Concrete structures. Case studies

Transcript

1 Concrete structures Case studies PIETRO CROCE Department of Civil and Industrial Engineering Structural division University of Pisa Leonardo da Vinci Assessment of existing structures Project number: CZ/11/LLP-LdV/TOI/134005

2 An existing building requires structural reassessment when: its reliability is inadequate, also due to misuse or human errors; the structure is modified and/or enlarged; the category of use of the structure is improved and/or its design working life is increased; the structure has been damaged or deteriorated by environmental, chemical or biological, attack or by more general time dependent effects; the structure has been damaged by accidental loads, e.g. earthquake or explosion, or by settlements or by other unintentional events like impacts, vibrations, water losses and so on.

3 According to the flow charts reported in section 4, the investigation process involves the acquisition of all relevant information concerning: the original design and structural conception of the building, as well as the reference structural codes, if any; the sequence of structural modifications during its life, addition or demolition of structural parts and/or deep maintenance interventions; actual material properties; actual damage and/or crack patterns; required performance level.

4 CASE STUDY N. 1 STRENGTHENING OF R.C. COLUMNS

5 General view of the building Damaged columns

6 Corroded rebars Cracking of concrete cover

7 Building plan with indication of columns to be strengthened

8 Usually, two different techniques are used in the rehabilitation of damaged r.c. columns, according as FRP or steel is used as reinforcing material. In these cases two aspects must be considered in the choice of repair technique: the needs of a good confinement od the concrete, which can be assured by both techniques, and the efficiency of the reinforcement in transferring the stresses from the original column core, which carries the permanent loads, and the new parts, which can be obtained in a much more easy and reliable way using steel. In fact, while the additional steel reinforcement can be mechanically bonded to the existing concrete column using shear connectors, the FRP longitudinal reinforcement should relies on the surface grip between the adhesive agent and the concrete, which can fail due to peeling or delamination.

9 Strengthening of the column

10 concrete cover removal rust removal and passivation of the reinforcing bars

11 execution of holes in concrete necessary to allows the passage of connecting devices (threaded rods) positioning of transverse steel plates and of connecting devices using epoxy resin to anchor the rods and epoxy mortar to regularize the surface

12 positioning of the longitudinal reinforcement and of the end joints, devoted to connect the reinforcement to the foundation and to beams

13 positioning of the longitudinal reinforcement and of the end joints, devoted to connect the reinforcement to the foundation and to beams

14 welding of steel mesh to the steel execution of the additional epoxy mortar layer (s=50 mm)

15 execution of the additional epoxy mortar layer (s=50 mm) execution of the surface finish

16 CASE STUDY N. 2 EXECUTION OF ADDITIONAL STOREYS

17 General view of the existing building

18 +16,05 enlargment and execution of additional storeys +13,30 +13,30 +13,30 +10,30 +10,30 +10,30 micropiles columuns to be strengthened beams tyo be strengthened + 7,00 + 7,00 + 7,00 additional columns additional concrete slabs and walls existing columns new beeams + 3,70 +3,70 +3,70 existing beams additional floors existing floors a tratteggio le parti sezionate 0,00 + 0,15 + 0,30-1,55 Summary of the additions and of interventions needed to reassess the building (longitudinal cross section)

19 Type 6 Type 6 Type 7 Type 6 Type 7 Type 5 Type 6 NEW BEAM 400X750 Type 7 Type 7 Type 6 Type 6 Type 6 NEW BEAM 400X750 Type 6 Type 6 Type 6 Type 6 Type 6 Type 6 Type Type 6 new concrete slab s = 250 mm 800 Summary of the additions and of interventions needed to reassess the building (foundations)

20 / / / /60 New beam 300x / / /60 30/60 30/60 16/60 16/ /36 30/60 16/60 30/60 30/60 16/60 30/ /60 16/60 30/ /60 16/60 16/ / / /60 16/60 16/60 16/ Floor reinforcement s = 40 mm mesh. Ø8/200 Beam strengthening new shear walls Column strengthening new beams 300x450 Summary of the additions and of interventions needed to reassess the building (first floor)

21 Preliminary investigation phase

22 Hinged connection between the new and the existing column

23 Foundation enlargement

24 F SECTION F-F F Micropiles and shear wall

25 Beam reinforcement

26 Some picture during the execution

27 The building at the end of the works

28 CASE STUDY N. 3 REPAIR AND STRENGTHENING OF AN EARTHQUAKE DAMAGED BUILDING

29 Views of the existing building

30 SECOND FLOOR Via Enrico Berlinguer A B F37 F D C Fx A Plan of the 2nd floor B 8.00

31 7.35 ROAD LEVEL PORTICO Front view PORTICO Side view

32 Shear type collapse mechanism

33 Damages induced by the earthquake

34 Damages at the ends of the columns

35 Shear wall 1X new connecting beam shear wall 2X 8 38x shear wall 1Y PORTICO B new connecting beam Y 28 38x Shear wall 3X shear wall 3Y X 29 FIRST FLOOR PORTICO Shear wall 3Y Shear wall 4Y Shear walls system

36 ferri Ø12/20" ferri di ancoraggio Ø16/40" Pos. 6b 2 staffe Ø10/10" Pos. 5 ferri Ø10/10" Pos. 6b 2 staffe Ø10/10" E E 4 ferri Ø24 di ancoraggio 4 ferri Ø24 di ancoraggio Pos. 6b 2 staffe Ø10/15" Pos. 5 ferri Ø10/15" giunzione saldata 4+4 ferri Ø16 Pos. 6b 2 staffe Ø10/15" 4+4 ferri Ø16 Pos. 6b 2 staffe Ø10/10" Pos. 5 ferri Ø10/10" Pos. 6b 2 staffe Ø10/10" Pos. 6a 2 staffe Ø12/10" Pos. 5a ferri Ø12/10" Pos. 6a 2 staffe Ø12/10" 6 ferri Ø24 di ancoraggio 6 ferri Ø24 di ancoraggio Pos. 6a 2 staffe Ø12/15" Pos. 5a ferri Ø12/15" Pos. 6a 2 staffe Ø12/15" giunzione saldata 6+6 ferri Ø ferri Ø16 Pos. 6a 2 staffe Ø12/10" Pos. 5a ferri Ø12/10" ferri di ancoraggio Ø16/30" Pos. 6a 2 staffe Ø12/10" Pos. 6a 2 staffe Ø12/10" Pos. 5a ferri Ø12/10" 6 ferri Ø24 di ancoraggio giunzione saldata Pos. 6a 2 staffe Ø12/15" Pos. 5a ferri Ø12/15" 6+6 ferri Ø16 Pos. 6a 2 staffe Ø12/10" 6 ferri Ø24 di ancoraggio Pos. 6a 2 staffe Ø12/15" 6+6 ferri Ø16 Vertical section of a shear wall Pos. 6a 2 staffe Ø12/10" Pos. 5a ferri Ø12/10" Pos. 6a 2 staffe Ø12/10" 6 ferri Ø26 di ancoraggio Pos. 4 staffe Ø10/10" Pos. 6 2 staffe Ø10/10" Pos. 5 ferri Ø10/10" 6 ferri Ø26 di ancoraggio Pos. 6 2 staffe Ø10/10" ferri Ø26/10" di ancoraggio L= ferri Ø ferri Ø16 D Pos. 6 2 staffe Ø10/15" Pos. 5 ferri Ø10/15" Pos. 4 staffe Ø10/15" Pos. 6 2 staffe Ø10/15" D giunzione saldata Pos. 6 2 staffe Ø10/10" Pos. 5 ferri Ø10/10" Pos. 4 staffe Ø10/10" Pos. 6 2 staffe Ø10/10" Fondazione esistente ferri Ø16/40 SEZIONE D-D

37 Execution of the shear walls

38 Execution of the beam and column repairs

39 Execution of the connecting beams

40 Execution of the connecting beams

41 Imagination is much more important than knowledge (Albert Einstein) Thank you for your kind attention