Mechanical behavior of timber-concrete composite members under cyclic loading and creep

Abstract

Composite structures have emerged over the past several years, and are being increasingly studied and applied in civil engineering projects. In this study, a composite structure was combined with timber under tension and concrete to resist compression. Although several connection systems to bind wood and concrete exist, an innovative system was applied in the present study based on a specific wood treatment and the use of adhesives. Eight hybrid timber-concrete composite (TCC) members were fabricated and tested under static and cyclic loading, and creep. The results indicate that the minimum and maximum loads (which represent dead and live loads, respectively) were constant during a cyclic bending test. The mid-span deflection evolved during the test. An analytical model based on the compatibility of the strains was developed to predict the evolution of the displacement at the mid-span and integrate the effect of creep phenomena. Although the TCC members were cyclically tested under the maximum nominal load (live load), the evolution of the mid-span deflection was governed by the creep phenomena. Finally, the composite TCC members were subjected to a residual bending test until failure. TCC members with ordinary concrete showed a progressive loss of bending stiffness during a four-point bending test. This was caused by progressive debonding of the concrete slab and a diminution of the load capacity compared with TCC members that were not cyclically loaded. Additionally, a TCC member with ultra-high performance fiber-reinforced concrete (UHPFRC) achieved similar mechanical behavior as the TCC member tested under a static load.