Incremental upper bound modeling of concrete failures in timber-concrete notched connections

This paper introduces a novel theoretical framework for developing incremental upper bound solutions, which is applied to predict the response of two local concrete failures in timber-concrete composite (TCC) decks with notched connections. The new approach enables a prediction of the capacity at the onset of failure as well as the entire post-peak response, thus not only allowing for the assessment of the ductility of the local failure but also the assessment of the global load-displacement response of the deck. The approach is based on a sequential update of the work equation, which, unlike the traditional upper bound approaches, allows for accounting for the materials' dependency on the progressing plastic deformations. The non-linear withdrawal response of the steel fastener embedded in the timber is captured using a constitutive fastener model developed for the purpose, and the softening behavior of the concrete is considered by shrinking the failure criterion depending on the crack opening. Each model prediction is evaluated in detail, parametric studies are carried out, and experimental comparisons are performed when possible. The study demonstrates that the new concept has a high potential and, at its current stage, already captures the compared experimental tendencies to a sufficient degree. However, further research and experimental validation, particularly benchmarking against current TCC applications, are needed to mature the model for practical application.