Optimized design of a load transfer concrete slab

Abstract: Hybrid buildings, designed for multi-use occupancies, require a different arrangement of supporting structures at each level of the support functionality. In these types of buildings, the structural model of a building is discontinuous, and therefore new, non-vertical, load paths need to be formed allowing the vertical load to transfer to the foundations. At the point of discontinuity, load transfer structures are commonly used solutions. Considering multiple alternatives of transfer structures, this thesis discusses more detail surrounding the load transfer of concrete slabs. The purpose of this thesis is to study the sustainability of the pre-design of load transfer slabs. The theory section of the thesis is divided into three sub-sections. In the first section, the principles of load transfer structures, focusing more detail surrounding the principles of transfer slabs, are discussed. In the second theory section, this thesis identifies important steps to consider for the structural design of a transfer slab. This section presents the mathematical equations used in the pre-design of a transfer slab. The third theory section focuses on the theory of the optimized pre-design of a transfer slab in selecting the main dimensions of the structural component. Subsequently, these sections are followed by a case study chapter. The research section compares the reinforcement ratio of the structural component in question presenting the effect of two unequal principles of placing the reinforcement within the component. The following principles of placing reinforcement in a slab are discussed: beam – and slab principles. The aim is to identify which of the two principles is more sustainable to use in terms of a lower amount of used material yet satisfies the building laws used in Finland. Another objective is to increase the sustainability of the design by observing the impacts of the selected variables on the bearing capacity, as well as the reinforcement ratio. Examined variables in this study include the thickness of the slab, the distance of the supports, and the strength of the slab as well as the diameter of the supporting columns. The aim is consider decreasing the amount of reinforcement used by modifying the variables.Based on the information gathered within the process of this thesis, in terms of sustainable material use, it is preferable to design a transfer slab according to the beam principle. From the studied variables, the thickness of a slab has the most significant impact on the bearing capacity. However, there is a limit for the thickness where the total utilization of the structural component can no longer be utilized, and the minimum reinforcement becomes the governing factor instead.