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Numerical Simulation of Residual Welding Stress in Reduced Beam Section Connection

Ghezi, Amir Fazel | 2025

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 58371 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Mofid, Masoud; Dehestani, Mehdi
  7. Abstract:
  8. The present study aims to comprehensively investigate the influence of welding-induced residual stresses on the seismic behavior of reduced beam section (RBS) connections in steel structures. These connections are widely adopted in the design of special moment-resisting frames due to their favorable ductility and energy dissipation capacity; however, the presence of residual stresses in the weld region may affect stress distribution, yielding initiation, and ultimately the seismic capacity of such connections. In this research, advanced numerical simulations were conducted in ABAQUS using nonlinear thermo-mechanical analyses to accurately model welding-induced residual stresses and to evaluate their effects on the cyclic performance of RBS connections. The research methodology was based on a multiscale approach that incorporated not only the mechanical response but also metallurgical changes in the heat-affected zone and phase transformation phenomena. To assess seismic performance, the connections were subjected to cyclic loading, and key parameters such as energy dissipation capacity, initial stiffness, and ductility index were extracted. The results indicated that the presence of residual stresses can reduce the energy dissipation capacity by an average of up to 6%. Although this reduction is relatively limited, its effect is most pronounced during the initial loading cycles, and the findings are consistent with previous experimental observations. It was also found that the influence of residual stresses is more significant in regions close to the weld, while the effect gradually diminishes with increasing distance from the cut section of the connection. Furthermore, a mathematical relation was developed based on the numerical results to predict the combined effects of temperature, residual stress distribution, and metallurgical transformations on the seismic response of RBS connections. This relation can serve as a practical tool in the seismic design of steel connections, contributing to improved safety and enhanced structural performance. The findings highlight the importance of considering residual stress effects and the optimal distance of the cut section from the weld zone in order to ensure stability and reduce the risk of sudden failure in RBS connections. In conclusion, the results of this study not only provide deeper insight into the seismic behavior of steel connections but also pave the way for future research aimed at achieving safer and more optimized connection designs and at developing more advanced seismic design codes
  9. Keywords:
  10. Reduced Beam Section ; Residual Stress ; Numerical Simulation ; Seismic Behavior ; Thermomechanical Stress Analysis ; Seismic Behavior

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