The "Pont de Pierre" of Bordeaux (France), built between 1810 and 1821, was, until 2014, the only link between the two borders of the Garonne River. Today, it is a strategical axis that is used every day by 100 000 passengers (on foot, by bicycle or by tram). Since its construction, the bridge has been affected by significant settlement. In 1992-1994 and 2002-2003, 16 micropiles drilled into the masonry of each pillar reinforced the first six pillars. A detailed monitoring analysis (before and after reinforcement) is undertaken to expose the effects of micropile reinforcement and the load transfer process. In addition, an analysis of tidal effects is also carried out. Then, a soilstructure interaction model and a soil-pile-soil model are developed and fitted to the previous analysis. The results are compared with the reinforcement design obtained by the safety factor approach. The importance of considering the relative stiffness between micropiles and timber piles to improve the design of reinforcements (micropiles) is highlighted. The analysis sheds light on the issue of strengthening the last 11 pillars projected for 2023-2025.