Low Carbon Pathways for Structural Design

To avoid an increase in greenhouse gas emissions, a depletion of resources, and waste accumulation, structural engineers have a major role to play in low carbon structural design. For example, cement- based materials represent one-third of all materials extracted each year [1]. This paper offers three pathways for lowering the embodied carbon of building structures – the emissions related to material extraction, production, transport, construction, maintenance and demolition – through the lens of three case studies of building structures in Switzerland. The first pathway focuses on the structural scale by reducing material intensities in terms of material use per unit of floor area. The second pathway focuses on the material scale by lowering the impact of the materials themselves through the choices of the materials typically used in structures. The third pathway focuses on potential changes to current construction practices by (re-)introducing reuse strategies in the building sector. A simplified version of Life Cycle Assessment (LCA) is used to evaluate each Swiss case study compared to current practice. The material quantities are collected from literature, architectural drawings, Bill of Quantities (BoQ), and Building Information Models (BIM). This research illustrates the challenges and opportunities of three pathways for low carbon structural design: the optimization of material efficiency, the use of low- carbon materials, and the reuse of structural elements from other demolition sites.

Component reuse in structural design: emerging practices and tools for the circular economy

Jan Friedrich Georg Brütting, Corentin Jean Dominique Fivet, Jonas Warmuth

Structural engineers play an increasing role in ensuring the transition towards a more sustainable construction sector: a) they are responsible for the design of the most resource- and energy-intensive part of buildings and infrastructure, and b) they regularly interact with architects, contractors, and clients, and hence are full stakeholders in the overall decision process. Traditionally, structural engineers follow two paths to reduce structure environmental impacts: 1) minimizing the volume of material, and 2) adopting low impact (e.g. low carbon) materials. A third strategy that has recently re-emerged in practice and research is the reuse of structural components over multiple service cycles, which allows drastically reducing raw material use, reprocessing energy, and waste. Therefore, employing reuse strategies in structural design has considerable potential to reduce structure environmental impacts further. Although reuse is not new, systematic adoption in practice implies an important paradigm shift: rather than manufacturing components after the structural system has been designed, the system must be synthesized from a stock of available components. The first part of our contribution provides an overview of historic and contemporary structures that efficiently reuse structural components. It also highlights the influence of component reuse on the structural design process. The second part presents a new computational tool for the conceptual design of structures from a stock of reclaimed elements. The tool combines Combinatorial Equilibrium Modelling, graphic statics, efficient Best-Fit heuristics, and Life Cycle Assessment to explore different design options in a user-interactive way and with almost real-time feedback. The method applicability is demonstrated through a realistic case study for the design of a complex 3D spatial structure made of reclaimed structural elements originating from deconstructed buildings in Switzerland. Results show that structures made of reused elements have a significantly lower environmental impact than solutions made of new material only. Link to the video: https://youtu.be/VCyD1yqXH8w

fib2021

Can timber lower the environmental impact of tall buildings?

Catherine Elvire L. De Wolf, Corentin Jean Dominique Fivet

The building sector is responsible for 30% of anthropogenic greenhouse gas (GHG) emissions (UNEP, 2009). Recent energy efficiency measures have helped reduce the operational carbon related to the use phase of the building, but a lack of industry attention hinders the reduction of embodied carbon related to the rest of its lifecycle: material extraction, transport, construction and demolition. Tall buildings are an evident solution to fight urban sprawl and hence reduce transportation emissions. In addition, the volume-to-surface ratio lowers the need for heating and thus reduces the use of operational energy. However, the challenge with current tall buildings is their inherent need for more structural materials. Research is needed to achieve structural efficiency in tall buildings by reducing the material quantities and choosing low carbon materials. For example, we can use mass timber to achieve skyscrapers that sequester carbon. Major engineering companies have studied the possibility of constructing timber skyscrapers. A new timber tower construction technique was recently validated, using reinforced concrete only for the connections. In composite structures, materials are used where they are most needed by combining their best qualities such as fire safety, high strength, and low density. This allows structural engineers to design using less material. This paper makes two contributions: it discusses the challenges of assessing the embodied carbon of timber materials and it characterizes the specificities of tall timber systems with built case studies.

Taylor & Francis Group2019

The development of material-adapted structural form

Sean Dooley

New structural materials can potentially change the technics and economics of the building and construction industry in a profound way. It is important to identify applications and develop forms that exploit a material's unique properties. The developer of a material can use the knowledge of how materials such as steel and reinforced concrete were first introduced to advance the development and application of new materials today. This project examines why structural forms have evolved as they have and what influences the process of creating form, or form-finding. The purpose of this analysis is to aid the development of structural forms that make the most efficient use of material and take advantage of a material's processing and constructive attributes. Such forms are called material-adapted. This thesis is based on the general history of structural materials used in construction. This research is summarized in six appended case studies that comprise the data of the thesis. The research has extended well beyond these case studies; some of this data is included in the main text. The research showed that the influences on form-finding are: Function; Material Properties; Processing Technologies; Connection Technology; Construction Process; Economics; Socio- Political Factors; Knowledge; and Technological Thought. A Form-Finding Influence Interaction Model summarizes the inter-relationships of these influences. It was first assumed that material-adapted form is determined by material properties alone. Further research showed this untrue. The hypothesis of this thesis is that material properties do not unilaterally determine material-adapted structural form. This statement is true because the nature of a material is a function of its properties and its processing and constructive attributes. A material's processing and constructive attributes are dependent on technology and organizational systems that are not specific to the material. It was further hypothesized that new materials are first used substitutionally in forms and applications of known materials. This concept was found to be misleading and untrue for a number of materials. The knowledge of this thesis was used to examine the current development of fiber reinforced polymer composite materials. It is shown that a material's development can be analyzed not only by the aforementioned influences, but also by characteristics of other material developments. This information is used to suggest how these materials might develop in the future.