can replicate the movement of bridges as a whole. Vertical lift sea bridges, for example, move upwards for ships to pass beneath. Railway swing bridges rotate horizontally around a pivot point to let ships sail through.
The movement of different types of railway bridges can be accurately simulated using CGI technology, making it possible to visualise how these bridges interact with their surroundings.
Positioning of total station survey equipment in railway bridge projects
Total stations are surveying instruments that work by emitting a laser towards a target, such as a prism, which reflects the laser beam back to the total station, which then calculates the distance based on the time it takes for the laser beam to return.
Reflective prisms can be mounted upon specific railway bridge markers, allowing the total station to measure the distance to these points accurately. This technique ensures precise measurements and alignments during construction and is useful for monitoring track degradation, movement, or warping of railway bridge elements across time.
The effectiveness of this strategy depends upon the precise positioning of the total station and prisms. Finding optimal vantage points is a time-consuming process and can result in construction delays and wastage of resources. These frustrations can be alleviated through the use of digital twins to help locate the ideal vantage points for total stations and the optimal placement of prisms, providing real-time insights and promoting data-driven decision-making.
Railway overpass and underpass connectivity and integration with the community
Railway overpasses and underpasses enhance connectivity and integration within the surrounding communities. They provide safe routes for pedestrians, cyclists, and motorists to cross or move beneath railway lines without waiting for trains to pass. This not only improves the efficiency of transportation networks, reducing travel times and congestion, but links neighbourhoods divided by linear infrastructure such as railway tracks, facilitating social and economic interactions, and contributing to a more cohesive community.
Designing and constructing overpasses and underpasses presents unique challenges. For example, this infrastructure must be carefully integrated into existing road and rail networks, which can be particularly complex in urban areas with limited space. Furthermore, construction often takes place in busy transportation corridors, requiring careful planning to minimise disruption.
Safety and risk management in railway bridge construction
Safety and risk management are non-negotiable when designing, constructing, and maintaining railway bridge structures. Safety precautions are necessary to prevent railway bridge accidents, including those related to structural damage, weight limit miscalculations, loading standards, and height clearances. For example, bridges accommodating electric trains need additional height clearance for overhead wiring. Pedestrian bridges above high-voltage electrified train tracks often require guard rails and safety nets to prevent electrocution. Meticulous planning and calculations are essential in these scenarios.
Digital twin technology helps to ensure that all safety requirements are met in designing railway bridges. With the high level of precision afforded by CGI simulations, engineers can anticipate and mitigate potential risks that might otherwise go unnoticed.
Bridge guard rails and safety barriers
Barrier rails and guard rails on bridges prevent falls and offer protection against potential hazards for both vehicles and pedestrians. Temporary barriers, like hoarding and fences, are also commonly used during construction to protect the site and deter unauthorised access. CGI technology makes it possible to accurately plan the positioning of safety barriers, hoarding, and fences so that construction is far more likely to proceed without hiccup.
Railway bridge signs and signals
Signs and signals are integral to any railway bridge project, serving to indicate changes in speed limits, height limits, and so on. Signs and signals must be positioned so as to be clearly visible to drivers and pedestrians. Selecting the optimal position can be difficult, but the task is crucial and is governed by stringent rules and regulations. Urban CGI Digital Twins simplify this process, allowing for strategic placement and testing of sightlines and visibility using parametric tools linked to control lines, as well as normal placement of assets.
Disaster-proofing strategies for railway bridges
Some risks and hazards associated with railway bridges are expected to occur rarely, if at all – including natural disasters, such as earthquakes, floods, and severe weather events. The unlikelihood of such scenarios does not reduce the importance of improving disaster-resilience or of training staff and crew for such a circumstance. After all, the disastrous repercussions of such events have been repeatedly demonstrated across history. For example:
- Tay Bridge disaster, Scotland (1879): The collapse of this railway bridge coincided with the crossing of a passenger train during a severe storm, resulting in the demise of everybody on board. Due to high winds and structural weakness, several bridge spans gave way, plunging the train into the icy waters below. A reassessment of engineering practices and increased scrutiny improving the safety of future structures followed this accident.
- Tangiwai railway disaster, New Zealand (1953): One of the deadliest railway accidents in New Zealand’s history occurred on Christmas Eve, 1953. Volcanic mudflow from the Mount Ruapehu volcano washed away the Tangiwai bridge just moments before a train was due to cross, resulting in 151 fatalities. The tragedy led to significant improvements in train communication systems and monitoring of volcanic activity in the area.
- Granville train disaster, Australia (1977): One of the worst rail disasters in Australian history occurred when a passenger train derailed and struck the supporting columns of a nearby road bridge. The bridge collapsed onto two passenger cars, causing 83 fatalities and more than 200 injuries.
- Yellowstone River bridge collapse, USA (2023): After heavy rains, a railway bridge over the Yellowstone River in Montana collapsed, causing a freight train to submerge, spilling hazardous materials, such as hot asphalt and molten sulphur, into the water supply. These chemicals can harm aquatic life and contaminate drinking water, requiring careful management during train derailment.
CGI technology can help you simulate disaster scenarios and high-risk weather conditions, including snow, wind, and rain. This makes it possible to visualise how the railway bridge will perform when subjected to various environmental stressors.
Rail bridge replacement, repair, and maintenance
Railway bridge maintenance manuals detail a host of railway bridge repair protocols, ensuring the structural integrity of the bridge in question. Maintenance involves a range of restoration procedures, including repairing deterioration, monitoring corrosion, structural replacements, and bridge widening projects. In the case of bridge replacement, old structures must be safely demolished to make way for new bridges which comply with modern safety requirements.
Maintenance and repair of existing structures requires a detailed management system, given the many tasks, activities, and components involved. Digital twins can be of great help in this arena. By placing sensors on bridges, real-time data can be fed into a simulated model, allowing for a comprehensive analysis of the structure. This allows real-time detection of structural wear and potential failures before they become critical issues. Rather than scheduled maintenance checks, repairs can be based on live data, making this process far more focused and efficient.
Sustainability and environmental concerns
A range of sustainability and environmental concerns are associated with the design and construction of railway bridges. Bridges can have a significant impact on the local landscape. Land may be cleared on a large scale, leading to the fragmentation of natural ecosystems. Bridges can alter the waterways through which they pass, impacting water quality (this can occur due to sediment runoff, physical disruption of water flows, and overshadowing – which can affect water temperature and light availability). They may also decrease biodiversity upon land as well as within aquatic ecosystems, disrupting migration routes, and increasing the risk of wildlife-vehicle collisions. Noise and air pollution can also have impacts during construction and operational phases.
Railway bridge design can also positively impact the environment. For example:
- Wildlife overpasses: These specially designed bridges create safe passages for wildlife over busy transportation corridors, reducing wildlife-vehicle collisions and helping maintain biodiversity by providing safe routes for animal migration.
- Sustainable materials: Using sustainable or recycled materials to construct the bridge can reduce the environmental footprint. Of interest, the Blackfriars railway bridge in London is equipped with a photovoltaic solar roof. This makes use of the large surface area typically available on bridges to generate renewable energy.
- Energy-efficient lighting: The use of LED (light-emitting diode) lights or other energy-efficient lighting systems can reduce the energy consumption of the bridge. These consume significantly less energy than traditional incandescent or halogen light bulbs and have a longer lifespan, reducing the cost and the frequency of replacements – making them advantageous for remote and hard-to-access railway bridges.
- Noise reduction designs: The sound produced by a train can be amplified while crossing a bridge due to the structure’s resonance. In residential areas or other noise-sensitive regions, noise mitigation techniques may require special attention. Some of the strategies employed include noise barriers (physical structures that help to block or deflect sound waves due to their acoustic properties), train track noise reduction designs, and vibration dampers (devices installed on the rails to help absorb and dissipate the vibrational energy produced by trains).
- Green spaces around and under the bridge: Incorporating green spaces is part of a broader trend toward ‘green infrastructure’ or ‘green architecture.’ A growing number of railway infrastructure developments integrate green spaces under raised railways for community and wildlife purposes.
- Efficient design: A well-designed railway bridge can accommodate more traffic (both rail and potentially pedestrian or bicycle traffic), reducing the need for additional transportation infrastructure and thus minimising environmental disruption.
Digital twins for planning help you to understand all of these environmental impacts early in the design process, allowing for necessary adjustments and mitigation methods where required. Stakeholders and other parties with a vested interest in local ecology are also better able to understand the ramifications of the project when it is presented in real-time 3D format. Valuable feedback can hence be given, helping to ensure the project meets sustainability goals as required.
Given the enormous costs and time constraints involved in railway bridge construction, it is important to streamline the construction process. Digital Twin technology depicts designs clearly and without ambiguity, allowing issues to be detected and solved far earlier in the planning process. With designs communicated in 3D form, there is far less room for unforeseen problems to arise, which has a direct and tangible flow-on effect on the cost of a project.
Why Urban CGI Digital Twins lead the way in railway bridge innovation
For over two decades, Urban CGI has provided visualisation and planning services to the railway industry. Based in Melbourne, Australia, we have clients both locally and globally. Our Digital Twin technology is known for its efficiency, accuracy, and customisation, helping you deliver tangible results in every phase of railway infrastructure planning.
Our CGI Digital Twin technology is used for a range of purposes, including instructional videos, virtual tours, and animations, transforming project data into vibrant visualisations with practical applications.
If you would like to learn more about how our technology can support your project, please reach out! We would love to discuss how we can help.
D. C. Iles, Design Guide for Steel Railway Bridges, The Steel Construction Institute (2004)
P. Mulqueen and Dr. S. Grave, Weathering Steel Railway Bridges in New Zealand (2013)
Design Manual for Bridges and Structures, Sixth Edition, New Jersey Department of Transportation (2016)
Alessio Pipinato (editor), Innovative Bridge Design Handbook: Construction, Rehabilitation and Maintenance, Second Edition (2021)
Sakdirat Kaewunruen, Mohannad AbdelHadi, Manwika Kongpuang, Withit Pansuk, and Alex Remennikov, Digital Twins for Managing Railway Bridge Maintenance, Resilience, and Climate Change Adaptation (2023)