In light of the global attempts to reduce material use by the construction industry, this research focuses on combining topology optimisation with additive manufacturing of steel. It is investigated whether an automated procedure can be developed to generate reliable strut and tie models for reinforced concrete elements, while satisfying the constraints that apply to 3D-printing using the Wire and Arc Additive Manufacturing(waam) technique. Additive manufacturing offers a fully automated production process where a large freedom in form can be achieved. Topology optimisation concerns with finding a good material distribution within a prescribed domain. A literature review was performed on current developments regarding both subjects. It was found that the waam-technique is very suitable for printing reinforcement designs. Sufficiently large models can be printed, and material properties can be achieved that match the properties of traditional reinforcement steel. This manufacturing process is expected to produce functional structures that can readily be used as reinforcement steel in buildings. Two main manufacturing constraints should be accounted for during design of the model. A minimum member inclination and a minimum member diameter are both expected to be necessary to ensure a smooth printing process. Several different topology optimisation algorithms are discussed in the second part of the literature review, and it is determined which algorithm is most suitable to continue with in the rest of this research. Examples are presented that explain the functionality of three important optimisation schemes: Bi-directional Evolutionary Structural Optimisation(beso, Solid Isotropic Material with Penalisation(simp) and Ground Structure Optimisation(gso). It was found that all three can be used to analyse reinforced concrete. Each algorithm has advantages and disadvantages, so there is no obvious best choice. However, motivated by the easy access to member forces and availability of a very good Python implementation, it is chosen to use gso for the remainder of this research. This Python script was modified to include the constraints that come with an additive manufacturing process. It was found that the minimum member inclination can straightforwardly be included. The new function that was proposed allows the user to specify a minimum inclination, and ensures that no members are generated within the design domain that violate this minimum angle. Experimenting with this new function revealed cases where material use increased significantly when this function was used. This lead to development of an alternative procedure to ensure a printable design. In this alternative procedure, an optimisation without any angle constraint is performed first. Then, in the form of a post-processing script, The complete model is rotated around two separate axes in an attempt to find a suitable printing orientation. The third and final proposition that was done in this part, consists of a post-processing script for the minimum member diameter. Including this minimum diameter in the optimisation would require rigorous changes to the optimisation script. Therefore it was chosen to investigate the performance of this post-processing script first. The case study that was performed in the third part of this research, proved that this post- processing script for member diameter is sufficiently efficient for practical implementation. Together with the ability to slightly suppress the amount of members that are generated in the design domain, the printing constraint for minimum diameter could relatively easily be enforced. A bigger challenge lies within ensuring the minimum member inclination. The 60◦ minimum that was set, proved to be very harsh on the solution space. In the example from the case study, no printable model could be generated without significantly reducing the material efficiency. However, it is argued that this minimum inclination constraint can possibly be relieved by recent developments in additive manufacturing techniques. An example of this could be a rotating printing surface, that has the potential to remove this angle constraint completely. Overall, the experience of combining topology optimisation, additive manufacturing and strut and tie modelling has been predominantly positive throughout this research. The combination of a state of the art manufacturing technique and a more performance driven design process with a labour intensive traditional calculation procedure has shown promising first results. In the example in this research, 30% less material was required to accommodate the tensile forces in the concrete.

To optimize steel halls for this thesis, an optimization tool is created. This tool creates a parametric model and optimizes this model to its costs. The connections in the tool are limited to beam-column connections. The optimization starts with the input variables of the model, the most important input variable is the type of the beam-column connection. This can vary between a hinged, semi-rigid or fully rigid connection. Other inputs are the list of profiles that need to be considered, the loads acting on the hall and the main dimensions and topology. With all of these inputs the parametric model can be created. This model is then put into the finite element software RFEM, which calculates all the internal forces and deformations in the structure. Then with python code created for this thesis the strength and deformations for the structure are checked according to NEN-EN 1993. In case the structure is not sufficient the profile sizes are increased. This keeps increasing until the structure is sufficient. For the connection design used in this study a database is created with all possible bolted end-plate connections of the four different connection designs used in this research. Of all these possible connections the stiffness and bending moment resistance were calculated with the component method. These values are added in the database. With the selected connection input a list is created from this database with all the connections that have a stiffness within the range of § 10% of the wanted stiffness. Then for each connection in this list the cost is calculated. This list is then sorted on the costs from lowest to highest cost. After the complete connection list is created, the first connection of this list is checked in the component based finite element software IDEA StatiCa for the deformations and strength. In case the connection is sufficiently strong according to the Eurocode, the stiffness of the connection with the actual forces is checked with the component method. This is a python script created for this tool. In case the stiffness is not within the wanted range it checks the second connection from the list. After the connection loop all the results of the optimized structure are saved. When all the results are saved, the loop is repeated for different topologies and different connection types. With these results the most cost-efficient structure design can be found including the connection design.

There are two main challenges in the construction industry: carbon emissions and densification in cities. Timber high-rise might prove as a suitable solution to both these challenges. However, there is a lack of implementation of timber high-rise. This research argues that a lack of thorough analysis of timber design alternatives in the conceptual design phase results in the exclusion of further evaluation of timber building designs. This research aims to analyze timber building design alternatives more thoroughly by the development of a tool, based on the Multidisciplinary Design Optimization (MDO) method. In Grasshopper, a parametric model is created with which timber building designs are generated, validated, and optimized. Two main optimization objectives and two constraints are considered in the tool: Firstly, the structural constraint: Each building must be designed according to the constraints as determined in the Eurocode. Secondly, the architectural constraint: Each building must satisfy the architectural design requirements for acoustics, building height, and daylight entrance. Thirdly. the environmental objective: minimize the shadow costs, which are determined according to the MPG methodology. The MPG methodology uses Life Cycle Analysis data to assess the embodied energy impact of structural materials. This embodied energy impact is expressed in shadow costs. Lastly, the economical objective: minimize the construction costs. Based on the mentioned constraints, the tool aims to indicate the design situations in which timber high-rise can be competitive to an assessed concrete design alternative, considering the combination of properties for shadow costs and construction costs. By research and development of the Multidisciplinary Design Optimization tool and analyzing two case studies, a conclusion can be made. Two concrete buildings, which are based on a current Arcadis project, are used as case studies. Both concrete buildings represent a design situation. The main difference between these design situations is the building dimensions. Building A3 represents timber building designs that are created for a design situation with a floor area of 28.8 x 28.8 m and a height of 60 meters. Building B3 represents timber building designs that are created for a design situation with a floor area of 21.6 x 43.2 m and a height of 50 meters. For both case studies, an optimization will obtain timber building designs with an optimal combination of properties for shadow costs and construction costs. This resulted in the following results. For the design situation based on the concrete building "The Rectangle", the Pareto optimal timber building designs, referred to as Building B3, were found to be competitive with "The Rectangle". For the other analyzed design situation, the Pareto optimal timber building designs referred to as Building A3, were not found to be competitive with the concrete building "The Square". Considering the boundary conditions and scope of this research, it can be concluded that a design situation with a rectangular floor plan is favorable over a design situation with a square floor plan and a design situation with a building height of 50 meter is favorable over a design situation with a building height of 60 meter. Also, based on analysis of the case studies the following conclusions were made. Firstly, when the effect of carbon sequestration is excluded in the calculation of shadow costs, the use of timber and concrete in the structural system was found to generate comparable results considering their shadow costs. The inclusion of the effect of carbon sequestration during the lifetime of a timber building results in a reduction of shadow costs of approximately 40% compared to a similar concrete building. Secondly, considering the boundary conditions and scope of this research the ULS is found to be normative for a slenderness up to 2.35. When the slenderness is greater than 2.35, the along-wind acceleration was found to become normative. Next, for all Pareto optimal building designs, the ULS check was found to be normative over the SLS check. Lastly, the mass of the Pareto optimal timber building designs was found to be approximately 8 times smaller than their respective concrete design alternatives, resulting in a foundation with less construction costs and shadow costs.