Design of a Curved Duplex Façade for a 67 m High Residential Tower at the Belgian Coast

Abstract

Designed by Neutelings & Riedijk and Bureau Bouwtechniek, the Heldentoren (Eng. Hero tower) is a 67 m high residential tower situated in Knokke-Heist at the Belgian coast. On floor level +2, +7, +12 and +17, the curtain wall façade spans two floors and is partially curved with a bending radius of 2.3 m for which 88.2(ANG, PVB)/15(Ar)/88.2(ANG, PVB) hot bent insulated glass units are used. Considering viscoelastic material behaviour of the interlayers, implementing the curved shape of the glazing and performing geometrically nonlinear analyses, however, will structurally result in more economical glass compositions. The structural design of this duplex façade faced some challenges: high aesthetical requirements by using slim profiles, the curvature resulting in horizontal in-plane reaction forces on the anchors and anchorages combined with large eccentricities, and the impossibility to apply traditional curtain wall design principles leading to the need of structural calculations on system level taking into account the stiffness of the connections between mullions and transoms. The node stiffness was obtained by designing stainless steel stiffeners. Glass bearers transferring the glazing’s self-weight directly to the mullions avoided torsion in the curved transoms. The adopted design method led to a reduction with a factor 4.2 for the bending moments and deflections of the mullions compared to traditional design principles. A mock-up of the duplex façade allowed the identification and solution of technical issues and installation-related difficulties by the façade builder. Potential consequences of these interventions with respect to the structural performance of the façade could be revised as well.