FRP REINFORCEMENTS FOR STRENGTHENING MASONRY STRUCTURES

Transcription

1 UNIVERSITY OF SALENTO Department of Engineering for Innovation FRP REINFORCEMENTS FOR STRENGTHENING MASONRY STRUCTURES Termoli (Italy) - 14 th JULY 2008 Maria Antonietta AIELLO, Francesco MICELLI, Carla CONTE - Final Conference - Earthquake Engineering Presentation of the book Strategies for reduction of the seismic risk

2 INTRODUCTION Masonry Vaults Masonry Columns Bond Shear Strengthening

3 MASONRY VAULTS Object Monumental Building situated in the Historical Centre of Lecce Convento dei Carmelitani Scalzi Volta a spigolo leccese Edge Vault

4 MASONRY VAULTS Vulnerability Analysis 1 Level The entire structure has been analyzed in terms of vulnerability evaluation to seismic actions: a linear dynamic 3D analysis and a 3D non linear push-over analysis have been developed on a three-dimensional equivalent masonry frame approach. 2 Level The complex structural configuration, the large variety of materials and the relevant dimensions of the building have suggested to focus the attention firstly on sub-elements, the vaults, organizing a sophisticated 3D finite element analysis (F.E.A.) and dynamic tests.

5 MASONRY VAULTS Finite Element Analysis After the accurate geometric design has been created, a model of the edge vault has been implemented using the Finite Elements Code SAP2000 Advanced The masonry components, vault and boundary arches, were modelled by using 4-joints shell elements and 3-joints shell elements for transitions only, all with a thickness of 20 cm

6 MASONRY VAULTS Finite Element Analysis The presence of the adjacent vaults has been simulated with the introduction in the model of internal reactions. Separate modelling of a system of consecutive vaults, that reproduce the real architectural texture. The masonry piers have been modeled as fixed at the base section and their section has been realized using only external 4-joints shell elements with thickness of 50 cm.

7 MASONRY VAULTS Material Characterization The raw stone has been extracted from different locations of the building and has been processed to obtain stone samples with defined dimensions. Experimental Investigation MASONRY PROPERTIES Average value Density γ [kn/m 3 ] 16 Compressive strength f m [Mpa] 3,5 Normal secant elastic modulus E [Mpa] 3500

8 MASONRY VAULTS Modal Analysis Output From this Finite Element Analysis (FEA) the following preliminary results for the vaulting system have been obtained: Analytical modal shapes Mode Mode Natural Frequencies Mode Comparison with numerical and experimental tests Natural frequency (FEM) [Hz] Participating Mass [%] Natural Frequency (Test) [Hz] Scatter [%] % 4, % 4, % 5,47 36

9 MASONRY VAULTS Seismic Retrofit Sheets of unidirectional carbon fibers, 250 mm wide, bonded at the vaults extrados. The presence of areas with abrupt variations in curvature evidences a high degree of interface weakness as regard possible sheets de-bonding. A CFRP anchorage system has been proposed, comprising unidirectional CFRP rebars for a length of 150 mm.

10 MASONRY COLUMNS Ductilility demands in masonry columns! Forces Plastic energy Structural response

11 MASONRY COLUMNS FRP-confinement Confinement with FRP composites presents significant advantages with respect to traditional confinement techniques: the cross-sectional dimensions of the column do not increase; the mass of the column does not increase, which means that the seismic action on the building remains unchanged; the low weight of FRP materials implies that the installation procedure is faster, easier and less dangerous for the operator, if compared with traditional strengthening techniques.

12 MASONRY COLUMNS Confinement of masonry columns: steel vs FRP Unstrengthened CFRP-confined Steel-confined

13 MASONRY COLUMNS Confinement of masonry columns: steel vs FRP Load (kn) F2 F1 S-2 C1 C2 S1 FB C1- unconfined C2- unconfined S1- steel-confined S2- steel-confined F1- FRP sheet-confined FB- FRP sheet+bars -confined Displacement (mm)

14 MASONRY COLUMNS CFRP-confinement of circular masonry columns Unstrengthened Continuous CFRP sheet CFRP strips

15 MASONRY COLUMNS CFRP-confinement of circular masonry columns R-F R-F-2 C-I-2 Load (kn) R-T-1 R-T-2 CI-2 unconfined R-T continuous CFRP -confined R-F CFRP strips -confined Displacement (mm)

16 MASONRY COLUMNS GFRP-confinement of square masonry columns Unstrengthened Continuous CFRP sheet

17 Confinement of square masonry columns pb= 16 cm pb= 8 cm

18 MASONRY COLUMNS CFRP-confinement of square masonry columns 900 Load (kn) Only FRP rebars FRP rebars+sheet SFB-1 SFB-3 SFC-3 SFBF-1 SFB-2 SFC-1 SFC Displacement (mm)

19 MASONRY COLUMNS 800 pb= 8 cm +61% ,4% Load (KN) pb= 16 cm SF-B1-1 SF-B1-2 SF-B1-3 SF-C-1 0 SF-C-2 SF-C-3 SF-B2-1 SF-B Displacement (mm)

20 MASONRY COLUMNS FRP-confinement of HOLLOW-CORE square masonry columns Load (kn) SAC-2 SAB-1-1 HOLLOW CORE LIMESTONE COLUMNS Sheet+rebars 1 sheet SAF-1-1 rebars only SAFB-2 SAD-1-1 FRP strips 2 sheets SAF Displacement (mm)

21 MASONRY COLUMNS SPECIMENS AFTER TESTING

22 BOND BEHAVIOUR FRP-MASONRY STONES INTERFACE ANALYSIS OF EXISTING STRUCTURES EXPERIMENTAL INVESTIGATION ANALYZED PARAMETERS Substrate Reinforcement Types of test Bond length Specimen configuration and geometry Curved Surface STRENGTHENED WITH FRP MATERIALS Durability under specific environmental conditions

23 BOND BEHAVIOUR FRP-MASONRY STONES INTERFACE ANALYSIS OF EXISTING STRUCTURES STRENGTHENED WITH FRP MATERIALS EXPERIMENTAL INVESTIGATION ANALYZED PARAMETERS Substrate Reinforcement Types of test Bond length Specimen configuration and geometry Curved Surface Durability under specific environmental conditions Lecce stone Yellow Naples tuff Grey Naples tuff

24 BOND BEHAVIOUR FRP-MASONRY STONES INTERFACE ANALYSIS OF EXISTING STRUCTURES STRENGTHENED WITH FRP MATERIALS EXPERIMENTAL INVESTIGATION ANALYZED PARAMETERS Substrate Reinforcement Types of test Bond length Specimen configuration and geometry Curved Surface Durability under specific environmental conditions CFRP sheet GFRP sheet

25 BOND BEHAVIOUR FRP-MASONRY STONES INTERFACE ANALYSIS OF EXISTING STRUCTURES STRENGTHENED WITH FRP MATERIALS EXPERIMENTAL INVESTIGATION SINGLE FACE SHEAR TEST TEST SET-UP BEAM TEST DOUBLE FACE SHEAR TEST

26 BOND BEHAVIOUR FRP-MASONRY STONES INTERFACE ANALYSIS OF EXISTING STRUCTURES EXPERIMENTAL INVESTIGATION ANALYZED PARAMETERS Substrate Reinforcement Types of test Bond length Specimen configuration and geometry Curved Surface STRENGTHENED WITH FRP MATERIALS Durability under specific environmental conditions R750 R1000 R1500 R infinito

27 BOND BEHAVIOUR FRP-MASONRY STONES EXPERIMENTAL INVESTIGATION Curved Surface INTERFACE ANALYSIS OF EXISTING STRUCTURES STRENGTHENED WITH FRP MATERIALS Curvature Radius[cm] Fmax (kn) Average value (kn) COV% 27,18 23,68 32, , , , , , , , , ,99 27,68 15% 22,05 (-20%) 13% 19,23 (-30%) 5% 12,90 (-53%) 7%

28 BOND BEHAVIOUR FRP-MASONRY STONES INTERFACE ANALYSIS OF EXISTING STRUCTURES TEST OF WATER ABSORPTION STRENGTHENED WITH FRP MATERIALS MATERIALS: epoxy primer, epoxy putty, epoxy adhesive, CFRP, GFRP PROCEDURE: the specimens of the three epoxy resins and of both composites, were placed in a desiccator with silica gel at ambient temperature. They were periodically weighed. A constant weight was achieved after about 10 months. All the specimens were, then, immersed in distilled water at 23 C ± 2 C. EFFECT OF A THERMO-HYGROMETRIC HYGROMETRIC TREATMENT MATERIALS: epoxy primer, epoxy putty, epoxy adhesive, CFRP, GFRP PROCEDURE: 6 months in climatic chamber at 40 C and 90% R.H. (corresponding to warm climate achievable in Mediterranean regions)

29 BOND BEHAVIOUR FRP-MASONRY STONES DSC TEST: Tg TEST OF WATER ABSORPTION Primer placed in a dessiccator with silica gel at ambient temperature GIORNI DI IMM. (gg) 0 38 Tg ( C) 50,48 34,14 Hrilas 23,16 8,07 days σ max [MPa] ε% E [MPa] ν 72 33,26 10, , ,91 33,78 9,80 11, , ,12 4,06 Primer immersed in distilled water at 23 C ± 2 C days σ max [MPa] ε% E [MPa] ν TENSILE TEST , , , ,38

30 BOND BEHAVIOUR FRP-MASONRY STONES DSC TEST: Tg GIORNI DIIMM. (gg) Tg ( C) Hrilas TEST OF WATER ABSORPTION ,98 31,24 6,00 1,84 Putty placed in a dessiccator with silica gel at ambient temperature 73 29,85 1,53 days σ max [MPa] ε% E [MPa] ν ,65 2, , , , , , ,31 Putty immersed in distilled water at 23 C ± 2 C days σ max [MPa] ε% E [MPa] ν 2,25 11,29 TENSILE TEST , , , , , , , ,31

31 BOND BEHAVIOUR FRP-MASONRY STONES DSC TEST: Tg GIORNI DIIMM. (gg) Tg ( C) Hrilas TEST OF WATER ABSORPTION Adhesive placed in a dessiccator with silica gel at ambient temperature ,85 37,58 37,11 21,37 13,11 12,73 days σ max [MPa] ε% E [MPa] ν , , , , ,96 33,19 33,89 15,31 14,57 4,86 Adhesive immersed in distilled water at 23 C ± 2 C days σ max [MPa] ε% E [MPa] ν TENSILE TEST , , , , ,39

32 BOND BEHAVIOUR FRP-MASONRY STONES INTERFACE ANALYSIS OF EXISTING STRUCTURES TEST OF WATER ABSORPTION STRENGTHENED WITH FRP MATERIALS CFRP placed in a dessiccator with silica gel at ambient temperature days σ max [MPa] ε% E [MPa] , TENSILE TEST CFRP immersed in distilled water at 23 C ± 2 C days σ max [MPa] ε% E [MPa] , , , ,

33 BOND BEHAVIOUR FRP-MASONRY STONES INTERFACE ANALYSIS OF EXISTING STRUCTURES TEST OF WATER ABSORPTION STRENGTHENED WITH FRP MATERIALS GFRP placed in a dessiccator with silica gel at ambient temperature days σ max [MPa] ε% E [MPa] , TENSILE TEST GFRP immersed in distilled water at 23 C ± 2 C days σ max [MPa] ε% E [MPa] , , , , ,

34 BOND BEHAVIOUR FRP-MASONRY STONES INTERFACE ANALYSIS OF EXISTING STRUCTURES STRENGTHENED WITH FRP MATERIALS EFFECT OF WATER - Bond Strength Fu [kn] Standard campione 50 testati daysdopo 50gg campione 176 testati daysdopo 176gg di immersione di immersione

35 BOND BEHAVIOUR FRP-MASONRY STONES INTERFACE ANALYSIS OF EXISTING STRUCTURES STRENGTHENED WITH FRP MATERIALS EFFECT OF WATER Effective Bond Length transfer length [mm] Standard campione 50 testati daysdopo 50gg campione 176 testati days dopo 176gg di immersione di immersione

36 BOND BEHAVIOUR FRP-MASONRY STONES INTERFACE ANALYSIS OF EXISTING STRUCTURES STRENGTHENED WITH FRP MATERIALS EFFECT OF A THERMO-HYGROMETRIC HYGROMETRIC TREATMENT Condizioni standard 40 C and 90% R.H CFRP 3846 (cov. 12%) 3524 (cov. 11%) =-8% GFRP 1769 (cov. 5%) 1346 (cov. 18%) Tensile strength [MPa] Epoxy Primer 49 (cov. 5%) Epoxy Putty 18 (cov. 4%) 21 (cov. 12%) Epoxy Adhesive 44 (cov. 11%) 12 (cov. 19%)

37 BOND BEHAVIOUR FRP-MASONRY STONES INTERFACE ANALYSIS OF EXISTING STRUCTURES STRENGTHENED WITH FRP MATERIALS EFFECT OF A THERMO-HYGROMETRIC HYGROMETRIC TREATMENT Condizioni standard 40 C and 90% R.H CFRP 3846 (cov. 12%) 3524 (cov. 11%) Tensile strength [MPa] GFRP Epoxy Primer 1769 (cov. 5%) 49 (cov. 5%) 1346 (cov. 18%) =-24% Epoxy Putty 18 (cov. 4%) 21 (cov. 12%) Epoxy Adhesive 44 (cov. 11%) 12 (cov. 19%)

38 BOND BEHAVIOUR FRP-MASONRY STONES INTERFACE ANALYSIS OF EXISTING STRUCTURES STRENGTHENED WITH FRP MATERIALS EFFECT OF A THERMO-HYGROMETRIC HYGROMETRIC TREATMENT Tensile strength [MPa] CFRP GFRP Epoxy Primer Epoxy Putty Epoxy Adhesive Condizioni standard 3846 (cov. 12%) 1769 (cov. 5%) 49 (cov. 5%) 18 (cov. 4%) 44 (cov. 11%) 40 C and 90% R.H 3524 (cov. 11%) 1346 (cov. 18%) 21 (cov. 12%) 12 (cov. 19%)

39 BOND BEHAVIOUR FRP-MASONRY STONES INTERFACE ANALYSIS OF EXISTING STRUCTURES STRENGTHENED WITH FRP MATERIALS EFFECT OF A THERMO-HYGROMETRIC HYGROMETRIC TREATMENT Condizioni standard 40 C and 90% R.H CFRP 3846 (cov. 12%) 3524 (cov. 11%) GFRP 1769 (cov. 5%) 1346 (cov. 18%) Tensile strength [MPa] Epoxy Primer 49 (cov. 5%) Epoxy Putty 18 (cov. 4%) 21 (cov. 12%) =+17% Epoxy Adhesive 44 (cov. 11%) 12 (cov. 19%)

40 BOND BEHAVIOUR FRP-MASONRY STONES INTERFACE ANALYSIS OF EXISTING STRUCTURES STRENGTHENED WITH FRP MATERIALS EFFECT OF A THERMO-HYGROMETRIC HYGROMETRIC TREATMENT Condizioni standard 40 C and 90% R.H CFRP 3846 (cov. 12%) 3524 (cov. 11%) GFRP 1769 (cov. 5%) 1346 (cov. 18%) Tensile strength [MPa] Epoxy Primer 49 (cov. 5%) Epoxy Putty 18 (cov. 4%) 21 (cov. 12%) Epoxy Adhesive 44 (cov. 11%) 12 (cov. 19%) =-73%

41 BOND BEHAVIOUR FRP-MASONRY STONES INTERFACE ANALYSIS OF EXISTING STRUCTURES STRENGTHENED WITH FRP MATERIALS EFFECT OF A THERMO-HYGROMETRIC HYGROMETRIC TREATMENT bond stress (MPa) unconditioned specimens conditioned specimens

42 BOND BEHAVIOUR FRP-MASONRY STONES INTERFACE ANALYSIS OF EXISTING STRUCTURES STRENGTHENED WITH FRP MATERIALS EFFECT OF A THERMO-HYGROMETRIC HYGROMETRIC TREATMENT Unconditioned specimens Conditioned specimens

43 SHEAR STRENGTHENING OF MASONRY PANELS

44 SHEAR STRENGTHENING OF MASONRY PANELS 60 cm 63 cm

45 SHEAR STRENGTHENING OF MASONRY PANELS TEST SETUP

46 SHEAR STRENGTHENING OF MASONRY PANELS Masonry panels with stone connectors Panel PNR_1 PNR_2 PRD_1 PRD_2 PRD_3 PR#_1 Reinforcing scheme Unreinforced Unreinforced Diagonal strips Diagonal strips Diagonal strips FRP grid Ultimate Load (kn) 11,8 12,8 37,5 44,6 37,3 57,3 224% Panel PNR_1 PNR_2 PRD_1 PRD_2 PRD_3 Reinforcing scheme Unreinforced Unreinforced Diagonal strips Diagonal strips Diagonal strips Ultimate Load (kn) 11,8 12,8 37,5 44,6 37,3 Panel Masonry panels with FRP connectors Reinforcing scheme Ultimate Load (kn) PR#_2 PR#_3 FRP grid FRP grid 60,1 43,2 335% PNRS_1 Unreinforced 32,1 PNRS_2 Unreinforced 33, % PRDS_1 Diagonal strips 76,8 + 88% PRDS_2 Diagonal strips 67,2 PRDS_3 Diagonal strips 80,1

47 UNIVERSITY OF SALENTO Department of Engineering for Innovation FRP REINFORCEMENTS FOR STRENGTHENING MASONRY STRUCTURES Termoli (Italy) - 14 th JULY 2008 Maria Antonietta AIELLO, Francesco MICELLI, Carla CONTE - Final Conference - Earthquake Engineering Presentation of the book Strategies for reduction of the seismic risk