Rocking of offshore lighthouses under extreme wave impacts: Limit analysis, analytic formulations and distinct element method

This study describes the structural response of historic lighthouses to extreme wave impacts. Located offshore on exposed rocks, 19th Century were built with large interlocked granite blocks and have survived weathering for nearly two centuries. Under impacts, this typology may uplift rock, whereas sliding is prevented by vertical interlocking. The thresholds calculated limit analysis method reveal why system capable bearing impacts without failure. ingenious keying proven be a major characteristic that contributes resilience these lighthouses. explained use analytic formulations rocking motion. Detailed impact conducted reference Wolf Rock lighthouse. corresponding 250-year effective return period identified using non-stationary Bayesian analysis. Moreover, flume tests scaled cylindrical structure performed identify force time-history shapes. Based waves: theoretical based existing models in literature measured time-histories from small-scale experiments, series synthetic sequences are generated purposes parametric analysis, Distinct Element Method, commercial software 3DEC, reveals influence duration shape function. For same impulse values, shorter time produce most intense opening joints, despite causing smaller horizontal displacements. Furthermore, variability revealed even impulse, maximum but different time-history.