SMCES Civil Engineering Seminar 2016 (Yangon)...
Transcript of SMCES Civil Engineering Seminar 2016 (Yangon)...
SMCES Civil Engineering Seminar 2016 (Yangon)
Seismic Retrofit of Existing Structures
by Dr. Methee ChiewanichakornP.E. (California), S.E. (California), LEED AP BD+C
Meinhardt (Thailand) Ltd.
Yangon Technology University
December 18th, 2016
OVERVIEW
Introduction
Description of Case Study Building
Component Laboratory Testing
Nonlinear Analysis Results
Comparison of Retrofit Schemes
using Conventional vs. Nonlinear
Based Approaches
Conclusions
HISTORY AND BACKGROUND
HISTORY AND BACKGROUND
California has a history of strong
earthquakes.
The most earthquake prone regions
in the state are also the most
heavily populated.
Building design and construction
has evolved as a result of lessons
learned in damaging earthquakes.
1933 LONG BEACH EQ
Magnitude 6.3 earthquake
resulted in loss of 115 lives and $40
million in property damage.
Led to the development of
building code requirements for
seismic resistant design of
buildings, especially schools.
1933 LONG BEACH EQ
1933 LONG BEACH EQ
1971 SAN FERNANDO EQ
Magnitude 6.5 earthquake
caused 65 deaths and over $500
million in property damage.
Produced an unanticipated
amount of damage to hospitals,
leaving the public in large areas
without medical assistance.
1971 SAN FERNANDO EQ
1971 SAN FERNANDO EQ
1971 SAN FERNANDO EQ
RESPONSE TO SAN FERNANDO EQ
Hospital Seismic Safety Act (HSSA),
also known as the Alquist Act.
The Alquist Act establishes
hospitals as essential facilities and
defines explicitly their expected
performance.
Acute care hospitals to withstand
and remain operational after a
major earthquake.
1994 NORTHRIDGE EQ
Magnitude 6.8 earthquake caused 57
deaths and over $20 billion in property
damage.
Forced evacuation of several hospital
facilities.
Hospitals constructed in accordance
with the Alquist Act survived the
earthquake with minimal structural
damage.
Non-structural damage impaired
operation of hospitals, even when no
structural damage occurred.
1994 NORTHRIDGE EQ
SENATE BILL (SB 1953)
After the January 17, 1994
Northridge Earthquake, State of
California passed a law (Senate
Bill 1953) that requires hospital
owners to evaluate and possibly
retrofit pre-1973 hospital buildings.
Addresses survivability of both
structural (SPC) and non-structural
(NPC) components.
SB 1953 MAJOR MILESTONES
STRUCTURAL PERFORMANCE CATEGORIES
SPC 3, 4 & 5 Reasonably capable of serving
the public after strong ground
motion.
SPC 2 No risk to life safety
SPC 1 Significant risk to life safety
STRUCTURAL PERFORMANCE CATEGORIES
Current StateSPC-1
Significant Risk of Life Safety
Retrofit StateSPC-2
Life Safety
CODE FRAME WORK
Followed two methodologies
1. Prescriptive (Code Based)
2. Performance Based
CODE BACKGROUND
Prescriptive(Code Based)2001, 2007 CBC
Performance BasedASCE 41-06
CASE STUDY: BUILDING DESCRIPTION
Structural Systems: Lateral Force Resisting
System: Concrete Shear
Walls.
Floor and Roof Framing: Formed Concrete Pan Joist
System.
Foundation: Concrete
Continuous Wall & Spread
Footings.
Number of Stories: 6
Year Constructed: 1961
CASE STUDY: BUILDING DESCRIPTION
CASE STUDY: BUILDING DESCRIPTION
Weakened Plane
Joint (WPJ)
CASE STUDY: BUILDING DESCRIPTION
Weakened Plane Joint (WPJ)
Weakened Plane Joint (WPJ): Half to two-thirds of typical wall
reinforcement at mid-span were cut and
grooves in concrete
ASCE 41-06 MODELING PARAMETERS
ASCE 41-06 MODELING PARAMETERS
Modeling Parameters, Drift % Acceptable Drift %
Performance Level
d e c Immediate Occupancy
Life Safety
Collapse Prevention
0.75 2.0 0.40 0.40 0.60 0.75
/h
CPLSIO
d e - d
c
y/h
nV
rV
Table 6-19: Wall Segments
COMPONENT TESTING
Horizontal Wall
Segment (HWS)
Vertical Wall
Segment (VWS)
TEST SPECIMENS – VERTICAL WALL SEGMENT (VWS)
hp = 62.5”
(1.60 m)
lp = 72” (1.83 m)
tp = 8”
(200 mm)
v = ~0.25%
h = ~0.35%
Prototype (Actual Building)
hp = 62.5”
(1.60 m)
lp = 72” (1.83 m)
tp = 8”
(200 mm)
v = ~0.25%
h = ~0.35%
Prototype (Actual Building)
hp = 48”
(1.20 m)
lp = 54” (1.40 m)
tp = 6”
(150 mm)
v = ~0.25%
h = ~0.35%
¾ Scale Test Specimen
TEST SPECIMENS – VERTICAL WALL SEGMENT (VWS)
TEST SPECIMENS – VERTICAL WALL SEGMENT (VWS)
Specimen Geometry (inches) Reinforcement3 P/Agf 'c4 Specimens
ID Height Length Thickness Edge1 Vert. Web2 Horiz. Web2 (kips) (#)
(1) (2) (3) (4) (5) (6) (7) (8) (9)
WP1-1-10 48 54 6 2 - #4 0.26% 0.35% 0.10 2
WP2-1-05 48 54 6 2 - #4 0.26% 0.35% 0.05 2
WP3-1-00 48 54 6 2 - #4 0.26% 0.35% 0.00 2
WH1-1-0 60 60 6 1-#4 1-#5 0.35% 0.26% 0.0 2
WH2-1-0 60 60 6 4 - #5 0.35% 0.26% 0.0 2
HORIZONTAL WALL SEGMENT – WEAKENED PLANE JOINT
COMPONENT TESTING SET-UP
COMPONENT TESTING SET-UP
Horizontal LoadVertical Load
Vertical Load
Reaction FrameOut-of-plane support
Specimen
FLAT
M
M
θ
θ
P1
P2 ΣP=0
TEST RESULTS – SPANDREL (HWS)
TEST RESULTS – SPANDREL (HWS)
TEST RESULTS – SPANDREL (HWS)
TEST RESULTS – SPANDREL (HWS)
TEST RESULTS – SPANDREL (HWS)
TEST RESULTS – SPANDREL (HWS)
TEST RESULTS – BACKBONE RELATIONSHIP
Results from Test 2
-150
-100
-50
0
50
100
150
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0
Lateral Displacement (in)
Forc
e (
kip
s)
Full History
Test Based
Test #2
TEST RESULTS – BACKBONE RELATIONSHIP
Results from Test 2
-150
-100
-50
0
50
100
150
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0
Lateral Displacement (in)
Forc
e (
kip
s)
FEMA Based
Test Based
New ASCE-41 Supplement
Backbone Curve for shear
controlled wall segments
- based on these testsTest #2
PRESCRIPTIVE/CODE BASED: ETABS MODEL
3D model
Fixed base
Elastic wall elements
Elastic diaphragms
ETABS Model
PERFORMANCE BASED: PERFORM-3D MODEL
3D model
Nonlinear soil spring
Nonlinear wall elements
Elastic diaphragms
PERFORM-3D Model
PUSHOVER ANALYSIS
Plastic Hinge
PUSHOVER ANALYSIS
Lateral displacement
Late
ral
forc
e
CollapseInelastic RangeElastic Range
Co
llap
se P
reven
tio
n
Lif
e S
afe
ty
Serv
iceab
ilit
y
Co
llap
se
Dam
ag
eL
evel
1
Dam
ag
e L
evel
2
CODE BASED: ASSESSMENT OF SEISMIC BEHAVIOR
Mechanism• Unclear
CODE BASED: ASSESSMENT OF SEISMIC BEHAVIOR
Mechanism• Unclear
PERFORMANCE BASED: ASSESSMENT OF SEISMIC BEHAVIOR
Not Desirable• Lack of ductility
• Potential loss of vertical load carrying ability
Possible Mechanism: Soft Story
PERFORMANCE BASED: ASSESSMENT OF SEISMIC BEHAVIOR
Not Desirable• Lack of ductility
• Potential loss of vertical load carrying ability
Possible Mechanism: Soft Story
PERFORMANCE BASED: ASSESSMENT OF SEISMIC BEHAVIOR
Desirable• Ductile response
• No loss of vertical load carrying ability
Possible Mechanism: Segmented Wall Rocking
PERFORMANCE BASED: ASSESSMENT OF SEISMIC BEHAVIOR
Desirable• Ductile response
• No loss of vertical load carrying ability
Possible Mechanism: Segmented Wall Rocking
PERFORMANCE BASED: FORMATION OF MECHANISM
Step 1: Undeformed
PERFORMANCE BASED: FORMATION OF MECHANISM
Step 2: Localized Damage
PERFORMANCE BASED: FORMATION OF MECHANISM
Step 3: Formation of Rocking
Mechanism
PERFORMANCE BASED: FORMATION OF MECHANISM
Step 4: Fully Rocking
Mechanism
PERFORMANCE BASED: PUSH-OVER CURVES (LB SOIL)
HOW DO THE METHODOLOGIES COMPARE?
CODE-BASED• Extensive wall
thickening
• Concrete infills at a
multiple openings
• Complete
foundation system
replacement
CODE-BASED• Extensive wall
thickening
• Concrete infills at a
multiple openings
• Complete
foundation system
replacement
PERFORMANCE-BASED• Almost no wall
thickening
• Concrete infills at a
few openings
• Isolated FRP
strengthening
• Isolated foundation
thickening
• FRP “Catch
Mechanisms” at
hospital
exits/corridors
HOW DO THE METHODOLOGIES COMPARE?
RETROFIT HIGHLIGHTS – PRESCRIPTIVE/CODE BASED
Foundation Retrofit
14’ wide x 5’ deep foundation retrofit
RETROFIT HIGHLIGHTS – PERFORMANCE BASED
Foundation Retrofit
Isolated Foundation Thickening
RETROFIT HIGHLIGHTS – CODE vs. PERFORMANCE BASED
Retrofit Work and Business Disruptions
Isolated concrete infill
FRP “Catch Mechanism”
FRP ”WPJ”strengthening
Performance Based
14’ wide x 5’ deep foundation retrofit
16” thick concrete wall thickening
24” thick concrete wall thickening
Prescriptive/Code Based
FRP Chords
RETROFIT SCHEMES: CONVENTIONAL VS. NONLINEAR
Prescriptive/Code Performance Based
Foundations New foundations below 90% of all perimeter walls
Strengthening of 5% of Existing Foundations
Shear Walls 90% of all perimeter walls need to be thickened 16” (380 mm) or 24” (610 mm) with new reinforced concrete walls
Reinforced concrete infill of 5% of existing openings
Thickening of 1% of existing perimeter walls.
Catch mechanisms in 5% of HWS
Repair of existing weakened plane joints in 2 walls
RETROFIT SCHEMES: CONVENTIONAL VS. NONLINEAR
Prescriptive/Code Performance Based
Diaphragms New interior chords at all levels
Thickening of existing concrete slab in selected locations
New FRP chords at two upper floors (mostly exterior)
Stair Towers Demolish and replace existing stair towers
No action required
Impact on Adjacent Buildings
At least 2 adjacent buildings need to be cut back to accommodate thickening of existing walls
Minimum impact to adjacent buildings
RETROFIT PHOTOS
Concrete Wall Thickening
RETROFIT PHOTOS
Foundation Thickening
RETROFIT PHOTOS
Concrete Wall Opening Infill
Beam/Joist FRP Strengthening
RETROFIT PHOTOS
Gravity Column FRP Strengthening
RETROFIT PHOTOS
FRP Anchors
RETROFIT PHOTOS
FRP Catch Mechanism at Corridor
FRP Anchors
RETROFIT PHOTOS
FRP Catch Mechanism at Corridor
RETROFIT PHOTOS
FRP Catch Mechanism at Corridor
RETROFIT PHOTOS
Diaphragm Strengthening
RETROFIT PHOTOS
Diaphragm Strengthening
Floor Plan
DiaphragmFRP
Collector
Wall
Steel Plate
(L-Shape)
RETROFIT PHOTOS
Collector Strengthening
Floor Plan
DiaphragmFRP
Collector
Wall
Steel Plate
(L-Shape)
RETROFIT PHOTOS
Collector Strengthening
Floor Plan
DiaphragmFRP
Collector
Wall
Steel Plate
(L-Shape)
Test Samples
RETROFIT PHOTOS
Collector Strengthening
BENEFITS OF NONLINEAR ANALYSIS
• Ability to explore actual post-elastic seismic
performance of existing structures
• Better identification of desirable collapse
mechanisms for the existing structure
• Better identification of efficient retrofit
options
• Improved communication of the expected
performance of the buildings
BENEFITS OF NONLINEAR ANALYSIS
• Potential reduction of retrofit costs
• Potential reduction of disruptions due to
retrofit work
BENEFITS FROM THE OWNER’S PERSPECTIVE
• Less retrofit means …
BENEFITS FROM THE OWNER’S PERSPECTIVE
• Less retrofit means …
• Less disruption• Happy patients & staffs
BENEFITS FROM THE OWNER’S PERSPECTIVE
• Less retrofit means …
• Less disruption• Happy patients & staffs
• Less cost• Happy hospital
leadership
• More capital for other
needs
BENEFITS FROM THE OWNER’S PERSPECTIVE
• Less retrofit means …
• Less disruption• Happy patients & staffs
• Less cost• Happy hospital
leadership
• More capital for other
needs
• Shorter schedule• Happy patients & staffs
CONCLUSIONS
• A nonlinear model has the potential of
greatly improving the understanding
of the seismic performance of existing
structures.
• Nonlinear based approach leads to
targeted retrofit that provides a higher
level of confidence that the building
will behave as expected and meet
the desired performance.
CONCLUSIONS
• Nonlinear based approach may lead
to a reduced amount of retrofit that is
less invasive than a retrofit based on
conventional code-based methods.
• With nonlinear based retrofit scheme,
cost saving can be maximized while
the disruption of the hospital
operations can be greatly minimized
during the construction.
Source: http://www.bvt.co.nz/faq-seismic-restraint-of-non-structural-building-elements/
NONSTRUCTURAL COMPONENTS
• What is “Nonstructural Components”?
• How important is “Nonstructural Components”?
NONSTRUCTURAL COMPONENTS
NONSTRUCTURAL COMPONENTS
Types of failure
1. Initial Failures
2. Displacement/Deformation Failures
NONSTRUCTURAL COMPONENTS
Inertial failures:
• Excessive shaking
• Component rocking
• Component sliding
NONSTRUCTURAL COMPONENTS
Electrical Switchgear
NONSTRUCTURAL COMPONENTS
Disruption to Patient Care
NONSTRUCTURAL COMPONENTS
Patient Records
NONSTRUCTURAL COMPONENTS
Boilers & Chillers
NONSTRUCTURAL COMPONENTS
Electrical & Communications Equipment
NONSTRUCTURAL COMPONENTS
•Displacement / Deformation failures:
• Excessive building inter-story displacements or drift
• Incompatible stiffness between the building structure and component
• Interaction between adjacent structural systems and nonstructural systems
• Multiple structure connection points
NONSTRUCTURAL COMPONENTS
Sprinklers & Water Lines
NONSTRUCTURAL COMPONENTS
Design Code / Standard
• International Building Code (IBC)
• ASCE 7
• ASCE 41
NONSTRUCTURAL COMPONENTS
Thank you
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