Passing-through tubular column joints for steel and composite constructions made by laser cutting technology

Piscini, Andrea; Salvatore, Walter (Thesis advisor); Hoffmeister, Benno (Thesis advisor)

Aachen : RWTH Aachen University (2020, 2021)
Dissertation / PhD Thesis

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2020. - Dissertation, University of Florence, 2020

Abstract

In steel moment-resisting frames, tubular columns have many structural and architectural advantages over open-section columns. Tubes are in fact particularly recommended for structural elements subjected to compression and bending forces in all directions, thanks to their higher radius of gyration and the axial-symmetric distribution of their mechanical properties. Therefore, the use of hollow profiles for the realization of columns can lead to a reduction of the total costs and furthermore to simplifications in the realization process of steel-concrete composite structures. However, the difficulties in realizing tubular column joints adopting open I-section beams, the most commonly used all around the world, severely reduce the use of tubular columns. Nowadays, beam-to-tubular-column steel and composite joints are commonly realized in two main ways: i) the connection is made by directly welding the beams or the beam stub to the wall of the steel tube; ii) supplemental plates are used to connect the beams to the circular column. Both ways have many disadvantages: the direct connection is the most convenient solution in terms of rapidity and easiness of fabrication but the performance of the joint is strongly limited by significant local distortions of the tube wall near the girder flanges; additional elements can assure a more effective transfer of the stresses from the beam flanges to the column wall or from the flanges of one beam directly to the beam placed on the opposite side, but their use implies a discontinuity in the column and requires extensive welding to reconnect the column pieces. To overcome these issues, innovative solutions with continuous passing-through elements inside the column were studied in the past years, highlighting several advantages from a mechanical point of view. Indeed, the continuous elements can pass by slots of limited size made on the column wall, without requiring the complete discontinuity of the column itself and the joint requires less cutting and welding operations, resulting in lower overall cost and better mechanical behavior. However, despite all the advantages, many problems arise from the fabrication and constructional points of view, limiting the effective performance of the joints. One of the solutions to overcome the difficulties in the fabrication and constructional processes of this joint typology lies in the application of modern Laser Cutting Technology to steel and composite structures. Several issues were studied in the present thesis, with both numerical and experimental tests, to define an appropriate fabrication process and to better characterize the mechanical behavior of the tubular column connections with passing-through elements, under vertical and horizontal loading conditions.

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