A design approach for cost effective, climate smart and buildable bridges

Doktorsavhandling, 2025

Bridges and transport infrastructure form the backbone of modern societies, enabling mobility, trade, and social connection; their construction constitutes on of society’s most significant investments. Therefore, it is essential that design and construction can be performed with high productivity and that bridges and other resource-demanding structures are constructed with the least amount of material.

The research conducted in this thesis is interdisciplinary, and therefore, a wide range of subfields and methods have been explored. The following fields have been approached in this thesis: bridge engineering, climate impact, productivity, optimisation and probabilistic risk analysis. To gain a comprehensive understanding of both the research field and the studied industry, a literature review and a quantitative study were conducted.

First, this thesis focuses on hindrances to productivity in the Swedish bridge-building industry. A quantitative study, using a self-completed questionnaire for data collection was conducted to identify the main obstacles. The results show that the contractor, client and design engineer have diverging long-term productivity incentives. The contractor and design engineer have a profit driven, private-oriented business model that focuses on project-oriented short-term goals, which may hinder long-term productivity.

Second, this thesis focuses on optimising the amount of material by using a set-based design (SBD) method. With this method, it has been shown that cross-sections in the bridges could be optimised, resulting in minimising the amount of material, which then also reduces cost and climate impact. SBD has also been used to compare different bridge types, making it possible to choose the most material-effective alternative. In addition to minimising the amount of material for a single bridge, SBD has been explored to optimise groups of bridges. The results shows that there is a gain cost and construction time due to the repetition effects.

Last, this thesis has studied load models and design loads for soil-steel composite bridges in Sweden. A probabilistic risk analysis was conducted, and the method consisted of three steps: (1) statistical extrapolations of measured loads, (2) finding the number of critical events, and (3) performing Monte Carlo (MC) simulations. The results show that a less conservative implementation is possible and has the potential to reduce the amount of material in the structure, thereby decreasing cost and climate impact.

This thesis has shown and demonstrated the potential to increase the sustainability of common infrastructure projects in Sweden.