In this study, the effect of unsteady aerodynamic force of ice-accreted transmission line on galloping analysis is investigated. First, unsteady aerodynamic coefficients of ice-accreted single conductor predicted by DES are validated by the wind tunnel test and verified by the galloping analysis based on the measured unsteady aerodynamic coefficients. The galloping analysis for ice-accreted 4-conductor transmission lines are then performed using steady and unsteady aerodynamic coefficients of single conductor, respectively. As a result, hysteresis of unsteady aerodynamic coefficient shows good agreement with the experiment. The mechanism of hysteresis is explained by the difference of pressure distribution on the ice-accreted conductor between positive and negative torsional directions. The galloping analysis using the unsteady aerodynamic forces improves the amplitudes of galloping predicted by the conventional quasi-steady approach.

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Aerodynamic stability of long-span roofs is investigated on the basis of computational fluid dynamics (CFD) with a large eddy simulation (LES). A forced vibration test is performed to obtain the unsteady aerodynamic forces for the first anti-symmetric mode. The CFD simulation method is first verified by comparing the results with the previous experimental results. Then, the unsteady aerodynamic forces, represented by the aerodynamic stiffness and damping coefficients, at the location of the anti-nodes of vibration as well as on the whole roof are computed for various wind velocities, vibration frequencies, and vibration amplitudes. The resonant effect and aerodynamic stability are discussed based on the results. Finally, the critical wind velocity that induces the aerodynamically unstable vibration is provided on the basis of the relation between the mass damping parameter and the non-dimensional wind velocity.

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Sea surface temperature change due to the global warming may affect the development of typhoons. In order to estimate extreme wind speed, a tracking model of typhoon simulation considering the sea surface temperature was developed before, but there were some discrepancies between estimation and observation. In this study, from the viewpoint of characteristics of a linear model in the updating calculation, data period for the modeling was restricted to summer based on the number of typhoons approaching to Japan. Focusing on the latitude of 31.5 degrees north where almost all typhoons start to weaken, the termination condition of the typhoons was clarified. In addition, if the value calculated by updating calculation in the model exceeds the threshold, it was recalculated from the time of occurrence of a typhoon. As a result, the typhoon central pressure difference approached the observed value by applying these improvements to the tracking model.

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