This master thesis' main objective is to develop a parametric design tool which improves the design process and explores the building typologies of a hybrid modular timber construction based on global and local structural requirements. The hybrid modular timber construction is core-less and combines load-bearing and corner-supported modules. The parametric design tool, which is named Habitat21, consists of an automatic placement function (Grasshopper), a manual placement function (Rhinoceros) and a structural analysis program (Karamba). The hybrid modular timber construction concept is tested by comparing the displacements in the x- and y-direction of a replicate of Hotel Jakarta, generated in Habitat21, with the original displacements in the x- and y-direction of Hotel Jakarta, generated by the case study of Gijzen. It appears that the replicated hybrid modular timber construction of Hotel Jakarta in Habitat 21 is able to approximately reproduce the original displacement in the y-direction of Hotel Jakarta calculated by Gijzen (difference of 0.642 mm). However, the displacement in the x-direction could not be reproduced in the same order of magnitude as the original displacement in the x-direction (difference of 13.081 mm). This could be caused by the fact the assumed inter-module connections, connection 1 and 4, of the hybrid modular timber construction concept were modelled as line elements with two hinges (”pendelstaven”), this could have influenced the displacement behaviour of the CLT shear wall mechanism. To examine the usability of the manual placement of the modules by Rhinoceros within Habitat21 a workshop with 5 participants (2 architects and 3 engineers) and two cases is performed. In the first case each participant created 3 buildings, each building was generated within 8 minutes, resulting in a total of fifteen different building typologies of the hybrid modular timber construction concept. Ten out of the fifteen building typologies satisfied the global structural requirements, five did not satisfy the global structural requirements. Two buildings were not stable in one or more directions, two buildings did not satisfy the unit check for the displacement in the x-, y- or z-direction and for one building an error occurred. To explore the diversity of the typologies from the fifteen buildings a typology score was given for each building. The highest score was 102 points and the lowest score was 10. This indicates a relatively large diversity in typologies. In the second case each participant worked on two buildings that both did not satisfy the global and local structural requirements but the second building had 2 extra design restrictions. The participants had 5 minutes per building to fix this. For the building with extra design restrictions three participants (all engineers) were not able to meet the local structural requirements. This suggests that the feedback from Habitat21 provided to the user in this case was not adequate. To examine the automatic placement of the modules by Grasshopper within Habitat21 the calculation time of the automatic placement of one extra CLT shear wall is analysed for 6 different buildings by using an iterative process. These buildings were all stable in the y- and z-direction but unstable in the x-direction. The calculation time for the placement of the extra CLT shear wall at a building with 4 modules and 8 possible positions was 6 seconds and the calculation time for the placement of the extra CLT shear wall at a building with 24 modules and 48 possible positions was 360 seconds. Combining the calculation times of the 6 different buildings it appeared that the calculation time increased exponentially when the amount of modules increased linearly. In conclusion, it was possible to discretize a hybrid modular timber construction in a parametric design tool. Furthermore, both engineers and architects were able to work with the tool and to independently create diverse typologies of a hybrid modular timber construction. The boundaries of the hybrid modular timber construction concept in Habitat 21 were determined by the inter-module connections, as found in the comparison study with Hotel Jakarta. The applicability of the parametric design tool and the hybrid modular timber construction concept could be increased by more research into inter-module connections and point supported cross-laminated timber slabs. Also, feedback about how the structural systems works could be implemented in the parametric design tool, where the user gets necessary feedback to fulfill the global or local structural requirements instead of using a trial and error design method. ... Read more

Recycling and reuse of structures and elements is important to reduce the carbon footprint of the building industry. Reuse requires much less energy than recycling and therefore has much potential. However, reuse is still rarely put in practice due to the many challenges constructing with reuse involves. One of these challenges is the complex design process. In this research, I have developed a tool able to design with reused elements. Topology optimization is combined with reclaimed elements with the aim to simplify the design process for steel truss structures. The member adding scheme of Linwei He. et al (2019) is used as a basis. Adaptations and additions are made to include geometry information and limited availability of reused elements. In the final tool, capacity utilization of elements is maximized, material volume of the structure minimized and percentage of reused versus new elements maximized. In conclusion, discrete topology optimization proved to be an effective method to simplify the complex design process. The tool can generate multiple different designs for every optimization problem with limited complexity. Volume increase or decrease compared to standard designs depends on availability of elements. In examples in this research volume increase could be limited to 20-30% with limited availability of elements. With large availability, multiple different designs could be obtained with an average unity check close to the maximum unity check. Recommendations are to improve applicability of the tool and to make an estimation of the reduction in carbon emissions and construction costs compared to designs with new elements. These estimations could increase attractiveness of designing with reused elements. Finally, accessibility of designing with reuse should be increased. It should be less difficult to obtain data of existing buildings planned for demolition to experiment with designing with reuse. ... Read more

The implementation of timber as a load-bearing and stabilizing material for high-rise structures has significantly increased over the last decades due to its potential of reducing the environmental footprint of a structure. Timber structures present a reduced global stiffness and self-weight compared to structures incorporating traditional construction materials, making them prone to high accelerations caused by wind load which affects the structural integrity and user comfort. The acceleration of a structure is a highly complex parameter that must be determined using modal analysis computed by a full-scale finite element model, and is significantly influenced by the magnitude of the wind and vertical loads, as well as the global stiffness of the structure. During the preliminary design phase, it is the responsibility of structural engineers to determine the feasibility of the design and estimate the amount of material required and the distribution of the structural elements. However, this process must be done under a limited amount of time, forcing engineers to rely on rules of thumb and previous experience, which are not currently available for the design of timber high-rise structures. Therefore, the goal of this investigation is to perform a parametric study to determine the influence of various parameters on the design of timber high-rise structures and assist structural engineers in making well-argued decisions during the preliminary design phase. The preliminary design parameters to be studied in the parametric study are: stability system design, connection stiffness and building height. The ranges for the parameters were selected based on extreme values such that clear trends regarding their influence on design could be visualized. This decision limits the design feasibility of some configurations studied in this investigation. The selected stability systems to be studied are glulam frame, CLT core and glulam diagrid. The design verification for each design alternative is done using ULS and SLS criteria provided by Eurocode, as well as a simplified method to estimate the dynamic response of the structure. Finally, the sizing of the structural elements and data collection was done by the implementation of evolutionary algorithms. From the data collected it was determined that the most influential design parameter for the design of timber high-rise structures is the stability system selection given that it determines the global stiffness, which showed a significantly higher influence on the dynamic response of the structure than its self-weight. Moreover, the efficiency of the different stability systems was assessed based on the maximum slenderness they could achieve compared to the amount of material they required. Based on this definition, it was determined that the glulam diagrid is two times more efficient than the CLT core and three times more efficient than the glulam frame. The efficiency of the glulam diagrid is caused by its high global stiffness provided by the triangular configuration of the diagonal elements. These observations prove that the effect of timber’s low density can be mitigated by the implementation of efficient stability systems. The influence of connection stiffness was determined to be directly related to the ability of the stability system to provide lateral stability to the structure. The influence of this parameter on form stable structures such as the CLT core and the glulam diagrid, proved to be nearly negligible, while for non-form stable structures such as the glulam frame it proved to be highly influential. However, it was also determined that the addition of rotational stiffness in the connections causes an exponential increase of the costs and environmental footprint of the structure, which decreases their design feasibility. Finally, the influence of building height on the design is visualized by its effect on the dynamic response of the structure caused by the logarithmic increase of the wind speed as this parameter increases, as well as a decrease of the global stiffness proportional to the efficiency of the stability system. ... Read more

The starting point of the thesis relates to the “Rotterdam Mountain” Project, envisioned by the Rotterdam Dreamers, which proposes an artificial mountain in the otherwise flat landscape of the Netherlands, supported by a cable network that is spanning between multiple high-rise towers. This network has the double function of supporting the weight of the mountain and connecting and stabilizing the towers. With the “Rotterdam Mountain” Project as a starting point, the thesis aims to investigate the structural feasibility and performance of a new typology for the design of high-rise towers, where a cable network interconnects and stabilizes them. The goal of the thesis is to investigate the design of such a system with respect to relevant parameters, as the relative position of the cable-net (RPC) or the spacing between towers (SBT). Such, a core system to which the cable-net is connected is used throughout the thesis. To understand the relative influence of different parameters, a parametric approach (in Grasshopper) is used, that allows for a rapid change of the initial properties of the system. The Grasshopper script is linked to the Robot Structural Analysis (RSA) software, where a non-linear analysis is performed. The outputs of the RSA analysis refer to both the serviceability limit state and ultimate limit state, as both the core and cable-net are designed to meet the stability and strength requirements imposed by the Eurocode. Based on the Eurocode checks, conclusions are drawn on the preliminary design of the system, by identifying multiple design zones with respect to the two relevant parameters: a zone where the stability of the core is governing (for a SBT of up to 90 meters, and an RPC of up to ~0.6), a zone where the strength of the core is governing (for a SBT higher than 90 meters or an RPC higher than ~0.6), or a zone where the influence of the cable-net is negligible (for an RPC lower than ~0.1). Conclusions are further drawn on the performance of the system, by comparing it to the simple core and outrigger systems. It is observed that the proposed core + cable-net system performs (at least) as good in terms of stability and strength with less material usage. A concrete weight reduction of the core of up to 50% is observed when compared to the simple core and a steel weight reduction of up to 20% is observed when compared to the outrigger. From an economic point of view, preliminary calculations have shown a reduction of the total weight of the structure of up to 14%, due to the increase in slenderness when the cable-net is placed. This is equivalent to a number of up to 5 extra floors that can be constructed with the same amount of material. With these remarks in mind, it is concluded that, based on this preliminary study, the cable-net stabilized towers can pose a feasible alternative to the design of high-rise towers, and they can be efficiently used for the ambitious “Rotterdam Mountain” project. ... Read more

As of writing this thesis little research has been done in truss layout optimization for multiple design alternatives. A hybrid scheme is proposed in which the fast gradient-based search of the Ground Structure Method (GSM) is employed for the search of optimal topology and size, while a population-based meta-heuristic algorithm explores the non-convex parameter space of geometry optimization. The scheme works by employing a meta-heuristic algorithm to optimize the nodal coordinates of a truss structure where for each iteration and each member of the population a small-scale (i.e. problems with a small number of degrees of freedom) GSM is performed, in order to obtain the optimal topology for the given nodal locations. Three variants of the scheme based on three different meta-heuristic algorithms are developed: Firstly, an Artificial Bee Colony (ABC) and Particle Swarm Optimization (PSO) variant are developed in combination with an original topology identification method, to extract design alternatives from the solutions found throughout the optimization process. The developed topology identification method identifies different design alternatives based on topological differences by making use of existing graph isomorphism testing algorithms from graph theory. Additionally, the topology identification method employs a multi-step filtering process to prevent members which are non-critical to the performance of the structure to influence the design alternative selection process. Finally, a Multi-Species Particle Swarm optimization (MSPSO) variant is developed without the need for a topology identification method. For all methods convergence speed in terms of number of iterations, topological variety and computation time per iteration have been evaluated and are compared. Of the developed methods, the ABC variant converges fastest towards a single good solution, however the topological variety is lacking. The slower converging MSPSO variant produces solutions with moderate topological variety, as well as reasonable material volumes. The PSO variant requires the least computation time per iteration of the developed methods. Its produced topological variety is closer to that of the ABC than the MSPSO variant and it has a slightly faster convergence speed than the MSPSO variant. Direct usage of the MOSEK API is made instead of the more commonly used CVXPY API which reduces GSM problem setup times for small-scale (28 degrees of freedom) problems by a factor of 13. Computation times for the hybrid method, from start to finish, for 3D structures with 4 to 8 movable nodes (12 to 24 geometric degrees of freedom) range from 15 to 50 seconds on standard desktop PC hardware. Because of the multiple design alternative nature of the hybrid method, and consequently the end-user does not require fast back-to-back optimization runs, these computation times are deemed acceptable. It is concluded that while in its current state the methods based on the hybrid scheme are unlikely to be suitable for usage in practice, further developments in methods to distinguish design alternatives could make the hybrid scheme, in particular the ABC variant, useful in the design of more material efficient truss structures. ... Read more

Theshortage in housing and office spaces, combined with the desire of people tolive in densely populated cities results in a lack of space. A proposedsolution can be found in the usage of high-rise buildings. Nowadays there ismore awareness for the environment, thus this research tries to reduce theenvironmental impact of a high-rise building by optimizing the material used inload-bearing structures. This research aims to give designers and engineersmore insight into the added value of structural optimization; in particular forthe material usage in the load-bearing structure of high-rise buildings. Theresearch objective is formulated as follows: What is the optimal topology for a reinforced concrete load-bearingstructure, situated at the perimeter of a high-rise building when optimizingthe material use?  A building isclassified as high-rise building when its roof is 70 m or more above groundlevel and accommodates work and/or living space. In literature the distinctionis made between three sorts of optimization: size, shape and topologyoptimization. Topology optimization has the most freedom, therefore it is morelikely to find a novel structure which minimizes the material use as much aspossible. In specific the Ground Structure Method (GSM) is used. The initialground structure is constructed by creating members between all nodes (fullconnectivity) which are located in the design space. The cross-sectional areasof the bars are the design variables in the optimization. An option is that thevariables turn to zero, thus elements are deleted resulting in less material.The conventional GSM starts with the full connectivity as initial groundstructure, deletes elements and calculates the new load distribution until athreshold is reached. In the end the load-bearing structure will consist ofcolumns, braces and beams, which are located at the perimeter of the floorplan. Literature indicates that (high-rise) buildings which are mainly loadedby horizontal loads would be optimal if they contain arches in the load-bearingstructure, or resemble the so-called Michell truss. However, the influence ofthe vertical load is often not taken into account, therefore this isinvestigated with the help of a parametric study. To compare the results withreality, a case study (Boston & Seattle, Rotterdam) is investigated.   The core of the research is the furtherdevelopment of the optimization code, based on the GSM, written by He et al.,where multiple load cases and demands for the material strengths are implemented.In contrast to deleting elements, the code uses an adaptive ‘member adding’scheme, which is firstly proposed by Gilbert and Tyas. This scheme solvesproblems faster than the conventional GSM, up to 8 times, and is able to solvelarge problems. This code is extended during this research with new functionswhich implement demands for fire, second-order, buildability, flexural bucklingand stiffness. Also it is possible to add self-weight to the optimization. Thestiffness is implemented by adding a constraint to the displacement of the topof the building, wherefore a recursive resizing algorithm is written based onthe article of Chan. Thus the extended code exists of two optimizations, firsta strength optimization and afterwards a stiffness optimization. The code iswritten in Python and for the purpose of post-processing exporting the data toExcel and Abaqus is possible.  With thehelp of the extended code, two design spaces are investigated. One design spaceis smaller, such that the computational time is low and many variations can beexamined during the parametric study on the total vertical to total horizontalload ratio (v/h-ratio). The other is based on a case study for comparison witha realistic situation. The verification of the code shows that the extrafunctions work properly for the investigated problems. If the functionsconcerning the stiffness optimization, inclusion of self-weight, fire,buildability and second-order are used, the extended code becomes unstable andthe computation time increases enormously when optimizing the case study.Therefore it is chosen not to include during obtaining the results. The resultsof the parametric study shows an expected pattern for the load-bearingstructure, for a v/h-ratio below 4. The pattern consist of arches, originatingfrom the Michell truss. The optimization of the case study, subjected to onerealistic load combination, showed no clear pattern for the load-bearingstructure. Post-processing steps, based on engineering judgement, are taken toclarify the solutions, which showed that the columns above the supports shouldbe large in comparison to the other elements and that the arches are the mostoptimal structure. Therefore an “optimized” load-bearing structure consistingof arches is proposed. The analysis of the “optimized” load-bearing structureshows us that most of the elements meet the strength requirements. To find theoptimal solution an iterative process would be needed, because increasing thecross-section of an element will decrease the stress but increase thestiffness, thus attracting more load.   Thedifference between the optimized load-bearing structure and the originalload-bearing structure of the case study is that the optimized uses archesinstead of (punched) structural walls and uses less material (±3%). From thepost-processing of the results it is concluded that increasing the strengthratio (compression to tensile) to 1.0, decreasing the total v/h-ratio orignoring the rigid-diaphragm working of the floor help clarify the results ofthe optimization.   This research extendsthe current literature with extra insights in the use of the Ground StructureMethod in an optimization code. Also, it confirms that the arches (originatingfrom Michel Truss) is an efficient manner to transfer the loads to thesupports. However, more research in the influence of the supports, the designspace and the material type on the clearness of the optimal solution is needed.  The advice for designers and engineersis to see what the possibilities are for arches to use in their load-bearingstructure, because these are efficient in transferring the loads so materialcan be saved. The current version of the code needs to be made more userfriendly, stabler and faster before it is recommended to be used by designersand engineers. The extended code is a first attempt to implement multiple rulesfrom the Eurocode in a optimization code.   ... Read more

An organized process is necessary to ensure that the building is built on time and within budget. This does not always go well however and four major difficulties can arise. One of the current solutions is performing variant studies. Designing variants is costly however, which limits the amount of analysed variants. The focus is set on improving this process, which will indirectly affect the four named issues. The advantages of structural parametric design (SPD) have the potential to increase the amount and complexity of variants. However, the disadvantage of large structures is the uncountable amount of possible calculations and parameters. Current SPD-tools have the same functionality in general, but differ in key ways which influences the choice for a tool. These mostly focus on some form of optimisation. This research however, focuses on generating options. The connection between a visual programming software (Dynamo) and FEA software (RFEM) named the DRC is chosen to achieve this. Attempting every possibility for the support structure is difficult. A method is therefore proposed called the "translation by component method" (TC-method), which gives the ability to more easily modify parametric models. This made it possible to divide the problem over several smaller scripts, called variants. Each variant is able to produce models, called options, which provide information about the critical load combination, the type of failure and the unity checks for most eurocode demands. The structural engineer can learn from each variant and apply this knowledge on subsequent variants. The engineer’s creativity is thus used to limit the amount of parameters and calculations. This process directs the engineer towards a solution. Options provide information for the architect as well, namely: the geometry of the support structure, the optimized cross sections and the costs of the option. The architect can use this information to weigh options against each other to fulfil the demands of the SoR as well as possible. This process is named optioneering. After the first variant was created, nine variants and 35 options were generated, analysed and reported within two weeks. Optimized options were obtained within 15 to 30 minutes. By learning from previous variants, it was possible to find a support structure which barely modifies the aesthetics of the structure. The options obtained during this process mostly have unique advantages and disadvantages which can be compared by the architect. A recommendation and summary is given for these results. The applied method for the DRC enhanced the process of the variant study by increasing the amount and complexity of variants. More information can be obtained and by learning from previous variants more informed decisions can be made for subsequent variants by the structural engineer. The architect has more freedom to choose the placement of structural elements and information of costs is earlier available. This can be used to better implement the demands of the SoR. The architect can take costs earlier into account as well which can be used to better estimate the costs-appreciation ratio of a certain choice. ... Read more

To reach the European Union climate targets of 2020 the rate of refurbishment must increase. The problem is that there are many barriers to refurbishment, which causes a low rate and low quality. The objective is to overcome these barriers and stimulate facade refurbishment. This thesis looks at the improvement, that can be made when replacing an existing skin by a new facade focusing on improving the structural efficiency and touch upon building physics.
The main driving forces of this thesis are parametric design and optimisation. A parametric design is crucial for this thesis to perform a variation study. Different shapes of the facade are simulated with a custom made genetic algorithm to optimise the shape of the facade. First of all, the cost can be influenced by minimising the amount of material by altering: cross-sections, beam distances, etc. Secondly, by changing the shape of the facade a more aerodynamic building can be created. When the curvature increases, the wind load can be reduced which can make the structure more efficient. The wind load on the facade is determined with the computational fluid dynamics (CFD). The part about building physics focusses on ventilation. A ventilation system is designed which emphasises the importance of integrating the ventilation system with the second skin. The design builds upon the results of the CFD simulation and the structural model. The performance of the system is quantified by determining the usage of natural resources. ... Read more

From the beginning of the 21st century, thin glass has been used as a screen protector for electronic devices and smartphones. During the last 10 years, several studies have been carried out to introduce the thin glass in the building industry. The advantages of this material are light weight, high strength and high flexibility. On the other hand, thin glass, due to its low thickness, has a limited bending stiffness. Therefore, it is challenging to apply this innovative material in the building field. Within this research, the stiffness of thin glass is increased by the realization of a thin glass cold bent sandwich panel.
The proposed sandwich panel is realized by using thin glass faces and a 3D printed polymeric core. Due to the high flexibility of the glass, the material can be easily bent and glued to the core. The curved core hold the cold bent glass in shape without the use of any frame.
To validate the numerical results, laboratory tests have to be carried out. The design of the curved sandwich panel revealed to be a feasible façade panel proposal. The feasibility is defined in terms of a structural façade element, which fulfill the limits of safety and comfort. The curved sandwich panel, proposed in the final design, results to be 280 times stiffer compared to a curved two layered thin glass laminated panel.
Furthermore, it was demonstrated that the proposed sandwich panel could guarantee a weight reduction of more than 80% in comparison to the glass used nowadays in building façades. This characteristic not only facilitates the assemblage of the façade, but also can bring to the usage of a lighter support structure. This can bring advantages both in terms of cost of the total structure and energy required to assemble the building. ... Read more

The building industry is fragmented. In the case of steel structures, two parties are involved in the design. The engineering firm designs the structure, and at a later phase the steel contractor designs all the detailing. This fragmentation restrict the possibilities of creating a cost optimal design. Currently, engineers often optimise on total weight. The result is that at a later phase, the steel contractor will need to design more complex joints, in order to create sufficient resistance in the joints of the slender structure. This can lead to higher total cost of the steel structure, compared to when joint design has been considered at the early phase. This situation leads to the following research question: “How can engineers optimise the production costs of steel trusses with welded connections?”. In this research, I will focus on trusses with welded connections which comply with transport dimensions. To answer this question, a parametric optimisation model is developed. This model combines three software packages Grasshopper, Karamba3D and IDEA Statica Connection . Grasshopper creates the wireframe geometry that resembles the structure. Karamba3D performs the structural analysis and defines cross-sections through size-optimisation. Finally, IDEA Statica Connection will design all joints, check the joints plates for the strain percentage, and optimise the welds according to the directional method.
The model shows that selected beams from the size optimisation in Karamba3D often fail the joint analysis of IDEA. This is because the strain criterion is exceeded. This failure can be resolved in the model either by modifying the cross-sections, changing the geometry of the structure, or applying stiffeners in the joint. When the truss does not show failure in the plates of the joints, the weld volume can be optimised. The optimisation model will automatically optimise the welds of each joint in the structure by using the directional method in IDEA. Optimising the welding volume, creates a significant reduction in welding volume compared to the full strength method. However, in the current state, deformation capacity in the joint cannot be guaranteed. This can prevent a plastic hinge to form and may cause premature brittle failure of the structure. To be able to use the welding volume optimisation, it should be complemented with an extra check to define whether the yield strength of the connected parts is lower than the rupture strength of the welds. Further research is recommended, to complement the weld volume optimisation with the needed additional check. Additional research into the cost-optimisation of steel structures with bolted connections and moment-resisting connections is also encouraged. ... Read more