Juan José López Cela
Professor of Applied Mechanics and Project Engineering at the Higher Technical School of Industrial Engineering of Ciudad Real, University of Castilla-La Mancha, and co-leader of the research group Mechanics of Continuum Media, Structural and Materials Engineering (COMES)
In this article, researchers from the Polytechnic University of Valencia and the University of Vigo study the resistance of steel bridges to local structural failures. It is published in the prestigious Nature journal, which, along with Science, represents one of the six indicators of the Shanghai Ranking (ARWU Academic Ranking of World Universities), which gives an idea of the academic relevance of the work.
The authors approach the study from an experimental and numerical perspective. To do so, they built a scale model of a real bridge span in their laboratory and, after inducing failures in specific parts of the structure, they performed tests on it and measured magnitudes of interest (displacements and deformations). These experimental results are validated with numerical simulations using the Finite Element Method.
The study considers a specific type of structure consisting of triangulated beams in which all the bars operate in tension or compression. Thus, under vertical loads, the lower and upper chords absorb the bending moment, and the interior bars (uprights and diagonals) resist the shear force. By physically removing bars from the model and through an exhaustive numerical study, the researchers were able to identify six different ways in which the remaining bars of the bridge are able to resist the loads to which it is subjected. The structure goes from behaving as a two-supported beam to experiencing different deformation modes (Figure 3 a) in order to continue transmitting the loads to the supports without collapsing. In my opinion, this is the article's greatest contribution.
It is true that the study is restricted to triangulated structures subjected to vertical loads and that longitudinal (braking or seismic loads) or transverse (wind) load states are not studied. Furthermore, although local failures in the laboratory are easy to provoke (simply by cutting the bar in question), it is not easy to imagine how they might occur in a real structure. However, these considerations do not invalidate its scientific interest, quality and rigor.