Nonlinear structural analysis of suspension bridges composed of natural fiber cables: application to the Inca Q’eswachaka bridge

Resumo

This study aims to evaluate the structural behavior of a suspension bridge composed of natural fiber cables. For this, a structural-computational analysis of the Q’eswachaka bridge is performed. The Q’eswachaka bridge is an Inca heritage structure that is rebuilt annually using Q’oya fibers (Festuca dolichophylla). A numerical model was developed in the structural analysis software Abaqus/CAE using a finite element mesh composed of truss elements. The mechanical equilibrium under self-weight and pedestrian loads is assessed considering geometric nonlinearities, assuming linear-elastic material behavior. The model’s validation is carried out at two distinct levels. Firstly, the FEM model is compared with a simplified analytical solution based on the response of an inextensible catenary cable. Secondly, an external contrast is performed using the classical experiment by Irvine Sinclair (1976) for cables under off-center loads. The proposed framework also includes a structural sensitivity analysis considering variations in key structural parameters such as the elastic modulus (E), cross-sectional area (A), linear weight (w), and initial sag. In addition, this work aims to identify critical behavioral thresholds. The methodology enables the estimation of the structural working range of the bridge under different service-load scenarios, avoiding destructive testing and preserving the integrity of the heritage asset. This approach provides a replicable basis for the structural evaluation and conservation of traditional suspension bridges, integrating empirical knowledge with advanced computational modeling.