SEISMIC RESISTANT WELDED CONNECTIONS FOR MRF OF CFT COLUMNS AND I BEAMS
2. DESIGN OF JONTS
4.2. Extension of the experimental program
Numerical simulations were performed also for the joints with larger cross section members. The contribution of the components considered in the design (i.e. beam, column stiffeners and column panel zone) to the joint rotation, are shown in Figure 18a for the RBS joint and in Figure 18b for the CP joint. As in the case of the joints designed for the experimental program, low rotations can be observed within the column panel zone and stiffeners, the main deformations being developed, for both cases, in the beam. In addition, the stress distribution and plastic strain, shown in Figure 19 and Figure 20, confirm the development of large plastic deformations in the beam. (a) 0 500 1000 1500 2000 2500 3000 3500 4000 0 0.05 0.1 0.15 0.2 Rotation [rad] Mo me n t [ k N m ] N3 - Column panel N3 - Stiffeners N3 - Beam (b) 0 500 1000 1500 2000 2500 3000 3500 4000 0 0.05 0.1 0.15 0.2 Rotation [rad] Mo m e n t [ k N m ] N4 - Column panel N4 - Stiffeners N4 - Beam
Figure 18. Contribution of components to joint rotation: (a) RBS joint, (b) CP joint
Figure 19. RBS joint: von Misses stresses, plastic deformation
Figure 20. CP joint: von Misses stresses, plastic deformation
In addition, for the joint with cover plates (CP) designed for the experimental program, a numerical analysis was performed with the aim to investigate the influence of the axial force within the column on the behaviour of the joint. The level of axial force introduced in the column was 0.5⋅Npl Rd, . Figure 21 shows the moment-rotation curves corresponding to the joint without axial force in the column and to the compressed column. No significant difference can be observed between the two cases, with the remark that the axial force lead to a very low increase in resistance. (a) (b) 0 200 400 600 800 1000 0 0.03 0.06 0.09 0.12 0.15 0.18 Rotation [rad] Mo m e n t [ k N m ] CP joint (N=50%Npl) CP joint (N=0)
Figure 21. CP joint: a) von Misses stresses, b) moment-rotation curves 5. CONCLUSIONS
The paper makes a short description of the dual-steel concept that is to be investigated through experimental tests on beam-to-column joints. The purpose is to assess the joint characteristics in terms of resistance, stiffness and rotation capacity. Components of each joint connection were identified and designed according to current design codes. The question is if there are components that were not taken into account in the design process. Therefore the experimental tests on joint specimens will help investigate the main components of the joints. The joint typology and the connection details between beams and columns were presented together with the assumptions taken into account in the design process. Additionally, due to the innovative joint configuration, a set of numerical simulations has been performed for the joints designed for the experimental program, as well as for joints with larger cross section members. Based on the results obtained, the numerical simulations prove a good configuration and design of the joints. For the joints where the plastic hinge formed in the beam, the other components (welded on-site connection, stiffeners, column panel) fulfil their job. In contrast, for the joints with strengthened beams, the simulations evidence a weakness of the joint configurations in terms of welded on-site connection and column panel. The axial force in the column was observed to have a low influence on the joint behaviour.
Connections in Steel Structures VII / Timisoara, Romania / May 30 - June 2, 2012 289 290 Connections in Steel Structures VII / Timisoara, Romania / May 30 - June 2, 2012
Further research activities will be devoted to the calibration of the numerical models based on joint tests. The joint characteristics obtained experimentally and from the numerical simulations will be applied on the investigated structures with the purpose to assess the seismic performance and robustness of dual-steel frames.
6. ACKNOWLEDGEMENT
The first author was partially supported by the strategic grant POSDRU/88/ 1.5/S/50783, Project ID50783 (2009), co-financed by the European Social Fund - Investing in People, within the Sectoral Operational Program Human Resources Development 2007-2013.
The present work was supported by the funds of European Project HSS-SERF: “High Strength Steel in Seismic Resistant Building Frames”, Grant N0 RFSR-CT- 2009-00024.
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