Studies have shown that urban areas globally grapple with high energy and material demands for new constructions while existing buildings often remain underutilized. This issue can be mitigated by designing buildings to be adaptable to future changes. Despite its clear advantages, adaptability as a circular strategy is notably absent from widely used circularity assessments like the Building Circularity Index (BCI) Tool. This research aims to develop a more advanced and holistic tool that integrates the Design for Adaptability as an Adaptability Index (AI) within the BCI assessment model. This innovative tool, known as the A-BCI Tool, incentivizes structures where designing for adaptability is crucial, even if other key performance indicators (demountability and smart material selection) are less emphasized. With this enhancement, the beneficial impact of adaptability in achieving circularity will be quantified, introducing a correction factor or "bonus" to the current method’s score, enabling a more thorough and accurate evaluation process. This research tackles the knowledge gap and problem through a three-stage methodology. The first stage involves a comprehensive theoretical study based on an extensive literature review to gather secondary data on the Circular Economy and circularity and adaptability assessment methods. The second stage uses insights from stage one to enhance the existing BCI, leading to the development of the A-BCI tool. The third stage collects vital primary data through an extensive design study centered on the C-pier project at Schiphol Airport. This study explores eight innovative design alternatives, of which one is conventional, and the rest are adaptable designs, carried out in two phases: an initial design and a compliance review following structural changes. The financial and environmental performance of these designs is evaluated using Life Cycle Assessment (LCA) and cost assessment, validating the A-BCI tool and demonstrating its strong alignment with circular design principles. The research seamlessly integrates an Adaptability Index that underscores the positive impact of designing for adaptability within the existing BCI assessment model. The results demonstrate that this innovative tool provides a bonus for adaptable designs, with the bonus varying based on the significance of incorporating adaptability and the building’s utility. Highly significant adaptability requires a higher level of adaptable design strategies implementation to achieve the same level of circularity as designs with lower significance of adaptability. The multi-objective study demonstrates that designing for adaptability is economically and environmentally advantageous when the likelihood of future changes is high. Adaptable designs, although initially requiring higher investments in both CO2e and costs, show significant reductions when changes occur, compared to the conventional design, as they demand no technical interventions. This data emphasizes that planning for structural changes can lead to substantial reductions in emissions and costs compared to slight initial increases. The remarkable reduction in emissions highlights the alignment of adaptable designs with Circular Economy principles. Keywords: Adaptability, Building Circularity Index (BCI), key performance indicators, Circular Economy, Functional useful life, Adaptable design strategies, Building Utility, Adaptability significance ... Read more

Timber as a construction material for high-rise buildings is gradually entering the construction industry. Timber is considered a sustainable option, because it is a natural material that absorbs CO2 rather than producing it.
However, using timber as a building material also introduces new challenges, one of which is the problem with lateral stability, due to the relatively low stiffness of the elements and their connections. This research investigates the value of a timber core in a building that has bracings in the façade. The study examines this value in both normal conditions and the accidental limit state in case of a fire situation. The key question being addressed is:
Can a timber core sustain lateral load as a secondary load path, in case of failure of the tability bracing?
First, a literature review is conducted to understand the material and relevant safety mechanisms. A parametric program is used to explore the core’s parameters, alongside a linear elastic 3D FEM (Finite Element Method) program that utilises members and surfaces to analyze the building structure. The considered building is a 10-story rectangular structure (28.8 x 21.6 meters) with glulam beams, glulam columns, and CLT floors. The building was designed on an infinite stiff foundation by using a timber core and timber bracings in the façade. The core consists of cross-laminated timber (CLT) panels, connected with slotted steel plates and dowels. The bracings are glue laminated timber and are connected with two slotted in steel plates and dowels. The CLT panel connections and the bracing connections were calculated by hand and implemented in the FEM model. Which was validated by hand calculations. Additionally, wind load, variable load and permanent load were applied on the model.
This model was used to answer the following question. What percentage of the lateral force can the core take?
The model with a timber core in the Urban Woods shows an 18% reduction in global deflection compared to the model without a timber core in the ultimate limit state. The deflection of both models where to be within the prescribed limit. Additionally to the deflection reduction, the forces in the bracing are reduced by 33% in the model with a timber core. The core parameters that influence these reductions are the connections between the core panels and the cut-outs in the timber core. A core parameter study has been carried out to answer the following question:
How do the core parameters influence the global deflection?
For the connections, increased stiffness enhances the contribution of the core to reducing global deflection, with reductions ranging from 0% to 22%. Using longer panels results in fewer connections, which makes up for 7% of the global deflection reduction at any given stiffness of the CLT connections. Regarding the cut-outs, a larger cut-out size results in a lower contribution to deflection reduction. The reduction in global deflection for different cut-out sizes ranged from 5% to 27%. As the number of floors increases, the value of a timber core diminishes.
In the accidental limit state of fire, strong wind and failure of a facade bracing element, the timber core will serve as a sufficient alternative load path. However due to the wind force reduction in the ALS the remaining bracing is also capable of withstanding the lateral wind force. When two elements are removed than the core will be necessary. The unity checks for the CLT elements and connections did suffice.
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The Netherlands is grappling with a substantial housing crisis, marked by an estimated shortage of 380,000 houses. To address this issue, an annual creation of 100,000 new housing units is deemed necessary. However, the current construction rate stands at only 70,000 houses per year, indicating a considerable gap in resolving the housing crisis. Recognizing the potential of urban densification, especially through vertical extension using Cross-Laminated Timber (CLT), presents a sustainable solution. Nevertheless, challenges arise, such as the unique approach to vertical extension and the structural constraints posed by CLT's lower strength compared to materials like concrete.

This research aims to identify the vertical extension potential of CLT in existing buildings by developing a parametric tool that considers various structural constraints. The ultimate goal is to contribute to informed decision-making practices for sustainable and effective structural design in vertical extensions.

The methodology comprises four phases: analysis, synthesis, simulation, and evaluation. The analysis phase examines existing vertical extensions, structural context, and spare capacity concepts, forming the basis for synthesis. A parametric tool is then created using Grasshopper and Karamba, employed in the simulation phase to conduct a parameter study based on the analysis phase findings. This study assesses the effects of the original structure's base geometry on spare capacity and evaluates the design of the extension itself.

The results of the parameter study reveal that the presence and placement of a stability core have the most significant impact on spare capacity in the existing building. The original construction grid and building height also influence spare capacity, though to a lesser extent. Additionally, wall layouts in the extension, such as core alignment, functional design, and façade-aligned layouts, significantly affect spare capacity utilization in both the original structure and the extension.

Variations in extension grid show differences in spare capacity utilization, with effects smaller in magnitude compared to wall layout variations and displaying less dependence on the original structure's geometry. In the vertical extension itself, failure tends to concentrate on connections between CLT panels and floors, particularly with wall layouts emphasizing functional design.

In conclusion, the research, coupled with the development of a parametric tool, successfully achieves its main goal. The tool's accuracy is validated through extensive assessments of horizontal load transfer from the extension to the original structure. The parameter study highlights the significant effects of various parameters on extension design and the original structure, emphasizing the tool's utility in exploratory design stages for vertical extensions. ... Read more

Currently, the building industry contributes to up to 50% of climate change. A way to reduce the impact is by replacing current building materials with more environmentally friendly materials, such as timber. Engineered wood products, such as cross-laminated timber (CLT) panels, have increased strength, stiffness, and stability which enables building higher buildings and floors with bigger spans. However, due to the low weight of timber, CLT floors are susceptible to unwanted high floor vibrations and therefore need to be verified on their footfall-induced vibration performance. Predicting the vibration performance is a complex problem as the load-bearing structure and architectural finishing have distinct structural behavior under small vibrations. Due to the novelty of the problem, the distinct behavior is not captured well in the current design codes. As a result, the Eurocode 5 guidelines on vibrations are currently being updated and extended. In support, this thesis addresses the critical issue of predicting the vibration performance of CLT floors, with a specific focus on the impact of architectural finishing.

To achieve this goal, a literature review was conducted to identify structural components that are often overlooked, but may lead to inaccuracies in vibration predictions. These factors include the connections between CLT panels and different types of floor finishing. A case study was then carried out using the building HOUTlab, which features CLT floors with a concrete floating screed. On-site measurements were performed at key locations, including at the inter-panel connection line and in the middle of the panel. This was done before and after architectural finishing was placed. Subsequently, analytical and numerical calculations were used to gain insight into the structural behavior of the system subject to footfall-loading by investigating the accuracy of common engineering practices and other assumptions regarding their structural behavior.

Onsite measurements, where the floor was loaded and the response was measured at the same location, showed that the root mean square velocity (vrms) values were much higher at the inter-panel connection line compared to in the middle of the panel. The vrms is a measure of the amplitude of the vibration. The initial finite element analysis (FEA), assuming a rigid inter-panel connection, inaccurately located the highest vrms values. When assuming a hinge, the FEA correctly allocated the critical vrms values but compromised the accuracy of frequency estimates. The experimental results revealed that adding architectural finishing increased the damping, reduced the vrms, and maintained a similar frequency, ultimately improving the vibration performance from level 3 to level 1 according to the preliminary Eurocode 5 (prEC5) standards. The prEC5 and FEA following common engineering practices accurately estimated the frequency before architectural finishing was placed but underestimated it by 39% after it was placed, indicating a higher increase in the bending stiffness of the floor than initially assumed. While prior calculations assumed slip between the floor layers due to the presence of the insulation layer, assuming full cooperation between the layers resulted in an overestimation of the frequency by 9%, suggesting that there is some cooperation, but the floors are not fully bonded...

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Timber high-rise buildings have been gaining in popularity. However, due to the low material stiffness of timber the stability systems of these buildings are often made with steel or concrete. To avoid this the material efficiency of the timber stability systems must be improved. The most material efficient stability systems for timber high-rise are the externally braced systems according to literature. The externally braced systems are the diagrid and external braced frame stability systems. In literature the diagrid is concluded to be more material efficient than the external braced frame. Nonetheless, in practice only external braced frame systems are used for timber high-rise buildings. This disconnect could be caused by the steel connections which are often simplified or overlooked in literature studies but have a large influence on the material usage of a timber stability system. The connections can increase the timber element size because the required connection does not fit, and the connections will decrease the global stiffness of the stability system. For this reason, the connections must be regarded when comparing stability systems.
One diagrid and two external braced frame designs will be compared with a parametric model. In this model other parameters will be studied as well. These parameters are: plot sizes of 27.2 x 27.2 m & 27.2 x 40.8 m, floor spans of 3.4 m & 6.8 m, permanent floor loads of 3.5 kN/m^2 & 5.3 kN/m^2 & 6.7 kN/m^2 and element widths ranging from 400 mm to 650 mm. The parametric model will first size the elements individually for the ULS checks and afterwards the elements will be sized per group for the SLS checks. The ULS checks start with a regular ULS member check, then a member check in the fire situation is performed and lastly the connection design component used. This connection design component will create slotted-in steel plate connections where the amount of steel per connection is calculated, and the timber element sizes are increased if needed. In the SLS checks the global lateral displacement is checked and the along-wind acceleration. The along-wind acceleration is often normative for the sizing of the elements in timber high-rise. With a higher global stiffness or higher building mass the acceleration decreases. To make a fair comparison in the results the amount of timber and steel of the internal structure is also added to the material required in the stability system in the façade.
From the results it is seen that all buildings are sized on the connection design or on the along-wind acceleration. The diagrid designs have a higher global stiffness so they are sized more often on the connection design whereas the braced frame designs are sized more often on the along-wind acceleration. The diagrid designs use 3x more steel than the braced designs. The results for the other parameters are:
Plot size: A smaller plot size requires a higher floor load to meet the acceleration requirement, therefore the large plot size is more material efficient.
Floor span: The floor span in the external braced frame has a large influence on the designs with a small plot size. That is because the facade with the smaller span becomes normative for the global displacement. When this happens a smaller floor span decreases the material efficiency significantly. In the larger plot size the influence of the floor span on the braced frame designs is insignificant. For the diagrid designs the larger floor span causes higher normal forces in the diagonals. This increases the material usage in the facade. However, considering the internal structure of the building the large floor span is still more efficient.
Floor weight: A higher floor weight is more timber efficient for a small plot size, and the lowest floor weight is the most material efficient for a large plot size. With a higher floor weight, the steel usage always increases since the connection designs are sized on the ULS checks only.
Element width: The steel efficiency increases when the element width increases. This is a result of the chosen connection design. The timber usage is similar for all the element widths.
Some of the designs with a small plot size and low floor weight are unfeasible since the elements in the facade are too large. This is a result of the choice to only increase the timber element heights and not the connection stiffness to improve the global stiffness. Therefore, it is recommended to study how the global stiffness can be improved more material efficiently. Other recommendations for further research are on the stability system design and the connection design. Since in this thesis many designs are fixed in simplified exploratory studies to decrease the design space of the parametric model.
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This research looked into the influence of negative skin friction on timber piles in Amsterdam. Tensile load tests were performed on new, instrumented timber piles at Overamstel in Amsterdam. The negative skin friction calculated from the test data was compared to the negative skin friction from NEN 9997-1 for a single pile. The test results came close to the values from NEN 9997-1. A reduction of the factor required for timber piles when calculating negative skin friction using NEN 9997-1 seems necessary, but further studies are needed.

Alpha factors were derived from the test data, and comparison to the alpha factors from compression load tests confirmed the influence of tapering on the timber piles.

The research also confirmed the suitability of fibre optic sensors for pile load tests on timber piles. ... Read more