Conception of post-tensioned stone bridges

Sammanfattning

Cement and concrete are the building blocks of today’s world, and yet their substantialcarbon footprint is pushing the industry toward cleaner alternatives. This paper bringstogether the heritage of structural stone with the innovation offered by contemporarylow-carbon construction techniques. The study focuses on urban pedestrian bridges connectingpopulated areas, subject to heavy pedestrian traffic and at times loaded acrossits entire surface.To address this demand, a parametric design methodology is used to compare variousconfigurations of post-tensioned stone bridges with spans of 10 m and 20 m. Key designparameters, including deck geometry, post-tensioning systems, joint typologies, andsupport conditions, are evaluated to determine structurally, economically and environmentallyefficient solutions. Two pedestrian bridge shapes are investigated using analyticalmodels and finite-element simulations: a straight deck and an arch deck using posttensioned thread bars or cables. Promising designs are then refined with respect to constructionfeasibility and dynamic pedestrian comfort, leading to adjustments in the deckcross sectional dimensions. The constructibility is further assessed through collaborationwith quarries, resulting in modular block assemblies suitable for prefabrication.Results demonstrate that post-tensioning enables highly slender stone structures by overcomingstone’s intrinsic weakness in tension. Due to its limited practical feasibility, theU-shaped deck was discarded in favour of the rectangular cross section. Overall, the studyshows that post-tensioned stone pedestrian bridges are structurally viable and environmentallycompetitive, offering reduced material consumption and lower carbon intensitycompared to conventional bridges. Remaining challenges include the reduction of the costof structural stone and the evaluation of long-term durability and life cycle analysis, whichare identified as key directions for future research.