Aerodynamic instability of a bridge deck section model: Linear and nonlinear approach to force modeling

The aerodynamic behavior of a bridge deck section model with a simple single-box shape was characterized in wind tunnel. At large nose-up mean angles of attack, a torsional instability arises, outlining a situation in which nonlinear aeroelastic effects may be critical. Such condition represents an interesting case to develop and validate nonlinear models for the aeroelastic problem. The experimental campaign allowed both to characterize the aerodynamic forces using forced motion tests and to study the aeroelastic behavior of the section model, when excited by actively generated turbulent wind. These aeroelastic tests are used to validate a numerical time-domain model for aerodynamic forces that takes into account the nonlinearities due to the reduced velocity and to the amplitude of the instantaneous angle of incidence. Results are critically analyzed and compared with those obtained with a linear model.