Introduction with problems of analysis and design of civil structures exposed to dynamic wind actions

Mastering of procedures used in dynamic analysis and design of civil structures exposed to wind actions

Introduction. Relevant meteorology. Wind forces and classification of vibrations due to wind action. Phenomenon of interaction of wind and structures. Vibrations due to vortex shedding. Notion and development. Flow around a circular cylinder. Frequency lock-in. Analytical models in analysis of the vortex-induced vibrations. Galloping vibrations. Stable and unstable vibrations. Den Hartog’s criterion of galloping vibrations. Jump phenomenon. Universal curve of galloping vibrations. Galloping vibrations of elastic bodies. Galloping vibrations with 2 degrees of freedom. Avoiding of galloping vibrations. Torsional divergence (static aeroelastic instability). Condition of the onset of the torsional divergence. Analysis of flutter and turbulent vibrations. Introduction and classification of flutter. Model of flutter with 2 DOF, differential equations of motion. Aeroelastic forces and aeroelastic coefficients in flutter analysis (flutter derivatives, Scanlan & Tomko). Modal superposition in flutter analysis. Condition of instability, eigenvalue problem. Characteristic polynomial and its roots. Stability analysis and determination of the critical wind speed. Analysis of the flutter with 3 DOF. Analytic formulation by modal superposition. Aeroelastic coefficients (18 for 3 DOF). Multimodal formulation in the frequency domain. Measures to avoid flutter. Active control of motion. Rain-wind vibrations of the cable-stayed bridges. History and phenomenon. Experimental and numerical models of rain-wind vibrations. Critical wind velocity for the onset of cable instability due to rain and wind. Experimental investigations of rain-wind vibrations of cable-stayed bridges. Conclusions and measures to mitigate rain-wind vibrations. Simpler numerical models of the rain-wind vibration analysis. Along-wind structural response. Representation of drag forces and the drag coefficient. Analysis of the structural response in direction of the averaged wind. Average and the equivalent wind forces. Dynamic factor. Deterministic modal analysis in direction of the wind. Euro code 1-4. Analysis of the wind actions upon structures according to the Euro code EC 1-4