[en] The reliability based design optimization is applied to long-span suspension bridges under probabilistic flutter constraint employing three RBDO methods, namely reliability index approach, performance measure approach and sequential optimization and reliability assessment. Uncertainties in extreme wind speeds at bridge site and flutter derivatives obtained in wind tunnel tests are taken into account. Two cases of RBDO problems are studied; in the first case, the bridge girder volume is to be minimized by varying the thickness of box girder plates while in the second case, the sum of the girder and main cable volume is sought to be minimized by considering both box girder thicknesses as well as the main cable area as design variables. For both cases, the optimum designs must satisfy a predetermined structural reliability level against flutter and other deterministic constraints. In order to solve this problem, the three RBDO methods mentioned above are programmed in Matlab code, which calls Abaqus finite element models to obtain structural responses and FLAS code, developed by our research group, to perform flutter analysis. Prior to the resolution of the RBDO problem, reliability analyses of bridge flutter are performed in order to obtain the safety level of the original bridge design. The proposed RBDO formulations are applied to two bridge example of the Great Belt East Bridge in Denmark and the Messina Bridge project in Italy. The results obtained by different RBDO methods are then compared for their accuracy and computational efficiency.

[gl] Aplicouse optimización probabilista (RBDO) a pontes colgantes de gran van considerando condicións de flameo mediante tres métodos diferentes, que teñen por nome en inglés, Reliability Index Approach, Performance Measure Approach e Sequential Optimization and Reliability Assessment. Considérase a existencia de incerteza na velocidade extremal de vento no emprazamento da ponte, e nas funcións de flameo obtidas experimentalmente en túnel de vento. Estúdanse dous casos de optimización probabilista; no primeiro unicamente optimízase o volume do caixón da ponte variando os espesores das chapas que forman o caixón, mentres que no segundo minimízase tanto o volume dos cables principais como o taboleiro da ponte. En ambos os casos, deséxase obter deseños óptimos que satisfagan un valor prefixado da seguridade estrutural fronte a flameo ademais doutras restricións de tipo determinista. Para resolver este problema, prográmanse en Matlab os métodos de RBDO mencionados anteriormente, código que executa un modelo de elementos finitos realizado en Abaqus para obter as respostas estruturais e o código FLAS, desenvolvido polo noso grupo de investigación, para realizar a análise a flameo. Antes de resolver o problema de RBDO realízanse distintas análises de fiabilidade para coñecer o nivel de seguridade estrutural da ponte co seu deseño orixinal. As formulacións de RBDO propostas aplicáronse a dous exemplos de pontes colgantes de gran van: o Great Belt East Bridge en Dinamarca e o proxecto da Ponte de Messina en Italia. Os resultados obtidos polos diferentes métodos de RBDO compáranse en termos de precisión e eficiencia computacional.