Sustainable structural design of high-rise

Abstract

High-rise buildings are a potential solution to the environmental impact caused by the built environment and the increasing demand for space in urban areas. As recent developments focus on reducing the impact by operational energy (OE) (heating, cooling, hot water and ventilation during use phase), impact by the embodied energy (EE) (production, construction, maintenance and demolition of materials) becomes increasingly significant. Structural materials account for the biggest part of embodied carbon (EC) in buildings. The number of studies that address the environmental impact of high-rise building structures has grown only recently, research is still limited. Moreover, it is doubtful to which extent these researches are applicable to the Netherlands.

This thesis aims to provide insight in the environmental impact of structural systems for high-rise buildings of 150, 200 and 250 meters in the Netherlands. Five different stability and three floor different systems were designed in cast-in-situ concrete, prefab concrete and steel. All of the models contained a concrete core. 2-dimensional static linear calculations were performed in order to determine the cross-sections and reinforcement.

Through parametric modelling, an automated design and analysis work-flow was developed and a total number of 146 models was assessed. The environmental impact was calculated by using the fast track life-cycle analysis (LCA) method. A cradle-to-gate analysis (production phase only, A1-3) was performed by using data from the Nationale Milieu Database (National Environmental Database) (NMD) and steel data from Bouwen met Staal, which contain the environmental impact for multiple impact categories, measured in environmental cost (shadow price). The construction and demolition phases were left out of scope.

It was found that all steel structures had a 6% to 35% higher cradle-to-gate environmental impact compared to concrete structures with the same stability and floor system. Furthermore, no significant differences were found between the cradle-to-gate impacts of cast-in-situ and prefab concrete models. Differences in impact between the materials are likely to be affected by inclusion of the construction phase (A4-5) and foundation structure. It is expected that the gap in environmental impact between steel and concrete is reduced by inclusion of these aspects. Floors were responsible for 32% up to 73% of the total environmental impact.

Regarding the stability systems, results showed that, when subjected to wind loads, systems with axially loaded elements scored significantly better than systems with elements loaded in bending. The outrigger structure decreased the total environmental impact of the concrete models by 5% to 16% and 20% to 26% of the steel models, compared to the tube structure. The braced tube only decreased the impact for the 200 and 250 meter models, with 7% to 12%, compared to the tube structures. The diagrid structure had the best performance at all heights and reduced the environmental impact by 17% to 28% for concrete and 28% to 41% for steel models, compared to the tube structures.