1

Performance of Ultra-High Strength Concrete and FRP Retrofitted RC Slabs under Blast

Loads

School of Civil, Environmental and Mining Engineering,School of Civil, Environmental and Mining Engineering,The University of AdelaideThe University of Adelaide

Chengqing Wu, Oehler DJ, RebentrostM, Leach J, Whittaker AS

1. Introduction

• Terrorism

• Ultra-high Performance Concrete

• Retrofitting technologies

Why?

Mechanical properties of conventional concrete and UHPFC

1. Introduction

1300 mm

1000 mm

A A Section A-A

100 100 100150 150200 200

1.4

20

Test Specimen

Blast Test 1:

Blast Test 2:

Blast Testing of FRP retrofitted RC members

ELASTICRANGE

PLASTICRANGE

1. Introduction

2 Test Program

RetrofittingRetrofitting Ultra high performance concreteUltra high performance concrete

0

20

40

60

80

100

120

140

160

0 0.005 0.01 0.015

StrainStrain

Com

pres

sion

Str

ess

(Co

mpr

essi

on S

tres

s ( M

PaM

Pa))

Blast Testing SpecimensNormal Reinforced Concrete Specimens

MajorBending Plane

2000

1000

A A Section A-A

1000

Minor Bending Plane

100

10

2 Test Program

2

Pultruded:

240 240155 155210

Adhesive

10040

100 100 40

100CFRP 1.4 mm

Retrofitted Reinforced Concrete Specimens

Ultra-high Performance Concrete Specimens

Two slabs of UHPFC with and without reinforcement were designed.

2 Test Program

Testing Set-up

2 Test Program

Blast SetupBlast Setup

Concrete SlabConcrete Slab

Explosive ChargeExplosive Charge

Data acquisition

LVDTPressure Transducer (PT)

LVDT

20 mm

50 mm

PT1

PT2

Slab

Support

Support

2 Test Program

Experimental air blast program

201010.3711.4 %2000*1000*100RUHPFCD3ARUHPFC

34331.130.75-2000*1000*100UUHPFCD1BUUHPFC

50830.540.921.2 %2000*1000*100RC+CFRP 2.8mm strip, one side (EB)3BRET-2

10441.51.51.2 %2000*1000*100RC+CFRP 2.8mm strip, one side (EB)3ARET-1

82130.751.51.2 %2000*1000*100NSC RC1ANRC-4

34400.931.41.2 %2000*1000*100NSC RC1BNRC-3

81391.531.2 %2000*1000*100NSC RC1ANRC-2

10073.031.2 %2000*1000*100NSC RC1ANRC-1

Explosive Used(g)

Scaled distance(m/kg1/3)

Standoff distance

(m)

Reo. Rate

Dimensionmm*mm*mmDescriptionSlab

NameBlast

2 Test Program

3

Performance of Testing Specimens

NRC-3 crack development (a charge weight of 3.4kg at stand-off distance 1.4m, energy 2536 kN.mm)

NRC-4 crack development(a charge weight of 8kg at stand-off distance 1.5m, energy 5464 kN.mm)

Normal reinforced concrete slabs

Retrofitted Experimental Results

FlexuralDirect Shear

Direct Shear

FRP Debonding

(a charge weight of 5kg at stand-off distance 0.92m, energy 10375 kN.mm)

FRP DebondingUnreinforced ultra-high

performance fibre concrete slab

2 Test Program

(a charge weight of 3.4kg at stand-off distance 0.75m, energy 3089 kN.mm)

NRC-3 crack development (a charge weight of 3.4kg at stand-off distance 1.4m, energy 2536 kN.mm)

Normal reinforced concrete slabs

Reinforced ultra-high performance fibre concrete slab

(a charge weight of 20kg at stand-off distance 1m, energy 93077 kN.mm)

3 Blast Resistance

1010 2020 3030 4040 5050 6060

Deflection (mm)Deflection (mm)00

100100

200200

300300

400400

500500

600600

700700

Resi

stan

ce (

Resi

stan

ce (

kNkN)) Ultra high strengthUltra high strength

RetrofittedRetrofitted

Normal reinforced Normal reinforced concreteconcrete

4

Resistance, reflected impulses and energy demands and capacities

Comparison and Discussions

Based on this diagram, almost all specimens (except NRC-1) tested in this study will collapse.

4. Conclusion 4. Conclusion

A series of blast tests have been carried out to investigate blast resistance of the NRC, the retrofitted, the UUHPFC and the RUHPFC slabs. It was found that:

Although EB FRP compressive face of retrofitting can increase ductility in blast tests, the effectiveness of the retrofitting was inconclusive as slab failure was not achieved throughout the experiments.

The UUHPFC slab suffered even less flexural cracks at middle span by comparison with those for NRC slabs when it was subjected to similar blast loads, showing UHPFC is of high ductility and high energy absorption capacity, and is therefore a more effective material against blast loading.

Blast testing also validated the superior blast resistance of the RUHPFC slab due to the excellent mechanical properties of UHPFC.

P-I diagrams specified by current codes are very conservative whenthey are used to assess damage levels of specimens tested in this study.

4. Conclusion 4. Conclusion

Questions?