Loading...

Evaluating the Seismic Performance Factors of Diagrid Structures and Improving their Behavior using Buckling Restrained Braces

Sadeghi, Saman | 2017

704 Viewed
  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 49514 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Rahimzadeh Rofooei, Fayyaz
  7. Abstract:
  8. In this study, seismic performance of steel diagrid structures is investigated using far-field earthquake records and their seismic performance factors, such as overstrength factor (Ω_0), ductility ratio (µ_T) and response modification coefficient (R) are evaluated according to the FEMA P695. To meet this objective, 12 archetype 3-D models of diagrid structure with two different height of 8 and 12 stories and three different diagonal angles of 45, 63.4 and 71.5 degrees are designed according to the ASCE 7-10 and using response modification factor R=3.6. With regard to the main horizontal beam connections with the diagrid system, equal number of models with pin and rigid type of connections were considered. At first, by implementing nonlinear static pushover analysis, overstrength factor and ductility ratio of models were evaluated. Then, by performing incremental dynamic analysis (IDA) using far-field record set, the “median collapse capacity” of models was determined, that is a key parameter for quantifying presumed response modification factor. In this study, results indicate that using 3.6 as performance factor for designing diagrids is not generally acceptable and this structural systems should be designed for smaller values of response modification factor. Finally, the effects of buckling restrained braces (BRB) on improving the seismic performance of steel diagrid systems are investigated. In that regard, a number of main diagonal members of six models are replaced with BRB elements. All the nonlinear static and dynamic analyses are repeated for these new models and their “ductility ratio” and “median collapse capacity” are evaluated. From nonlinear static analyses, it is concluded that equipping diagrid systems with BRBs, increases their ductility, but for diagonal angles greater than 63 degrees, this effect starts to diminish. Also, results of IDA revealed that equipping diagrids with BRBs, increases median collapse capacity of the models, as well as their displacement parameters. The OpenSees program was used for modeling and static and dynamic analysis of the prepared structural models
  9. Keywords:
  10. Response Modification Factor (R) ; Pushover Analysis ; Incremental Dynamic Analysis ; Static Pushover Analysis ; Buckling Restrained Braces Frame (BRBF)System ; Federal Emergency Management Agency (FEMA)P695 Code ; Seismic Performance ; Diagrid Structures

 Digital Object List

 Bookmark

No TOC