High strength steel for seismic resistance of beam-to-column connections: novel metal investigation

Ozkula, Gulen

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https://hdl.handle.net/2142/26290 Copy

Description

Title

High strength steel for seismic resistance of beam-to-column connections: novel metal investigation

Author(s)

Ozkula, Gulen

Issue Date

2011-08-26T15:21:41Z

Director of Research (if dissertation) or Advisor (if thesis)

Elnashai, Amr S.

Department of Study

Civil & Environmental Eng

Discipline

Civil Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• bainite steel
• high strength steel
• ductility
• semi-rigid connections
• extended end-plate
• yield line

Abstract

The use of high strength steels (HSS) has been gradually increasing since 1930s. However, research and knowledge about HSS lagged, preventing its widespread applicability in seismic resistance structures. Due to the lack of sufficient theoretical and experimental studies regarding ductility, deformation of structures, and rotational capacity of connections made by HSS, current codes recommend that connections remain in the elastic range. Under seismic events, high demands for local and global deformation are imposed on structural elements, connections and details. Designers should look into strain and deformation of the steel and ensure that the material meets the required criteria given in the design code. Since HSS needs further investigation, using steels greater than S460 is prohibited in the current design codes. In order to develop a more practical HSS, research within the last few decades has focused on the problem of creating steels with greater strength, good weldability and reason¬able ductility. This thesis focuses on semi-rigid ---partial strength--- connections with components made from new bainitic steel, an alloy possessing greater ductility, strength and weldability due to its particular microstructure formation at a temperature range of 250-550 ºC. Connections between members are the regions where the material is exposed to higher deformation demands. Thus, use of bainitic steel in extended end-plates is of great benefit due to its higher strength and ductility. The behavior of extended end-plate connections is evaluated using component based mechanical model. Yield line method is used to measure the geometry of the end-plates. Furthermore, comparisons of bainitic steel with conventional high strength and normal steels are presented. In this thesis S960 and A36 are chosen as conventional HSS and normal steel, respectively. It is shown that HSS in semi-rigid connections which are designed to yield at the joints instead of the beam ends results in more economical column sections, end-plate cross-sections, and bolt sizes. Utilizing HSS in semi-rigid connections also reduces the weight of the structure and hence its inertial load. Moreover, the results of this research show that using bainitic and S960 HSS eliminates the necessity of continuity plates and web stiffeners in connections. Hence, significant savings in construction period and labor cost can be achieved.

Graduation Semester

2011-08

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http://hdl.handle.net/2142/26290

Copyright and License Information

Copyright 2011 Gulen Ozkula

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