Long-term and collapse tests on a timber-concrete composite beam with glued-in connection

The paper reports the results of a comprehensive
experimental test performed on a 6m span timber-concrete composite beam with glued rebar connection. The beam had first been subjected to sustained load in unsheltered outdoor conditions for 5 years. Eventually a ramp loading test up to failure was performed. The long-term test showed an increase in deflection mainly during the first two years, while the
slip rose during the whole testing period. Thermohygrometric variations of environment caused an important fluctuation of all quantities on both yearly and
daily scale. By comparing experimental and analytical
results, it is highlighted that composite beams in outdoor conditions should be assigned to the 3rd service
class according to the Eurocode 5 (EC5). Analytical
predictions based on approximate formulae suggested
by such regulation are found to be not conservative
for the long-term behaviour and fairly accurate for the
collapse behaviour. Since the simplified formulae proposed
by the latest versions of the EC5-Parts 1.1 and 2 largely underestimate the actual connection stiffness and strength, it is recommended that realistic values of
these properties, such as those obtained through pushout
tests, be used when designing timber-concrete composite
beams.