Parametric Design for Optimized Concrete Through Girder Bridge Design

Abstract

This master thesis explores the optimization of concrete through girder bridge design using a
parametric design approach, focusing on reducing material usage and optimizing for costs and environmental performance through iterative design improvements. The research addresses a critical need in the Netherlands, where numerous bridges are approaching the end of their design life and require replacement or renovation, by allowing for rapid and efficient concrete through girder bridge design.

The primary objective is to develop a comprehensive parametric model that allows for systematic evaluation and iterative optimization of design parameters. By integrating python scripting, computational algorithms and external finite elements modelling software, the study aims to provide a parametric design tool that serves as a novel approach the bridge design that yields:
-Flexible tool for structural engineers
-Iterative optimization of structural designs by:
o Minimization of material usage
o Lower environmental impact
o Lower construction costs
-Quicker design process
-Reduction of the cost of change during the design cycle

Key research features include focusing on single-span, single-track train bridges with spans of 25-45 meters and ensuring compliance with Dutch Eurocode and Prorail standards. To achieve this a comprehensive literature review is conducted and a case study of the train bridge spanning the channel is used.
The parametric model also computes an indication of environmental impact and material costs such that generated designs can be evaluated on these criteria.

To evaluate the effectiveness of the parametric model a reference design is considered that fits the scope constraints of the parametric model, namely the through girder bridge at the station of Bilthoven.
To optimize the design of this bridge three redesigns have been generated using the parametric model. The three considered redesigns are:
-Design featuring the same cross-section geometry as the reference design
-Design featuring a 'cut-out' in the centre of the cross-section to save material
-Design featuring an optimized geometry by reducing girder width
For each redesign the pre-stressing and reinforcement layout has been iteratively optimized by getting material usages as close as possible to 100%.

From the three considered redesigns, the optimal redesign manages to reduce material costs by 10.78% and environmental impact costs 11.07%. This is achieved by reducing the thickness of the girder cross-section from 1500 mm as in the reference design to 1200 mm and iteratively optimizing the reinforcement and pre-stressing layout.

The study concludes that the developed parametric model successfully optimizes concrete through girder bridge designs, resulting in significant reductions in material usage and environmental impact for a preliminary design. The model demonstrates the potential for achieving more sustainable and cost-effective bridge designs while meeting all the requirements.
By addressing the combination of structural engineering, computational modelling and sustainability, this thesis contributes to a novel approach of bridge design that can potentially change infrastructure development practices in the Netherlands.