Graduation of Koen Broeders

A software-based optimization for design of steel halls

• Professor of graduation: Prof. dr. M. Veljkovic

• Supervisors graduation: Ir. P.A. de Vries (TU Delft), ir. L.P.L. van der Linden (TU Delft), ir. D. Ntoumpis (Temporary Works Design)

Engineering a structure in the civil world, could mean optimizing a structure to a certain variable. This optimization could be to weight, strength or costs. The most common way of optimizing steel halls is an optimization to weight. A limitation of this method is that the connection design is not considered in the optimization process. The connections can play a big role in the costs of a steel hall. The type of connection (hinged, semirigid, rigid) influences the profiles used in the structure. To create a more precise cost optimization of a steel structure, it is important to include the connection design from the start of the optimization process. To create this optimization process knowledge-based engineering can play a role, because this can help including all the engineering and design rules in the optimization process.

To optimize steel halls for this thesis, a steel hall optimization tool is created. This tool creates a parametric model and optimizes this model to its costs. The tool of this research is 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 IdeaStatiCa for the deformations and strength. In case the connection has limits 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 cheapest structure design can be found including the connection design.

This tool could help answering the question on how knowledge-based engineering influences the cost optimization of steel halls. The results of this tool are linked to the theories of cost optimization of steel structures including bolted connections. With the results of this tool, it is seen that the semi-rigid connections result in the cheapest structure. It can also be seen that the lightest option is not the cheapest option. This tool has its limitation to bolted end-plate connections and single storey steel halls. Although this tool can be expanded with different types of connections. In this case a database needs to be created for these connection designs. Also, the connection parameters need to be added to the design parameters. The method used for cost optimizations can be used for all types of steel structures with rolled profiles, in this case the topology needs to be updated.