PERFORMANCE EVALUATION OF STEEL BEAM-CFDST COLUMN JOINTS WITH INTERNAL STIFFENING RIBS UNDER SEISMIC LOADS

A high fidelity nonlinear finite element model developed and verified with experimental literature proves the ability of the model to accurately simulate the complex response of joints under cyclic lateral loading conditions. The internal stiffening ribs greatly enhance the structural efficiency of the joint. The results show that the load transfer mechanisms are indeed better, and stress concentration at the connection interface is significantly reduced, leading to better ductile behavior of the system. The cyclic loading protocol employed was a displacement controlled one (peak ±80mm) and successfully represented large seismic demands. The joint showed a stable force-deflection profile, indicating that the force-deflection behavior of the CFDST column was not adversely affected during the seismic event. The analysis results show a peak total deformation of 108.32mm at the beam tip, and a peak equivalent (von-Mises) stress of 17,480MPa (at the connection interface) at the final time step of 35s. Average stresses of 538.77MPa under the peak loading also justify that the stiffening system is well capable of handling the high level of stress as it is confined to the connection interface. The results clearly confirm the importance of the stiffening ribs in the interior of the joints to improve the seismic reliability of CFDST joints. This research sets up a solid numerical foundation for the further parameter studies, namely, to optimize the geometry of ribs and the configuration of bolts for practical design applications.  

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