Robert Le Roy

New wood composite bridges

ABSTRACT This research explores the possibilities of wood composite structures with a view to designing durable lightweight composite decks. The paper examines a new wood structure technology in which an ultra-high-performance fiber-reinforced concrete (UHPFRC) slab is fastened to glulam beams. Fasteners representing most existing groups are first experimentally investigated on small beams (span one meter). The modes of functioning of each type and the various failure modes are identified. The paper proposes a method for assessing the interface shear stiffness. This method is based on analysis of flexural test results using a slip versus shear stress relation. It is shown that glued assembly of the two materials yields the best shear stiffness and highest ultimate strength. The practical aspects of surface preparation before gluing are considered. The results of a bending test carried out on a composite structure having a span of three meters, made of UHPFRC glued to two glulam beams, validate this fastening technique.

Rhéologie des suspensions à matrice cimentaire : approche expérimentale multi- échelle

ABSTRACT The proposed approach consists in studying the behaviour of a concrete starting from four uncoupled suspensions scales: suspending fluid, corresponding to water and the additives, cement paste, mortar and concrete. Rheometric tests using controlled shear rates or shear stresses were carried out on each uncoupled suspension. The experimental data exploitation led us to propose a widened parametric analysis. The influence solid concentration and the particles size on the evolution of the rheological parameters such as the yield stress and the apparent viscosity was identified. In addition, the rheological behaviour of an uncoupled suspension is directly controlled by the behaviour of the uncoupled suspension from size range immediately below.