A timber-concrete composite (TCC) combines timber and concrete, utilising the complementary properties of each material. The composite is designed in such a way that the timber resists combined tension and bending, whilst the concrete resists combined compression and bending. This construction technique can be used either in new build construction, or in refurbishment, for upgrading existing timber structures. Its use is most proliﬁc in continental Europe, Australasia, and the United States of America but has yet to be widely used in the United Kingdom.To date, the topping upgrades used have been 40mm thick or greater. Depending on the choice of shear connection, this can lead to a four-fold increase in strength and stiffness of the ﬂoor. However, in many practical refurbishment situations, such a large increase in stiffness is not required, therefore a thinner topping can sufﬁce. The overarching aim of this study has been to develop a thin (20mm) topping timber-concrete composite upgrade with a view to improving the serviceability performance of existing timber ﬂoors. Particular emphasis was given to developing an understanding of how the upgrade changes the stiffness and transient vibration response of a timber ﬂoor.Initially, an analytical study was carried out to deﬁne an appropriate topping thickness. An experimental testing programme was then completed to: characterise suitable shear connectors under static and cyclic loads, assess the beneﬁt of the upgrade to the short-term bending performance of panels and ﬂoors, and evaluate the inﬂuence of the upgrade on the transient vibration response of a ﬂoor.For refurbishing timber ﬂoors, a 20mm thick topping sufﬁciently increased the bending stiffness and improved the transient vibration response. The stiffness of the screw connectors was inﬂuenced by the thickness of the topping and the inclination of the screws. During the short-term bending tests, the gamma method provided a non-conservative prediction of composite bending stiffness. In the majority of cases the modal frequencies of the ﬂoors tested increased after upgrade, whilst the damping ratios decreased. The upgrade system was shown to be robust as cracking of the topping did not inﬂuence the short-term bending performance of panels. Thin topping TCC upgrades offer a practical and effective solution to building practitioners, for improving the serviceability performance of existing timber ﬂoors.
|Date of Award||11 Jun 2014|
|Supervisor||Richard Harris (Supervisor), Pete Walker (Supervisor), Kevin Paine (Supervisor) & Julie Bregulla (Supervisor)|