The effects of post‐tension in the behavior of thin funicular concrete shells

Abstract The design of thin funicular concrete shells is typically based on the reversed shape of a membrane deformed by dead loads. Under similar loading scenarios, these structures are highly efficient, being primarily submitted to membrane compressive stresses. However, for non‐uniform and/or asymmetrical loading conditions, bending occurs, generating tensile stresses that significantly decrease the efficiency of this type of shell. This paper presents a numerical investigation on the adoption of bonded post‐tensioned strands as a mitigation strategy for tensile stresses due to bending in funicular shells built in plain concrete, that is, without steel reinforcement. A centered tendon layout is proposed, based on the principal stresses' directions under the most demanding and unfavorable load conditions. Results indicate that prestress can enhance the load‐carrying capacity of funicular shells, although with limited effect due to the null eccentricity of the strands and presenting detailing constraints at the support regions. The simultaneous use of ultra‐high‐performance fibre‐reinforced concrete is recommended to provide higher safety margins, reduce the required amount of prestressing, and improve the shell's behaviour under both service and ultimate limit states.