Abstract
Nowadays, using high-ductility structures in construction and significant buildings is highly appreciated. To use better ductile structures, effort has been made in this research to introduce box-plate, box-plate with UNP, box-plate with L-plate and ordinary beam-to-column connections. Eleven models with different shapes and thickness were analyzed and compared in this research, and they underwent hysteretic loading. Parameters such as restraint percentage, stiffness, strength, plastic hinge location, and ductility under cyclic loads were calculated for each model. It was found, from their moment-rotation curves that the bending capacity and ductility of the box-plate with UNP connection was greater than any other rigid connections, and those of the latter were greater than those of the normal, typical ones. It was also shown that stress concentration in box-plate with UNP connections disappear over the top and bottom flange plates.
Highlights
Before the North Ridge Earthquake in 1994, structures that had lateral resisting systems with rigid frames were considered as the most ductile and most earthquake resisting compared with other similar systems, but the earthquake resulted in lots of damage in steel rigid structures that had welded beam-to-column connections
Using the FEM Software and the ANSYS Software, the study showed that local stress concentration was reduced, plastic hinge was formed at a good distance from the column, the system showed appropriate ductility, and according to the diagrams, the tested models reached 3 % of the required plastic bending moment while the connection remained in its elastic state [2]
It is obvious that in the box-plate connection, the web plate on its side is connected to the column plate, and its two sides are connected to the beam flange plate by 6 mm weld. (For better analyses, appropriate mesh sizes were selected for modeling, but the meshes were smaller for welds and connection plates because of their higher importance)
Summary
Before the North Ridge Earthquake in 1994, structures that had lateral resisting systems with rigid frames were considered as the most ductile and most earthquake resisting compared with other similar systems, but the earthquake resulted in lots of damage in steel rigid structures that had welded beam-to-column connections. Numerous studies were done and they showed that the reason for all the damage was different brittle fractures in the welded connections; such fractures prevent the connections’ inelastic behavior and reduce the structure ductility. The study showed that it prevented brittle fractures (in the beam penetration part), and reduced stress concentration at the connection end which prevented the flange failure. Using the FEM Software and the ANSYS Software, the study showed that local stress concentration was reduced, plastic hinge was formed at a good distance from the column, the system showed appropriate ductility (without any brittle fractures), and according to the diagrams, the tested models reached 3 % of the required plastic bending moment while the connection remained in its elastic state [2]
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