Bridge Design Process
The bridge design process is meticulous and strategic and begins with understanding the client’s needs and stakeholder limitations. For every footbridge, access bridge, or accommodation bridge, it is essential to evaluate whether a new bridge is necessary, if an existing one can be assessed or even if an alternative route around can be found. A ground investigation, topographical survey and utility survey will all be required to inform the design. Planning consent and ecology surveys may also be necessary.
Bridges that may be adopted after construction by a local authority (therefore not remaining private) or convey public rights of way, will require early engagement with the local authority to establish their approval process. This usually involves the production of an AIP (Approval in Principle) document, which outlines what you are planning to build and how you will go about designing and constructing it. For bridges over watercourses, railways, or private land, additional approvals from entities like the Environment Agency National Permitting Service, Ordinary Watercourse Consent, Canal & River Trust, Network Rail and Defence Infrastructure Organisation may be required.
The design phase combines hand calculations and computer analysis to develop an optimal structural solution, which is then conveyed through detailed drawings for the contractor. Throughout construction, the designer provides clarification via RFIs (Requests for Information) and updates drawings to reflect any design changes.
Materials and Technology
In bridge construction, the choice of materials – whether concrete, steel, or timber – is determined by the specific performance requirements and design goals of the bridge. Concrete is commonly used for access bridges due to its strength and durability, while steel and timber are often chosen for footbridges for their aesthetic appeal and flexibility. Key components include bearings, which allow for thermal expansion and contraction, and parapets to protect users.
Assessment Techniques
Assessing existing bridges is crucial to ensure their safety and integrity. This process begins with a visual inspection to evaluate the bridge’s condition and may involve more detailed assessments like load capacity calculations. In the UK, highways document CS 450 mandates periodic inspections to identify deficiencies and plan remedial works. Techniques range from visual surveys to intrusive methods like concrete core sampling and non-intrusive methods like ultrasonic thickness gauging.
Innovative Solutions
At AWA Structural Engineering we have experience in innovative solutions like bespoke precast concrete elements, which enhance product quality and reduce on site programme time. These elements are designed for ease of installation, even in challenging site conditions. For instance, designing ‘stitches’ that tie large sections together on-site with small in-situ concrete joints or proprietary couplers allows for manageable handling and installation.
Sustainability
Sustainability is integral to our bridge design and assessment processes. We prioritise using familiar materials efficiently and maximising design life through clever detailing. This approach ensures minimal disturbance to the environment, especially when building over watercourses. We consider the bridge’s load over its lifespan and how water and soil movement will interact with the structure.
Regulatory Compliance
Bridge design and assessment must adhere to stringent regulatory and safety standards outlined in the DMRB (Design Manual for Roads and Bridges) and the MCHW (Manual of Contract Documents for Highway Works). Bridges are designed and detailed according to the Eurocode design suite, which replaced British Standards 15 years ago. Compliance with CDM 2015 (Construction Design and Management regulations) is essential, assigning specific duties to clients, contractors, and designers to ensure risk reduction and effective planning.
Future Trends in Bridge Design and Assessment
Emerging trends in bridge engineering, such as the use of Fibre-Reinforced Polymer (FRP) and the adoption of Eurocodes for both design and assessment, promise exciting advancements. These innovations will likely enhance the durability, efficiency, and sustainability of future bridge projects.
Client Collaboration
Collaboration with clients is key to meeting their needs and requirements. Our extensive experience in obtaining stakeholder approval helps us navigate the often complex and slow approval process. Unlike building structures, bridge projects are led by Civil or Structural Engineers, making our experience and niche expertise invaluable.
If you have a bridge project that needs our involvement, don’t hesitate to get in touch, you can call us on 01794 524447 or email mail@awaengineers.com
