The Structural Function of the Dutch Buttressing of the East Curtain Wall of Elmina Castle, Elmina, Ghana

Abstract

Elmina Castle is the first of a series of European trading bases along Africa's west coast, and it is the oldest and best preserved early European building in Sub-Saharan Africa. The structure shows a combination of mud-mortared and lime-mortared sandstone masonry macro elements and has undergone reconstructions and modification throughout time under Portuguese and Dutch occupation. This study focuses on the structural analysis of Elmina Castle's east curtain wall, which features two massive masonry buttresses built only along selected portions of the wall. The hypothesis that these buttresses were built in correspondence of deep voids in the foundation bedrock platform is numerically evaluated using pushover analysis. The lateral capacity is determined based on energy considerations using nonlinear FE models in Abaqus/CAE Explicit and concrete damaged plasticity. Results indicate that, at a later Dutch stage of structural modification, loose soil filling might have caused rotational instability of the curtain wall, requiring the addition of the buttresses.