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Numerical Modeling of the Behavior of Base Plates with Various Degrees of Rigidity

Shafieifar, Mohamad Reza | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 43485 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Khonsari, Vahid
  7. Abstract:
  8. Connections have a crucial role in the behavior of every structure. Amongst various types of connections used in steel structures are those used to connect the columns to the foundations, namely Base Plates. As other types of connections, base plates control the behavior of the structure in various respects including affecting the effective length of columns. The main task of any base plate is to distribute the forces of the column on the foundation in such a manner that the stresses in concrete are below their allowable values. Different configurations, with or without various attachments, are used for designing the base plates hence achieving various types of behavior with various levels of rigidity, rotational stiffness, rotational capacity, etc. Therefore, in many circumstances the traditional assumption of considering base plates as either ‘Rigid’ or ‘Hinged,’ is not a correct assumption. In this work, six different types of base plates were studied numerically using a commercial Finite Element software. As a result, moment-rotation curves of these base plates, including their initial rotational stiffness, in the absence and also in the presence of Axial Loads, were obtained and compared. This provides the readers with the required information on the characteristics of each type of the studied base plate, enabling them to select the right bases plate for various circumstances. Moreover, the stress distribution in concrete was studied for each model. This study rules out the contact stress distribution patterns suggested by ACI and some other codes of practice which use triangular distribution with maximum contact stress at the edge of the base plate. For all the studied cases the contact stress distribution underneath the base plates was triangular but with the maximum stress occurring somewhere between the column flange and the edge of the plate, depending on the stiffness of the base plate – at the edge for very rigid base plates and under the column flange for flexible ones. Finally, a method for finding the contact stress distribution is proposed by the author
  9. Keywords:
  10. Stress Distribution ; Base Plate ; Moment-Rotation Curve ; Steel Structures ; Finite Element Modeling ; Numerical Analysis ; Semirigid Base Plate

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