The Effect of Slab and Transverse Beams on the Behaviour of Full-Scale Pre-1970's RC Beam-Column Joints

Abstract eng:
Past research and empirical evidence has shown that beam-column joints play a critical role in the cyclic behaviour of reinforced concrete (RC) structures and that a good understanding of the complex mechanical interactions in beam-column connections is necessary to ensure the desired hierarchy of failure is achieved. Development of such understanding requires specifically designed numerical and experimental studies that depict realistic structures. However, reviews of published experimental literature show that most experimental studies on the seismic behaviour pre-1970’s RC beam-column connections focus on the testing of sub-assemblies without slabs or transverse beams, which are unrepresentative of reality. This paper presents the first part of a study being carried out to shed light on how (and by how much) slabs and transverse beams contribute to the seismic performance of gravity-designed interior beam-column connections, and the consequences of ignoring or wrongly representing this contribution. It presents the results of experiments on three full-scale beam-column joints. One of these test specimens is designed to Eurocode 8 and two are of typical pre-1970’s design, with one specimen containing a slab and transverse beams, whilst the other represents the typical cross-shaped specimen tested in many other studies. The paper also presents preliminary nonlinear three-dimensional finite element (FE) models to complement the experiments, and extend them to look at the case of a pre-1970’s specimen with transverse beams and no slab. As expected, the experimental and numerical results clearly demonstrate that the progression of damage and failure mechanisms in beamcolumn connections with and without slabs and transverse beams differ significantly. The experimental findings also generally confirm inferences from the limited published experimental evidence that the contribution of slabs and transverse beams can be underestimated by current guidelines. These observations have implications when considering common simplifications made in the numerical modelling of RC moment resisting frames when assessing their seismic performance.

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