The idea of a bridge over the top of Bridge Valley Road was originally proposed by FODAG and the scheme has been developed on a non-commercial basis over the past three years. Extended consultation process included the local community, stakeholders and general public. Apart from providing safe access, the scheme also offers a wide range of additional long-term benefits that no other bridge could provide.
The scheme offers a wide range of future benefits, such as:
– Safe crossing for pedestrians and cyclists
– Disability access
– A bridge with 300+ years life expectancy and minimal maintenance costs
– Apprenticeship, training programmes (e.g. stonemasonry) during construction
– New career opportunities in bridge building
– New industry sector in bridge building for Bristol with international reputation
– Re-learning historical crafts / skills
– Community engagement
– Post-construction income generation (courses, know-how, research, increased tourism, etc.)
Strategic long-term objectives
Apart from the immediate benefits, the project also has a number of wider objectives. The proposed bridge is intended to serve as a feasibility study for new stone bridge construction and provide information on the building costs for comparison with concrete and steel bridges. The project is also intended to investigate how best traditional construction procedures can be adapted for 21st century use. While masonry arch bridges have proved to be highly sustainable structures over the centuries, a number of questions need to be explored before they can again become viable options for new construction.
Masonry arch bridges can be highly suitable structure for up to 30m span single or multi-span bridges. Areas of application will need to be identified (local roads, viaducts, rural areas, etc.).
There are no current design codes for masonry arch bridges in Europe or America. One of the few countries where masonry arch bridges are still designed and built is China. Simple design approaches for a limited range of standard bridge geometries and applications will need to be put together initially to help develop confidence in new masonry bridge construction. Design guidelines/codes may be developed subsequently for wider application.
Masonry arch bridges were widely built in the UK and Europe over the centuries and are generally assessed and maintained regularly. In countries with few masonry arch bridges, such as the US, knowledge is relatively scarce and limited information is available on assessment and maintenance procedures. Guidelines for assessment and training needs will need to be identified across the countries to help efficient long-term maintenance of the masonry arch bridge infrastructure.
Case studies are needed to be put together on the long-term feasibility of masonry bridges to provide awareness and build up confidence. With 2000 years worth of potential case studies it is a matter of capturing the lessons learnt and presenting them in suitable formats.
Masonry bridges are the most sustainable bridges with the longest life-expectancy ever built (e.g. low CO2 emission, natural materials, low-tech construction processes, low maintenance needs, reuse/recycling of materials). Increased awareness of sustainability provides a significant driver for appreciating masonry bridges as highly suitable options.
Naturally, it will take time before masonry bridges are widely appreciated as viable solutions for the 21st century. With 2000 years of experience behind us, we have the unique opportunity for re-introducing masonry bridges for future generations and making a lasting contribution to history.