This research explores the optimization of modular ribbed concrete floor systems as a strategy for circular construction. Ribbed floors can reduce material use and embodied carbon compared to flat slabs, but conventional customized solutions lack scalability while standardized waffle slabs are less efficient. To address this trade-off, a modular design approach is combined with a Deep Generative Design workflow using a Variational Autoencoder (VAE) and Gradient Descent (GD).

The discrete modular configurations are represented as bitmaps, decoupling geometry from structural performance and enabling efficient training of a simple VAE model. Trained on datasets generated in Grasshopper with Karamba3D, the VAE can predict and generate new designs while scaling to larger problem sizes. Optimization is performed by sampling in latent space and refining results with GD.

The workflow flexibly integrates new objectives and constraints without retraining, such as stock availability or embodied carbon. In benchmark tests, the VAE-based optimization outperformed a generic evolutionary solver, achieving lower elastic energy and better stock compliance. The approach demonstrates the potential of deep generative methods for scalable, constraint-aware optimization of modular ribbed floor systems, while challenges remain for extending to more complex structural models. ... Read more

Given the importance of modularity in structural design, understanding the performance of modular shell structures is essential for improving both circularity and construction efficiency in spatial structures. To enhance sustainability and aesthetics, timber gridshells can be used to integrate sustainable building materials with complex pattern topologies. Modularity not only contributes to circularity of building materials, but also eases assembly, reducing both cost and construction time. By investigating different segmentation strategies, their impact on structural behaviour and buildability can be identified. This knowledge supports the optimisation of modular gridshells, leading to more efficient construction solutions.

This research aims to explore optimal segmentation strategies for timber gridshells, considering structural behaviour, element reusability and the efficiency of production, assembly and transport. A timber geodesic gridshell dome serves as a case study, but the findings contribute to modularity of gridshells in general. The main research question is: How can the modular segmentation of timber gridshells be designed to optimise their structural and construction efficiency?

For this research a method is developed to generate modular gridshells and optimise their design by evaluating both structural performance and construction efficiency. The modular designs consist of pinned splice joints that longitudinally connect two beams of different modules. Various modular designs are created by defining the location of these intermodular joints, thereby determining the overall modular geometry in the structure. A structural analysis gives understanding of the structural behaviour and the required material use. A construction analysis provides insight into reusability and efficiency of production, assembly and transport. A multi-objective comparative analysis is conducted to identify the most favourable designs based on project goals and stakeholder preferences.

Findings show that this modular approach improves assembly efficiency and the reusability of elements. It is particularly advantageous to choose a modular gridshell over a classic one when the primary design objective is reusability. However, the modular segmentation method negatively affects structural performance and increases material usage, primarily due to the use of pinned splice joints, which reduce overall stability. Additionally, applying modularity results in lower production and transport efficiency.

The results further indicate that larger modules improve structural stability and reduce the required material, due to fewer splice joints. Larger modules also result in higher assembly efficiency and reusability. However, increasing module sizes may exceed maximum transport size limits. It could also lead to a higher number of module types, reducing production and assembly efficiency. Furthermore, the module shape significantly influences the number of splice joints, underlining the importance of careful geometric consideration to minimise joint quantity. Additionally, increasing the rotational stiffness of splice joints could improve the structural performance.

In conclusion, it is crucial to consider project objectives and stakeholder interests in the structural design of a gridshell. Moreover, this research concludes that modular gridshell designs perform best when:
• Module sizes are maximised within transport constraints;
• Module shapes are designed to minimise the number of splice joints;
• An increase in module size comes with a minimisation of number of module types. ... Read more

With the rising urgency of building more sustainably and emitting less carbon dioxide into the atmosphere, optimising material use is becoming increasingly relevant. Globally, the civil engineering sector contributes to 8% of total CO2 emissions through cement production. In addition to reinforced concrete, it is estimated that 40% of these emissions originate from steel reinforcement. By optimising reinforced concrete elements, material waste can be reduced by up to 40%, while still meeting the required strength capacity. Due to the use of standard-sized steel bars and conservative detailing, this often results in significant oversizing of reinforcement. However, optimising reinforcement requires a change from using standardised steel reinforcement bars, mats, and cages towards long filament fibres. For example, when reviewing floors or walls with an open space, such as a door opening, around these locations the reinforcement net cannot continue its path, and the reinforcement needs to be strengthened locally. In these cases, the long filament fibres are capable of being placed in less fixed shapes and can be adjusted on a local scale to improve the strength. These filaments can be made from impregnated glass or carbon fibres, which harden over time.

Besides reducing the oversizing of steel, filament winding could also be made interaction-based, meaning that the winding is not limited to a fixed scaffolding point but can also intertwine with earlier wound filaments, reducing the material of these scaffolding elements. This led to the central question: How can material usage be reduced in both the filament and the scaffolding by using a construction process of continuous robotic winding? This research focuses on the topology and sequencing of tensile wound structures using automated robotic filament winding with a nylon rope. This study introduces a novel approach to filament winding by changing rope intersections into functional support points, replacing the need for traditional fixed scaffolding.

To create interactions, the separate winding layers must be connected to each other. This is achieved by transforming the concept of Reidemeister moves from knot theory into either back-and-forth or looped connections. To allow interactions to become connections, the 2D winding plane is combined with a 3D workspace. Additionally, scaling up the external scaffolding increases the number of possible intersection points that can be used to form interactions. In this research, scaffolding does not refer to the conventional way of supporting a structure, but the term is used to indicate fixed attachment points around which the fibre can be wound. These scaffolding supports are used to allow the wound structure to be created, but the shape of these supports can differ for each setup.

The research first identifies the design guidelines needed to create an interaction-based winding system. First of all, repeating patterns must be avoided, as they act like pulley systems and relocate nodes unpredictably. It is recommended to wind perpendicular to a single spanned rope, allowing a margin of 10 degrees. This prevents the nylon rope, which is used during this research, from sliding off and creating undesired topologies. Furthermore, connections help resist nodal movement and ensure all ropes are integrated into the interaction. For the winding sequence, it is preferable to begin winding between fixed supports to build resistance in the system before introducing interaction-based knots. Finally, straight-line winding is preferred over angled winding between fixed supports. Using these guidelines, a final design was developed based on a certain topology with spanned ropes. This reduced the number of scaffolding supports by 33%, from 12 to 8, while keeping the same topology. In contrast, the rope length increased by only 2%, from 6.42m to 6.56m. Another key observation is the nodal displacement in the interaction-based system. The average vector deviation amounted to 1.6cm, which is 6.3% of the distance between the supports. An additional winding resulted in a slight deviation, meaning that the system becomes stiffer and the nodes begin to behave like fixed supports.

In conclusion, the use of interaction-based methods enables a reduction in scaffolding material by replacing internal supports with rope intersections. Although this approach results in a slight increase in filament length, the difference is minimal. By minimising nodal displacement and improving the autonomy of the robotic arm to avoid collisions, continuous filament winding has significant potential to be applied effectively to non-fixed support setups based on interactions. ... Read more

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

The presented research aims to design and optimize a timber observation tower, with a primary focus being the influence of topological and curvature parameters on its stability and lateral stiffness in resistance to non-uniform wind load profiles.

Having recognised the environmental benefits and urgency to find other alternatives, there's a clear necessity to incorporate wood as the main construction material into the infrastructure projects, like observational towers. By conducting a study on hyperboloid towers implemented in the last 100 years, this project questions the necessity of in plane stiff platforms, flexurally stiff rings and continuous vertical members as being pivotal to the stability and lateral stiffness of the global structure when subjected to non-uniform wind loads. In addition, the study intends to investigate how the narrowness of the hyperboloid might affect the lateral stiffness of the structure. Thus, by utilizing parametric tools (Grasshopper, Karamba3D and Beaver plug-in), the study aims to design a timber tower structure comprised of fully segmented members as well as incorporation of circular (flexurally stiff) rings, aiming to address the questions raised. In terms of structural member arrangement, the study will investigate two topologies: one featuring a diagrid pattern that emulates a geometrical shape of an antiprism, and a custom pattern inspired by the post and beam approach, which resembles a regular prism shape. The study emphasizes the tower's multi-functionality and adaptability throughout its lifespan. Tower's main structural framework is a pivotal element in providing required stiffness and strength by excluding the need for in-plane reinforcement provided by arbitrarily placed platforms.

The key realisation of this research was the kinematic behaviour exhibited by the segmented, triangular tower, adversely impacting its stability characteristics. The study used a combination of analytical and graphic kinematics techniques, along with a physical mock-up model, to confirm the kinematic behavior of the tower given that even sided polygons for rings are incorporated. This revelation would have an impact on how a structure like that would perform as well the way it would be built. Further research unveils the strong influence of ring type on structural stiffness showing that segmented rings render tower structures less stiff than ones employing curved ring members, regardless of the pattern. In terms of the direct comparison between tower patterns, custom one demonstrated a more consistent and stable performance in general, particularly achieving higher stiffness levels when employing segmented rings. As regards the triangular pattern, the stiffest response against wind loads has been exhibited through the use of curved rings. In addition, the study validates that adopting a hyperboloid shape along with smaller shape factors for the global tower geometry yields more favorable lateral stiffness characteristics. Finally, the study navigates through the exploration of the most optimal connection design, illustrating how considerations related to detailing have necessitated a re-evaluation of the most optimal tower configuration, which initially was chosen to be a triangular one equipped with curved rings. A qualitative assessment of a potential joint within this specific tower variant has confirmed that designing such a connection is significantly more complex. This is due to the necessity of ensuring the continuous flow of the curved ring, emergence of a kink within the insertion of the plate and how that is needed to be addressed.

Alternatively, these considerations have motivated the design process to converge into a new hybrid design, integrating segmented rings with a curved top ring defined by the custom pattern. This choice has been made by conducting a separate parametric study of the new tower design and ensuring that the new connection design fulfills elastic slipping modulus and ultimate strength requirements. The final topology that showed higher stiffness metrics was the custom one. It's also highlighted that maintaining the top of the tower constrained leads to favorable effects on stability and stiffness, irrespective of the chosen topology. The resulting structure is optimized for mass by strategically reducing member cross-sections in accordance with connection scheming while adhering to both SLS and ULS criteria. ... Read more

This research addresses the implementation of learning algorithms and generative design in string-based topology exploration methods. It aims to generate diverse structural patterns for shells and surface structures that align architectural, engineering, and construction objectives. By integrating reinforcement learning (RL) and quad-mesh grammars, surface topology is explored through quantitative metrics, demonstrating the strength and generality of this approach. The research ultimately promotes creative exploration during the conceptual stages of structural design, emphasizing collaboration between form-designers and form-analyzers to harness emerging computational techniques.

The quad-mesh grammar was first formulated within a Markovian decision framework to integrate with open-source RL Python packages. States, actions, and rewards were defined with sufficient generality to avoid over fitting while evaluating the RL agent's ability to navigate between two specified string-action sequences and their associated mesh layouts. Initially, simple tasks involving four design steps were tested, followed by more generalized target terminal states with longer design sequences. The impact of different reward structures and varied model parameter setups on convergence and accumulated rewards was also analyzed.

The findings indicate that reward functions based solely on topological and grammatical characteristics did not fully guide the agent from an initial coarse mesh to a target state. However, extended design episodes demonstrated potential for improved RL outcomes. The DQN struggled with non-optimal policies due to negative rewards and sparse positive reinforcement, suggesting that customized model architectures or alternative RL algorithms could enhance performance. The exploration phases yielded suboptimal but diverse mesh configurations, highlighting the need for additional structural and geometric parameters, as well as more complex grammar operations to improve diversity while mitigating computational challenges. These insights underscore the importance of balancing feasibility, exploration, and optimization in computational design workflows. ... Read more

In many structures, space frames are used as the main load-bearing system. Especially for structures that are designed to have large spans or free-form in design. The reason is that space frames have a very high structural performance. Besides, they are also material and cost-efficient. Challenges for space frames are that they often require complex designs and the elements used are unique. Joint design is also difficult for these irregular constructions. This thesis explores the possibility of structurally optimising space frame design by using topologically reconfigurable modules, taking into account circularity. The focus lies on planar, square on square double-layered grids. The research question to be answered is the following:

”What kind of topologically reconfigurable modular system enables the generation of efficient space frames that are suitable for circular construction?”

The first design step is the initial topological design of steel cubic modules. This forms the basis of the catalog. With Grasshopper and Karamba3D (parametric FEM software) single-span trusses are then designed to determine the required cross-sections of the elements. The beams and columns are given SHS cross-sections for different spans and the diagonals are given various CHS cross-sections. With the software IDEA StatiCa various intra- and intermodular joints are designed and the rotational and translational stifffnesses analysed for
the different modules.

The former Grasshopper model is extended with a GA called Galapagos which is a plugin just like Karamba3D. This is used for topological optimisation of a given space frame structure. A GA is an evolutionary algorithm that is inspired by the natural selection process that Darwin described. The fittest genes in every population of solutions are used in further iterations. This process continues until the total number of iterations is reached or a threshold is met [1]. The algorithm reconfigures the different modules and minimises the weight of the structure
while staying within the constraints of maximum deflection, maximum material utilisation, and avoiding buckling. Logarithmic barrier functions are used for these constraints and together with the minimisation of the weight a fitness function is made. The lower the value of the fitness function, the better the solution is. The joint stiffness for each of the joint types for different |M|/N ratios is known. In the model, an initial stiffness is assigned to the joints. Then, depending on the moments and forces found in the joints, a new stiffness is assigned corresponding with the relations found in the stiffness analysis. The resulting stiffness loop describes non-linear behavior.

A verification is performed for the joints in the model. It was observed that the model was sensitive to small differences in stiffness within the joints of a standard truss. There were torsional moments observed that also resulted in an uneven distribution of the forces in the truss. To overcome this problem the stiffness of all joint groups is changed at once instead of individually. This resulted in more logical results where the support reactions were symmetric again. The model is then verified with a simple structure to see if the performance of the algorithm matches the expectations. A simple 2 x 2 grid is constructed and the model is tested. The simulation could not be performed until 50 generations because the stiffness loop led to a large accumulation of memory on the computer. It was concluded that the loop was not needed and therefore omitted because mostly only 1 iteration was needed. The model then was tested again on the small-scale model and compared to a couple of intuitively good-performing structures. This resulted in the conclusion that the model performed well and converged towards a final solution. However, since there were 106 different configurations possible the best solution was not reached in the end. It is recommended to always perform a couple of simulations to get a good solution.

After verification, the model is validated with a different FEM software called RFEM 5. Single grasshopper modules are structurally analysed in Karamba3D and imported in RFEM as well. The results show similarity in the order of magnitude of the stresses and the way the stresses are distributed. Furthermore, the reaction forces are also similar. The percentual differences between both models for the minimum and maximum stress are all below 5% except for module type 4. The absolute differences are in the order of 0.01 kN/cm2. Besides, a small frame is analysed in Karamba3D and RFEM as well to check if the deflection is in the right order of magnitude which is also the case. The percentual differences for the maximum and minimum stress are 6.40% and 7.85%, and for the deflection 12.15% and thus slightly larger than for the modules. However, for the deflection, the difference is just 1.5 mm for a structure with a span of 16 m which is a small difference. The Karamba3D model is valid and also conservative because the observed stresses are larger than in the RFEM model for the same
load condition.

A literature case study is performed on a space frame located in India. It is compared to the topologically reconfigurable model to check if the order of magnitude of the deflections and stresses is normal for this type of truss. First, a standard Pratt truss is modelled in Grasshopper to see if it is possible to design a feasible structure. This structure stayed within the limits of the constraints for the applied load which meant it worked. The case study truss is of a different size than the small structure used in the verification. With the catalog of 6 different modules and 66 possible locations for the modules as many as 10101 configurations would be possible. For this reason, the simulations are performed with 1 module type first (module type 6) and then with 2 (module types 3 and 4), greatly reducing the amount of possible
configurations. These are respectively 10^71 and 10^19. There are more solutions for the simulation with 1 module type because this module has a larger number of orientations than the other two modules combined. The outcome of the case study was that the algorithm did
not find better or equal solutions than the truss structure. This was because the convergence of the model was very slow, even for a simulation of more than 200 generations (10050 solutions) the best solution had a fitness value much larger than the truss structures. The issue was mainly that the extreme utilisation of some of the members was too large which made them fail. The BLF and displacement were within the boundaries. Comparing it with the case study the maximum stresses were indeed larger but the deflection was in the same
order of magnitude. The Pratt truss with reconfigurable members which resembled a regular truss was in the right order of magnitude for deflection as well. This truss does not have extra parallel beams since not entire cubes are joined together but single beams and columns.

An application is analysed to see how the model acts when the supports are irregular. From this setup, it was unclear what would be an optimal solution. The selected modules for this problem did not give the option to create a regular truss-like structure. The model found a slightly better solution than the one initially found using intuition and expert judgment. The value of the fitness function decreased from 0.84 to 0.80, which is a 5.5% decrease. The conclusion from this case study is that when the optimal solution is unclear and the design
space is large the model can find a relatively good solution. Combining this expert judgment and computational design can improve a model even more.

Overall the model can be used to design planar steel space frames with varying support conditions. These space frames are circular in design because their parts can easily be deconstructed and reused in similar structures. This is a huge advantage because it can save a lot of material and construction time as well. The modules themselves have the extra advantage that they can also easily be changed to a different type by varying the diagonals. This makes the system flexible in design. However, the optimisation efficiency is not very good.
The algorithm does not find optimal solutions that can be used in practice for a large design space. The type of structure is also much heavier in general compared to conventional space frames. This is because joining entire modular cubes together requires more steel. There are numerous parallel members that do not appear in regular space frames where beams, columns, and diagonals are individually placed in the structure. This makes stress on the members relatively high and therefore unfeasible. To use the system is therefore a consideration for the designer. When focussing on modular and circular construction this system is very useful but it is less structurally efficient. The model with ”modular elements” could potentially be used for a more structurally efficient system if the convergence towards a solution can be improved (with a different algorithm) and the speed at which solutions are calculated as well. ... Read more