The climate emergency calls for a global shift towards a low-carbon economy, to preserve natural resources and biodiversity, while limiting global warming and its consequences. This project focuses on the impact of distribution centres, intended for the storage of commercial goods. Warehouses are characterised by large flexible spaces and simple structural systems, most often with steel or concrete frames aiming at efficiency and low costs. The aim of this research is to create a sustainable single-storey warehouse with a significantly lower environmental impact compared to reference designs with steel and concrete frames. Considering a new-build project with no reuse of existing elements, a meaningful target for embodied carbon reduction is set to 50% of the environmental impact score of reference steel and concrete warehouse designs.
A selection of sustainable design strategies are investigated, giving insight into which actions designers shall take in priority to effectively reduce the embodied carbon of a warehouse. Reducing upfront emissions (LCA modules A1-A3) requires looking into short-term sustainability measures like reducing material use or using low carbon alternatives wherever possible. Replacing fossil-based products by renewable carbon sequestering materials like timber or other biobased alternatives contributes to lowering the impact of a building, by storing biogenic carbon for the lifespan of these elements. A sustainable use of wood presumes that its design lifespan is at least equal to forest rotation periods to maintain or increase the forest timber stock, combined with sustainable forest management practices. Biogenic carbon storage may be extended by designing for long-term reuse or recycling. Greening the envelope of a building takes advantage of ecosystem services provided by vegetation, like improving air quality, enhancing thermal performance or supporting biodiversity. Many systems can be applied on facades and roofs, depending on project-specific requirements (plant species, layout, load-bearing capacity), to effectively introduce vegetation in the built environment.
The first design step investigates the embodied carbon reduction potential of substituting steel or concrete by timber in the load-bearing frame of a warehouse. Reference steel and concrete structures are selected, and baseline timber designs are created with similar geometrical characteristics and stability systems, to compare their environmental impact on a fair basis. The second design step of the research aims at further reducing the impact of not only the frame, but also other parts of the timber warehouse (foundation pads, floor slab, envelope). Big ticket items responsible for the most impact are identified and tackled in priority: in both timber designs, the floor slab and envelope are responsible for the largest share of embodied carbon. Based on the results of design steps 1 and 2, the 50% embodied carbon reduction target can be achieved by substituting steel or concrete in the frame by timber (-31%), replacing sandwich panels on steel supports by biobased materials in the envelope (-13%), and reducing the floor slab thickness by 50mm (-7%), when considering only fossil emissions. If biogenic carbon storage is accounted for, using biobased materials in the frame (-65%) and in the envelope (-58%), without modifying the floor slab, results in a carbon positive warehouse design. These results are only valid assuming long-term carbon storage in biobased materials, supported by circular design measures. Greening the envelope also contributes to making warehouses more sustainable, provided that benefits from ecosystem services outweigh environmental costs from additional materials.

Buildings influence the environment due to the emission of greenhouse gases, energy use, water consumption, and waste generation. The load-bearing structures of buildings also have a significant share in these emissions. Currently, European and national regulations oblige to focus on sustainability in designs as well. In this research, it is therefore investigated how the environmental impact of a specific case study can be reduced (the Base design). This is a distribution centre’s load-bearing structure and is a sway steel structure with one mezzanine floor made from concrete and steel. In the first part of this research, the design choices to reduce the yearly environmental impact of a distribution centre’s load-bearing structure are investigated. This is done by following three circular economy strategies to improve the Base design. The first strategy focuses on the building’s initial material use, where it is aimed to reduce the current impact of these materials as much as possible. This strategy is applied in a non-sway steel structure and a non-sway timber structure. The second strategy focuses on the afterlife of a building. This led to a steel sway structure where Design for Deconstruction is applied, which means that extra attention is given to the connections to ensure reuse is possible at the end of life. The third strategy focuses on extending the use stage, meaning that the design is optimised for multiple functions. This is implemented in two designs where the principle of Design for Adaptability is applied. In the second part of the research, several environmental impact calculation methods to measure the environmental impact are investigated. It is decided to consider the current product impact (Stages A1-A3 of a Life Cycle Assessment) and the final stage (Stage D), where benefits and loads beyond the system boundary are calculated. As a result, the yearly environmental impact is calculated for the different design alternatives and is given in a shadow price (in euros) per year. This is done separately for the main load-bearing structure and the mezzanine floor load-bearing structure. From the environmental impact calculation of the design alternatives, it can be concluded that there are several ways to reduce the environmental impact of a distribution centre. Though, the following design aspects influence this most significantly. Firstly, it is concluded that environmentally friendly material should always be chosen over other materials to reduce the environmental impact of a building. More specifically, it is recommended to design a timber sway structure (Alternative B) if the reference service life of the building is unknown or if a long reference service life is expected. For a short reference service life, it is recommended to focus on the afterlife of a building. This strategy is most effective if this is combined with a reduction in initial material use. For the main load-bearing structure, Alternative A with an end of life scenario with a high chance of reuse results in the lowest yearly environmental impact. For the mezzanine floor, the demountable floor design with a high chance of reuse of Alternative C leads to the lowest yearly environmental impact. Besides, using the building for a longer time is also an effective measure to reduce the yearly environmental impact. The reference service life may extend if a building is designed for multiple functions. This can be assessed by asking the client about their expectations of the use of the building. By assessing this issue in the design phase, it can be decided to include some overcapacity to ensure a longer reference service life.

Practical combinations of floor configurations and support conditions are studied for the development of a lightweight timber building method that is suitable for multi-family residential buildings. Classical vibration theory forms the base for a methodology that is developed to assess transmittance of vibrations to adjoining floor fields. Especially when the source is out of sight, humans humans are tend to classify vibrations as annoying for low vibration levels. With the introduction of new engineered timber products made wood a more suitable and used material for residential buildings. Strength- and stiffness variation is reduced by homogenizing the material and regarding soundproofing innovative concepts have been improved, such as floating screeds and resilient materials. Based on these products and acoustic concepts, 32 design combinations are studied. A distinction between forced- and free vibrations is made and related to low- and high-frequency floors. Forced vibrations are in structural dynamics described by the particular solution, and free vibrations by the homogeneous solution of the equation of motion. This solution is found through the method of separation of variables, which multiplies the space- and time-related parts. Mode shapes are studied regarding transmittance and effective measures for prevention. Fundamental frequencies of floors supported either rigid and flexible are determined with one-dimensional undamped continuous systems where supported beams are represented by equivalent springs. All floors are transformed into Single Degree of Freedom systems to include damping. These systems are assessed making use of modal superposition, for steady-state- and transient response. The behaviour of floors under walking load harmonics provides the resonant response, and free vibration of the system due to initial conditions the transient response. Since the perception of vibrations by humans is frequency-dependent, vibrations are weighted accordingly. Eurocodes currently available are found to provide guidance regarding human-induced vibrations of lightweight structures marginally. Non-timber Eurocodes do not provide an assessment method, EN1990 only provides requirements when no assessment has to be done, and current code for timber structures prescribe criteria that are not sufficient as found in the literature. The future revision of Eurocode 5 holds several methods for assessment of vibrations but is generally focussed on rigidly supported floors. In extending to this code methods are developed to acquire fundamental frequencies of flexible, supported floors, and by transformation into SDOF systems an equation is developed for the appropriate determination of modal mass for two-span or beam supported floors using a simple formula. 32 combinations of floor configurations and support conditions are assessed at the excited field and at adjoining floor fields, where both steady-state and transient response are combined. Based on this assessment, transient responses are found to contribute significantly for low-frequency floors, where generally is assumed that the mass is sufficient to neglect this response.

Limitations in the modern housing market supply and the high demand for city centre living space ask for a robust urban densification way of building. This results in the exploration of innovative vertical extension projects, such as the ’De Karel Doorman’ case in Rotterdam. However, demanding the construction method to be extreme light-weight revealed an unexpected normative serviceability phenomenon. The reducedmass did not dissipate enough vibrational energy induced by human activities such as walking, leading to an excessive and disturbing perception of vibrations. This caused nuisance for both the home situation where the motion takes place as for the neighbouring floor fields. The critical motion-related limit state has to be satisfied to create a comfortable living environment. This thesis aims to further develop the concept of light-weight steel and timber building structures focussing on vibration comfort. This is done by exploring structural measures that can steer the vibrational floor response for both the induced situation as for the transmittance to adjacent fields. Broadening research shows the general impact of the damping, natural frequency and modal mass. From this starting point, new practical building tools are developed to affect and control the path and magnitude of vibrations positively. General guidelines are provided that show the demands for a structural assembly to create suitable apartments. The proposed measures to steer the vibration comfort were researched using both the conventional handcalculation method from the SBR-guideline and by more accurate finite element analyses from SoViST and Autodesk Robot. The resulting OS-RMS90 values indicate the response velocity of the floor and have to meet the limit criteria proposed for the specific function of a building. For the light-weight residential building concept, these criteria were set to 0,8 [-] and 0,2 [-] for respectively the home and neighbouring situation. It was found that for light-weight building structures the implementation of a large amount of stiffness is inevitable in both the floor assembly as in the junction. The consequence of additionalmass and height can be balanced by using efficiently shaped profiles and smart placement of the joists. For the supporting beams, these demands encourage the use of rectangular hollow structural sections whereas for the floor assembly I-joists are recommended. Additional transverse stiffness stretches the clustering of natural frequencies for orthotropic plates but is most effective for two-way span floors. A smaller span will result in improved comfort levels but will complicate the structural assembly by introducing more elements and connections. Besides the overall performance enhancing measures, it was found that the limit criterion for neighbouring apartments is harder to achieve without additional interventions. Introducing more substantial obstacles for the vibrations to overcome along the path, will reflect the transmittance and hence steer the floor response towards improved comfort levels. The use of an alternating floor field can provide in this issue as it avoids the mode-coupling of natural frequencies from adjacent elements. One other recommendation is the differentiation of the home-separating and in-home junctions. This results in maintaining more vibration energy in the home situation and limits the nuisance caused from excitements in a neighbouring apartment. The as-built ’De Karel Doorman’ revealed the impact of additional stiff elements in the wall that substantially increase the bending and torsional stiffness in the junction. It was found that these elements mitigate the nuisance caused by footfalls to imperceptible values for adjacent floor fields. However, these elements do leave a mark on the flexibility of the floor plan. Light-weight building structures face new challenges and acknowledge the shift from strength-design to serviceability-design criteria. Regarding vertical extension projects, not just the building engineering aspects but also the practical implementation was found to contribute in the consideration for structural assembly measures.