Strengthening the Chillon viaducts deck slabs with reinforced UHPFRC

Abstract

Located in Switzerland, Chillon viaducts are two parallel highway posttensioned concrete bridges built in the late 1960s. The concrete of the deck slabs of these bridges shows signs of early stages of the alkali-aggregate reaction (AAR), which will induce, in time, a decrease of the concrete strength. To insure structural safety for future traffic demands, it was decided to strengthen the slab by adding a layer of 40 mm of an Ultra High Performance Fiber Reinforced cement-based Composite (UHPFRC) material, reinforced with steel rebars. Strain-hardening UHPFRC, with its low permeability, is used as a waterproofing layer protecting the slabs from the water to reduce the rate of AAR. UHPFRC has excellent mechanical properties and also acts as an external tensile reinforcement for the slab, increasing its bending and shear resistance and extending the fatigue life. To investigate this increase in structural resistance, an analytical calculation is done using models previously developed based on extensive experimental campaigns. Finally, the choice of UHPFRC for strengthening was also the most efficient in terms of intervention duration and cost.

Life Cycle Analysis of Strengthening Existing RC Structures with R-PE-UHPFRC

“…The basic idea was the efficient use, as an "everlasting winter coat", of a thin UHPFRC overlay in zones of severe mechanical and environmental exposure where the outstanding UHPFRC properties, in terms of durability and strength, could be exploited effectively with the UHPFRC alone or could be associated with rebar for strengthening applications. This idea was successfully implemented for the rehabilitation and strengthening of road and railway infrastructures, as well as buildings, for over 15 years and was extended to marine structures by Denarié [7][8][9].…”

Flexural and Shear Tests on Reinforced Concrete Bridge Deck Slab Segments with a Textile-Reinforced Concrete Strengthening Layer

“…For reinforced or prestressed concrete bridges, which represent the majority of the German bridge population [ 3 , 14 ], established strengthening methods are available, such as additional external prestressing [ 15 ], insertion of shear connectors, additional concrete in the compression zone or external application of CFRP sheets or lamella [ 16 , 17 , 18 ]. Innovative materials, such as UHPC [ 19 , 20 , 21 , 22 ] or textile-reinforced concrete (TRC) [ 23 , 24 , 25 ] enable considerable material savings through increased performance. This results in a more resource-efficient use of materials with a reduced additional dead weight and an extended service life.…”

Long-term strain measurements of traffic and temperature effects on an RC bridge deck slab strengthened with an R-UHPFRC layer

“…The Chillon viaducts, in service since 1969, are two parallel structures with a total length of 2.1 km each and spans varying from 92 to 104 m. This post-tensioned concrete structure was strengthened in 2014/2015 by a layer of reinforced ultrahigh-performance fibre-reinforced cementitious composite (R-UHPFRC) cast on top of the deck slab, since structural and fatigue safety was of concern. The layer of UHPFRC accommodating steel reinforcement bars was casted to increase the stiffness and structural resistance of the deck slab and the box girder, and to serve as a waterproofing layer protecting the existing reinforced concrete [2]. A monitoring campaign was commenced in May 2016 to verify the effectiveness of the UHPFRC-strengthening [3].…”