Design variables for steel and aluminium in high-rise rooftops

Abstract

This dissertation reports a case study in the design and construction solutions for a major corrosion failure of the aluminium louvres and steel brackets on the roof and façade of levels 26-29 of the Westfield Tower 2, Bondi Junction. This work was undertaken during early 2005.

Aims: • Consideration of the roles and responsibilities of designer and engineer working on metallurgical corrosion issues in high-rise buildings • Undertaking of a literature survey of corrosion issues involving riveting and welding of aluminium and galvanising of steel • Undertaking of stress calculations for all components to ensure compliance with the requirements of design principles • Confirmation of the stress calculations through finite element modelling • Examination of all materials issues in order to prevent re-occurrence of structural degradation and corrosion • Consideration of relevant environmental effects on the materials • Implementation of these design solutions using novel aerospace materials and methods • Prediction of future performance through factorial and matrix method approaches.

Outcomes: • It is hoped that the text provides a documentary basis for future guidance of designers and engineers working in areas related to the subject of the present work. • It also is hoped that the work on aerospace technologies will broaden the scope of designers and engineers in the potential that these materials and processes have in building considerations. • The manual stress calculations and finite element modelling confirm that the implemented designs are consistently within design specification and that, from the mechanical perspective, no problems are anticipated. • Further, since considerable care was taken to ensure that galvanic and other forms of corrosion were avoided through the appropriate use of design, materials, and implementation approaches, no further corrosion has been observed at the site. • The development of a generic factorial approach and a specific matrix method, applied to corrosion and welding considerations, was informative but these still are at speculative stages owing to the difficulty of obtaining relevant meaningful data and the problem of assigning weighting factors on what is viewed as a fairly subjective basis.