Cast-in channels are an efficient and easy way to install adjustable connections to hang heavy loads in tunnels, buildings, bridges and other structures. These steel parts collaborate with concrete with the use of shear bolts, forming a composite section. Except from supporting heavy loads, cast-in channels can increase the bending capacity of the section. In this study, using the theory of composite structures, the possible positive effects in the bending behavior of the section will be investigated for many types of steel sections, the effective width that is achieved depending on the shear connection used will be defined and other parameters about the influence of these parameters on the behavior of the section will be examined.

The investigation will examine the problem analytically using the knowledge for the behavior of composite sections from EC-4 and computationally with finite element analysis. Different steel sections will be checked for concrete height of 300mm and bolt distances. The hanging loads will be the weights of typical equipment and structures, such as jetfans in a road tunnel or glass panels in skyscrapers.

At the end, there will be a comparison of the different approaches, presentation of the results and suggestions of how they can be used in the design of future projects. The conclusions include:

•     Evaluation of the increase of the bending capacity of reinforced concrete sections due to the presence of the steel parts

•     Assessment of the ideal section depending on the hanging loads of the design

•     Assessment of the ideal distance and section of the shear bolts depending on the used composite section and the hanging load

•     Results from the parametrical analysis of the uses of different parts, different shear connections and different effective axial force.

From the results we can highlight the rise of the bending capacity of the concrete section because of the cast – in channels, the relief of the steel reinforcement because of the existence of the channels, the statement that part of the reinforcement can be replaced from these steel parts and the suggestion of setting a lower limit of the effective width of the composite section equal to 1m.