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Transcript of Seismic Strengthening of RC Building...
Tyfo® FIBRWRAP® Systems
FYFE Japan Co., Ltd.
Seismic Strengthening of RC Building
Structures
Dr. Basem ABDULLAH
Tyfo® FIBRWRAP® Systems
FYFE Japan Co., Ltd.
His
tory
of
Ear
thq
uak
e In
Jap
an
Tyfo® FIBRWRAP® Systems
FYFE Japan Co., Ltd.
Seismic-resistant Building Design Standards in Hong Kong
Buildings in Hong Kong are currently not required by law to meet specific seismic-resistant design standards.
The strongest earthquake ever recorded in Hong Kong measured intensity of VI to VII on the MMS.
Internationally, Many major cities and economies located in areas of seismicity comparable to that of Hong Kong, including Shanghai, South Korea, Thailand, Australia, France, Germany and New York City, have all introduced seismic –resistant design standards for new buildings.
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Seismic Design Code for Building in Japan
Seismic Design Code for Building was introduce for the first time in 1924 when the Urban Building Law was revised as a consequence of the 1923 Kanto great earthquake disaster. (Seismic coefficient =0.1)
In 1950, the Building Standard Law replaced the Urban Building Law. (Seismic coefficient =0.2)
The Seismic Design Code for Building was radically changed in 1981 in the largest revision since 1924.
The Seismic Capacity Evaluation Standards and Guidelines for Seismic Rehabilitation of RC Buildings were introduced in 1977 and revised in 1990 and 2001.
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Enhancing the Seismic Performance of Existing Buildings
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Ductility (F)
Lateral Load Capacity (C)
Strength Upgrading
Ductility Upgrading
Strength and Ductility Upgrading
Enhancing the Seismic Performance of Existing Buildings
Existing Building
Demand Seismic Performance
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Ductility (F)
Strength (C) Strength Upgrading
Ductility Upgrading
Strength and Ductility Upgrading
Strengthening Methods for Enhancing the Seismic Performance of Existing Buildings
Before Strengthening
Demand Seismic Performance For Retrofitting
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FYFE Japan Co., Ltd.
Str
eng
then
ing
Met
ho
ds
for
En
han
cin
g t
he
Sei
smic
Per
form
ance
of
Exi
stin
g B
uil
din
gs
Strength Upgrading Adding Wall
Infilling wall Adding wall for increasing thickness Infilling Opening Wing wall
Adding Steel with boundary Frame Steel framed brace Steel framed panel
Adding exterior steel frame Steel framed brace
Adding structural frame Core wall Mega Frame Buttress Exterior Frame
Others Shear wall with grid-shaped block Shear wall with precast panel Unbonded brace
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Strengthening Methods for Enhancing the Seismic Performance of Existing Buildings
Ductility Upgrading
RC jacketing With wire fabric With welded hoop
Steel jacketing With square steel tube With circular tube
FRP Wrapping
With Continuous fiber sheet With FRP shape
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Strengthening Methods for Enhancing the Seismic Performance of Existing Buildings
Prevention of Damage Concentration
Improvement of vibration property Reduction of eccentricity Improvement of stiffness irregularity Reduction of pounding risk at
expansion joint
Improvement of extreme brittle member Installing seismic slit Improvement of failure mode
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Strengthening Methods for Enhancing the Seismic Performance of Existing Buildings
Reduction of seismic forces Mass Reduction
Remove water tank on the building Remove roof concrete for water proofing Removing upper stories
Seismic isolation Base isolation at grade level Base isolation below grade level Mid-story isolation
Structural response control device Active mass damper (AMD) Tuned mass damper (TMD) Metallic damper Oil damper
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Strengthening Methods for Enhancing the Seismic Performance of Existing Buildings
Strengthening of foundation
Strengthening of foundation beam Strengthening of pile
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Strengthening Methods for Enhancing the Seismic Performance of Existing Buildings
Strength Upgrading
Ductility Upgrading
Tyfo® FIBRWRAP® Systems
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Infilling Wall
Steel Framed Brace (Internal)
Steel Framed Brace (External)
Buttress Beam
Strengthening Column
Strengthening
Shear Wall with Opening
Adding Seismic Slit
Str
eng
then
ing
Met
ho
ds
for
En
han
cin
g t
he
Sei
smic
Per
form
ance
of
Exi
stin
g B
uil
din
gs
Tyfo® FIBRWRAP® Systems
FYFE Japan Co., Ltd.
Enhancing the Seismic Performance of Existing Buildings by Adding Infilling Wall
Tyfo® FIBRWRAP® Systems
FYFE Japan Co., Ltd.
Enhancing the Seismic Performance of Existing Buildings by Steel Framed Brace
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Enhancing the Seismic Performance of Existing Buildings by Steel Framed Brace (External)
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Enhancing the Seismic Performance of Existing Buildings by Adding Buttress
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Enhancing the Seismic Performance of Existing Buildings by Adding Installing Seismic Slit
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Enhancing the Seismic Performance of Existing Buildings by Using Fiber Reinforced Polymers
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Enhancing the Seismic Performance of Existing Buildings by Dampers
Steel Damper Gum
Oil Damper
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Enhancing the Seismic Performance of Existing Buildings by Adding Shear walls with Grid-Shaped
Block
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Concept of Seismic Evaluation
The “Seismic Capacity Evaluation Standard” and “Guidelines for Seismic Rehabilitation of RC Buildings” are used in conjunction with the guidelines for seismic retrofitting of RC buildings.
The seismic capacity of the building is quantified by the seismic index Is. This index should be evaluated at each story and to each direction.
𝐼𝑠 = 𝐸𝑜 ∗ 𝑆𝐷 ∗ 𝑇 Where : 𝐸𝑜 = Basic Seismic Index of Structure. 𝑆𝐷 = Irregularity Index 𝑇 = Time Index ( to account for the degree of deterioration of the building)
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Concept of Seismic Capacity Evaluation
The Basic Seismic index of Structure 𝐸𝑜
The Eo index is a basic value that specifies the seismic performance of a building.
The Eo index is the criteria used for evaluating the seismic performance of a building based on the strength and ductility of the building.)
𝐸0 =𝑛+1
𝑛+𝑖 𝑓 𝐶, 𝐹
Where : C : is the strength index F : is the ductility index 𝑛+1
𝑛−𝑖 : is the shear-story modification factor
n : is the number of stories i: is the story being analyzed
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Concept of Seismic Capacity Evaluation
The Basic Seismic index of Structure 𝐸𝑜
Building A Many walls, considerably
strong but low in ductility
Building B Rigid-frame structure with less walls and not so strong but large in
ductility
Horizontal Displacement
Ho
rizo
nta
l F
orc
e Critical failure Point
Seismic response
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Concept of Seismic Capacity Evaluation
The Basic Seismic index of Structure 𝐸𝑜
The basic seismic index is a function of the strength index C, and the ductility index F.
Horizontal Displacement
Ho
rizo
nta
l F
orc
e a
b
c
𝐸𝑜 = 𝐸1
𝐸𝑜 = 𝐸2
𝐸𝑜 = 𝐸21 + 𝐸
22
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Concept of Seismic Capacity Evaluation
The Basic Seismic index of Structure 𝐸𝑜
Three level screening procedures are recommended to Estimate Is, which are dependable on the characteristics of the story to be analyzed.
• The first level screening procedures is the simplest, which used for stories with a large density of walls. The ultimate strength is estimated based on the concrete shear strength and cross section Area of the columns and walls
• The Second procedures requires the calculation of the ultimate strength capacity and ductility of columns and walls. The beams are usually assumed to be rigid. This procedure is used for “weak column-strong beam” frames
• The third procedures implies to calculate the ultimate capacity and ductility for the vertical members as well as beams. All the possible mechanisms of failure are taken into account.
For general concrete building ………. 𝐼𝑠 ≥ 0.6
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FRP for Seismic Strengthening of RC Buildings
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Advantages of Using FRP as Strengthening Material for Concrete Structure
Non destructive and easy to install
Much lighter system / High strength to weight ratio.
Does not require heavy or special equipment.
Can be used in space constrained areas.
Can incorporate different finishing coats.
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FRP Performance Characteristics
Increases bending strength of flexural elements.
Increases shear strength of beams columns and walls.
Increases vertical load capacity of columns.
Increases ductility under cyclic loading.
Does not corrode and can contain further corrosion.
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Strengthening Applications for Concrete Structure
Beam Strengthening Slab Strengthening
Wall Strengthening
Column Strengthening
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JBDPA Guidelines for Strengthening with FRP
The Japanese guidelines for seismic retrofitting of RC building with FRP materials (JBDPA, 1999 revised 2010) provide specification on the characteristics of the FRP materials used in Japan, their proper handling and installation.
Design and detailing recommendations are provided in the guidelines, which mainly target the shear strength of either columns or beams.
The guidelines are part of the “ Guidelines for Seismic Rehabilitation of RC Buildings” (JPDPA, 1977 1st revised 1990 2nd revised 2001), a comprehensive publication that documents different retrofitting methods utilized in Japan.
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JBDPA Guidelines for Strengthening with FRP
Materials
The JBDPA guidelines describe the properties of PAN-class high-strength carbon fiber sheets, and aramid fiber sheets. In its turn, aramid is sub-classified as aramid 1 and aramid 2.
Characteristic Carbon Fiber Aramid Fiber
3400 MPa Class Aramid 1 Aramid 2
Type of Fiber PAN-class High-Strength Homopolymer Copolymer
Tensile Strength 3400 MPa 2060 MPa 2350 MPa
Young Modulus 230 GPa 118 GPa 78 GPa
Weight 300 g/m2 623 g/m2 525 g/m2
The viscosity of the adhesive resins influences the efficiency of the strengthening work. Thus, If sagging is likely to occur, a resin of high viscosity is recommended. Also , if smooth impregnation in the fiber is required, a resin with low viscosity should be used.
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JBDPA Guidelines for Strengthening with FRP
Design Approaches for Strengthening of Columns
In order to determine the required amount of FRP strengthening, the Japanese guidelines provide expressions to calculate the flexural and shear strengths, and ductility index of RC members.
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Design Approaches for Strengthening of Columns
Ultimate Flexural Capacity of Columns
The ultimate flexural capacity of RC column is calculated from the following expressions.
For 𝑁𝑚𝑎𝑥≥ 𝑁 > 𝑁𝑏 :
𝑀𝑢 = 0.5𝑎𝑔𝜎𝑦𝑔1𝐷 + 0.024 1 + 𝑔1 3.6 − 𝑔1 𝑏𝐷2𝐹𝑐𝑁𝑚𝑎𝑥 −𝑁
𝑁𝑚𝑎𝑥 − 𝑁𝑏
For 𝑁𝑏 > N ≥ 0 :
𝑀𝑢 = 0.5𝑎𝑔𝜎𝑦𝑔1𝐷 + 0.5𝑁𝐷 1 −𝑁
𝑏𝐷𝐹𝑐
For 0 > 𝑁 ≥ 𝑁𝑚𝑖𝑛 :
𝑀𝑢 = 0.5𝑎𝑔𝜎𝑦𝑔1𝐷 + 0.5𝑁𝑔1𝐷
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Design Approaches for Strengthening of Columns
Ultimate Flexural Capacity of Columns
The ultimate flexural capacity of RC column is calculated from the following expressions.
For 𝑁𝑚𝑎𝑥≥ 𝑁 > 𝑁𝑏 :
𝑀𝑢 = 0.5𝑎𝑔𝜎𝑦𝑔1𝐷 + 0.024 1 + 𝑔1 3.6 − 𝑔1 𝑏𝐷2𝐹𝑐𝑁𝑚𝑎𝑥 −𝑁
𝑁𝑚𝑎𝑥 − 𝑁𝑏
𝑁𝑏 = 0.22 1 + 𝑔1 𝑏𝐷𝐹𝑐
Balanced Axial Force:
Ultimate Axial Force in compression:
𝑁𝑚𝑎𝑥 = 𝑏𝐷𝐹𝑐 + 𝑎𝑔𝜎𝑦
Where: N : Axial force in the column, 𝑎𝑔: overall area of the
longitudinal reinforcement of the column;𝑔1: Ratio of distance between the centers of longitudinal reinforcement in tension and compression to the column width; 𝑏, 𝐷: Dimensions of the column; 𝜎𝑦: specified yield
strength of the longitudinal reinforcement. 𝐹𝐶 : Compressive strength of concrete; ℎ0 = clear height of column;
Ultimate Axial Force in Tension:
𝑁𝑚𝑖𝑛 = −𝑎𝑔𝜎𝑦
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Design Approaches for Strengthening of Columns
Ultimate Flexural Capacity of Columns
The ultimate flexural capacity of RC column is calculated from the following expressions.
For 𝑁𝑏 > N ≥ 0 :
𝑀𝑢 = 0.5𝑎𝑔𝜎𝑦𝑔1𝐷 + 0.5𝑁𝐷 1 −𝑁
𝑏𝐷𝐹𝑐
𝑁𝑏 = 0.22 1 + 𝑔1 𝑏𝐷𝐹𝑐
Ultimate Axial Force in compression:
𝑁𝑚𝑎𝑥 = 𝑏𝐷𝐹𝑐 + 𝑎𝑔𝜎𝑦
Where: N : Axial force in the column, 𝑎𝑔: overall area of the
longitudinal reinforcement of the column;𝑔1: Ratio of distance between the centers of longitudinal reinforcement in tension and compression to the column width; 𝑏, 𝐷: Dimensions of the column; 𝜎𝑦: specified yield
strength of the longitudinal reinforcement. 𝐹𝐶 : Compressive strength of concrete; ℎ0 = clear height of column;
Ultimate Axial Force in Tension:
𝑁𝑚𝑖𝑛 = −𝑎𝑔𝜎𝑦
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Design Approaches for Strengthening of Columns
Ultimate Flexural Capacity of Columns
The ultimate flexural capacity of RC column is calculated from the following expressions.
For 0 > 𝑁 ≥ 𝑁𝑚𝑖𝑛 :
𝑀𝑢 = 0.5𝑎𝑔𝜎𝑦𝑔1𝐷 + 0.5𝑁𝑔1𝐷
𝑁𝑏 = 0.22 1 + 𝑔1 𝑏𝐷𝐹𝑐
Ultimate Axial Force in compression:
𝑁𝑚𝑎𝑥 = 𝑏𝐷𝐹𝑐 + 𝑎𝑔𝜎𝑦
Where: N : Axial force in the column, 𝑎𝑔: overall area of the
longitudinal reinforcement of the column;𝑔1: Ratio of distance between the centers of longitudinal reinforcement in tension and compression to the column width; 𝑏, 𝐷: Dimensions of the column; 𝜎𝑦: specified yield
strength of the longitudinal reinforcement. 𝐹𝐶 : Compressive strength of concrete; ℎ0 = clear height of column;
Ultimate Axial Force in Tension:
𝑁𝑚𝑖𝑛 = −𝑎𝑔𝜎𝑦
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Design Approaches for Strengthening of Columns
Ultimate Flexural Capacity of Columns
The shear force associated to the flexural capacity Mu can be computed as
𝑄𝑚𝑢 =𝛼𝑀𝑢ℎ0
α = experimental value which equal to 2
Validation of the equation for Flexural Strength of Columns
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Design Approaches for Strengthening of Columns
Ultimate Shear Capacity of Columns
The ultimate shear capacity of RC column is calculated from the following expressions.
𝑄𝑠𝑢 =0.053𝑝𝑡
0.2318 + 𝐹𝑐
𝑀𝑄𝑑 + 0.12
+ 0.85 𝑃𝑤 𝜎𝑤𝑦 + 0.1𝜎0 𝑏𝑗
Where: 𝜎0 : Axial Stress (No larger than 8 MPa), 𝑀 𝑄 : Shear span ; 𝑏: width of the column after strengthening; 𝑑: effective
depth (distance from the extreme compression fiber to centroid of longitudinal tension reinforcement); j: Distance between the tensile and compressive force resultants (j=0.8D), 𝑝𝑡 = Ratio of tensile reinforcement =𝑎𝑡 𝑏𝑑 % ; 𝐹𝐶 : Compressive strength of concrete; 𝑃𝑤𝑠= ratio od existing shear steel reinforcement to area of
contract surface = 𝑎𝑣 𝑏𝑑 (%); 𝑝𝑤𝑓= ratio of FRP reinforcement to area of contact surface =𝐴𝑟𝑒𝑎𝐹𝑅𝑃
𝑏𝐷(%);
𝜎𝑤𝑦𝑠: Specified yield strength of existing transversal reinforcement; 𝜎𝑓𝑑 = tensile strength for FRP for shear
design.
𝑝𝑤𝜎𝑤𝑦 = 𝑝𝑤𝑠𝜎𝑤𝑦𝑠 + 𝑝𝑤𝑓𝜎𝑓𝑑 ≤ 10 MPa
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Design Approaches for Strengthening of Columns
Ductility Factors and Ductility Index of Columns
The ductility index F is a function of the ductility factor μ, and can be
expressed by the following relationships obtained from a degrading tri-linear hysteresis model.
𝐹 = ∅ 2𝜇 − 1
∅ =1
0.75 1 + 0.05𝜇
𝜇 = 10𝑄𝑠𝑢
𝑄𝑚𝑢− 0.9 , where 1 ≤ 𝜇 ≤ 5
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Conclusions
In this presentation the following were introduced The concept for enhancing the seismic performance of existing building
Methods for strength and ductility upgrading of concrete structures The concept of Seismic Capacity Evaluation of RC building
FRP for Seismic Strengthening of RC buildings JBDPA Guidelines for strengthening with FRP
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Thank you