Fregate Island Development

Hotel

Fregate Island, Seychelles

Civil and Structural Engineers

The Fregate Island Redevelopment presented a series of exceptional structural challenges, driven by ambitious free form architecture, extreme remoteness, and the requirement for long term durability in a marine environment. Successfully resolving these challenges relied heavily on a BIM driven, model based engineering approach, combined with advanced analytical techniques and highly coordinated reinforcement detailing.

A primary architectural objective was the achievement of maximum glazing and visual transparency within the villas. This required the development of non conventional vertical load paths, with gravity and lateral forces transferred through carefully concealed structural elements integrated within walls,
cores, and architectural features. These strategies were extensively developed and validated within the federated 3D BIM environment, allowing load paths, interfaces, and tolerances to be assessed holistically and coordinated across disciplines.

The architectural form—derived from the aerodynamic geometry of a bird’s wing—introduced complex double curved surfaces and continuously varying structural thicknesses. These organic forms required the application of advanced shell analysis techniques, including finite element modelling of thin reinforced concrete shell behaviour. The shell geometries were digitally controlled within the BIM environment to ensure alignment between analytical models, reinforcement layouts, formwork geometry, and construction sequencing.

To mitigate supply chain risk and programme uncertainty associated with imported steelwork in a remote island context, Brohnsonn strategically adopted reinforced concrete as the primary structural material, exploiting its durability, availability, and suitability for sculptural construction. This approach was first realised through the successful delivery of thin, wave like concrete roof shells over the villas, where shell thicknesses, curvature, reinforcement density, and support conditions were carefully optimised through iterative analysis.

The use of explicit 3D reinforcement modelling to construction level LOD was critical in delivering these elements. Complex reinforcement arrangements within thin shell sections and highly congested zones were developed, reviewed, and validated directly within the coordinated BIM environment. This enabled early resolution of bar spacing, anchorage, laps, and congestion—significantly reducing the risk of clashes, constructability issues, and late stage design changes.

Following the successful execution of the villa roofs, the structural language was scaled and intensified to accommodate larger span concrete shells at the main public facilities, and further evolved into highly complex sculptural shell forms at the spa complex. These elements represent two of the most technically demanding structural features delivered in the Seychelles, requiring close integration between shell analysis, 3D reinforcement detailing, and BIM based coordination.

Model based workflows allowed geometric control, reinforcement visualisation, and multidisciplinary coordination to be maintained throughout design development and into construction. The ability to issue 3D enabled reinforcement drawings and schedules significantly reduced interpretation risk on site and supported accurate execution of complex geometry in a challenging construction environment.

Together, these innovations demonstrate Brohnsonn’s ability to leverage BIM, advanced analytical methods, and construction level reinforcement modelling to transform highly ambitious architectural concepts into robust, buildable, and enduring structural solutions, even within the logistical and environmental constraints of a remote private island development.