Precast Bent System for

frizzflowerUrban and Civil

Nov 29, 2013 (3 years and 6 months ago)

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Precast Bent System for
Bridges in Seismic Regions


Marc Eberhard, John Stanton

Olafur

Haraldsson
, Todd
Janes
, Hung Viet Tran



University of Washington

NEES & PEER Annual Meeting

San Francisco, 8
-
9 October 2010

Acknowledgments

WSDOT

TRANSNOW

Valle Foundation

FHWA, Highways for Life Program

PEER

Background

Accelerate
on
-
site bridge

construction.

Use precast concrete components.

Connection
details:

seismic
-
resistant

construct

Construction
Procedure

1) Excavate footing.

2) Position and brace precast column.

Construction
Procedure

3) Place footing reinforcement and cast.

Construction
Procedure

4)
Set cap
-
beam, grout bars into ducts.

Construction
Procedure

5) Place girders, diaphragms and deck.

Construction
Procedure

Precast

P
restressed


CIP

RC (ref)

Precast

RC

Cap
-
Beam

to
Column

Column
to


Spread Footing

Column to


Drilled
S
haft

Connections

Column
-
to
-
Cap
-
Beam

Connection


Cap Beam Connection:


Many small bars and ducts

Courtesy: BERGER/ABAM Engineers

Tight
tolerances.

Precast column

Precast cap
beam

6 # 18 rebar

8.5” corrugated
steel ducts

High strength
grout

Cap
-
Beam Connection:

Large bars

Cap
-
Beam Connection:


Conclusions



Failure
occurs in the column.




Large
-
bar
precast connection
behaves
the
same as a
cast
-
in
-
place
connection.

Column
-
to
-
Footing

Connection


Footing
Connection:
Construction

Headed
bars

Footing
Connection:
Headed Bars

Strut
and Tie
Model.

Footing Connection

Hooked bars facing out

(Conventional
cip
)

Load transfer is
tangential to hook.

Ineffective!

Footing Connection:

Construction

Spread Footing Connection

Vertical
(gravity) load.

Lateral
(seismic)
load.

Spread Footing
Connection:

Test

After seismic testing. Foundation undamaged.

Spread Footing Connection



Gravity Load Test

Column crushed at:

3.5 * (1.25DL + 1.75LL).

No damage to footing. No sign of punching failure.

Spread Footing Connection


Constructability:

-
Column has no projecting bars.

-
No “form
-
savers”.

-
Easy to fabricate and transport.

Spread Footing Connection


Structural Performance:


Terminators provide better anchorage than
hooked bars facing outwards.


Failure in column. Footing undamaged in
lateral load and vertical load tests.


Seismic performance as good as, or better
than, conventional
c.i.p
. construction.

Implementation

Bid Opening:


October 14
th

Pre
-
Tensioned System


Pre
-
Tensioned
System

PC cap
-
beam

Sleeved
strand

Bonded
strand

c.i.p
.
footing

Bonded
rebar

Cracking
plane

Pre
-
Tensioned System

1.
Pre
-
tensioning solves corrosion problems
perceived to exist in post
-
tensioning.

2.
Pre
-
tension in a plant.


Good QC.


Special equipment and extra site time for
post
-
tensioning are not needed.


Can add
rebars

for energy dissipation
.

Thank You