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CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -1-
EDCE: Civil and Environmental Engineering CIVIL 706 - Advanced Earthquake Engineering
Retrofitting methods
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -2-
Content
• Strategies
• Weakening
• Steel bracing
• Reinforced concrete shear walls
• Jacketing
• Masonry reinforced by composites
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -3-
Seismic retrofitting strategies
• In the plane strength-ductility
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -4-
Seismic retrofitting techniques
Passive – Additional new lateral bracing system
! Reinforced concrete shear walls ! Steel bracing
– Seismic improvement of elements (columns or shear walls) of the existing structure
! By jacketing (concrete, steel, composites …) ! By composite strips ! By additional post-tensioning
Semi-active
– Seismic isolation – Additional energy dissipation devices
! By friction ! By liquid mass
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -5-
Seismic retrofitting strategies
• Illustration: initial situation
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -6-
Seismic retrofitting strategies
• 1st option: additional RC shear walls
Increase in strength Increase of seismic forces and
decrease of deformations
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -7-
Seismic retrofitting strategies
• 2nd option: columns jacketing
Increase in ductility and strength Increase of damping and
displacements
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -8-
Reinforcement not always optimal
• Mind the first intuition
Increase of seismic demand (for constant ductility and damping)
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -9-
Reinforcement not always optimal
• Seismic isolation of fireman building in Basel
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -10-
Reinforcement not always optimal
• Example: moment-resisting steel frame
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -11-
Reinforcement not always optimal
• Beam weakening (dog bone)
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -12-
External steel bracing
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -13-
Architectural … challenge !!
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -14-
Physic building at ETH Zurich
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -15-
Reinforced concrete shear walls
• Building in Fribourg
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -16-
Jacketing: deficient overlapping
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -17-
Jacketing: RC bridge piles
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -18-
Steel jacketing: RC bridge pile
• Elliptic jacketing - rectangular pile
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -19-
Jacketing: composites
• Easy to apply, light, resistant, durable …
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -20-
Unreinforced masonry buildings
• Example in Yverdon
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -21-
Masonry: conventional techniques
• Reinforced plaster
Anchor Ø 6mm
Welded mesh Ø 4-6mm@150 - 200 mm
Existing wall
Reinforced cement coating
Welded mesh Ø 4-6mm
250-400 mm
25-30 mm250-400 mm
250-400 mm
25-30 mm
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -22-
Masonry: conventional techniques
• Shotcrete
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -23-
Masonry: conventional techniques
• Shotcrete: static-cyclic tests
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -24-
Masonry: conventional techniques
• External or internal post-tensioning
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -25-
Composites: carbon fiber
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -26-
Dynamic tests EPFL-ETHZ
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -27-
Experimental results
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -28-
Experimental results
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -29-
Dynamic tests: test parameters
1. Aspect Ratio (0.7, 1.4) 2. Mortar Type
3. Material Type (glass, carbon, and aramid) 4. Fiber Product (fabric, grid, and plates) 5. Upgrading Configurations
Wall parameters
Strengthening materials
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -30-
Experimental results
URM Long Specimen (L1-REFE)
32 kN
Upgraded Long Specimen (L1-WRAP-G-F)
65 kN
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -31-
-20
Long URM (L1-REFE)
Long Upgraded (L1-WRAP-G-F)
Horizontal Displacement (mm)
Forc
e at
Wal
l Top
([k
N)
-80
-60
-40
20
40
60
-20 -15 -10 -5 5 10 15 200
0
Hysteresis curves: before and after
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -32-
Sample Hysteretic Behavior
∆ [mm]
-70
-60
-50
-40
-30
-20
-10
0
10
20
30
40
50
60
70
-20 -15 -10 -5 0 5 10 15 20
F [k
N]
L2-GRID-G-FTest Run 19UG1R 220%
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -33-
Different FRP products and configurations
1. Long Walls
+Fabrics of
Glass FRP
+Grids of
Glass FRP
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -34-
+Plates of
Carbon FRP
2. Short Walls
+Fabrics of Glass FRP
Different FRP products and configurations
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -35-
L2-GRID-G-F L1-WRAP-G-F Compression Failure FRP Rupture
Failure Modes 1.Masonry Compression &Tearing of the FRP
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -36-
Failure Modes 3.Debonding and Anchorage Failure
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -37-
Failure Modes No Failure Was Reached
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -38-
Masonry infill frames
• Truss model (FEMA 356)
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -39-
Masonry infill frames
• Truss model (NZSEE 2002)
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -40-
Masonry infill frames
• Truss model (NZSEE 2002) potential column shear
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -41-
Masonry infill frames
• Truss model (NZSEE 2002) potential column shear
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -42-
Masonry infill frames
• Truss model (NZSEE 2002) short column effect
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -43-
Masonry infill frames
• Truss model (FEMA 356) opening considerations NZSEE:
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -44-
Lightly RC squat shear walls
• Static-cyclic tests (doct. thesis Greifenhagen)
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -45-
Lightly RC squat shear walls
• Static-cyclic tests (doct. thesis Greifenhagen)
ρh ~ 0.003
ρv ~ 0.003
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -46-
Lightly RC squat shear walls
• Test program
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -47-
Lightly RC squat shear walls
• Specimen reinforcement
ρh=0.28%
ρv=0.31%
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -48-
Lightly RC squat shear walls
• Specimens after failure
M3
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -49-
Lightly RC squat shear walls
• Results (failure modes and crack pattern) sliding shear sliding rebars failure rocking concrete fail. crushing diag. tension rebars fail.
wall M3 wall M4
wall M2 wall M1
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -50-
Lightly RC squat shear walls
• Results (hysteretic curves)
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -51-
Lightly RC squat shear walls
• Diagonal tension failure: specimen M3
Ultim.
LS67
LS65
LS69 Crack pattern M3
CIVIL 706 - Retrofitting methods EDCE-EPFL-ENAC-SGC 2016 -52-
Lightly RC squat shear walls
• Summary of test results Shear capacity • Brittle shear failure is not observed. • Tests provide evidence for inherent shear strength of concrete. • Peak shear stress: 1.4 .. 1.9 N/mm^2 • Dimensionless shear capacity: 0.28 < c < 0.52 Deformation capacity • Negative effect of lacking horizontal reinforcement not evidenced. • Flexural deformation dominates the plastic response. • Observed drifts: 0.90 .. 2.20%. • Low to moderate ductile behavior is observed (5.6 < µΔ < 8.0). Energy dissipation and stiffness • Dissipated energy nearly is equal to 70 % of introduced energy. • Stiffness decreases by 80 % up to µΔ = 1.0 and by 95% up to failure.