seismic behaviour of steel structures
DESCRIPTION
SEISMIC BEHAVIOUR OF STEEL STRUCTURESTRANSCRIPT
Teaching Resources © IIT Madras, SERC Madras, Anna Univ., INSDAG Calcutta 1
SEISMIC BEHAVIOUR OF STEEL STRUCTURES
Teaching Resources © IIT Madras, SERC Madras, Anna Univ., INSDAG Calcutta 2
Seismic Behaviour of Structural Steel • Ductile, equally strong in compression and tension
• Mild versus high strength steel
• Produced with high quality control. Aids in Capacity Design yield ratio = expected yield strength/specified min. yield strength • Welding subjected to fatigue
SEISMIC BEHAVIOUR OF STEEL STRUCTURES
Robustness of Steel Structures
Teaching Resources © IIT Madras, SERC Madras, Anna Univ., INSDAG Calcutta 3
SEISMIC BEHAVIOUR OF BRACING MEMBERS
Fig. 6 Hysteretic behaviour of a slender brace
P (comp.)
2
0 -1 -2 2 3 4 1 -3 -4 -5 -2
-1
0
1
5
P (ten.)
d
buckling
d
P • Bracings used either for lateral strength or for lateral stiffness • used in pairs
• slenderness limited to a value such that C = T/2 • solid cross-sections preferred
Teaching Resources © IIT Madras, SERC Madras, Anna Univ., INSDAG Calcutta 4
SEISMIC BEHAVIOUR OF BEAM-COLUMNS
Seismic Behaviour of I-sections
Hysteretic behaviour of an I-section
M/My
f/fy
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Seismic Behaviour of Rectangular Hollow Sections (RHS)
M/My
f/fy
Hysteretic behaviour of rectangular hollow section
SEISMIC BEHAVIOUR OF BEAM-COLUMNS-1
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Seismic Behaviour of Circular Hollow Sections (CHS)
M/My
f/fy
Hysteretic behaviour of circular hollow section
SEISMIC BEHAVIOUR OF BEAM-COLUMNS-2
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Seismic Behaviour of Concrete-Filled Tubes (CFT)
Failure Mode of a concrete-filled RHS
SEISMIC BEHAVIOUR OF BEAM-COLUMNS-3
• Efficient use of steel
• Concrete in confined state
• Local buckling delayed in RHS
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Types of moment connections
(a) (b)
(c) (d)
SEISMIC BEHAVIOUR OF CONNECTIONS
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5
2
0 -1 -2 2 3 4 1 -3 -4 -5 -2
-1
0
1 M/My
f/fy
Hysteretic behaviour of bolted angle connection
SEISMIC BEHAVIOUR OF CONNECTIONS-1
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Sway frames and non-say frames Braced and un-braced frames Concentrically Braced Frames (CBF) Eccentrically Braced Frames (EBF)
(a)Diagonal bracing
(b)Cross or X-bracing
(c )Chevron bracing
(d)Eccentric bracing
Link Beams
Bracing systems in Steel Frames
SEISMIC BEHAVIOUR OF FRAMES
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Failure of Concentric Braced Frames
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Desired and Undesired Collapse Mechanisms in Capacity Design
(a) Desired (b) Undesired
D
q
q
D
CAPACITY DESIGN
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Lead Plug
Laminated rubber bearing pad
SPECIAL DEVICES AND SYSTEMS
Either isolate or dissipate Base Isolation Vibration Control Active and Passive Visco-elastic dampers used as sliding supports for beams/trusses Tuned Mass Dampers(TMD) Tuned Liquid Dampers(TLD) Hydraulic Actuators Weak links, stoppers etc as inelastic dampers