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A Study of the Strain Rise Phenomenon in Steel Components, and its Detrimental Effect on the Seismic Performance of Structural Elements

Sadrara, Ali | 2021

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 54723 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Moghaddam, Hassan
  7. Abstract:
  8. In this thesis, the strain rise phenomenon and its adverse effect on the deformation capacity of steel elements, members, and connectors were investigated. The high-rate increase in plastic strains was termed strain rise. In this study, the sharp increase in plastic strains and its causes were investigated through conducting experiments and extensive numerical analyses. The causes of strain rise were fallen into two categories as primary and secondary. To limit the adverse effect of strain rise two methods of decreasing the initial stress concentration and expanding the plastic volume were proposed. The strain rise in the saddle and pre-Northridge connections as a result of primary effects was investigated. It was found that the primary strain rise led to a premature fracture in these connections and reducing the initial stress concentration resulted in postponing the strain rise. Strain rise due to secondary causes in Square Hollow Section (SHS) and Circular Hollow Section (CHS) braces and built-up box columns were investigated. It was shown that after local buckling, the plastic strains increased sharply, and consequently, premature fracture occurred. A method was proposed for predicting the cycle of local buckling in SHS and CHS braces under arbitrary cyclic loading. Furthermore, a method was proposed for predicting ductile fracture due to ultra-low cycle fatigue in structural members with primary and secondary causes. It was shown that the proposed method enjoyed high accuracy and low computational cost
  9. Keywords:
  10. Deformation Capacity ; Cyclic Behaviour ; Steel Structures ; Strain Rise Phenomenon ; Monotonic Behaviors ; Fracture

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