Bridges

New Zealand has ideal growing conditions for Pinus radiata (Radiata Pine), a suitable species when treated for creating strong and durable laminated beams. Timber is a store of carbon and utilising it in construction can make a huge contribution to reducing carbon on our projects. Our transport system accounts for nearly 20% of the country's greenhouse gas emissions. Towards achieving the target of zero carbon by 2050, the New Zealand government has set an interim target of 50% reductions by 2030. To this end, in late 2021 Waka Kotahi NZ Transport Agency launched a transformative initiative to make glulam timber the preferred material choice for highways bridges of up to 30m span. This initiative began with a series of focus groups including design consultants, contractors, academics, suppliers and clients. The feedback gathered from these sessions provided input into the design of a plan and a programme to implement the challenging mission statement: "That every highway bridge that is constructed today in New Zealand using standard concrete hollowcore or super tee beams will instead be constructed using modern, engineered timber".

The plan, implemented in January 2022 consists of three complementary objectives running in parallel:

1. Development of design guidelines for timber bridges
2. Identification and curation of pilot projects to build using glulam timber
3. Liaison and involvement with timber product suppliers in New Zealand

The paper covers the challenges of developing a technical standard using international guidance. This includes the assumptions made, philosophical approach to design and analysis and a summary of technical considerations made. Key issues addressed will include durability, seismic performance, design-life, performance monitoring and asset management.