Construction World July 2015

PROJECT PROFILE

tenants. The additional capital cost of this investment can range from negligible to approximately 4% with a base isolation system. Down- stream advantages include secure tenants, lower insurance premiums and fundamentally a safer built environment. While base-isolation systems, such as friction pendulum bearings, have been in use for some time, we have developed innovative ‘rocking’ and ‘sliding’ frame systems in collaboration with major universities in New Zealand. Material, technology and sustainability The global impact of buildings means that engineers and designers need to start creating more sustainable high-rise buildings. Currently, buildings account for 40% of global energy use, 15% of water use and 30% of the waste that is generated. Although the drive to deliver good, functional and economical designs for high-rise buildings is not changing fundamentally, the focus on produce energy efficient and sustainable designs is expected to increase at an accelerating pace. Tall buildings are proportionally more material and energy-hungry than lower rise buildings. In high- rise buildings the structure is a large portion of the overall cost and embodied energy, and hence, the structural engineer can significantly influence the overall sustainable design outcome. Sustainable structural design goals can be achieved by addressing the following three objectives: reduce, reuse and recycle. Advanced analysis and design methodologies allow us to design increasingly more efficient structures (with just the required amount of material and no more). Also, new material technology is opening the way for the reduction of the embodied energy per unit of material (in terms of transport energy, sustainable supplies, and the like). The use of industrial by-products such as fly-ash, slag and silica fume as a cement substitute can drastically reduce the embodied energy of concrete. ‘Re-use’ is about adapting the use of a high-rise building while keeping the original structure. There are growing examples of adaptive reuse of high rise buildings globally. To achieve future reusability of high-rise buildings, an important design consideration is the provision of ‘planning flexibility’. This can be achieved in the design phase by a generous choice of structural grid, live load allowances and the like (i.e. use longer spans and larger live loads that are more adaptable to future reuse). The emergence of building information modelling (BIM) as a repository of information for asset management (as-built drawings, mill certificates and the like) is also expected to facilitate future reuse opportunities. Future high-rise buildings are likely to be designed with more consideration given to the recyclability of structural components. While the trend in the development of higher strength steel and concrete is not stopping, use of new material with superior perfor- mance and/or superior sustainability is gaining significant momentum. While timber buildings of taller than ten stories have already been achieved, there are significant research and development projects underway globally aiming to construct buildings as tall as 40 stories in steel-reinforced timber. The other growing trend is in offsite fabrication of high-rise buildings. As labour costs escalate relative to material costs and as the construction safety and quality gain increasing attention, solutions involving prefabricated or manufactured structural components and building modules are gaining popularity. There is a growing trend in construction of high-rise buildings from fully modular systems.

The Burj Khalifa is the tallest man-made structure in the world, standing at 829,8 m.

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CONSTRUCTION WORLD JULY 2015