Formalising the R of Reduce in a Circular Economy Oriented Design Methodology for Pedestrian and Cycling Bridges

Abstract

The construction industry consumes over 32% of the annually excavated natural resources worldwide. Additionally, it is responsible for 25% of the annually generated solid waste. To become a more sustainable industry, a circular economy is necessary: resources are kept in use as long as possible, aiming to reduce and recirculate natural resources. In this paper, the investigation focuses on pedestrian truss bridges of the types Warren and Howe. Many pedestrian bridges currently find themselves in their end-of-life phase and most commonly these bridges are demolished and rebuilt, thus needing a lot of new materials and energy. The aim is thus first and foremost to reduce the amount of necessary new materials. For this reason, a design tool will be created, using the software ‘Matlab’, in which truss bridges can be evaluated and compared in the conceptual design stage. The tool is based on the theory of morphological indicators: the volume indicator, displacement indicator, buckling indicator and first natural frequency indicator. These allow a designer to determine the most material efficient Warren or Howe truss bridge design with user-defined constraints concerning deflection, load frequency, buckling and overall dimension. Subsequently, the tool was tested and compared to calculations made in the finite element modelling software Diamonds. In total, 72 steel bridge structures were tested. From these it could be concluded that the manual calculations in Diamonds in general confirmed the results obtained with the automated design tool based on morphological indicators. As such, it allows a designer to converge more quickly towards the best performing structure, thus saving time, materials, and corresponding costs and energy.

Predicting material consumption in a Circular Economy oriented design methodology for pedestrian and cycling bridges

“…The algorithm was subsequently tested on a total of 36 truss bridges, resulting in a success rate of 90%. An important observation in this study is that the volume predicted with the MIs is not realistic [1]. As the MIs predict the most suited structural typology with the least material use for the concerning span, they can be used for the said material efficiency evaluation.…”

“…Introduction A Circular Economy (CE) oriented design methodology for pedestrian and cycling bridges is nonexistent [1,2]. As such, said design methodology needs to be developed incorporating the four Rs of the CE -Reduce, Reuse, Recycle, Recover.…”

“…They formalise the choice for the most efficient structural typology which leads to material savings [13]. However, Anastasiades et al (2022) explain that these MIs are all inter-connected rendering their practical application very complex. Therefore, Anastasiades et al (2022) combined the MIs for Warren trusses into an automated algorithm.…”

“…The results of the FEMs that deviate are indicated in italics. Anastasiades et al (2022) explain that the MIs do not take actual cross sections into consideration for the different bars in the truss. They consider a form factor to express the cross section's efficiency.…”

“…For the calculation of the FEMs, only standard, but efficient, profile sections were used. Bars in compression were assigned CHS profiles, Lshaped sections were used for the diagonals in tension, and for the bars in the lower beam of the truss, standard I-shaped sections were chosen [1]. Anastasiades et al (2022) continue that compression bars are optimised for buckling, rather than strength.…”