damage observations in an industrial plant affected by the ......mar 12, 2015 · region eastern...
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Damage Observations in an Industrial Plant
Affected by the 12-5-2008 Sichuan-China
Earthquake
By Yaron Offir Engineers LTD
Emad Nsieri (M.Sc)
Yaron Offir (M.Sc)
Daniel Dubois (B.Sc)
Yaron Offir Engineers LTD
Seismic Design Risk Assessment Structural Dynamics
קריית שדה התעופה, מרכז קונגרסים אווניו 24.11.2009
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Outline • Earthquake Details, Damages and Casualties • Seismic Activity • Recorded Ground Motions and Response Spectrum • Observations of Structural and Non-Structural Damages in a Chemical Plant • Conclusions and Recommendations
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Earthquake Details
Epicenter Location
Epicenter
CHINA
N
N
Epicenter at Wenchuan County
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Date-Time 12/05/2008 at 14:28
Region Eastern Sichuan Province, China
Epicenter Wenchuan County
Magnitude Mw = 7.9
Intensity XI in Wenchuan area
Focal Depth 20 km
Fault Longmen Shan fault
Fault rupture 300 km
Distances 90 km N-W of Chengdu
545 km S-W of Beijing
Aftershocks 235 Aftershocks greater than 4.0 Mw
Affected area ~450,000 km2
Earthquake Details Map of Main Faults
Sichuan Province
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Damage Chemical plants: Heavy damages caused extensive shutdowns
Buildings: 24 million damaged, 216000 destroyed including 7,000 school buildings
Bridges: 4840 totally or partly damaged
Roads and railways: ~50,000 km damaged
Tunnels: 98 totally or partly damaged
Landslides: 10 million m3 of slide materials, and falling rocks
Surface rupture: Vertical displacement of 2.0-10.0 at several locations
Death ~90,000
Injured ~375,000
Homeless people ~5.0 million
Economic loss 120-150 billion USD$
Damage and Casualties
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Destructive earthquakes within the past century close to Sichuan Province
Past earthquakes – Sichuan Province
Seismic Activity
(Agha et al., 2008, 14WCEE)
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Strong Ground Motion Records
(Xiaojun et al. 2008, 14WCEE)
N
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Strong Ground Motion Records
PGA=0.97g
PGA=0.67g
PGA=0.97g very high!
Wolong station, 19 km from epicenter (Xiaojun et al. 2008, 14WCEE)
Two main shocks!!
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Strong Ground Motion Records
PGA=0.97g
PGA=0.67g
PGA=0.97g very high!
Wolong station, 19 km from epicenter (Xiaojun et al. 2008, 14WCEE)
Sa=3.0g !!
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Qingping station, 88 km from epicenter (Xiaojun et al. 2008, 14WCEE)
PGA=0.84g
PGA=0.82g
PGA=0.64g
Strong Ground Motion Records
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Seismic Zoning Map in China
(GB 18306 – 2001)
PGA=0.20g for return period of 475 years
N
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Response Spectrum and Chinese code
Design spectrum substantially underestimated spectral acceleration (base shear strength)
Wolong station in Wenchuan during the main shock of
12 May 2008 5% damping (Intensity XI)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
Fundamental period (seconds)
Spec
tral
ac
cele
ration
(g)
East-West component
North-South component
Vertical component
Chinese Seismic Code 1989, 475years, 5% damping, Intensity VII
2001
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Response spectrum from site specific study in Israel
vs. Israeli code IS 413
(5% damping and return period 475 years)
New design spectrum substantially underestimating spectral acceleration at short periods!!!
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Damage Observations: Chemical Plant
“Hundreds of people have been buried under two chemical plants collapsed in Shifang (Deyang prefecture) and more than 80 tons of ammonia have spread into the environment (source: Chinese Government News Agency Xinhua).” Facility damages caused extensive shutdowns and business interruption.
Location: Shifang town, Deyang ~150 km from epicenter ~60 km fault rupture
Damage:
1. Structures
2. Piping Systems and Tanks
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Damage Observations: Structures
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Response Spectrum and Structure Response
Assumption: Stiff structures with low
fundamental periods were highly
vulnerable to this earthquake due to the
high seismic force demands
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Damage Observations: Stiff Structures
Destruction of low rise masonry infilled frame RC buildings
In-plane failure of masonry infill
walls
Out-of-plane failure of
masonry infill walls
Poor seismic performance
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0<T <0.5
Members at stiff structures collapsed/experienced severe damage during the earthquake event
Damage Observations: Stiff Structures
Structures with poor seismic performance
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Damage Observations: Prefabricated Structures
Collapse of prefabricated structure with pre-cast elements
Inadequate connection between pre-cast
beams and supporting columns led to very
low seismic resistance
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Damage Observations: Residential Buildings
Catastrophic collapse of pre-cast hollow
core plank floors and roofs widely used
in school and residential buildings due to
low cost, simple and rapid construction.
Poor connection between floor/roof
slab and supporting beam
Poor seismic performance
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Damage Observations:
Existing Construction Details
• Pebble aggregate used in columns (poor inspection): low compression and shear strength
• Column ties: smooth bars, wide spacing (30-40cm), insufficient end-hooks (unconfined concrete section)
• Rebars: buckling, tearing
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Poor construction
details
Low quality of
construction material
Strong ground motions
Non-ductile behavior
Low strength
High seismic force
demands
Poor seismic
performance
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
Sp
ectr
al a
ccele
rati
on
(g
)
Fundamental vibration period (seconds)
Damage Observations:
Poor Constructions Details and High Seismic Demands
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Evaluation of ductility seismic demand
SDOF structure
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T=2√(M/Keff)=0.3 sec., Sa=2.6
mD≈R=Sa/(Vy/Wt)=7.0 (high ductility demand)
Evaluation of ductility seismic demand
Ductility Capacity
mD=1.0 (brittle)
mD=6.0 (ductile)
Cross Section
Yield of column ties
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Damage Observations: Flexible Structures
Structures with good seismic performance
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Damage Observations: Flexible structures
Flexible RC frame structure remained intact
0.5<T <1.0
Structures with good seismic performance
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Damage Observations:
Piping Systems and Tanks
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RC structure collapsed on ammonia tanks: damage mainly to pipelines and release of 80 tons of ammonia
Damage Observations: Piping Systems
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Damage Observations: Piping Systems
No damage Pipeline fractured
Pipeline damages due to stiff connection supports
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Pipeline damages due to large relative displacement between
pipeline ends
Damage Observations: Piping Systems
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ALA (2002): seismic design and retrofit of piping systems
Piping systems need to be designed for two effects:
1. Inertia forces
2. Relative displacements between supports
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Sliding of ammonia tank from its support
Damage Observations: Unanchored Tanks
Poor Performance
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Low quality of construction material: concrete floor crushed due to rocking of tank
Pipe rupture due to large displacement
Damage Observations: Tanks
Poor Performance
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Braced sphere tank: non-ductile seismic response of steel tie-rods (buckling and tension failure)
Damage Observations: Spherical Tanks
Poor Performance
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Existing Sphere
Proposed Seismic Upgrading Measures
Seismic Upgrading of Sphere by Installing Viscous Dampers
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Conclusions and Recommendations
Observed large scale destruction of industrial plant caused
casualties, high financial loss and extensive shutdowns.
Follows are actions to significantly reduce public risk and
financial loss from the damaging effects of a potential
earthquake:
• Increase awareness of earthquake risks
• Identify seismic hazard (site specific study)
• Identify problematic structures in industrial plants lacking seismic resistance and defining their seismic failure modes
• Provide effective and practical retrofitting techniques and develop cost-effective retrofit program
• Implementation of retrofitting techniques
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תודה רבה
YARON OFFIR ENGINEERS LTD C.I.R BLDG, Technion Campus,
Haifa 32000, Israel Tel: 972-4-8323102 Fax: 972-4-8323286
Mobil: 972-54-4654022 offir.com-www.yaron