Behaviour of joints: Simple and efficient steel-to-concrete joints

Abstract

The use of the structural systems combining members of different nature, such as reinforced concrete walls with steel/composite beams and columns, presents a competitive solution benefiting from the structural efficiency of each type of member. This type of solution requires to the designer multidisciplinary knowledge where the main obstacle lies in the joints between members of different nature, as are the reinforced concrete wall to steel/composite beam joints. In such joints, the main problem is the lack of solutions for easy execution and simplified models for evaluation of their properties. Over the past decades, the development of the component method has demonstrated the effectiveness of the methodology in assessing the behaviour of steel and composite joints. Consequently, its extension to structural steel-concrete joints is convenient and requires the integration of "new" components associated with the failures modes that develop in the reinforced concrete member. Thus, it becomes necessary to characterize and to include these components in global models for evaluation of the joint behaviour. Aiming at the study of steel-to-concrete joints, the RFCS project entitled "New market chances for steel structures by innovative fastening solutions" was developed. In the project, three joint configurations were investigated for different structural requirements. The present thesis is also the outcome of the author’s involvement in this project. Its main objective is a transversal approach to structural steel-to-concrete joints using a configuration developed within the referred project. In its “complete” version, the joint configuration provides a semi-continuous/continuous solution to connect a composite beam to a reinforced concrete wall. Though, the adaptability of the configuration allows its modification to perform under different structural requirements, as pinned joint. In this thesis a sequential approach is carried out, evolving from the simplest configuration to the “most complete”, with numerical and analytical characterization of the components, connections and joints. The experimental validation is performed whenever possible with the contribution of the results available in the literature and produced in the experimental campaign of the referred project. Thus, analytical and numerical models are proposed for characterization of the behaviour of joints between composite beam and reinforced iv concrete wall independently of the structural idealization: pinned, semi-continuous and continuous. Finally, at the structural level, a simplified study is performed to investigate the performance requirements of the steel-to-concrete joints. The analysis considers the structural calculation of three portal frames (mixed steel-concrete solution) which incorporate the behaviour of joints. The structural requirements for the different limit states are extracted and compared with the properties of the approached joints.