Long-term experiments of composite beams and connections

Composite steel–concrete solutions are commonly used in Australia for floor building applications. In these situations secondary beams are usually connected to primary beams or columns by means of composite web side plate connections, also known as fin or single plate joints, with the slab continuous at the connection. The rigidity of this arrangement can lead to extensive cracking at the joint and to significant compressive forces in the web side plate connection, which can compromise one of the design limit states. In this context, this paper focuses on serviceability limit state and presents the results of two sets of experiments aimed at investigating how the time-dependent behaviour of the concrete affects the response of such joints. The first set included six simply supported specimens subjected to a sustained negative moment with the connection placed at their mid-span. These were used to study the behaviour of the negative moment region of a continuous floor beam in isolation. The second set consisted of a full-scale two-span continuous composite beam with the joint specified at the internal support. The long-term response of these composite members was monitored measuring the changes in deflection, end rotation, strain and slip occurring over time. Design considerations are provided at the end of the paper and it is envisaged that these new experimental data will be useful for the validation and benchmarking of analytical and numerical models.