Composite Wood-Concrete Panels - Effect of Cyclic Loading and Creep

Abstract

Since several years, composite structures emerged and are more and more studied and used in civil engineering. Wood-concrete structures have the advantage to improve the mechanical behavior on two points, the load capacity and the stiffness. The principle is to combine concrete which resists under compression and timber under tension. Several systems of connection exist to bond wood and concrete but an innovative system is used in this study based on a specific treatment of the wood and adhesives. Three configurations of hybrid panels are fabricated and tested under cyclic loads and creep. The results show that minimum and maximum loads, which represent the dead and live loads respectively, are quite constant during the cyclic bending test. The mid-span deflection evolves during the test. An analytical model based on the compatibility of the deformations is developed to predict the evolution of the displacement at the mid-span and integrates creep phenomena. Even if the panels are cyclically tested under the maximum nominal load (live load), the evolution of the mid-span deflection is governed by creep phenomena. Finally the composite panels are submitted to a residual bending test to failure. Panels with ordinary concrete present a progressive loss of bending stiffness during the 4-points bending test due to a progressive debonding of the concrete slab and a diminution of load capacity compared to panels that was not load cyclically. In the contrary, the panel with ultra-high performance fiber reinforced concrete has a similar mechanical behavior than the panel tested under static load