grlweap-hammer-pile-soil-backgound.ppt

5/28/2018 grlweap-hammer-pile-soil-backgound.ppt

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Frank Rausche, Garland Likins

2011,Pile Dynamics, Inc.

GRLWEAP Fundamentals


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CONTENT

Background and Terminology

Wave Equation Models

Hammer

PileSoil

The Program Flow

Bearing graph Inspectors Chart

Driveability


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1800s Closed Form Solutions & Energy Formulas

1950: Smiths Wave Equation

1970: CAPWAP

1976: WEAP, TTI (mainframes)

1980s: GRLWEAP (PCs)1986: Hammer Performance Study

1996, 2006: FHWA Manual updates

Some impo rtant developments in

Dynam ic Pi le Analysis

WEAP = Wave Equation Analys is o f Piles


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WAVE EQUATION OBJECTIVES

Smiths Basic Premise: Replace Energy Formula Use improved pile model (elastic pile)

Use improved soil model

(elasto-plastic static with damping) Allow for stress calculations

Later GRLWEAP improvements: realistic Diesel hammer model (thermodynamics

comparison with pile top measurements

development of more reliable soil constants

driveability and inspectors chart options

residual stress analysis option


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GRLWEAP App l ication

WHEN? Before pile driving begins

After initial dynamic pile testing ( refined )

WHY? Equipment selection or qualification

Stress determination

Formulate driving criterion Blow count calculation for desired capacity

Capacity determination

from observed blow count


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Some WEAP Term ino logy

Hammer Ram plus hammer assembly

Hammer assembly All non-striking hammer components Hammer efficiency Ratio of Ekjust before impact to Ep

Driving system All components between hammer and pile top

Helmet weight Weight of driving system

Hammer cushion Protects hammer - between helmet and ram

Pile cushion Protects pile - between helmet and pile top

Cap Generally the striker plate + hammer

cushion+helmet

Pile damping Damping of pile material

Soil damping Damping of soil in pile-soil interface

Quake Pile displacement when static resistance

reaches ultimate


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Some WEAP Term inology

Bearing Graph Ult. Capacity and max. stress vs. blow countfor a given penetration depth

Inspectors Chart Calculates blow count and stresses for given

ult. capacity at a given penetration depth

as a function of stroke/energy

Driveability analysis Calculate blow count and stresses

vs. depth based on static soils analysis

SRD Static Resistance to Driving

Soil set-up factor Ratio of long term to EOD resistance

Gain/loss factor Ratio of SRD to long term resistance

Variable set-up Setup occurring during a limited driving

interruption


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THE WAVE EQUATION MODEL

The Wave Equation Analysis calculates the

movements (velocities and displacements) of

any point of a slender elastic rod at any time.


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GRLWEAP Fundamentals

For a pile driving analysis, the rod is

Hammer + Driving System + Pile

The rod is assumed to be elastic(?) and

slender(?)

The soil is represented by resistance

forces acting at the pile soil interface


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GRLWEAP - 3 Hammer Models


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Ram : A, L for s t i ffness, mass

Cyl inder and upper frame =

assembly top mass

Drop height

External Combustion Hammer Modeling

Ram gu ides for assembly s t i ffness

Hammer base =

assembly bot tom mass


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External Combustion HammersRam Model

Ram segments

~1m long

Combined Ram-

H.Cushion

Helmet mass


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External Combustion HammersCombined Ram Assembly Model

Combined Ram-

H.Cushion

Helmet mass

Ram segments

Assembly segments


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Diesel Hammer Combustion Pressure Model

Precompression-

Combustion-Expansion-

pressures from

thermodynamics

Ports

Compressive Stroke, hC

Cylinder Area, ACH

Final Chamber Volume, VCH

Max. Pressure, pMAX

hC


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DIESEL PRESSURE MODELLiquid Injection Hammers

Time

Pressure

pMAX

Port

Open

Compress ion

Expansion


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Downward =

upward stroke

Program FlowDiesel Hammers

Fixed pressure, variable stroke

Downward =

rated stroke

Calculate pile and

ram mot ion

Find upward

strokeOutput

Strokes

match?

Setup hammer,pi le, soi l m odel

Next Ru?

N

N


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Potent ial / K inet ic Energy

WP

WR

h

EP= WRh (po tent ia l or rated energy)

WRvi

EK

= EP

(- hammer eff ic iency )

vi= 2g h

EK= mRvi2 (kinet ic energy)

Max ET= F(t) v(t) dtTransferred EnergyEMX

ETR = EMX/ ER= transfer ratio


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GRLWEAP hammer efficiencies

The hammer eff ic iency reduces theimpact veloc i ty of the ram ; reduct ion

facto r is based on exper ience

Hammer eff ic ienc ies cover al l losseswhich canno t be calcu lated

Diesel hammer energy loss due to

precompress ion o r cush ion ing can becalcu lated and , therefo re, is no t covered

by hammer eff ic iency


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GRLWEAP diesel hammer efficiencies

Open end d iesel hammers : 0.80(un certainty of fal l height, fr ict ion , al ignment)

Closed end d iesel hammers: 0.80(un certainty of fal l heigh t, fr ict ion, power ass ist ,

a l ignment)


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Other ECH efficiency recommendations

Single acting A ir/Steam hammers: 0.67(fa ll height, preadm iss ion , fr ict ion, al ignm ent)

Double acting A ir/Steam/Hyd raul ic: 0.50

(preadm iss ion , reduced pressu re, fr ict ion, al ignment)

Drop hammers w inch released: 0.50(un certainty of fal l heigh t, fr ict ion, and w inch losses)

Free released drop hammers (rare): 0.67(un certainty of fal l height fr ict ion)


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GRLWEAP hydraulic hammer

efficiencies

Hammers w ith internal mon itor : 0.95(un certainty of h ammer al ignment)

Hydraul ic hammers (no mon itor): 0.80

Power ass isted hydraul ic hammers: 0.80

(un certainty of fal l height, al ignm ent, fr ict io n, power ass ist)

If no t measu red, fal l height mus t be assumed

and can be qu ite variablebe caut iou s !


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VIBRATORY

HAMMER MODEL


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VIBRATORY HAMMER MODEL

2-mass system with vibratory force

FV = me2 re sint

FL

FV

m1

m2

Bias Mass with Line Force

Connecting Pads

Oscillator with eccentric

masses, me, radii, reand

clamp


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GRLWEAP Hammer data f i le


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Pile: Soil:

Hammer:

(Masses and

Springs)

Driving System:Cushions (Springs)Helmet (Mass)

Hammer-Driving System-Pile-Soil Model


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Driving System Modeling

The Driving Systems Consists of

Helmet including inserts to align hammer and pile Hammer Cushion to protect hammer

Pile Cushion to protect concrete piles


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GRLWEAP Driv ing System Help


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GRLWEAP Driv ing System Help


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GRLWEAP Pile Model

To make realistic calculations possible The pile is divided into N segments

of approximate length L = 1 m (3.3 ft)

with mass m = A L and stiffness k = E A / L

there are N = L / L pile segments

Divide time into intervals

(typically 0.1 ms)

C t ti l Ti I t t


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Computational Time Increment, tt is a fraction (e.g. ) of the critical time, which is L/c

tcr

L

L/c

t

Time

Length


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Driving system

model(Concrete piles)

Pile Cushion + Pile Top:

Spring + Dashpot

Helmet + Inserts

Hammer Cushion: Spring

plus Dashpot

Non linear springs


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Non-linear springsSprings at material interfaces

Hammer interface springs

Cushions

Helmet/Pile

Splices with slacks

N li ( hi ) i


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Non-linear (cushion) springs

Parameters Stiffness, k = EA/t

Coeffic ient of Restitut ion , COR

Round-out deformat ion,r , orcompress ive s lack

Tension slack , s

r

k /COR2k

s CompressiveDeformation

CompressiveForce


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Material Modulus(ksi)

Aluminum

Micarta

350

Conbest 280

Hamortex 125

Nylon 175-200

Material Modulus(ksi)

Plywood 30 new

75 used

Oak(transverse)

60

Oak

(parallel)

750

Hammer cushion Pile cushion


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L= L/N 1m

Mass density, Modulus, E

X-Area, A

Spring (static resistance)Dashpot (dynamic resist)

Mass mi Stiffness ki

The Pile and Soil Model


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Soil Resistance

Soi l resistance slow s pi le movement andcauses pi le rebound

A very s lowly moving pi le on ly encoun tersstat ic resis tance

A rapid ly moving p i le also encoun ters dynamicresistance

The stat ic resistance to d r iv ing may di f fer fromthe soi l resistance under stat ic loads

Pore pressu re effects Lateral movements

Plugging for op en pro f i les

Etc.


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The Soil Model

Segment

i-1

Segment

i

ki-1,Rui-1Ji-1

Segment

i+1

ki,Rui

Ji

ki+1,Rui+1

Ji+1

RIGID SOIL

SURROUNDING

SOIL/PILE

INTERFACE


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Smiths Soil Model

Total Soil Resistance

Rtotal= Rsi+Rdi

Segment

i

ui

vi

Fixed


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Shaft Resis tance and Quake

qiRu i

qi

Rs i

ui

-Ru i

Recommended Shaft Quake

( qi)

2.5 mm ; 0.1 inch es

R d d T Q k


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Recommended Toe Quakes, qt

0.1 or 2.5 mm

0.04 or 1 mm onhard rock

qt

Rqt Rut

u

D/120: very d ense/hard

soi ls

D/60: so fter/loo se soils

Displacement pi lesNon-displacement

pi les

D

S ith S il D i M d l (Sh ft T )


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Smiths Soil Damping Model (Shaft or Toe)

Pile

Segment

Smith d amping factor,

Js [s /m or s /f t ]

Rd= R

sJsv

Fixed

reference

(soi l aroundpile)

veloc i ty v

Rd= RuJsv

Smith-v iscous d amping

factor Jsv i [s/m o r s/f t ]

dashpot

A lternat ive Soi l Models


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A lternat ive Soi l Models

Coy le-Gibson Resu lts (1968)

Sand Clay

Recommended damping factors


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Recommended damping factors

after Sm ith

Shaft

Clay: 0.65 s/m or 0.20 s/ft

Sand: 0.16 s/m or 0.05 s/ft

Silts: use an intermediate value

Layered soils: use a weighted average

ToeAll soils: 0.50 s/m or 0.15 s/ft

Numerical treatment:


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Numerical treatment:

Force balance at a segment

Acceleration: ai=(Fi Fi+1+WiRi) / mi

Velocity, vi, and Displacement, ui, from Integration

Mass mi

Force from upper spring, Fi

Force from lower spring, Fi+1

Resistance force, Ri(static plus damping)

Weight, Wi

Wave Equation Analysis calculates displacement of


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Calculate displacements:

uni = uoi + voi t

Calculate sp r ing disp lacement:

ci= uni - uni-1

Calculate sp r ing forces:

Fi= kici

k = EA / L

uni-1

mi

mi+1

mi-1

uni

uni+1

Fi, ci

Wave Equation Analysis calculates displacement of

all points of a pile as function of time.

Set or Blow Count Calculation from


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Set or Blow Count Calculation from

Extrapolated toe displacement

R

Set

Final Set

Maximum Set

Quake

Ru

Extrapolated

Calculated


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B low Coun t Calculat ion

Once pile toe rebounds,max toe displacement is known,

example: 0.3 inchor 7.5 mm

Final Set = Max Toe DisplacementQuake= 0.30.1 =0.2 inch

= 7.5 - 2.5 = 5 mm

Blow Count is Inverse of Final SetBCT = 12 / 0.2 = 60 Bl / ft

BCT = 1000 / 5 = 200 Bl / m

A lt t i B l C t C l l t i


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A lternat ive B low Count Calculat ion

by RSA

Residual Stress Analysis is also calledMultiple Blow Analysis

Analyzes several blows consecutively with

initial stresses, displacements from staticstate at end of previous blow

Yields residual stresses in pile at end of

blow; generally lower blow counts

RESIDUAL STRESS OPTION


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RESIDUAL STRESS OPTIONBETWEEN HAMMER BLOWS, PILE AND SOIL STORE ENERGY

Set for 2 Blows

Convergence:

Consecut ive Blows

have same

pi le com pression/sets


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COMPUTATIONAL PROCEDURE

Smiths Bearing Graph

Analyze for a range of capacities

In: Static resistance distribution assumed

Out: Pile static capacity vs. blow count

Out: Critical driving stresses vs. blow count

Out: Stroke for diesel hammers vs. blow count

Bear ing Graph :


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Bear ing Graph :

Requ i red B low Coun t

For requ ired capacity

Find min imum blow count

Bear ing Graph :


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Bear ing Graph :

Capaci ty Determ inat ion

Find indicated capaci ty

For observedb low count


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Stat ic Analysis

Ram veloci ty

Prog ram Flow Bear ing Graph

Model hamm er &

dr iv ing system

Model PileDynam ic An alys is

Pile stresses

Energy transfer

Pile veloc it ies

Choose first RuCalculate Blow

Count

Distr ibute RuSet Soi l Cons tants

Time Inc rement

Output

Increase

Ru?

Inc rease RuInput

N


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PURPOSE OF ANALYSIS

Preliminary Equipment Selection

Hammer OK for Pile, Capacity

Includes stress check

Driving Criterion

Blow Count for Capacity and Stroke

O


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OUTPUT REVIEW

Blow Counts Satisfactory?

Stresses Less Than Allowable?

Economical Hammer, Pile?

If not, consider reanalyzing with different

hammer system, pile size.

INSPECTORS CHART


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OK

Bad

INSPECTOR S CHARTConstant capacityanalyze with variable energy or stroke


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Question for Driveability:WHAT IS RUDURING DRIVING?

We call it Static Resistance to Driving (SRD),

because we lose shaft resistance during driving.

Will we regain resistance by Soil Set-upprimarily along shaft (may be 10 x in clay)

Driveability requires analyze with full loss of

set-up (or with partial loss of set-up for a shortdriving interruption)

S t f t


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Set-up factors

Soil Type Setup Factor

Clay 2

Silt Clay 1

Silt 1.5Sand Clay 1.2

Fine Sand 1

Sand - Gravel 1

Thendean , G., Rausche, F., Svin kin , M., Lik ins, G. E., Sept ember, 1996.

Wave Equat ion Correlation Studies. Proceeding s o f the Fi f th Internat ion al

Conference on the App l icat ion of Stress-wave Theory to Pi les 1996:

Orlando, FL; 144-162.

For Driveab i l i ty:
http://www.pile.com/Reference/openPaper.asp?sessionID=37http://www.pile.com/Reference/openPaper.asp?sessionID=37http://www.pile.com/Reference/openPaper.asp?sessionID=37http://www.pile.com/Reference/openPaper.asp?sessionID=37http://www.pile.com/Reference/openPaper.asp?sessionID=37http://www.pile.com/Reference/openPaper.asp?sessionID=37http://www.pile.com/Reference/openPaper.asp?sessionID=37http://www.pile.com/Reference/openPaper.asp?sessionID=37http://www.pile.com/Reference/openPaper.asp?sessionID=37http://www.pile.com/Reference/openPaper.asp?sessionID=37http://www.pile.com/Reference/openPaper.asp?sessionID=37http://www.pile.com/Reference/openPaper.asp?sessionID=37http://www.pile.com/Reference/openPaper.asp?sessionID=37http://www.pile.com/Reference/openPaper.asp?sessionID=37http://www.pile.com/Reference/openPaper.asp?sessionID=37


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Ru

Ru/SF

Driv ing

Time

Set-up Time

Wait ing Time

Remold ingenergy

Re-Drive

Ru/SF

Set-up facto r, SF

y

Stat ic capaci ty changes

Capacity inc reases (Set-up ) after driv ing stops

Capaci ty decreases (Remolds ) dur ing redr ive

P Fl D i bilit


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Analys is

Program FlowDriveability

Model hamm er &

dr iv ing system

First depth o f

analysis

- soi l model -

Next G/L

Pi le length and

model

Calculate Ru

for f i rst gain/ loss

OutputIncrease

Depth?

Inc rease Depth

Input

Increase

G/L?

N

N


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COMPUTATIONAL PROCEDURE

Driveab i li ty Analys is

Analysis as the pile is penetrated

Input capacity with depth (static analysis)

Generates a driving record

Predicts blow count with depth

Stresses, (diesel stroke), with depth

St t i S i l A l i


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Stat ic Soi l Analys is

Approximate for Bearing Graph: Percent Shaft Resistance

Resistance Distribution

Detailed for Driveability

Shaft Resistance vsDepth

End Bearing vsDepth

Set-up Factor

D i bilit


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Driveability

PURPOSE OF ANALYSIS


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PURPOSE OF ANALYSIS

Preliminary Equipment Selection

Hammer OK for Pile, Capacity

Driving Criterion Blow Count for Capacity and stroke

Driveability

Acceptable Blow Count throughout Acceptable Stresses throughout

Contract No.: Structure Name and/or No.:

Project:

Pile Driving Contractor or Subcon tractor:County:

Contract No.: Structure Name and/or No.:

Project:

Pile Driving Contractor or Subcon tractor:County:


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Pile Drivingand

Equipment

Data Form

County:

(Piles driven by)

Manufacturer: Model No.:

Hammer Type: Serial No.:

Manufacturers Max imum Rated Energy: (ft-lbs)

Hammer Stroke at Maximum Rated Energy: (ft)

Range in Operating Energy: to (ft-lbs)

Range in Operating Stroke: to (ft)

Ram Weight: (kips)Modifications:

Striker Weight: (kips) Diameter: ( in)

Plate Thickness: (in)

Material #1 Ma terial #2

(for Composite Cushion)Name: Name:

Hammer Area: (in 2) Area: ( in2)

Cushion Thickness/P late : ( in) Thickness/P late : ( in)No. of Plates: No. of Plates:

Total Thickness of Hamm er Cushion:

Helmet

(Drive Head) Weight: (kips)

Pile Material:Cushion Area: (in 2) T hic kn es s /S h ee t: (i n)

No. of Sheets:Total Thickness of Pile Cushion: (in)

Pile Type:

W al l T hic kn es s: ( in ) T ap er :Cross Sectional Area: (in2) Weight/Ft:

Pile

Ordered Length: (ft)

Design Load: (kips)Ultimate Pile Capacity: (kips)

Description of S plice:

Driving Shoe/Closure Plate De scription:

Submitted By: Date:Telephone No.: Fax No.:Telephone No.: Fax No.:

County:

(Piles driven by)

Manufacturer: Model No.:

Hammer Type: Serial No.:

Manufacturers Max imum Rated Energy: (ft-lbs)

Hammer Stroke at Maximum Rated Energy: (ft)

Range in Operating Energy: to (ft-lbs)

Range in Operating Stroke: to (ft)

Ram Weight: (kips)Modifications:

Striker Weight: (kips) Diameter: ( in)

Plate Thickness: (in)

Material #1 Ma terial #2

(for Composite Cushion)Name: Name:

Hammer Area: (in 2) Area: ( in2)

Cushion Thickness/P late : ( in) Thickness/P late : ( in)No. of Plates: No. of Plates:

Total Thickness of Hamm er Cushion:

Helmet

(Drive Head) Weight: (kips)

Pile Material:Cushion Area: (in 2) T hic kn es s /S h ee t: (i n)

No. of Sheets:Total Thickness of Pile Cushion: (in)

Pile Type:

W al l T hic kn es s: ( in ) T ap er :Cross Sectional Area: (in2) Weight/Ft:

Pile

Ordered Length: (ft)

Design Load: (kips)Ultimate Pile Capacity: (kips)

Description of S plice:

Driving Shoe/Closure Plate De scription:

Submitted By: Date:Telephone No.: Fax No.:Telephone No.: Fax No.:

R

a

m

Anvil

Requ ired Inpu t Data


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Requ ired Input Data

Hammer Model Energy level (stroke)

Driving system Hammer cushion material (E, A), thickness Helmet weight (of entire assembly) Pile cushion material (E, A), thickness

(for concrete piles only)

Requ ired Inpu t Data


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Requ ired Input Data

Soil (from Borings with elevations)

Type of soils

N-values vs depthor other strength parameters

Elevation of water table

Data Entry


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Data Entry

Resistance distribution

Simple

From soil input wizard

For driveability

Soi l propert ies vs depth:

Shaft un it resis tance requires calculat ion

End bearing - requ ires calculat ion

Quakes and damp ing

Set-up factor

Analys is depths

Availab le Help Ind irect


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Availab le Help - Ind irect

GRLWEAP Help Direct: F3


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Area calcu lator from any area input f ie ld.

Final Recommendat ion


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a eco e dat o

Perform sensi t iv i ty studies on parameters

Plot upper and lower bound resul tsNote: low hamm er eff ic iency no t always con servat ive

Read the helps and disc laimersOn sc reen or af ter pr int ing them

Compare resul ts w i th dynam ic test ing

Summary


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Summary

There are 3 dist inc t ly di f ferent hammer models

External Combust ion Hammer models

Diesel hammer and pressure models

Vibratory hammer model

There are 3 components in dr iv ing system model Hammer Cushion

Helmet and Inserts

Pile Cushion (concrete pi les on ly)

Model Parameters can be found inGRLWEAP Help Section or Hammer data file.

SUMMARY continued


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SUMMARY continued

The wave equation analysis works with Static

Resistance to Driving (SRD) plus a Damping orDynam ic Resistance

Impo rtant analys is opt ions inc lude:

Bearing Graph

Inspectors Chart

Driveabi l i ty Graph

The who le package is geared towards standard

analyses; some research opt ion s exist

S C O S


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Summary: W.E. APPLICATIONS

Design stagePreliminary hammer selection

Selection of pile section for driveability

Selection of material strength for driving

Construction stage

Hammer system approval

Contractors use to select equipment

One means of estimating blow count

Inspectors chart for variable hammer stroke

Summary: Purpose of analys is


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y p y

Develop dr iv ing cr i ter ion

Final Set (Blow coun t) for a requ ired capaci ty

Final Set as a fun ct ion o f energy/stro ke

Check d r iveabi l i tyFinal Set (B low Count) vs. dep th

Stresses vs . depth

Opt imal equ ipment

To Minim ize Driv ing Time

grlweap-hammer-pile-soil-backgound.ppt

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Transcript of grlweap-hammer-pile-soil-backgound.ppt