Innovative Retrofit of Concrete and Masonry Buildings

Transcription

1 Innovative Retrofit of Concrete and Masonry Buildings Murat Saatcioglu, PhD., P.Eng. Distinguished University Professor and University Research Chair Department of Civil Engineering University of Ottawa Ottawa CANADA

2 Seismic Retrofit Strategy? Retrofit individual non-ductile elements for improved strength and deformability (jacketing, surface-bonded FRP etc.). System level retrofit for structural bracing and lateral drift control (bracing by added shear walls, steel braces, active control, supplementary damping devices etc.)

3 Deficiencies in Concrete Columns Shear Deficiency Kobe Earthquake 1995 Chi Chi Earthquake 1999

4 Deficiencies in Concrete Columns Lack of Confinement Nortridge 1994 San Fernando 1971

5 Deficiencies in Concrete Columns Splice Deficiency

6 FRP Wrapping of Columns

7 Lightly Loaded Square Bridge Column (P = 0.15P o ) Moment, M (kn-m) BR-SS-R BR-SS-R Short Short Square Square Column Column L L = = 1500 mm Continuous bars 33 CFRP plies (wrapping) Axial Load = 1160 kn (15% P 0 ) P = 1160 kn (15% Po) L F P -600 M h = 500 mm M=FL+P % -6% -4% -2% 0% 2% 4% 6% 8% Drift Ratio

8 Heavily Loaded Square Building Column (P = 0.35P o ) Moment (kn.m) Lateral Drift (%) RS Displacement Ductility (m D )

9 FRP Design The Canadian Standards Association CSA S806 Design and Construction of Building Structures with Fibre-Reinforced Polymers has design provisions.

10 Comparisons with Experimental Data

11 External Prestressing (RetroBelt) Hardware required

12 Installation on a Circular Column

13 Installation on a Square Column

14 Shotcrete Cover

15 Shear Deficient Column Drift (%) F D P L M BR-S1 12 # 25 Bars # mm Lateral Displacement (mm)

16 Retrofitted Shear Deficient Column Drift (%) F L D P M BR-S2 Ext. Prestressed to 25% of ultimate with a spacing of 150 mm Lateral Displacement (mm)

17 Confinement Deficient Column Drift (%) L = 2000 mm P = 15% P o Moment, M (kn m) BR-C6 F L P -600 M = FL + PD D Lateral Displacement, D (mm)

18 Retrofitted for Confinement Drift (%) L = 2000 mm P = 15% P o Moment, M (kn m) BR-C7 F L P -600 M = FL + PD D Lateral Displacement, D (mm)

19 Moment, M (kn m) Splice Deficient Column % -8% -6% -4% -2% 0% 2% 4% 6% 8% 10% Drift Ratio End of test (5% Drift)

20 Moment, M (kn m) Retrofitted Splice-Deficient Column % -8% -6% -4% -2% 0% 2% 4% 6% 8% 10% Drift Ratio After the test (10% Drift)

21 Use of High Strength Packaging Straps for Transverse Prestressing Pneumatic Tensioner Pneumatic Sealer Seal

22 Use of High Strength Packaging Straps for Transverse Prestressing Precast concrete raiser units were manufactured to complete square and rectangular sections to circular and elliptical shapes,

23 Use of High Strength Packaging Straps for Transverse Prestressing

24 Use of High Strength Packaging Straps for Transverse Prestressing Flexure-dominant circular column Shear-dominant square column

25 Non-ductile R/C Frames A large number of reinforced concrete frame structures, with or without masonry infill walls, are seismically deficient. They were either designed prior to the enactment of modern seismic codes, or built in areas where code enforcement poses challenges.

26 Bracing by Diagonal Prestressing

27 Bracing by Diagonal Prestressing Unretrofitted capacity : 270 kn 250 kn

28 Buckling Restrained Brace (BRB) for R/C Frames

29 Masonry Infill Walls

30 Retrofitted Frame with Infill Wall Fiber anchor, inserted into hole in column with epoxy Strip width: 2 feet

31 FRP Anchors Wooden guides Anchors FRP anchors in place Predrilled holes

32 FRP Anchors

33 Force-Displacement Hysteretic Relationship Retrofitted Specimen (-3%) (-2%) (-1%) Force, kn (1%) (2%) Displacement, mm (Drift) BL-2 Retrofitted Unretrofitted (3%)

34 Retrofit with Diagonal FRP Strips

35 Force-Displacement Hysteretic Relationship Retrofitted Specimen (-3%) (-2%) (-1%) Force, kn (1%) (2%) Displacement, mm (Drift) BL-3 Retrofitted Unretrofitted (3%)

36 Retrofitting by Diagonal Prestressing Reference specimen, reflecting as built conditions Retrofitted specimen, diagonally prestressed to 30% of ultimate on both sides

37 Force-Displacement Hysteretic Relationship Retrofitted Unretrofitted BR-2 (-4%) (-3%) (-2%) (-1%) (1%) (2%) (3%) (4%) Displacement, mm (Drift)

38 Retrofitting Walls with Steel Strips Reinforced Concrete Walls Unreinforced Masonry Walls Reinforced Masonry Walls

39 Seismically Deficient Reinforced Concrete Wall

40 Reinforced Concrete Wall Without Retrofit With Retrofit

41 Unreinforced Masonry Wall Without Retrofit With Retrofit

42 Reinforced Masonry Wall Without Retrofit With Retrofit

43 PRM Wall FRP Retrofit with FRP Anchors

44 PRM Wall FRP Retrofit with FRP Anchors FRP Anchors Rounding of FRP

45 PRM Wall FRP Retrofit with FRP Anchors

46 PRM Wall FRP Retrofit with FRP Anchors Unretrofitted Wall Envelop

47 URM Walls FRP Retrofit with Ductile Steel Sheet Anchors

48 URM Walls FRP Retrofit with Ductile Steel Sheet Anchors Stainless steel developed 60% elongation prior to tensile rupture

49 URM Walls FRP Retrofit with Ductile Steel Sheet Anchors Foundation concrete was cut FRP anchors were placed and epoxy glued. They were also bolted to delay buckling

50 URM Wall FRP Retrofit with Ductile Steel Sheet Anchors

51 URM Wall FRP Retrofit with Ductile Steel Sheet Anchors Unretrofitted capacity : 55 kn

52 Thank You Questions and Comments?