الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Although much effort has been invested in recent years to seismically retrofit buildings having unreinforced masonry walls and reinforced concrete frames, steel buildings and bridges have also received a significant attention. In buildings having steel frames, this interest in seismic retrofit stems from the realization, following the 1994 Northridge earthquake, that the welded beam-to-column connections in moment resisting frames were likely to fail in a brittle manner, prior to the development of significant inelastic response, thus negating the design intent and possibly causing safety hazards.
A cooperative effort by the National Institute of Standards and Technology (NIST), the American Institute of Steel Construction (AISC), the University of California at San Diego, the University of Texas at Austin, and Lehigh University, examined three techniques for retrofitting of existing steel moment connections. All these efforts were done because welded steel beam to column joint is one of the most important elements of steel structure, especially when the structure lies in a seismic zone. In this study a connection joint of cover-plate-haunch connection (WCPH) was brought forward on the basis of improving haunch connection and cover plate connection. This kind of connection joint not only overcomes the shortcomings that bilateral haunch connections affect the flatness of floor and the interior appearance, but also strengthens connection performance.
Also the study concentrated on the famous seismic connection of reduced beam section (RBS). Both connections are compared to the ordinary welded connection (OWC) in which the beam is directly welded to column flange using butt weld. Both SAP2000 and ANSYS finite element software programs were used to perform a time history analysis and investigate node stress, plastic zone distribution and hysteretic behavior.