Conclusion

It proved possible to create a model through Grasshopper allowing real-time op-timisation on the mateiral efficiency of the structural design. Through a struc-tural model designed parametrically in Grasshopper, it was possible to conduct real-time analyses by the FEM-tool Karamba. The results were visualised in Rhino as statements and more detailed resutls were exported to Microsoft Excel in order to compare different solutions. Through six optimisation steps it was possible to reduce the material consumption for steel by 74.3% and for wood by 68.9%.

The modelled program is tailored for the specific case and could be used to facilitate an additional integrated design process combining architectural and engineering professionals to further reduce the environmental impact, with re-spect of the design.

Further optimisation of the frames is possible as optimisation is an iterative and ongoing process. A problem in the early design stage is the lack of knowledge and quick changes implemented in the design, thus many assumptions of quick and rough estimates and calculations must be carried out. As the design pro-gresses the optimisation will progress as well. As the design stage propro-gresses the increased knowledge of the design and materials allow for 3D optimisation whereas the early design stages can be satisfied with quick estimates based on 2D calculations.

Optimising in 2D must be done with a holistic mindset, thus optimising for material efficiency of the structure and realising the side effects from the op-timisations. The optimisation could thus be depending on the window sizes, stating a minimum distance between the frames. Trade offs must also be con-sidered, as it was seen with the roof height in the optimisation. By reducing the roof height, the roof surface decreased as well, eventually decreasing the mate-rial needed for the roof structure. In larger constructions as this one, substantial optimisations can thus be reached as a consequence of another optimisation.

A risk in connection with optimisations is that the optimised parameter might influence others negatively as well. Throughout the dsign phase the optimisa-tion, the assumptions should lead to objective design decisions based on the literature and trial and error calculations.

Conducting snow and wind simulation instead of using the Eurocode 1, 0-4, further optimisations could be possible. Having more accurate loads would lead to a more realistic investigation of the structure.

As stated in the beginning of the report this is not a fully conducted structural analysis thus further studies of the connections etc. need to be checked. For the optimisation purpose and early design stage it would be too time consuming to conduct a full structural calculation. Especially for the wooden structure a FEM-program able to calculate with materials having different properties in different directions would be needed.

The beams connecting the rows of frames in the depth of the building is not taken into consideration, which means the overall weight of the structure will increase. The atriums are not taken into consideration either, which will lead to a reduction in material use. Both the connecting material of e.g. walls or beams as well as the openings for the atriums would be conducted at a later design stage in 3D and investigated through more advanced calculations.

Further optimisations are thus available by modeling the structure holistically, optimising all building elements and adding in product and material selection.

As stated by Hansen and Knudstrup [Hansen and Knudstrup, 2005], the co-operation between the architect and engineer is important in order to gain a sustainable building. One of the main issues identified is to find a common language as the architects often focuse on senses and subjectivity and the engi-neer on measurable results and objectivity. The investigation performed in this section would be sufficient for initial collaboration between the architects and engineers in order to minimize the environmental impact of the building.

Chapter 5

On-the-fly Life Cycle Analysis

In this chapter the simple life cycle assessments carried out on-the-fly¹ will be introduced and the results presented. The environmental impact from the two structures consisting of either steel or wood will be measured.

1The activity is developed dynamically rather than being a result of something that is statically predefined

5.1 Introduction

In order to carry out on-the-fly life cycle assessments during the optimisation process, the online software Quantis Suite was used. This software was chosen due to its availability and simple and easy user interface allowing non-experts to develop life cycle assessments within a short time.

As previously described in section 2.2, the Global Warming Potential (GWP) was used as an indicator for the overall sustainability of the structure in the previous calculations. By using Quantis Suite it was possible to look at five different impact categories which will be described later on.

For the early design stage a broad knowledge base is needed in order to make wise decisions. At this stage, indications on where to change the design in order to optimise it is important as well as indications of the possible optimisation of e.g. CO₂.

Both the wooden and steel structure is analysed in order to discuss the advan-tages and disadvanadvan-tages of the two building materials and compare them to one another. The estimated life cycle assessment carried out in this section is not a full LCA as it is based on the load-bearing structure of the building, which was analysed throughout this project. The environmental impacts are consid-ered whereas the economical and social impacts are not included. The LCA is used as an indicator for the potential environmental impacts of the structure.

It focuses on the up- and downstream burden of the materials throughout the life cycle of the structure and its embodied environmental impacts.

The LCA carried out in Quantis Suite is thus not a full life cycle assessment but a rough estimation giving indcations of the structures’ environmental impact.

The simplified results will help understand the impacts caused by using steel and wood respectively.