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Retrofit Measures
or
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Pur ose
To describe typical retrofit measures for:
Abutments Footings
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Abutment retrofit measures
Approach slabs
Anchor slabs
Diaphragm walls
ransverse s ear eys Transverse soil anchors
Soil and gravity anchors
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Abutment retrofit measures
California settlement (approach) slab
Design as SS 10 min Spans soil to deck
Connection FD isFD
F D S a
DL
0.6 Friction Coeff
Sa=Spectrum Acc
DL=Dead Load
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Abutment retrofit measures New Zealand settlement slab
ng e o ers ong u na res s ance
Still have smooth approach
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Abutment retrofit measures
Waffle slab retrofit
2h
es s ance=. s
Resistance 16 pile=40 kips ultimate
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Abutment retrofit measures
Anchor slab retrofit
Vertical capacity is of no concern
Must be securel connected to su erstructure Use damping ratio of 10%
Longitudinal forces will reduce 20%
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Abutment retrofit measures
Must act composite Utilize dowels to provide
shear transfer
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Abutment retrofit measures Concrete transverse shear keys
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Abutment retrofit measures
Concrete transverse shear keys
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Abutment retrofit measures
Transverse soil anchors
Lateral resistance methods: Lateral capacity of piles
Passive pressure on wingwalls
Friction on bottom of footing Anchor slabs (previously discussed)
When these are not sufficient, consider soil anchors
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Abutment retrofit measures
Wingwall cross-tie
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Abutment retrofit measures Abutment soil shear keys
-Pp=.96h ksf
Design tips
-To be fully effective:
clear space=2h
-Design shear for full passive pressure-Use R=2 for flexure
-Abutment connection designed
for overstrength moment
h
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Abutment retrofit measures
Wing overlay
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Abutment retrofit measures
Wing overlay
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Abutment retrofit measures
CIDH pile shear key
Designed for lateralcapacity only
More effective when
fixed at top
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Abutment retrofit measures
Deadman anchor
Extend anchors to avoid backfill movement Embed tie rods in concrete trench for protection
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Abutment retrofit measures
Deadman anchor
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Abutment retrofit measures Soil anchors
Prestress ensures anchor is solid
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Abutment retrofit measures Abutment friction anchor
se w granu ar so s w e se emen
15 degree slope compresses slab as longitudinalmovemen occurs
Steel piles resist uplift
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Footin retrofit measures Footing strengthening
or s a y
Check moment at top
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Footin retrofit measures Footing concrete overlay
se over ay o ncrease nega ve momen capac y
Use added depth to check positive moment
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Footin retrofit measures
Reinforcing splice detail
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Footin retrofit measures
Prestressing
Use to help positive moment
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Footin retrofit measures ste 1
Determine design forces
Limit to flexural capacity of pier
Use overstren th moment Material stronger than expected
Confinement of concrete
Strain hardening of steel
Increase axial load from EQ
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Footin retrofit measures ste 2
Check OT capacity
If exceeded-check stability with a rocking analysis This may eliminate retrofit requirements
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Footin retrofit measures ste 3
Design for shear
Difficult to retrofit Increase footing depth with overlay
Add prestressing bars
Add vertical bars through drilled holes (must passbottom layer with hooks (anchors) to be effective or
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Footin retrofit measures ste 4
Design for flexure
Top reinforcing lacking very often Add overlay with steel and dowels
should be within thickness of footing from column
Extra depth helps positive moment Place prestress as close to column as possible
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Footin retrofit measures ste 5
Design dowels to connect to existing concrete
Should transfer shear stress at interface Use shear friction approach-friction=1.0
,
bottom is required-(difficult to do this)
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Footin retrofit measures ste 6 Check column-to-footing joint shear
Overlay capacity
Yield line theory
Easier to ust make overla thickerExample 10.1
retrofit of
footing
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Pil t f ti ti
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Pile to footin connection
Steel pipe piles filled with conc and rebar
Good connection to new footing
Can be drilled in low head room
Very stiff for lateral loads
Good connection to new footing
Pil t f ti ti
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Pile to footin connection Prestress tie down
roo oa e own
Pile capacity limits
amoun o
prestress
ue o oo ng
rotation, limited useto short columns
(before fully
effective-rotation
S
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Summar
To describe typical retrofit measures for:
Abutments Footings
Ab t t t fit
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Abutment retrofit measures
Approach slabs
Anchor slabs Diaphragm walls
ransverse s ear eys Transverse soil anchors
Soil and gravity anchors
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What questions do you have?