introduction to earthquake engineering · plastic hinge prof. dr.-ing. dorka ... braced full-scale...
TRANSCRIPT
Introduction to
Earthquake Engineering
Behaviour of structures
under earthquakes
Prof. Dr.-Ing. Uwe E. Dorka
Stand: September 2013
Conventional rc-frame structure under Kobe earthquake
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
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Non-linear cyclic behaviour of frames
3
From Müller, Keintzel (2)
Failure in soft storey
From Petersen (9)
Plastic hinge
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
Non-linear cyclic behaviour of walls
4
flexural failure shear failure sliding failure rotation of foundation
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
Behaviour of reinforced concrete structures
5
Flexural cyclic behaviour in plastic hinges
From Wakabayashi (1) From Earthquake Spectra (10)
j
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
Concrete columns
6
Buckling of longitudinal reinforcement
From Wakabayashi (1)
From Earthquake Spectra (10)
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
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Behaviour under combined bending and axial load:
From Wakabayashi (1)
From Petersen (9)
From Wakabayashi (1)
Concrete columns
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
Short columns
8 Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
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Short columns
From Wakabayashi (1)
Extreme pinching of hysteresis loop and failure in shear
From Wakabayashi (1)
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
Rc frame corners
10
pinching effect and deterioration due to large shear
From Wakabayashi (1)
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
Complicated details in rc-frames:
11
From Müller, Keintzel (2)
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
Shear walls
12
From Wakabayashi (1)
From Wakabayashi (1)
Brittle behaviour, but large capacity!
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
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From Wakabayashi (1) From Earthquake Spectra (10)
Coupled shear walls
Brittle failure in shear!
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
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Coupled shear walls
From Müller, Keintzel (2)
From Müller, Keintzel (2)
Large shear in connecting
beam leads to “Impossible”
detailing requirements for
an rc-solution!
Better: steel beam, but
special attention must be
paid to the connection!
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
Pre-cast structures
15
From Wakabayashi (1)
From Earthquake Spectra (10)
“Domino effect” due to
sudden connection failure
often leads to total collapse!
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
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Behaviour of steel structures
Conventional steel structure under Kobe earthquake: soft storey
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
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Plastic hinges
Local buckling under cyclic loading
From DGEB (8)
Steel beams
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
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Moment-rotation hysteresis loop of a steel beam
From Wakabayashi (1)
Steel beams
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
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Hysteresis of column with P-D effect
From Wakabayashi (1)
From Petersen (9)
Steel columns
Instable load bearing due to negative post-yield stiffness can lead to total
collapse of structure
Rapid deterioration due to local
buckling
Columns should not yield, only beams!
Strong column – weak beam concept!
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
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Cyclic buckling of struts
From Wakabayashi (1) From Wakabayashi (1)
From Earthquake Spectra (10)
Steel struts
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
From Wakabayashi (1)
21
Braced full-scale portal frame under constant vertical load and cyclic horizontal load.
Combined action of beam plastic hinges and cyclic
strut behaviour: stiff but ductile!
P= 0,5*Npl
H HP= 0,5*Npl
Braced steel frames
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
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Steel connections
Both Pictures from earthquake Spectra (10)
Brittle fracture in welds
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
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Both Pictures from earthquake Spectra (10)
Steel connections
Brittle fracture in welds
and rupture of bolts
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
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From Wakabayashi (1)
Seismically sound connections in
frame corners
Steel connections
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
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Behaviour of timber structures
Modern Japanese residential structure under Kobe earthquake:
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
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From Wakabayashi (1)
Behaviour of timber structures
Insufficient connections can lead to brittle failure
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
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From Wakabayashi (1)
Timber wall with cladding
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
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From Wakabayashi (1)
Load-deflection relationship for a timber wall with cladding under cyclic shear
Timber wall with cladding
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
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Behaviour of masonry structures
From Wakabayashi (1)
Typical crack pattern between openings and at corners
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
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Behaviour of masonry structures
Typical crack pattern between openings and at corners
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
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From Earthquake Spectra (10)
Collapse of chimneys and
out-of-plane failure of roof
gable walls due to insufficient
lateral support
Behaviour of masonry structures
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
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Horizontal load-deflection relationship for a wall subjected to cyclic shear and
constant vertical load showing rapid deterioration of hysteresis loop
From Wakabayashi (1)
Masonry walls
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
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Masonry in-filled rc-frames
Non-linear mechanism with compression strut developing in masonry wall causing shear failure in rc-columns
From Wakabayashi (1)
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
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From Earthquake Spectra (10)
Behaviour of historic structures
Many old historic structures
behave well having sustained
several earthquakes during their
history
“Intact” historical structural systems
are usually quite safe, sometimes
with surprising effects
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
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Behaviour of historic structures
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
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Behaviour of historic structures
“New” (18th – 20th century) historic
structures are often derived from
“non-seismic” countries like Britain
or Germany with modern structural
systems not capable of resisting
large earthquakes
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
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Behaviour of historic structures
Modern alterations often lead to a change in behaviour and collapse
Car parking or shops create soft storeys
Rc- additions change
historic load paths
etc.
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
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Behaviour of bridges
Both Pictures from Earthquake Spectra (10)
Relative motion of single-
span deck caused drop-off
Horizontal shear failure in deck due
to differences in deformations of
supporting frames (short frame vs.
long frame)
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
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Both Pictures from Earthquake Spectra (10)
Brittle shear failure in columns
(short column effect) and
frame corners
Behaviour of bridges
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
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From Petersen (9) Both Pictures from Earthquake Spectra (10)
Toppling due to P-D effect
Behaviour of bridges
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
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Both Pictures from Earthquake Spectra (10)
Bearing failure due to large
mass effect
Behaviour of bridges
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
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Both Pictures from Earthquake Spectra (10)
Insufficient retrofit due to neglect
of differential motion between
large masses:
“band-aid” solution!
Behaviour of bridges
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes
References
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(1) Wakabayashi –
Design of Earthquake-Resistant Buildings
McGraw-Hill Book Company
(2) Müller, Keintzel –
Erdbebensicherung von Hochbauten
Verlag Ernst & Sohn
(3) Deutsche Gesellschaft für
Erdbebeningenieurwesen - DGEB
Schriftenreihe der DGEB, Heft 2
Elsevier
(4) Petersen
Statik und Stabilität der Baukonstruktionen
Vieweg
(5) Jack P. Moehle
Earthquake Spectra – April 1995
Prof. Dr.-Ing. Dorka | Behaviour of structures under earthquakes