Current trends in the engineering of tall buildings are being driven by the demand for taller buildings sited in congested urban areas, the desire for large essentially column free interior area, the need for improved safety against fire and terrorist attacks, and lastly, the increasing emphasis on sustainable development of the built environment. These requirements have led to new engineering solutions for structural schemes, floor schemes and energy dissipation devices such as large scale tuned mass dampers; and standards for assessing the sustainability of a design.
The lecture was concerned primarily with new structural solutions. Outrigger schemes were discussed first. Examples of recent applications such as the Jim Mao tower in Shanghai and the Taipei 101 tower located in Taipei were discussed. Taipei 101 has a unique structural form, and also has a large spherical mass pendulum clamper installed at the top.
Diagrid structural systems were discussed next. These systems are emerging as structurally efficient as well as architecturally pleasing structural systems for tall buildings. Recent applications described were the Swiss Re Headquarters Building and the Hearst Headquarters; Sir Norman Foster was the Architect for both buildings. A simple motum based methodology for determining preliminary member sizes is presented. Results of parametric studies carried out on a set of buildings ranging from 20 to 60 stories, to generate optional values of the grid geometric parameters are described. These studies suggest that the optional inclination angle is between 60º and 70º. They also suggest that the perimeter diagrid system is approximately three times stiffer than the typical core so that one neglects the core stiffness. Under typical loadings, the design of buildings taller than 20 stories is governed by serviceability constraints on displacement, not by strength.