Retaining the existing 57-year-old curtainwall on Transpower House, Wellington

Abstract

ABSTRACTThe Author was charged with retaining the 57-year old curtainwall of Transpower House at 96 The Terrace, Wellington New Zealand. The curtainwall system is unitized, made of both geometric and bespoke curtainwall extrusions. The curtainwall assembly includes both welding and screw-fixing. Many joints of the aluminium frame are cracked. Many ‘movement’ joints are closed and appear to have no movement capability to absorb seismic movement, yet the curtainwall has survived more than 50 years of seismic events. The building and its façade were designed at a time when there were virtually no Standards. The aluminium extrusions used were generally made thicker than was required for structural adequacy. The author has overseen a process of structural and weathertight analysis of the curtainwall and a monitoring programme. Design analysis required some stabilization at the corners of the building where wind pressures are highest. The monitoring programme checks 8 points on the curtainwall bi-annually for seismic movements, opening of cracks and general deterioration. The alternative to replacement is to ensure that the curtainwall is structurally adequate, reasonably weatherproof and to monitor for any changes and movements. The curtainwall was assessed for seismic capability using Eq-Assess.