New Technologies in Reinforced Concrete

Professor Des Bull

Holcim Adjunct Professor in Concrete Design

Department of Civil and Natural Resources

Engineering

University of Canterbury

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Conventional Buildings�pre �1980

� Concrete

� Frames – beams and columns

� Walls

� Combination of walls and frames

� Lack on modern seismic engineering

� Little “toughness” or “resilience”

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Harcourts, Madras St �pre �1980s

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22 Feb 2011Harcourts, Madras St

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Aftershock June 13 2011

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Aftershock June 13 2011

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Aftershock June 13 2011

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Conventional Buildings�post 1980

� Concrete

� Frames – beams and columns

� Walls

� Combination of walls and frames

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Desirable post�elastic mechanisms in moment resisting frames

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Critical Structural Issues

� Conventional Beams:

� Yield or go plastic

� Elongate under cyclic loading from earthquake

� Concrete worst

� Then steel

� Then timber (in connection hardware)

� Loss of floor support

� Loss of load path across

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Plastic Hinge in a RC Beam

� Conventional Beams:

� Yield or go plastic

� Elongate under cyclic loading from earthquake

UoC Test

J Matthews

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Elongation of the beams –push the columns

� Loss of connection: floor , supports

? ?

Matthews et al 2008

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Clarendon,

Chch 2011

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Clarendon, 1987

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N�W corner column

Corner pushed

out

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UoC testing Corner column � top view

J Matthews

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Clarendon

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Clarendon

� Middle bay

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UoC Testing –Partial Collapse of the first h/c unit

J Matthews

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UoC testing - Total Collapse of theFloor

Inte

rsto

rey d

rift (

%)

Inte

rsto

rey d

rift (

%)

1.0 1.0

2.5 2.5

3.5

3.5

1.0 1.0

2.0 2.0

0 0

Inte

rsto

rey d

rift

(%

)

0.5

2.5

0.5

2.5

0

J Matthews

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Post�tensioned Frames & Walls

� PREcast Seismic Structural Systems (PRESSS)

� Japan & USA research programme

� Beams and columns

� Walls

� Tested San Diego 1995

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Slab

Slab

Pivot

BeamColumn

Pivot Slab

BeamColumn

Pivot

BeamColumn

EQ EQ

Pivot or hinge detail

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PREcast Seismic Structural Systems (PRESSS)

UT�GAP connection

Palmieri, Saqan et al.

1996 TCY gap connection

in PRESSS five�storey frame

Nakaki et al., 1999

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Early Japanese reinforced concrete slotted beam (1999)

Ohkubo, Matsuoka et al. 1999

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Conventional concrete frame

� Fracture of main bars

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Slotted Beams & “Non�tearing” floors

� New configurations of typical building materials

� At slab level – beam pivots – like a small hinge

� Very little damage to the floors – doesn’t “tear”.

� Structural Steel and Concrete options

� Timber will work too.

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The Non�Tearing Floor System

BeamColu

mn

Top Hinge

Beam gap

BeamColu

mn Single crack across slab

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Slotted reinforced concrete beam

E Au 2010� FRST “Future Buildings” Programme

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Accommodation of rotation via opening and closing of slot

(a) Positive (gap opening) moment (b) Negative (gap closing) moment

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Slotted Beam

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Start of TestSlotted Beam

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2.0 % DriftSlotted Beam

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3.5 % DriftSlotted Beam

inside

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EoT 4.5% DriftSlotted Beam

Steel tube % � PVC plastic tube % X

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1.0 % DriftSlotted Beam

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2.0 % DriftSlotted Beam

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3.5 % Drift

Top of beam and floor

Conventional Frame

post % 2004

Slotted Beam

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EoT 4.5 % DriftSlotted Beam

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Conventional RC Frame

J Matthews

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2 Storey, “Non�tearing” Precast Concrete Floor / slotted beams

C Muir

et al

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2 Storey, “Non�tearing” Precast Concrete Floor / slotted beams

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� Lower damage than would be expected in a monolithic structure

Slotted Beam at ULS Monolithic Beam at ULS (MacPherson, 2005)

2 Storey, “Non�tearing” Precast Concrete Floor / slotted beams

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46Slotted system floor at ULS Monolithic system floor at

ULS (Lindsay, 2004)

2 Storey, “Non�tearing” Precast Concrete Floor / slotted beams

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ResultsResults

Exterior joint strain penetration Interior joint strain penetration

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Replaceable external mild steel energy dissipaters

� Instead of internal mild steel bars

� Very hard to repair

Pampanin (2005) and Pampanin, Amaris, Akguzel, and Palermo (2006)

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Non�tearing floor connection detailsVariations on the Concept

� “self,centring”

Two�storey,

one�bay

frame tested

Amaris et al., 2008

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Alternative solutions of steel shear corbel/bracket

“Hercules” systems,

proprietary of B.S. Italia srl

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Walls

� Conventional

� Damaged and costly to repair, if possible.

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Grand Chancellor

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123 Victoria St

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New Technologies –rocking wall

Gravity / post%tensioning Gravity / post%tensioning

Restoring

force

Earthquake

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Rocking walls: post�tensioned, bar dampers and viscous dampers

(c) Reinforcement,

confinement and steel

bracket details

(b) Connection

detail

(a) As�built post�

tensioned wall

Marriott et al 2008

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New Technologies in Reinforced Concrete

� Thank you.

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