Optimisation of Structures Excited by Wind under Consideration of Stochastic Actions and Various Limit States

• Applicants: Professor Dr. Tom Lahmer; Professor Dr. Guido Morgenthal
• Subject Area: Structural Engineering, Building Informatics and Construction Operation ; Applied Mechanics, Statics and Dynamics
• Term: from 2017 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 329120866

Civil structures are exposed to complex wind actions as a result of the effects in the atmospheric boundary layer. Slender structures such as bridges, towers and mastes may be prone to significant vibrations induced by the aerodynamic effects arising from the wind. Phenomena of practical relevance are vortex induced vibrations, buffeting and flutter.The aerodynamic behaviour of structures is influenced primarily by their geometry, which proposes mathematical shape optimisation strategies linked to computational fluid dynamics simulations as a means to improve their aerodynamic performance. The selection of relevant limit states and the stochastic description of effect and resistance parameters allow the reliability based assessment of the structural response as the target of the optimisation procedure.This project aims to develop a methodological framework for the robust optimisation of structural response under the effect of a stochastically described natural wind field in respect of various limit states. To this end, existing numerical simulation procedures based on the pseudo-threedimensional Vortex Particle Method with extensions for turbulent inflow conditions and fluid-structure coupling are extended to allow the computationally efficient analysis of the relevant effects. Specifically, the stochastic parameters of the wind field are to be reproduced, the structural response is to be analysed in respect of the limit states and the parallelised simulations are to be linked to the optimisation strategies.Additionally, existing models for a phenomena based analysis of the excitation mechanisms such as quasi-static aerodynamic force coefficients, force amplitudes of vortex shedding, Strouhal Number, Scanlan Derivatives and admittance functions are employed to increase the efficiency of the optimisation and to allow a de-coupling of the fluid and structural. The validation and interpretation of simulation and optimisation results will be supported by experiments in the wind tunnel and the use of visualisation tools in the new Digital Bauhaus Lab of Bauhaus University.In conclusion, the project will yield a validated method for the efficient and parallelised simulation of wind excitation of line-like structures exposed to natural wind in the context of a limit state based optimisation. This will also be relevant for similar problems in structural dynamics. Sample analyses will be used to showcase the ability of the method to improve aerodynamic performance in relation to various limit states.

• DFG Programme: Research Grants