Background to modification factors in structural membrane design

Abstract

The novel European design standard for membrane structures DIN CEN/TS 19102 was published in 2024. Besides others, it provides rules for the stress verification of structural membranes – technical textiles and foils – in the ultimate limit state. The basis is a strength value measured in monoaxial short term tests under room temperature for virgin materials. To enable a stress verification for the end of the lifetime and also in load cases that consider biaxial stresses, long term loads and temperatures other than room temperature, the basic strength value can be modified by modification factors, the so‐called k‐factors. Moreover, the panel size can be considered by a modification factor. Hereby, the various increasing and decreasing effects on the tensile strength can be considered.

This contribution provides background information to the various modification factors and explains experimental determination of them. Limits and uncertainties of the experiments proposed in DIN CEN/TS 19102 are explained. Furthermore, DIN CEN/TS 19102, Annex C provides typical values for the modification factors. These numbers are reviewed and assessed in the light of latest research results.