Nonlinear Behaviour of Aluminium and Passive Brackets in Ventilated Facades: Experimental Tests and Numerical Modelling.

Abstract

This paper presents the results of experimental tests and numerical analyses of the behaviour of brackets used in substructures of ventilated facades. Two representative solutions were compared: a traditional aluminium bracket and an innovative passive bracket with a composite interlayer. The aim was to assess their load-bearing capacity, deformation and failure mechanisms, and the suitability of the calculation methods used. Laboratory tests were carried out at ITB's accredited Laboratory of Building Elements in accordance with the European Assessment Document (EAD 090034-00-0404). The aluminium bracket was tested under standard environmental conditions. In parallel, finite element (FE) analyses were performed, including elastic-plastic modelling for metallic systems and material and geometric nonlinear analyses for the passive bracket. The results revealed fundamental differences in the behaviour of the two solutions. The aluminium bracket exhibited a predictable plasticisation mechanism, the ability to redistribute stresses, and a gradual loss of capacity. Linear analyses proved sufficient in this case and were consistent with the tests. The passive bracket, by contrast, showed quasi-brittle behaviour, strong temperature sensitivity, and no plastic reserve, resulting in a sudden failure mechanism. For this case, the use of classical linear models leads to unsafe simplifications and underestimated results. The study demonstrates that the development of passive facade bracket technology requires a nonlinear approach and extended long-term testing covering the rheology of composite materials and environmental effects. The findings also reveal a normative gap: current design guidelines and EAD documents focus on metallic solutions while overlooking the specific behaviour of passive brackets. The results constitute an important contribution to knowledge on the safety and durability of ventilated facades and may serve as a basis for developing dedicated design procedures and for updating normative documents.