Inelastic behaviour of hybrid reinforced concrete beam and steel column systems
Creators: name: Moharram, Moustafa Ibrahim Shawky
Publisher: name: Imperial College London
Year: 2018

description: There is a growing recognition of the merits of faster construction in terms of monetary benefits and reduction in urban disruption. To this end, the synergetic use of reinforced concrete floor and steel column systems in multi-storey buildings offers an attractive structural solution that can provide significant benefits in terms of speed of construction, reduction in column sizes and favourable structural performance. However, a detailed understanding of the inelastic behaviour of such systems as well as reliable representation of their ultimate failure criteria, remain largely lacking. The research presented in this thesis examines the inelastic response of hybrid structural systems in which steel columns are connected to reinforced concrete beams using fully embedded structural steel profiles. Such hybrid configurations are not conventional reinforced concrete members and cannot directly follow the design philosophy stipulated in reinforced concrete design codes such as Eurocode 2. They cannot also be classified as fully composite steel/concrete members where design rules and safety checks from composite codes such as Eurocode 4 apply. Reliable design and assessment of such hybrid systems necessitate modifications to typical procedures used for reinforced concrete members including a detailed evaluation of the governing ultimate criteria. In order to achieve this, a combination of experimental examinations, numerical studies, parametric investigations and analytical assessments, is employed in this research. The main aim is to provide detailed insights into the complex nonlinear behavioural interactions that take place in such hybrid systems, and to offer reliable representations for the underlying force transfer mechanisms and associated ultimate criteria governing the response. The experimental programme includes fourteen full-scale hybrid specimens which are designed to mobilise various modes of failure, ranging from the most ductile to the highly brittle. The length and cross-section of the steel shear-key, embedded into the reinforced concrete beam, are varied within the test specimens. Validation and calibration of detailed numerical models are carried out against the hybrid test results as well as other available tests on reinforced concrete members, using the nonlinear finite element program ABAQUS, in conjunction with the concrete damage plasticity (CDP). The validated numerical models are then used to carry out detailed parametric assessments into the influence of various geometrical and material properties on the response of the hybrid systems considered in this research. The effective contribution from the shear-key to the overall shear forces transferred to the column is also examined and discussed. Findings from the experimental results and parametric investigations are finally used to develop detailed analytical models that capture the inelastic behaviour. The thesis culminates with proposed simplified design procedures and discussions on the practical application of such hybrid structural systems.