Fatigue Assessment for a Composite Bridge in Steel Arches According to ABNT NBR Standard Requirements: 16694:2020

• DOI: 10.22533/at.ed.3173112304047

• Palavras-chave: Mixed bridge; Fatigue check; Standard ABNT NBR 16694: 2020; Finite element analysis.

• Keywords: Mixed bridge; Fatigue check; Standard ABNT NBR 16694: 2020; Finite element analysis.

• Abstract:

  Bridge structures, when subjected to repeated action of mobile load, present stress variations in the structural elements and that under this stress condition can cause the phenomenon of fatigue, characterized by the appearance of cracks and subsequent propagation, which can lead to the collapse of the structure. The verification of resistance to fatigue in structural projects of road bridges in straight composite beams must be carried out according to the requirements of Annex A of the ABNT NBR 16694:2020 standard, which specifies the permissible limit of the stress variation range for categories of constructive details and for a number of request cycles. The present work aims to evaluate the fatigue of the structural elements of the superstructure of a composite bridge in metallic arches in order to meet the requirements presented in Annex A of the ABNT NBR 16694:2020 standard. The composite bridge in metallic arches studied here has a deck in composite straight beams and was designed to serve the water main system of the São Francisco River and is also used as a pedestrian walkway. Initially, a finite element model was elaborated for the composite bridge structure in steel arches. Next, loadings were established for the frequent combination of fatigue. The design stress variation range was determined from tensile stress results from finite element analysis. The fatigue evaluation for the structural elements of the composite bridge in metallic arches was only carried out for the regions of the weld fillet between the web of the spar beam profile and the vertical stiffener where the initiation and propagation of cracks in this region causes the failure of the flange tension and can lead to the collapse of the beam. Thus, the permissible range of voltage variation was established for the constructive detail of the welded connection in question and according to the representation indicated in Table A.1 of Annex A of the ABNT NBR 16694:2020 standard. In the end, it was confirmed that the range of design stress variation is lower than the admissible range of stress variation and thus the composite bridge structure in steel arches is safe to fatigue.