Conception de pre-dalles en betons innovants pour les ponts

More than 75% of all the 12 000 bridges on Quebec's territory were constructed between 1960 and 1980 (Moffatt 2004). The slabs of a large number of these works reached their service life and will soon need rehabilitation or replacement. This kind of roadwork disturbs traffic flow and generates managing costs that can become an important part of the construction budget. Therefore, the acceleration of the construction projects is of great interest and using a precast preslab constitutes an alternative which could substantially reduce the time needed for the project's realisation as well as their direct and indirect costs.;The first part of this study presents the results of the analysis that allow determining the positive maximal transverse moments caused by a CL-625 truck passage on the studied benchmark bridge (CSA 2006).;The design objective of this study's first part consisted in optimizing the preslabs' size by varying its thickness and the quantity of its half height located reinforcement. The preslabs were designed with four different concretes: a 50 MPa High Performance Concrete (HPC50), a 50 MPa and a 70 MPa High Performance Fibre-Reinforced Concretes (HPFRC50 and HPFRC70), and a 120 MPa Ultra-High Performance Fibre-Reinforced Concrete (UHPFRC120), The design had to satisfy the maximum tolerable crack width in service of 0.2 mm (MTQ 2004) and resist to the weighted efforts as specified in the Canadien Highway Bridge Design Code (CSA 2000). Bending tests were performed on the preslabs. The preslabs design showed that in order to respond to the conception's criteria, the more performing the concrete is the thinner and less reinforced may be the preslab. Taking note of the impressive bending strength of the UHPFRC120, we proposed a new preslab concept: a bi-layer type of preslab.;The second part of the study consisted in defining the parameters of the bond area between the preslab and the slab. Uniaxial tension and shear tests were performed on the specimen's bond area which included two concretes of different ages and nature. Three bond areas (trowelled, exposed aggregates and ribbed finish) and concretes (HPC50, HPFRC50 and UHPFRC120) types were studied. This characterization enabled to determine four variables essential to the preslab/slabs system modelling in the ATENA software (Cervenka 2002): the tensile and shear strength of the bond area as well as the initial elastic normal and shearing stiffness of the bond area.;When a bridge is located over a road or a salt water river, the lower side of the slab is submitted to severe environmental exposures. Water and chloride infiltrations in the concrete accelerate the reinforcement's corrosive process and can lead to its long term deterioration. Therefore, using a very durable material to fabricate the slab satisfies a relevant need. The bridges' slab performance can be greatly improved through using High and Ultra-High Performance Fibre-Reinforced Concretes. These materials present a very high mechanical strength, a longer durability due to their low permeability and an excellent workability. Consequently, using fibre reinforced concrete preslabs can be highly convenient because it accelerates the short and long term repairing works and provides more durable constructions.;The third part of the study consisted in conceiving and analysing the preslab/slabs systems tested with a midspan loading in static and cyclic bending conditions. Five system types were studied: one made of a HPC50 preslab, one of HPFRC50 with an exposed aggregates finish, one of HPFRC-N50 with a ribbed finish, one of UHPFRC120 and one bi-layer type of UHPFRC120-HPFRC50. Two specimens of each type where made by Beton Brunet. One of each was only tested for static bending, while the other one was submitted to both cyclic and static loads. This leads to define the load's cyclic influence on the residual strength of the specimens. The cyclic load did not greatly affect the behaviour of the preslab/slabs systems. The bond area between the preslab and the slab did neither present any delamination nor vertical movement during the static and cyclic tests performed on the five studied systems.