Versoix Bridge - Switzerland

SAMCO Final Report 2006 F04 Case Studies

Project Description: The Versoix Bridge is located near to the city of Versoix, crossing the river with the same name. It lies on the A1 highway between Lausanne and Geneva, Switzerland making an important connection between two major Swiss cities (60’000 vehicles per day). 1996 – 1998, the bridge was refurbished and enlarged to accommodate an additional security lane in both directions. Since an important amount of new concrete was added asymmetrically to an existing structure, the issues of differential shrinkage could occur and decrease the structural performance.

Versoix Bridge – Versoix, Geneva, Switzerland

Quick Facts: • Name and Location: Versoix Bridge - Versoix, GE, Switzerland • Owner: Canton of Geneva • Structure category: Short and medium span bridges (36 m to 56 m) • Spans: 2 border spans of 36 m and four central spans of 56 m • Structural system: twin bridges, two prestressed continuous girders stiffened by diaphragms supports along with steel beams cantilevered deck • Start of SHM: 1996 • Number of sensors installed: 120 • Instrumentation design by: IMAC-EPFL, Swiss Federal Institute of Technology, Lausanne

Description of Structure: The old Versoix Bridge consisted of six spans twin concrete bridges. The deck of each bridge was laid on two continuous girders stiffened by diaphragms. Both bridges are refurbished and widened. The girders are reinforced with new prestressed concrete, while the decks are cantilevered at the external side and supported by inclined steel beams.

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Old Concrete New Concrete

Sensor

Cross-section of the Versoix Bridge and position of the SOFO sensors

Purpose of Instrumentation: The aim of instrumentation of the Versoix Bridge is to monitor long-term performance with particular care to the consequences of interaction between the existing and new part of the structure. Thus, the following parameters were monitored: average strain in concrete including early and very early age, old-new concrete interaction, and average curvature analysis in both horizontal and vertical plan, detection of torsion and distribution of both horizontal and vertical displacements. Fiber optic sensors of type SOFO were used and, long-term automatic and remote monitoring was performed. Thermocouples of type “K” were used in order to distinguish thermal strain and load cells at abutments to control the force.

Sensor Details: Type Number Location SOFO fibre optic sensors 104 Span No. 1 –2 “K” thermocouples 12 Span No.1 – 2

Load cells 4 Abutments

Examples of Outcomes: The early age measurements allowed the prediction of cracking long before it became visible, and the optimization of the concrete mix for successive pours. The sensor pairs at interface confirmed the excellent adherence between the old and new concrete. The vertical displacement was measured during the load test by double integration of the curvatures.

Abutment pile 1 pile 2

2 0 1.00 11.00 21.00 31.00 41.00 51.00 61.00 71.00 81.00 91.00 101.00 -2 -4 Vertical Displacement Calculated -6 Error

Vertical Displacement [mm] Displacement Vertical Mechanical gages -8 (IBAP-PFL) +- Error -10 Situation on the bridge vertical displacement during the load test

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Horizontal bending of the bridge due to asymmetrically added new concrete was successfully observed and measured. The single sensors were used to follow the long-term shrinkage of concrete and the seasonal deformations due to temperature

changes. 0.4 Sensor A11

Strain (calc. Shrink. +Temp.) 0.2 Shrinkage and creep (calculated) Temperature (measured) 0.0

Strain [mm/m] -0.2

-0.4

20 10 0 -10 10.09.96 15.10.97 19.11.98 24.12.99 27.01.01 Temperature [°C] Temperature[°C]

five years measurement of single sensor and evaluation of rheologic strain

Benefits of Using SHM Technologies in the Project: The SHM technology in case of the Versoix Bridge provided the following benefits: • Long-term data collecting concerning the structural behavior of the bridge • Improvement of concrete mix composition after the first pouring was done • Possibility to verify the interaction between the existing and new concrete After seven years of monitoring the following conclusions are carried out: • The structure is perfectly monolithic and no delaminating is detected • The evolution of concrete performances is in range of model prediction

References: Vurpillot, S., Casanova, N., Inaudi, D., Kronenberg, P., Bridge spatial deformation monitoring with 100 fiber optic deformation sensors, SPIE 5 th Annual Meeting on Smart Structures and Materials, San Diego, USA, Vol 3043, p 51 - 57, 1997.

Inaudi, D., Casanova, N., Vurpillot, S., Glisic, B., Kronenberg, P., Lloret S., Deformation monitoring during bridge refurbishment under traffic, 16 th Congress of IABSE, Luzern, Switzerland, on CD, 2000.

Glisic, B., Inaudi, D., Structural Monitoring of Concrete Bridges during Whole Lifespan, 82 nd Annual Meeting of the Transportation Research Board (TRB), January 12-16, 2003, Washington DC, USA, on CD paper no. 03-3012.

Submitted by: Dr. Daniele Inaudi CTO SMARTEC SA Via Pobiette 11, CH-6928 Manno, Switzerland Phone: +41 91 610 18 00 Fax: +41 91 610 18 01 Email: [email protected]