PDA Testing : 1997 Proper Practice
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PDI powerpoint lectureNOTHING is more important than your
safety!
If you perceive something as unsafe, don’t do it
Watch where you stand (particularly during lifts) and plan an exit strategy in anticipation.
“Case Method” requires measuring Force ( F ) and Velocity ( V ) versus time at same point on pile (usually near top).
Pile Testing
F (t) = E A ε (t)
Convert ACCELERATION to V V (t) = a(t) dt
Testing of any pile type
Solution to meet all needs:
lightweight strain and acceleration transducers
PR acc PE acc
Not good for steel-to-steel
Need good sensors in good condition PE acc – rugged, better in very cold temps, any pile type PR acc - any pile type, better for steel-to-steel impacts Strains - handle with care
“Rain proof”
In-house • 7 to 11 week survival at
near-surface conditions • Nominal 70 ft (7 day test) • One failed at 140 ft • Survived 320 ft for 7 days • Failed at 460 ft
• Test all sensors BEFORE attaching sensors to the pile
• Tap the strain and acceleration sensors to see response (select by TRIGGER channel)
Do NOT excessively beat on PR gages!
( can also deform strain transducers! )
PDA testing - data acquisition
• Need Minimum 2 strains per pile to compensate for bending
– Place symmetrically about neutral axis – Need 4 strains to assess 2 axis bending
PDA testing - data acquisition
PDA testing - data acquisition
Proper attachment for concrete piles
Important
Gap
NO
AXIAL !
PDA testing - data acquisition
How to put on sensors (piles or shafts) Axial with pile ~2 diameters from top
restrike – at convenient location Firmly bolted
PDA testing - data acquisition
Avoid – “cracks” (gaps make false strain readings) – welds (particularly spiral welded) – section changes
CAL TEST ( “CT” ) • save this input, verify calibration of the PDA itself
(but NOT of sensors)
• VMX and MEX • for known inputs • give known outputs ±2%
Unacceptable
•PAX ( 8G ) have 10,000 µε total range (huge)
• PAX shows test range available (+3000 to -3000 µε) (PAK has 2000 µε range)
• PAX says “OK” then is OK to test
8G - Balance
Support cable weight
Damaged Cables are by far the largest cause of repairs;
Wireless eliminates cables
~2 D Radio
Do not climb to attach
sensors or cables
Sensor-Transmitter Protection
• H-piles – no issue • Pipe piles – use protectors • Concrete piles – protectors
or - sensors in indentations
604 k597 k
Why Wireless? Eliminates cable
reliability aids site logistics easy clean up (no cable in the mud)
Allows attaching on ground speeds testing process properly attached
Easy to transport – very lightweight
PAX – allows 2 strain and 2 acceleration 8G – allows up to 16 channels of data (any type)
Pi le
Si te
A Pile
Site B
Internet connection
Experienced Engineer controls PDA as if on-site; monitors pile in real time.
CAPWAP analysis starts immediately after testing.
Later same day
PAX Remote SiteLink® Operation
• PDA is operated by office engineer (improve efficiency) • Some site assistance • Improves scheduling of tests • Faster results, reduced cost testing • Likins, G, Hermansson, I, Kightley, M, Cannon, J, Klingberg, D, March, 2009. “Advances in Dynamic
Foundation Testing Technology”. Geotechnical Special Publication No. 185. American Society of Civil Engineers: pp. 591-598.
PAX
select 200 msec
PDA testing - data acquisition
2 strains compensate bending
Even with large bending, the two velocities are very similar.
2 strain and 1 acceleration are minimum 2 strain and 2 acceleration are recommendedimportant
Minimum 2 strains to compensate for
bending in pile
Minimum 2 strains per pile (symmetrical) to compensate bending
• Use 4 strains for drilled shafts • place at 90o in pairs at 180o
• F1 and F2 opposite, F3 and F4 opposite • Use 4 strains for spiral weld pipes
( if problems with data ) • (EX-9 shows benefit for sprial pipes)
PDA testing - data acquisition
PDA testing - data acquisition
PDA testing - data acquisition
PDA testing - data acquisition
PDA testing - data acquisition
• Pile properties (at sensor location) – Area AR – “Diameter” @sensor location circumference – Length (from sensors to toe) LE – Material properties
• Density SP • Modulus EM • Wavespeed WS
• EM = ρ c2 = (SP / g) WS2
– Embedment (LP) for CAPWAP – Uniform?
PDA testing - data acquisition
• Concrete • SP known • WS and EM unknown
– measure WS
– measure SP and WS!
PDA testing - data acquisition
Typical concrete WS is 4,000 m/s or 13,000 ft/s, but varies according to concrete strength and age
Approx. guide below, but WS needs to be measured
E = f (f’c) 0.5 : WS = ( E/ρ )0.5 = f ( f’c )0.25
f'c f'c EM-dyn EM-dyn WS-dyn WS-dyn psi MPa ksi MPa ft/sec m/s
2,000 14 2,804 19,518 9,249 2,830 3,000 21 3,434 23,883 10,235 3,131 4,000 28 3,965 27,575 10,999 3,364 5,000 35 4,434 30,831 11,630 3,557 6,000 42 4,857 33,772 12,172 3,723 7,000 49 5,246 36,477 12,650 3,869 8,000 56 5,608 38,997 13,080 4,001 9,000 63 5,948 41,361 13,470 4,120
10,000 70 6,270 43,600 13,830 4,230
Concrete/Timber - find WS ?
RISE
PEAK
WC 3556 m/s
8G – PDA-S
Use “Blow by Blow Auto Edit” Set “Blow by Blow Edit” before saving
Drilled shafts with casing Concrete filled steel pipe piles
(common practice) H pile full length in grout/concrete
Testing Uniform Composite Piles
Because of higher impedance - can activate more capacity during restrike cases when setup causes refusal
Why or when do we want to test concrete filled piles?
Concrete: Ac, ρc Steel: As, ρs
Uniform Composite Piles
estimate WS = √{EM/ρ} (if see WS from test, use it)
Example: concrete filled pipe
• Concrete strain = Steel strain this is required !
•if high percent steel, attach to steel “windows” make significant (bad) stress concentration effect (do not make windows)
•if low percent steel, (use “windows”) attach to concrete
EAsteel / EAtotal < 10%
Concrete filled pipe Must hit thru concrete
213 mm x 8.2 mm pipes (8 3/8” x 0.322 pipes)
circumference 668 mm (26.3 inch), so 42% steel removed Steel is about 50% of EA and 44% of EA/c
No windows 140 mm (5.5”) Windows
Sensors on steel Sensors on concrete
badgood
Reduces excavation Protects reinforcing
Remove after testing
Drop weight 1%, 2%, …5% of Ru (2% helps activate end bearing)
Four strains standard: To assess data quality by 180o pairs
To give backup (few blows allowed)
Poor top preparation
Poor attachment leads to bad data (damage sensor?)
42 inch nom. shaft
engaged, proportionality lost
Ideal
2
3? Know which are opposite !
Pay attention to details ! 4 strains allow backup and assess data quality
Turn off mate if one fails
250 kN
Thin cushion
If you perceive something as unsafe, don’t do it
Watch where you stand (particularly during lifts) and plan an exit strategy in anticipation.
“Case Method” requires measuring Force ( F ) and Velocity ( V ) versus time at same point on pile (usually near top).
Pile Testing
F (t) = E A ε (t)
Convert ACCELERATION to V V (t) = a(t) dt
Testing of any pile type
Solution to meet all needs:
lightweight strain and acceleration transducers
PR acc PE acc
Not good for steel-to-steel
Need good sensors in good condition PE acc – rugged, better in very cold temps, any pile type PR acc - any pile type, better for steel-to-steel impacts Strains - handle with care
“Rain proof”
In-house • 7 to 11 week survival at
near-surface conditions • Nominal 70 ft (7 day test) • One failed at 140 ft • Survived 320 ft for 7 days • Failed at 460 ft
• Test all sensors BEFORE attaching sensors to the pile
• Tap the strain and acceleration sensors to see response (select by TRIGGER channel)
Do NOT excessively beat on PR gages!
( can also deform strain transducers! )
PDA testing - data acquisition
• Need Minimum 2 strains per pile to compensate for bending
– Place symmetrically about neutral axis – Need 4 strains to assess 2 axis bending
PDA testing - data acquisition
PDA testing - data acquisition
Proper attachment for concrete piles
Important
Gap
NO
AXIAL !
PDA testing - data acquisition
How to put on sensors (piles or shafts) Axial with pile ~2 diameters from top
restrike – at convenient location Firmly bolted
PDA testing - data acquisition
Avoid – “cracks” (gaps make false strain readings) – welds (particularly spiral welded) – section changes
CAL TEST ( “CT” ) • save this input, verify calibration of the PDA itself
(but NOT of sensors)
• VMX and MEX • for known inputs • give known outputs ±2%
Unacceptable
•PAX ( 8G ) have 10,000 µε total range (huge)
• PAX shows test range available (+3000 to -3000 µε) (PAK has 2000 µε range)
• PAX says “OK” then is OK to test
8G - Balance
Support cable weight
Damaged Cables are by far the largest cause of repairs;
Wireless eliminates cables
~2 D Radio
Do not climb to attach
sensors or cables
Sensor-Transmitter Protection
• H-piles – no issue • Pipe piles – use protectors • Concrete piles – protectors
or - sensors in indentations
604 k597 k
Why Wireless? Eliminates cable
reliability aids site logistics easy clean up (no cable in the mud)
Allows attaching on ground speeds testing process properly attached
Easy to transport – very lightweight
PAX – allows 2 strain and 2 acceleration 8G – allows up to 16 channels of data (any type)
Pi le
Si te
A Pile
Site B
Internet connection
Experienced Engineer controls PDA as if on-site; monitors pile in real time.
CAPWAP analysis starts immediately after testing.
Later same day
PAX Remote SiteLink® Operation
• PDA is operated by office engineer (improve efficiency) • Some site assistance • Improves scheduling of tests • Faster results, reduced cost testing • Likins, G, Hermansson, I, Kightley, M, Cannon, J, Klingberg, D, March, 2009. “Advances in Dynamic
Foundation Testing Technology”. Geotechnical Special Publication No. 185. American Society of Civil Engineers: pp. 591-598.
PAX
select 200 msec
PDA testing - data acquisition
2 strains compensate bending
Even with large bending, the two velocities are very similar.
2 strain and 1 acceleration are minimum 2 strain and 2 acceleration are recommendedimportant
Minimum 2 strains to compensate for
bending in pile
Minimum 2 strains per pile (symmetrical) to compensate bending
• Use 4 strains for drilled shafts • place at 90o in pairs at 180o
• F1 and F2 opposite, F3 and F4 opposite • Use 4 strains for spiral weld pipes
( if problems with data ) • (EX-9 shows benefit for sprial pipes)
PDA testing - data acquisition
PDA testing - data acquisition
PDA testing - data acquisition
PDA testing - data acquisition
PDA testing - data acquisition
• Pile properties (at sensor location) – Area AR – “Diameter” @sensor location circumference – Length (from sensors to toe) LE – Material properties
• Density SP • Modulus EM • Wavespeed WS
• EM = ρ c2 = (SP / g) WS2
– Embedment (LP) for CAPWAP – Uniform?
PDA testing - data acquisition
• Concrete • SP known • WS and EM unknown
– measure WS
– measure SP and WS!
PDA testing - data acquisition
Typical concrete WS is 4,000 m/s or 13,000 ft/s, but varies according to concrete strength and age
Approx. guide below, but WS needs to be measured
E = f (f’c) 0.5 : WS = ( E/ρ )0.5 = f ( f’c )0.25
f'c f'c EM-dyn EM-dyn WS-dyn WS-dyn psi MPa ksi MPa ft/sec m/s
2,000 14 2,804 19,518 9,249 2,830 3,000 21 3,434 23,883 10,235 3,131 4,000 28 3,965 27,575 10,999 3,364 5,000 35 4,434 30,831 11,630 3,557 6,000 42 4,857 33,772 12,172 3,723 7,000 49 5,246 36,477 12,650 3,869 8,000 56 5,608 38,997 13,080 4,001 9,000 63 5,948 41,361 13,470 4,120
10,000 70 6,270 43,600 13,830 4,230
Concrete/Timber - find WS ?
RISE
PEAK
WC 3556 m/s
8G – PDA-S
Use “Blow by Blow Auto Edit” Set “Blow by Blow Edit” before saving
Drilled shafts with casing Concrete filled steel pipe piles
(common practice) H pile full length in grout/concrete
Testing Uniform Composite Piles
Because of higher impedance - can activate more capacity during restrike cases when setup causes refusal
Why or when do we want to test concrete filled piles?
Concrete: Ac, ρc Steel: As, ρs
Uniform Composite Piles
estimate WS = √{EM/ρ} (if see WS from test, use it)
Example: concrete filled pipe
• Concrete strain = Steel strain this is required !
•if high percent steel, attach to steel “windows” make significant (bad) stress concentration effect (do not make windows)
•if low percent steel, (use “windows”) attach to concrete
EAsteel / EAtotal < 10%
Concrete filled pipe Must hit thru concrete
213 mm x 8.2 mm pipes (8 3/8” x 0.322 pipes)
circumference 668 mm (26.3 inch), so 42% steel removed Steel is about 50% of EA and 44% of EA/c
No windows 140 mm (5.5”) Windows
Sensors on steel Sensors on concrete
badgood
Reduces excavation Protects reinforcing
Remove after testing
Drop weight 1%, 2%, …5% of Ru (2% helps activate end bearing)
Four strains standard: To assess data quality by 180o pairs
To give backup (few blows allowed)
Poor top preparation
Poor attachment leads to bad data (damage sensor?)
42 inch nom. shaft
engaged, proportionality lost
Ideal
2
3? Know which are opposite !
Pay attention to details ! 4 strains allow backup and assess data quality
Turn off mate if one fails
250 kN
Thin cushion
