REPAIR AND STRENGTHENING OF REINFORCED CONCRETE COLUMNS AND BEAMS ICRI – International Concrete...

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REPAIR AND STRENGTHENING OF REPAIR AND STRENGTHENING OF REINFORCED CONCRETE REINFORCED CONCRETE

COLUMNS AND BEAMSCOLUMNS AND BEAMS

ICRI – International Concrete Repair Institute

Transportation Structures

2010 Fall Convention

Pittsburgh October 20-22

2/83ICRI 2010 – Pittsburgh October 20-22

UHPFRCC

Ultra High Performance Fiber Reinforced Cementitious Composites

-UHPC – Ultra - High Performance Concrete -HPFRCC – High Performance Fiber Reinforced Cementitious Composites -ECC – Engineered Cementitious Composites -HPECCMF – High Performance Engineered Cementitious Composites Multiple Fine Cracks

UHPFRCC

Jacketing

Tensile tests according Italian Standard

0 1 2 3 4 5

S tra in [‰ ]

0123456789

1 0111 21 3

a]L = 330 mm

t = 13 mm

bp = 30 mmt

Characterization in tension – stress deformation

Adhesion tests

GF5 Ordinary concrete

Preparation of the support

Strengthening of columns

Existing column

fc=15MPa

Existing column

-500 -250 0 250 500 750 1000 1250 1500 1750 2000

M [kNm]

Strengthened column

UHPFRC fc=170MPa

fct=11MPa

Stress distributions

-1000 0 1000 2000 3000 4000 5000 6000 7000 8000

M [kNm]

N[kN]un-reinf

Strengthened column

Traditional jacketing

-1500 -500 500 1500 2500 3500 4500 5500

M [kNm]

un-reinf

fc=30MPa

-1000 -500 0 500 1000 1500 2000 2500

M [kNm]

un-reinf

FRP_LT

Strengthening with FRP

Comparison

-1500 -500 500 1500 2500 3500 4500 5500 6500 7500 8500

M [kNm]

FRP_LT

un-reinf

Seismic retrofitting

School building in Zagarolo

In situ tests fc=11MPa

Strengthening with GF5 UHPFRCC

UHPFRCC130MPa

Column tests

Load history

Drift [%]0-7 -6 -5 -4 -3 -2 -1 1 2 3 4 5 6 7

-140 -120 -100 -80 -60 -40 -20 0 20 40 60 80 100 120 140Displacement [mm]

Results

Numerical prediction

Joint tests

Load history

Jobsite application

FASE 4:realizzazione della seconda parte di cassero

fino all'estradosso del solaio esistente

cassero ancorato sul precedente getto di Refor-tec GF5 ST-HS

solaio

carotaggi

staffature di rinforzoin acciaio

DETTAGLIO A

Jobsite application

forotavola chiodata

per evitare la fuoriuscitadi materiale

Jobsite application

Beam strengthening

HPFRCC

Jacketing

3 BEAMS: ASR, BCR, ACR (300x500x4550 mm)

ASR: RC beam with 2 rebars having a 16mm diameter 0.3%)

BCR: concrete beam without rebars + jacketing in HPFRCC

ACR: RC beam ( 0.3%) + jacketing in HPFRCC

Experimental program

0 20 40 60 80D isp lacem ent [m m ]

500 Load [kN ]

Results

0 4 8 12 16 20D isp lacem ent [m m ]

300 Load [kN ]

Sandblasting of the beams

Jobsite application

Waterjetting

The pouring

Jobsite application

Thixotropic UHPFRCC application

Jobsite application

Protection of material with a thermal jacket

Jobsite application

First example of application:

PROJECT OF SEISMIC ADJUSTMENT OF THE “HOSPITAL COTUGNO” OF BARI

Object:Hospital Cotugno

Place:Bari

Repair:Seismic rehabilitationReinforcement of beam and pot floor with a cooperating cover layer

Quantity:22’000 m2 (15 mm)

Material:Micro-concrete fiber-reinforcedHPFRCC

The other Jobsite applications

PROBLEMNECESSITY OF SEISMIC RETROFITTING OF THE STRUCTURE

The project foresees the realisation of RC shear walls destinated to resist the horizontal seismic actions

PROBLEM: TRASFER OF THE STRESSES OF THE FLOOR TO THE SHEAR WALLS; THE EXISTING FLOOR, WITH A STRUCTURALLY COOPERATING TOP DECK OF 2 cm, WAS NOT ABLE TO FULLFILL THIS FUNCTION

SOLUTION

TO OBTAIN THE DIAPHRAGM EFFECT HAS BEEN INSTALLED ON THE TOPPING OF THE FLOOR A STRUCTURAL COOPERATIVE DECK WITH LOW THIKCNESS (15 mm) IN FIBRE-REINFORCED CONCRETE WITH VERY HIGH MECHANICAL PERFORMANCE, FORMULATED AD-HOC BASED ON THE STRUCTURAL REQUIREMENTS

APPLICATION 1. VERIFICATION OF THE ADHESION TO SUBSTRATE

APPLICATION OF SAMPLE IN JOBSITE TO VERIFY THE ADHESION OF THE PRODUCT TO THE SUBSTRATE IN

THAT SITUATION:

• CONNECTORS WITH STUBS IN REFOR-tec® GF5/ST HS, OBTAINED THROUGH SIMPLE DRILLING

• METAL CONNECTORS (DRILLING + FISCHER)

• NO CONNECTORS- ONLY SANDBLASTING AND WATERJETTING

• NO CONNECTORS – ONLY WATERGETTING

THE CURING PERIOD COMPLETED, MEASUREMENTS DEMONSTRATE THE ADHESION TO THE SUBSTRATE :

OPTIMAL ADHESION OF THE REINFORCING COVERLAYER REFOR-tec® GF5/ST HS EVEN WITHOUT CONNECTOR SYSTEM,

ONLY AFTER ADEQUATE SURFACE PREPARATION

APPLICATION OF THE MATERIAL

LIGHT TAMPERING

IMMEDIATE APPLICATION OF CURING COMPOUND UR 20

DETAIL OF THE APPLICATION – RETAKING OF THE FLOORS

TESTING-CONTROLLING THE ADHESION TO THE SUBSTRATE

RESULTTHE APPLICATION OF SEVERAL THOUSEND SQUARE METERS

WITHOUT CUTTING JOINTS AND WITHOUT ANY CRACKING.

PERFECT ADHESION OF THE MATERIAL TO THE SUBSTRATE

ADVANTAGES IN RESPECT WITH A TRADITIONAL CONCRETE COOPERATIVE DECK

1. Low application thickness (15-20 mm )

2. Adhesion the substrate without necessity for connectors or resins

3. No reinforcement nets

4. Very high ductility and resistance to cyclic load

5. Increase of the bearing capacity in terms of bending moment and stiffness and a reduction of the deflection of the floor

6. Speed of application thanks to self-levelling material properties

Limited increase of load

Repair after fire

Beams residual properties

4 Ø 16mm

Felicetti & Meda (2005)

Concrete

Eurocode 2

Thermal analysis

ISO 834

Analytical model

Coccia & Rinaldi 2006

steel concrete

N h Ast

0 60 120 180

Fire duration [m in]0

300 M om ent [kN m ]

Beams residual properties

Beams repair

0 60 120 180

F ire duration [m in]0

0 250 500 750 1000

Temperature [C]0

T/fct20

HPFRCC

0 250 500 750 1000 1250

Tem perature [°C ]0

4Therm al conductiv ity [W m /K ]

HPFRCEC2

Mindeguia et al. (2007)

950°C

De Chefdebien et al. (2007)

HPFRC thermal properties

Fire resistance of the repaired beam

0 60 120 180

Fire duration [m in]0

0 60 120 180

F ire duration [m in]0

400 M om ent [kN m ] In itia l dam age60'

Fire resistance of the repaired beam

Column residual properties

Column repair

Initial damage 90′ - new fire 90′

Initial damage 180′ - new fire 180′

Seismic retrofitting ofshear walls

Reference model: stair block element of an

existing three storey building

Experimental model:

1:3 scaled R/C wall

Experimental test

t =15mm

Proportioned to resist

vertical loads only

Proportioned to resist seismic loads

aggregate dmax=15mm

F5/70mm longit. rebars

F4/100mm stirrups

Experimental test

0 0.04 0.08 0.12 0.16 0.2

Stra in0

1500 Stress [M Pa]

L / LF / A

High strength,

waved steel mesh made

of bent wires

Tensile test on steel mesh single wire

High performance steel mesh

0 10 20 30

D isp lacem ent [m m ]0

20 Load [kN ]

W ithout concrete

10m m th ick concrete

20m m th ick concrete

Specimen A

Specimen B

high performancefiber concrete

high strength steel meshwith bent wires

1 1 Section 1-1

bare high

strength

steel mesh

High performance jacket

I phase:R/C wall sandblast

Wall sandblast

II phase:Positioning ofthe steel mesh

Application of the steel mesh

II phase:Positioning of

the steel mesh

III phase:15 mm HPC

jacket casting

Jacket casting

50 100 150

Top d isplacem ent [m m ]

100 Load [kN ]

-150 -100 -50

-80 -30 20 70 120

top displacement [mm]

with jacket - experimental

envelope curve

drift 3.6%u/y = 9

y= 12mm; u= 109mm)

Results

Deformed shear wall at collapse Deformed shear wall at collapse

drift = 3.5%

Results

Fiber element

base section

fiberelement

FE model

fibersection

Existing R/C wall

Strengthened R/C wall

(Spacone et al. 1996)

FE analysis

FE analysis: results

-80 -30 20 70 120

top displacement [mm]

with jacket - experimental

with jacket - numeric

unreinforced - numeric

Conclusions

- The proposed technique allow a significant increase of the bearing capacity in terms of bending moment, axial force and stifness of pillars and beams

- A simple sandblasting has ensured the perfect bond between the base concrete material and the strengthening UHPFRCC layer;

- The strengthening has provided a remarkable increase of stiffness of beams and floors; as a consequence, the midspan displacement at serviceability limit state has been reduced of about 12 times; This behaviour is comparable to the application of a prestressing load;

- The small thickness of the jacket does not change significantly the elements geometry

- Increase of thermal and static resistance of structural elements after the fire

-The jacket enhance the durability of the structure

REPAIR AND STRENGTHENING OF REINFORCED CONCRETE COLUMNS AND BEAMS ICRI – International Concrete...

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