Analysis and construction of transfer structures: a case study

Abstract

A transfer structure of a building is a structure that alters the load path of the gravity loads, shifting the line of thrust laterally to a different vertical alignment. They usually represent major elements of a structure and their impact on building cost and construction time can be substantial. The design for deflection control is frequently the primary consideration when defining the geometry of a transfer element, given their usual long spans and the high magnitude of the forces involved. Considerations of robustness and disproportionate collapse may also be key for the design of transfer structures as these are often regarded as critical elements for the overall stability of the building. Furthermore, the sequence of construction should be modelled through a construction-staged analysis, as it greatly affects deflections as well as final forces distribution. This paper provides guidance and highlights the key aspects that are likely to determine the structural design of transfer structures, as well as typical construction methods and challenges. It also presents a comparative study between two different types of transfer structures for the same building: an alternative composite scheme for the post-tensioned concrete transfer grid of the St. Gabriel Tower (Lisbon) was designed and the most relevant factors are highlighted.