Retrofitting methods

Transcription

1 Retrofitting methods EDCE: Civil and Environmental Engineering CIVIL Advanced Earthquake Engineering EDCE-EPFL-ENAC-SGC Content Strategies Weakening Steel bracing Reinforced concrete shear walls Jacketing Masonry reinforced by composites EDCE-EPFL-ENAC-SGC

2 Seismic retrofitting strategies In the plane strength-ductility EDCE-EPFL-ENAC-SGC 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 EDCE-EPFL-ENAC-SGC

3 Seismic retrofitting strategies Illustration: initial situation EDCE-EPFL-ENAC-SGC Seismic retrofitting strategies 1 st option: additional RC shear walls Increase in strength Increase of seismic forces and decrease of deformations EDCE-EPFL-ENAC-SGC

4 Seismic retrofitting strategies 2 nd option: columns jacketing Increase in ductility and strength Increase of damping and displacements EDCE-EPFL-ENAC-SGC Reinforcement not always optimal Mind the first intuition Increase of seismic demand (for constant ductility and damping) EDCE-EPFL-ENAC-SGC

5 Reinforcement not always optimal Seismic isolation of fireman building in Basel EDCE-EPFL-ENAC-SGC Reinforcement not always optimal Example: moment-resisting steel frame EDCE-EPFL-ENAC-SGC

6 Reinforcement not always optimal Beam weakening (dog bone) EDCE-EPFL-ENAC-SGC External steel bracing EDCE-EPFL-ENAC-SGC

7 Architectural challenge!! EDCE-EPFL-ENAC-SGC Physic building at ETH Zurich EDCE-EPFL-ENAC-SGC

8 Reinforced concrete shear walls Building in Fribourg EDCE-EPFL-ENAC-SGC Jacketing: deficient overlapping EDCE-EPFL-ENAC-SGC

9 Jacketing: RC bridge piles EDCE-EPFL-ENAC-SGC Steel jacketing: RC bridge pile Elliptic jacketing - rectangular pile EDCE-EPFL-ENAC-SGC

10 Jacketing: composites Easy to apply, light, resistant, durable EDCE-EPFL-ENAC-SGC Unreinforced masonry buildings Example in Yverdon EDCE-EPFL-ENAC-SGC

11 Masonry: conventional techniques Reinforced plaster mm mm mm Reinforced cement coating mm mm Anchor Ø 6mm Existing wall Welded mesh Ø 4-6mm Welded mesh Ø mm EDCE-EPFL-ENAC-SGC Masonry: conventional techniques Shotcrete EDCE-EPFL-ENAC-SGC

12 Masonry: conventional techniques Shotcrete: static-cyclic tests EDCE-EPFL-ENAC-SGC Masonry: conventional techniques External or internal post-tensioning EDCE-EPFL-ENAC-SGC

13 Composites: carbon fiber EDCE-EPFL-ENAC-SGC Dynamic tests EPFL-ETHZ EDCE-EPFL-ENAC-SGC

14 Experimental results EDCE-EPFL-ENAC-SGC Experimental results EDCE-EPFL-ENAC-SGC

15 Dynamic tests: test parameters Wall parameters 1. Aspect Ratio (0.7, 1.4) 2. Mortar Type Strengthening materials 3. Material Type (glass, carbon, and aramid) 4. Fiber Product (fabric, grid, and plates) 5. Upgrading Configurations EDCE-EPFL-ENAC-SGC Experimental results 32 kn 65 kn URM Long Specimen (L1-REFE) Upgraded Long Specimen (L1-WRAP-G-F) EDCE-EPFL-ENAC-SGC

16 Hysteresis curves: before and after Long URM (L1-REFE) Long Upgraded (L1-WRAP-G-F) Force at Wall Top ([kn) Horizontal Displacement (mm) EDCE-EPFL-ENAC-SGC Sample Hysteretic Behavior L2-GRID-G-F Test Run 19 UG1R 220% F [kn] [mm] EDCE-EPFL-ENAC-SGC

17 Different FRP products and configurations 1. Long Walls +Fabrics of Glass FRP +Grids of Glass FRP EDCE-EPFL-ENAC-SGC Different FRP products and configurations 2. Short Walls +Plates of Carbon FRP +Fabrics of Glass FRP EDCE-EPFL-ENAC-SGC

18 Failure Modes 1.Masonry Compression &Tearing of the FRP L2-GRID-G-F FRP Rupture EDCE-EPFL-ENAC-SGC L1-WRAP-G-F Compression Failure Failure Modes 3.Debonding and Anchorage Failure EDCE-EPFL-ENAC-SGC

19 Failure Modes No Failure Was Reached EDCE-EPFL-ENAC-SGC Masonry infill frames Truss model (FEMA 356) EDCE-EPFL-ENAC-SGC

20 Masonry infill frames Truss model (NZSEE 2002) EDCE-EPFL-ENAC-SGC Masonry infill frames Truss model (NZSEE 2002) potential column shear EDCE-EPFL-ENAC-SGC

21 Masonry infill frames Truss model (NZSEE 2002) potential column shear EDCE-EPFL-ENAC-SGC Masonry infill frames Truss model (NZSEE 2002) short column effect EDCE-EPFL-ENAC-SGC

22 Masonry infill frames Truss model (FEMA 356) opening considerations NZSEE: EDCE-EPFL-ENAC-SGC Lightly RC squat shear walls Static-cyclic tests (doct. thesis Greifenhagen) EDCE-EPFL-ENAC-SGC

23 Lightly RC squat shear walls Static-cyclic tests (doct. thesis Greifenhagen) ρ h ~ ρ v ~ EDCE-EPFL-ENAC-SGC Lightly RC squat shear walls Test program EDCE-EPFL-ENAC-SGC

24 Lightly RC squat shear walls Specimen reinforcement ρ h =0.28% ρ v =0.31% EDCE-EPFL-ENAC-SGC Lightly RC squat shear walls Specimens after failure M3 EDCE-EPFL-ENAC-SGC

25 Lightly RC squat shear walls Results (failure modes and crack pattern) sliding shear rebars failure sliding rocking wall M1 wall M2 concrete fail. diag. tension crushing rebars fail. wall M3 wall M4 EDCE-EPFL-ENAC-SGC Lightly RC squat shear walls Results (hysteretic curves) EDCE-EPFL-ENAC-SGC

26 Lightly RC squat shear walls Diagonal tension failure: specimen M3 LS65 LS67 Ultim. Crack pattern M3 LS69 EDCE-EPFL-ENAC-SGC 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: 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: %. Low to moderate ductile behavior is observed (5.6 < µ Δ < 8.0). Energy dissipation and stiffness Dissipated energy nearly is equal to 70 % of introduced energy. Stiffness decreases by 80 % up to µ Δ = 1.0 and by 95% up to failure. EDCE-EPFL-ENAC-SGC