MILLAU VIADUCT - STUDY OF THERMAL BEHAVIOR OF THE APRON BY ANALYSIS OF TEMPERATURE MEASUREMENTS IN THE METAL BOX

Abstract

The Millau viaduct crossing the tarn valley in southern France isa multi-span cable-stayed bridge, with a total length of 2460 m.It was formally inaugurated on 14 December 2004. Thisexceptional structure was the object of a large scaleinstrumentation program, which aims firstly monitoring the long-term behavior of the structure and secondly verifying designassumptions (Wind, temperature...). Given the fundamentalinfluence of thermal actions on the behavior of the structure, theorthotropic steel box girder was equipped with 27 temperaturesensors in a section located in span P2-P3, to allow continuousrecords.The purpose of this paper is to present the results of the studycarried out by the Eiffage TP engineering department guidance of Michel Virlogeux who had led a similar study on thesteel box deck of the Normandy Bridge [1], the results of whichwere also allowed to define the assumptions of thermal actionsselected for detailed design of the Millau viaduct.The analysis carried out by exploiting a series of recordingsmade over a period of 7 years from 2005 to 2011, helped toaccurately know the thermal behavior of the deck, namely theevolution of extreme values of the average temperature of thebox, values of thermal vertical and transversal gradients, and thesimultaneity of these two actions by means of a statisticalanalysis. It was also determined the correlation of thesevariables with meteorological data (temperature and thermalradiation), but also with the opening of expansion joints.Finally, the results obtained allowed to verify the relevance ofthermal assumptions underlying the design of the structure.