Mock-up ot the cable-stayed bridge of Mourom (Russia)
India, Vietnam, Turkey, Russia, etc.: climatologists and aerodynamics experts at CSTB Nantes have played their part to assure that bridges being built in many parts of the world resist extreme climatic conditions. They are specialized in studying the behaviour of bridges under the effects of wind, and design and engineering offices, architects and public works contractors are calling upon large numbers of CSTB experts to check the stability of bridges under wind loads. "In general, requests apply to an examination of the different times in the life cycle of the bridge, from the "construction" phase until the “service with and without traffic" phase, says Gérard Grillaud, controller of the Wind and Structures domain and more particularly simulation of highly critical construction steps, for example when launching a deck."
CSTB’s methodology for typical projects includes a sequence of well-defined steps. The first and absolutely essential step is to compile, analyse and validate climatic and geographic data (topography) on the projected bridge site. The next step is to define wind tunnel tests to be carried out. These are determined as a function of the configuration and specific features of the bridge to be studied. Once the customer has accepted the proposal, Wind and Structures technicians will take over: a mock-up of the central part of the deck is made – this is usually the part of large suspension bridges or cable-stayed bridges most sensitive to wind - and then installed in the wind tunnel. It is suspended in the wind tunnel using a spring system which simulates the bridge stiffness and is then instrumented. All types of sensors and cameras are used to observe the behaviour of the mock-up (vertical bending, torsion) as a function of the wind velocity in the wind tunnel test section.