Bermingham

www.profound.nl 

Sixth International Conference on the Application of Stress-Wave Theory To Piles 1 

Orlando, Sao Paulo, 2000. 

Statnamic, the engineering of art 

P. Middendorp 

Profound, The Netherlands 

ABSTRACT: In present standard engineering practice there seems to be a big gap between engineering 

and art. It is the experience of the author that engineering and art can exist as an excellent combination. This 

will be illustrated by examples from history and the author’s personal experience. One example will be 

treated extensively: the continuous development of the Statnamic load testing method as a marvelous combination 

of engineering and art. The start of the Statnamic concept is described as an interaction between an artist 

and engineers together with developments on the theoretical approaches and technical applications. Further 

the present Statnamic state of the art will be discussed briefly. 

1 INTRODUCTION 

Art was of minor interest to the author when he was 

starting his engineering study at the Technical University. 

Within a short time his interest got a strong 

impulse when he met his present wife, a painter and 

artist, at that time studying at the Royal Academy of 

Art in The Hague. After assisting here with some 

projects he experienced that the “logical” thinking of 

engineers is in no way superior to the “associative 

and intuitive” thinking of artist in finding practical 

solutions, but that both are complimentary and when 

combined into an artist-engineer as a person or a 

team, can result in marvels. 

Still a strong interest of artists for engineering can 

be observed in modern art, for example Panamerenko 

(1996). The artist-engineers are still among us 

and it was the privilege of the author to cooperate 

for long period with one of them: Patrick Bermingham, 

the inventor of Statnamic and the nowadays 

President of the Berminghammer company. 

During his career the author was impressed by the 

many creative solutions of engineers all over the 

In the 15 th century the “artist-engineer”, was a socially 

prominent and respected figure, commissioned 

by powerful and wealthy patrons, well paid and often 

regarded as one of the brightest ornaments in 

sovereign courts. The most famous example of 

course is Leonardo da Vinci (P.Galluzi, 1996). 

Because of cultural changes and specialization a 

gap has been generated between engineering and arts 

and most engineers are not aware nowadays of their 

artist-engineer forefathers. 

Figure 1. Leonardo da Vinci. Automatic 

file-making machine




world. Many engineers are not aware that their creative 

solutions can be considered art and that they act 

idea of Fellenius at that time was that dynamic pile 

testing would become independent of the piling contractor, 

the pile driving rig, and in many instances 

contractor’s unionized labor, as well make him and 

others free to perform dynamic load testing after a 

good and long set up time. This idea was not original 

because several such devices were already around, 

but Fellenius just needed a local practical tool. 

At that time Bermingham had just finished a professional 

education as a sculpturer in London and 

worked also for the Bermingham pile driving and 

hammer manufacturing company. From his childhood 

on Patrick was interested in both engineering 

and art and supplied, for example, several ideas for 

improvement to the Berminghammer pile driving 

hammers. 

It was not such a strange idea that the Berminghammer 

Company chose Patrick to come up with a 

design for a drop hammer. Patrick contacted Fellenius 

and suggested a pile loading system design 

from a fully different viewpoint compared to standard 

engineers. 

“Why do engineers want to drop the weight, why 

do they not send it up into the air?” 

Figure 2. Early sketch of a Statnamic piston and 

cylinder arrangement by Patrick Bermingham 

as “engineer-artist”. In this paper the author wants to 

illustrate his view by using the Statnamic development 

as an example in which one “artist-engineer” 

and many “engineer-artist” contributed with creative 

ideas and solutions. 

Intuitively he converted Newton’s Law from 

Force = Mass times Acceleration 

To 

Mass times Acceleration = Force (Load) 

This concept needed a few months to evolve and 

The Statnamic development will be described by 

introducing the start of Statnamic together with 

some milestones, theoretical approaches and technical 

applications. Further the present research and 

developments will be mentioned and problems that 

still have to be solved. 

2 THE STATNAMIC CONCEPT 

Patrick Bermingham (1998) got the first idea about 

the Statnamic concept in Hamilton in 1985 while 

watching a static load test with kentledge, when he 

first thought about utilizing the inertia of the 

kentledge (Fig. 2). 

According to Fellenius (1995) the idea for the Statnamic 

concept was born in 1987 when he asked Patrick 

Bermingham to design a drop hammer for impacting 

a pile to perform dynamic load tests. The 

Figure 3. First Statnamic device with accelerometer 

and early catch mechanism.




Bermingham made a first prototype (Figure 3) and 

started experiments by shooting masses upwards in 

Hamilton, Ontario in April 1988. He determined the 

feasibility of accelerating a mass upwards from the 

top of the foundation rather than dropping a mass 

onto the foundation 

Bermingham also tried out several concepts of 

catching the reaction mass when falling back from 

launching and also here creative ideas from the “artist-engineer” 

can be observed, especially the gravel 

catching mechanism based on the reliable gravity of 

the earth (Fig.4). With the gravel mechanism a 

gravel container is placed around the reaction mass 

and the space between gravel container and reaction 

mass is filled with gravel. During testing four successive 

stages can be distinguished. In stage 1 the 

Statnamic device is ready for launching. In stage 2 

the reaction mass is launched upwards by highpressure 

gases. During this stage the pile is loaded 

and a Statnamic test performed. Because of the momentum 

the reaction mass will remain moving upward 

in stage 3 and the gravel will flow under the 

reaction mass and over the pile head because of 

gravity. In stage 4 the reaction mass will fall back 

and will be caught by the gravel inside the container 

and the impact load will not be transferred to the pile 

head but to the subsoil. This creative, simple and 

elegant principle is still applied as one of the methods 

in absorbing the energy from the falling reaction 

mass. 

Figure 4. First Statnamic trial tests. 

Bermingham presented his results and ideas to 

several parties and also to the author at the OTC 

(Offshore Technology Conference) at Houston in 

1988. Based on the combination of his engineering 

background and experience with ideas of artists, the 

author immediately recognized the beauty and 

power of Bermingham's idea for pile testing applications. 

Berminghammer and TNO agreed to start a joint 

development and decided to do the first prototype 

testing immediately after the Third Stress Wave 

Conference at Ottawa in 1988. With the help of 

Fokke Reiding and Matthew Janes they realized that 

the long duration feature of the load allowed a fully 

different approach in instrumentation and analysis 

compared to dynamic load testing. 

It was decided to base the load measurement on a 

calibrated load cell, to make the measurement independent 

from pile material properties and to measure 

displacement directly by the use of an electronic 

theodolite. The electronic theodolite was a rather 

expensive instrument and a new tool for measuring 

displacement was developed based on a laser and a 

laser sensor, which is still in use. So the basis of 

measurements became load-time signals and displacement-time 

signals similar to static load testing. 

3 FIRST DEVELOPMENTS 

Figure 5. Successive stages of Statnamic 

Testing. 

In May of 1988 the first model tests where performed 

with instrumentation provided by T'NO. 

These first two days of testing confirmed the ability 

of the very small Statnamic device to produce loads



of up to 5 tons with duration of up to 30 ms. From 

this point onwards the direction of Statnamic was 

upwards. A second model was built and sent to 

TNO in Holland where the instrumentation would be 

developed. In the laboratory at TNO, Statnamic 

tests were performed using a calibrated load cell and 

a new laser measuring system developed specifically 

for the Statnamic test. Both measuring systems 

worked very well the first day and they have remained 

virtually unchanged to this date. 

The next step was to build a Statnamic tester, 

which incorporated the instrumentation and was 

large enough to test a real pile in the ground. A 0.6 

MN tester was built, which was one tenth of full 

scale, but still able to test small piles driven into real 

soil. This load-testing device was first used to test 

piles in the Berminghammer yard in Hamilton, 

McMaster University, and Ashbridges Bay. Since 

that time it has performed tests in Europe, Japan, and 

the United States. The primary objective of this 

equipment was to prove the durability of the instrumentation 

in all weather conditions, and to prove the 

practicality of the equipment in the field. This 

equipment was also used to make the first comparisons 

between conventional static load tests and the 

new load test method. The 0.6 MN device proved 

that Statnamic testing could be performed in all 

types of adverse weather including rain and snow. It 

also proved the simplicity and practicality of the system 

in the field and the first load test comparisons 

proved an unexpectedly close agreement with conventional 

static load tests. The success of this first 

prototype enabled Berminghammer to manufacture 

of a full-scale 5MN tester. 

Statnamic was first called Inertial load testing 

Figure 7. Set up of a 5MN Statnamic device with 

gravel catch mechanism 

(Bermingham, P., et all., 1989. The author gave the 

method its present name Statnamic, realizing that 

the method was positioned between Static load testing 

and Dynamic load testing. 

From the very beginning Statnamic was an international 

development rather than a regional or national 

development. Testing of driven and cast insitu 

piles was carried out in Canada, Holland, 

Germany and the United States during the first two 

years. 

At this time all of the testing was conducted with 

the aim of gaining a better understanding of the behavior 

of piles subjected to very quick loading cycles. 

Statnamic and static load tests were conducted 

side by side as well as on the same pile in as many 

different soil types as possible. Every effort was 

made to collect as much data as possible and to 

avoid making predictions about the static behavior 

of a foundation until we could collect a wide range 

of test results. Today many companies and universities 

are still collecting and expanding this worldwide 

database. 

Figure 6. Patrick Bermingham launching a 

0.6MN device 


The first two years of research revealed a great 

deal about pile behavior when subjected to a Statnamic 

load of 120ms duration. It was observed that 

in the elastic range there was a very good agreement 

between static load deflection and Statnamic load 

deflection, it was observed that in very soft soils and 

clays it was possible to apply a much larger load




than a static load prior to plunging the pile. In stiff 

non-cohesive soils and rock sockets it was observed 

that there was very close agreement between Statnamic 

load test results and static load tests performed 

along side. It was also observed that the sequence 

of loading a foundation had a great effect on 

the perceived similarity of test results and this had to 

be taken into account. It was also observed that during 

a typical Statnamic test the pile would reach 

maximum displacement at some time after peak 

force had been applied. In other words the pile 

would continue to move downwards while the applied 

load at the pile top was decreasing. At the 

point where the pile reached maximum displacement 

the velocity of the pile was zero and then the pile 

would begin to rebound as the load was further decreased. 

This observation which was present in 

nearly all test results except very stiff piles on rock, 

lead to the development of the Unloading Point 

Method (UPM) by the author (P. Middendorp, 

1992). 

4 METHODS OF ANALYSIS 

From the very start of development there has 

been a determined effort to make Statnamic a means 

of measuring rather than a prediction method. This 

has meant putting a very strong emphasis on using 

accurate measuring equipment and recording equipment. 

The measured data will then be more reliable 

and may then be examined more closely. From the 

beginning we have been observing the behavior of 

foundations subjected to very rapid loading with a 

view to being able to better understand the mechanism 

of failure during a Statnamic test. In the end it 

is hoped that Statnamic testing will stand alone as a 

rapid test with a distinct method of analysis, which 

will measure the load deflection behavior and determine 

the factor of safety of the foundation. 

The first approach to analyzing failure was to 

look to the displacement curve and to analyze the 

rate of change of displacement, or velocity of the 

pile. Normalizing the load and plotting load vs. velocity 

was examined in an effort to pinpoint the load 

at which the velocity begins to increase. This only 

worked well when the foundation experienced a 

plunging failure, and it did not work well when the 

pile was in a cohesive material. 

Statnamic test results were also evaluated with a 

simple 2.5mm offset method, which was analogous 

to the Davisson failure criterion but much more conservative. 

All three of these methods of determining 

the point of failure were far too subjective to be of 

any great value. 

In January of 1993, while reviewing the results of 

pile 7 at Texas A&M the author noticed that during 

the unloading of the test the velocity of the shaft 

reached zero at a load, which corresponded closely 

to the ultimate static resistance. The foundation began 

to rebound as the load was further decreased. 

PDA users had observed the significance of the 

point of zero velocity in the 1970's and some attempts 

were made to make use of it. However, during 

pile driving the point of zero velocity at the pile 

head does not correspond to zero velocity anywhere 

else in the pile unless the pile is very short and rigid. 

The author’s observation provided both a practical 

means of determining a significant point on the 

static load displacement curve and also a means of 

estimating the damping coefficient directly from the 

test results rather than from a soil boring. This 

Unloading Point Method (UPM) assumed that the 

damping was a constant, which was zero when the 

velocity was zero, and that the pile was behaving as 

an elastic body, which could be treated as a lumped 

Initially no attempt was made to convert the results 

of Statnamic load testing into quasi-static load 

test results, because they would loose integrity in the 

process. What was recognized was that every Statnamic 

test result was unique and that very small differences 

in the relative stiffness of two different 

foundations could be measured accurately. Much 

like the dynamic resistance of a driven pile, it is very 

useful even though there is no direct correlation to 

static resistance. 

The Statnamic test has been described as applying 

a controlled strain while monitoring corresponding 

deflection. When a test is performed, a predetermined 

load is applied and the resulting deflection is 

measured. 

DLT 

DLT 

signal matching 

yes 

pseudo 

STN 

no 

UPM & stress wave 

corrections 

N w < 6 

no 

N w > 1000 

no 

N w > 12 

yes 

yes 

STN 

UPM, no stress 

wave corrections 

Static load displacement behaviour 

SLT 

Figure 8. Stress wave influences as function of 

wave number N w




mass and a spring. Subsequent research has concentrated 

on testing these assumptions and determining 

the limit of their validity. The unloading point 

method has provided a very simple universal method 

of analysis and was first published at the 4 th International 

Conference on Stress Waves in 1992. The basic 

principles of the method have been presented in 

the Appendix. 

The UPM method is based on the assumption that 

stress wave phenomena can be neglected. The author 

studied the validity of the method with the stress 

wave program TNOWAVE (1996) by varying the 

pile length with constant load duration. To quantify 

the stress wave influence he assumed a wave number 

constant N w = D/L, in which D = c.T and T the 

duration of the load, c the stress wave velocity and L 

the pile length. In this way it was possible to indicate 

when stress wave phenomena could be neglected 

and when they should be taken into account. 

A valuable extension to the UPM method is the 

“Modified UPM” (M-UPM) by Justason (1997). The 

method simply involves the averaging of the top and 

toe velocity and acceleration for calculating the inertia 

and damping. The method can be applied to any 

length of pile, but becomes more necessary as the 

pile becomes longer (low N w numbers). The standard 

UPM method assumes that pile top velocity and 

pile toe velocity are in the same range. The M-UPM 

method is particularly useful when the pile top and 

pile toe velocity are not in the same range (elastic 

pile, high toe resistance). Averaging the pile top and 

pile toe velocities and accelerations yields more accurate 

inertia and damping forces. The method 

yields the best results when used in conjunction with 

an embedded toe accelerometer. 

Prof. Gray Mullins of the University of South 

Florida made an additional improvement to the M- 

UPM method, the "Segmental Unloading Point" S- 

UPM. This method uses measured strain gage data 

to separate the pile into "segments" and perform an 

M-UPM on each segment. The data for each segment 

are added together to produce a total "derived 

static" load-displacement for the top of the pile. The 

S-UPM can be applied to any pile, so long as the 

pile has strain gages distributed over the pile shaft. 

The first application was the Taipei Financial Center 

in Taiwan - 1999. 

The S-UPM method is briefly described below. 

The Segmental Unloading Point Method extends the 

applicability of M-UPM to long piles. All assumptions 

of the Unloading Point Method remain valid. 

The Segmental Method assumes each segment of a 

pile behaves as a single degree of freedom system. 

The method requires embedded strain gauge data. A 

measure of toe displacement is desirable. All results 

are based on measured quantities. 

F = ε E A 

i 

i 

i 

i 

where F i is the measured force at level i, ε i is the 

measured strain at level i (typically an average of all 

strain gages at level i), E i is the calculated (or assumed) 

elastic modulus at level i, and A i is the calculated 

(or assumed) area at level i 

⎛ ε + ε ⎞ 

+ ⎟ 

⎝ 2 ⎠ 

i i+ 

1 

u 

i 

= ui 

1 

− ⎜ Li+ 

1 

where u i is the calculated displacement at level i, 

L i is the length of the pile segment between levels i 

and i+1 

d ⎛ ui 

+ ui 

⎜ 

dt ⎝ 2 

+ 1 

vi 

= 

⎞ 

⎟ 

⎠ 

wherev i 

is the first derivative with respect to time 

of the average displacement for the pile segment between 

levels i and i+1 

a 

i = 

where 

time of v 

i 

dvi 

dt 

ai 

is the first derivative with respect to 

The Unloading Point method is performed on 

each pile segment using the following equation: 

F − S − c v = m a 

i 

− Fi 

− 1 

i 

i 

i 

where S i is the equivalent static force for the 

segment between F i and F i-1 

S i represents the friction forces on the each pile 

segment, with the exception of the bottom pile segment, 

which also has some component of end bearing. 

m i is the mass of the pile segment between i 

and i-1. 

The cumulative derived static force at each level 

can be calculated by the following equation: 

F 

∑ 

= n STATn 

i= 

1 

S 

i 

where n is the pile level number, and F STATn is the 

cumulative derived static force at each level. 

i 

i




The derived static load displacement curve can be 

drawn at each strain gage elevation using F STATn and 

u i . 

Each of the above variables represents an entire 

data set measured over time. 

The S-UPM was first used for the Taipei Financial 

Center for 80m piles in 1999 

5 THE HYDRAULIC CATCH MECHANISM 

Hydraulic catching systems eliminate the need for 

gravel and gravel structure since the upward moving 

reaction masses are caught at the top of their flight 

by four hydraulic actuators (or rams). These 3.2m 

stroke rams are activated by four low pressure (100 

bar) nitrogen accumulators, which store compressed 

nitrogen gas over hydraulic oil. As the weight on the 

rams is released during a test, the compressed nitrogen 

quickly expands to force hydraulic oil into the 

rams causing them to chase the reaction masses to 

the apex of their flight. The hydraulic oil is routed 

(in series) through one-way valves at the base of 

each ram, which restricts reverse flow, and thus the 

downward movement of the masses. Each of the 

four rams is independent of the others providing redundancy 

and safety. The masses remain at this position 

until the user redirects the additional fluid in 

the rams back into the accumulators. At which time, 

a subsequent load cycle can be performed. 

Figure 9. Statnamic device with hydraulic 

catch mechanism (4 MN) 

The foundation industry not only wanted to perform 

larger Statnamic tests but also more of them and at a 

higher frequency. Also in this case Patrick Bermingham 

and design engineers came up with a creative 

solution. In 1995, the hydraulic catching mechanism 

was built to provide a means of testing, without using 

the conventional gravel container, or gravel. 

This simple piece of equipment makes it possible to 

test up to ten individual piles and to perform multiple 

load-cycles. The catch mechanism provides the 

luxury of multiple load cycles within a matter of 

minutes, the ability to inspect the ignition circuit 

without disassembly, the benefit of single truck mobilization, 

and its avoids the environmental problems 

with gravel retrieval with testing over water. 

By transferring the initial weight of the masses to 

the rams at the onset of the test it is possible to perform 

Statnamic testing without a pre-load condition. 

Additionally, hydraulic catching systems have no 

minimum required jump-height for the silencerreaction 

mass assembly, which is a concern for 

gravel catching systems. By removing this restriction, 

low load tests can be performed with much 

greater than 5% reaction mass. Such tests can produce 

long duration load pulses greater than 0.5 seconds, 

thus reducing inertial and damping forces for 

large portions of the test. 

Although the set-up time for a 4MN gravel or hydraulic 

catching systems is comparable, multiple cycles 

can be performed in a matter of minutes when 

using the latter. Further, the breakdown typically 

takes less time. In using gravel-catching systems, 

great care is exercised in the preparation of the ignition 

circuitry. An inadequate igniter connection 

could cost a project as much as a day of delay time. 

This of little concern when using the hydraulic 

catching system due to the ability to raise the entire 

stack of reaction masses with the hydraulic rams so 

as to access the fuel basket. 

A substantial portion of all Statnamic testing costs 

stems from the mobilization of equipment. Typically, 

a 4 MN test requires two tractor-trailers to 

ship the combined weight of the equipment and 

reaction masses (27,000 kg total) where only 20,000 

kg is permitted per truck in the USA (30,000 kg in 

Europe). The device can be equipped with two reaction 

mass options: (1) an entire set of six concretefilled 

steel masses, which requires two trucks to 

ship, or (2) a set of six empty, structurally reinforced 

steel cans. The empty cans option allows single 

truck mobilization to distant sites with a total




shipped mass of 19,000 kg. Once at the site the cans 

can be filled with sand, gravel, water or any combination 

to attain the required mass 

3MN and 4MN hydraulic catching systems are 

now in use in the United Kingdom, the USA and the 

Netherlands for 3MN and 4MN systems. In 2000 a 

mechanical catch mechanism will be constructed for 

a 16 MN device. 

the company AFT. Loads of up to 10 MN have now 

been applied in lateral load testing. 

6 BATTER PILE TESTING 

Drop hammers and dead weight static load tests 

are fully dependent on gravity. One of the big 

advantages of Statnamic is its independence of gravity 

because generating the load it is based on inertia 

Figure 11. Lateral load testing preparations for a 

7.5MN test. 

Major pioneering developments have been performed 

by Dan Brown (1998) of Auburn University 

USA in the analysis of lateral Statnamic tests. 

8 WATER REACTION MASS TESTING 

Figure 10. Over water Statnamic testing on a 

batter pile 

forces. This means that the test can be performed in 

any direction: under batter, lateral and even allows 

to perform a tension test on a pile. In Figure 9 an example 

of the application of batter pile testing is presented. 

It is almost impossible to perform static load 

test in this over water pile testing situation. The 

flight of the reaction mass is guided by a support 

beam 

A most significant development is the use of water 

as a reaction mass when testing piles over-water 

or near-water. By being able to mobilize the inertia 

of the ocean or a river, very large tests may be per- 

7 LATERAL LOAD TESTING 

Lateral STN testing is becoming popular in the 

USA and was strongly encouraged by Barry Berkowitz 

of the FHWA. The first lateral test with a large 

device was at the Salt Lake City, Utah Airport in a 

research project with Kyle Rollins of Brigham 

Young University USA and a 14MN device was 

used. Mike Muchard and Don Robertson of Applied 

Foundation Testing perfected lateral load testing. 

They developed a "jig" for holding the piston and a 

"sled" for holding the silencer and masses. 

A very significant job was for the Mississippi 

DOT in 1998 to simulate a ship impact of 7.5MN by 

Figure 12, Set up of Statnamic water reaction 

mass testing




formed with testing equipment weighing only 1 % of 

Geert Jonker of IHC Foundation Equipment envisioned 

the idea to extend the use the water reaction 

Figure 13. Water reaction mass containers 

the test load. The necessary 5% or10% reaction mass 

would be provided by water confined within a vessel 

and submerged below the surface of the water. This 

weightless reaction mass makes it possible to perform 

very large tests of longer duration than are 

practical today. The use of water reaction will also 

make it possible to drive piles underwater with a 

tool, which will be virtually weightless. 

Statnamic testing using water reaction mass was first 

done by Berminghammer in 1998 in Hamilton Harbour. 

These tests went to 600kN. The first fieldtesting 

was performed for the Port of Lake Charles 

in Louisiana in 1999 by Applied Foundation Testing 

assisted by Berminghammer. The loads were up to 

5 MN. 

9 PILE DRIVING WITH WATER REACTION 

Figure 14. Water reaction mass testing 

mass into a pile-driving tool. Berminghammer, IHC 

and TNO are now working together to build an underwater 

Statnamic hammer, which will consist of a 

large inertial mass, made of water and a Statnamic 

tool capable producing multiple loading pulses. 

This tool will be used to push an anchor pile into the 

seabed and measure its capacity at the same time. 

In the coming years, we will see driving small 

onshore and offshore piles according to the Statnamic 

principle. 

10 EVENTS 

To share the experience among pile engineers and 

to improve the Statnamic test technology the first International 

Statnamic Seminar was held in Vancouver 

in 1995 with 25 papers and 54 participants. The 

Japanese research group on Rapid Pile Load Test 

Methods organized the Second International Statnamic 

Seminar in 1998 with 48 papers and 132 participants. 

The third Statnamic seminar is planned in 

the Netherlands in 2002. 

Figure 15. Artist’s impression of a water reaction 

pile-driving tool. 

In March of 2000, the Japanese Geotechnical Society 

(1998) published a standard for “Method for 

Rapid Load Test of Single Piles”




An ASTM standard for Statnamic type pile testing 

is in progress. 

Creeping phenomena cannot be determined with 

Statnamic, dynamic load testing and in many cases 

not even with static load testing. 

11 RESEARCH AND DEVELOPMENTS 

Companies and universities have accumulated up 

to date more than 700 case histories throughout the 

world. The total number of contract Statnamic tests 

worldwide has exceeded 1000, with testing now occurring 

at a frequency of more than one each day. 

The largest volume of testing to date has occurred in 

Malaysia, with the number of contract tests exceeding 

300. Similar numbers of contract tests have now 

been performed in the United States. The UK and 

Japan are close behind in their numbers of tests. 

An important contribution to the development of 

Statnamic was supplied by the Japanese Geotechnical 

Society, which established the research group of 

Rapid Pile Load Test Methods in 1993. Professor 

Osamu Kusakabe of Tokyo Institute of Technology 

chaired the group. A strong promoter and initiator of 

Statnamic in Japan was Makoto Tsuzuki of Fugro 

Japan. The research group included 30 private institutes 

and companies as members. The activities of 

the Research Group aimed at cataloging the existing 

knowledge about rapid load tests, examining the basic 

characteristics and the applicability of the test, 

and producing scientific interpretations of the Statnamic 

test results. 

The University of South Florida (1998) conducted 

over 150 Statnamic tests in conjunction with 

privately and federally funded test programs. The 

tests programs have included: (1) axial load tests on 

piles and shafts in sands, clays, or rock-sockets, (2) 

lateral load tests on pile groups and shafts, and (3) 

plate load tests on sands and full-scale spread footings 

on sands and vibro-compacted soils (stone columns). 

The application of Statnamic produces excellent 

results in stiff and/or granular soils, although loading 

rate effects have to be taken into account. The influence 

of soil viscosity alongside buildup of pore water 

pressure in fine grained soils requires further development 

of analysis tools and experience. 

(E.L.Hajuk et. al. 1998). 

The soil viscosity shows up in two different 

ways: 

- Creeping, this means continuing settlements 

under constant pile load 

- Velocity dependent soil behavior 

The velocity dependent soil behavior can be split 

up in soil damping phenomena and strain rate dependency. 

Soil damping phenomena can be derived 

straightforward from a Statnamic test. Strain rate 

dependency for fine-grained soils is still subject to 

study, for example by the University of Sheffield 

UK (A.F.L. Hyde. Et all, 1998). Well-documented 

data from pile load test projects is becoming available 

to support the insight in strain rate effects 

(Holyman, et al., 2000). 

12 CONCLUSIONS 

The success of Statnamic stems for a significant 

part from the concepts and ideas generated by “artist-engineers” 

and “engineer-artists”. 

According to Brandl (2000): an excellent engineer 

requires not only a firm theoretical knowledge 

but also comprehensive experience as well as engineering 

feeling and intuition in equal parts. The author 

would like to add: the ability to be creative and 

think in unconventional ways. 

The success of Statnamic can be further explained 

by the high degree of international cooperation and 

research, which has brought the technology to the 

forefront. 

The Statnamic community originated from the 

stress wave community and the author is sure that 

they will remain in close contact. Both have a common 

interest in the research of dynamic phenomena 

of soils and the development of tools for the load 

testing of piles. The incorporation of the ideas of 

“artist-engineers” and “engineer artists” will guarantee 

more marvels in the development of pile testing 

applications and other fields of engineering. 

13 REFERENCE: 

Bermingham, P., Janes, M., ”An innovative approach 

to load testing of high capacity piles”, Proceedings 

of the International Conference on Piling 

and Deep Foundations, London, 1989 

. 

Middendorp, P. Bermingham, B Kuiper, Statnamic 

load testing of foundation piles. 4th International 

Conference on Stress Waves, The Hague, Balkema, 

1992




Galluzi, P., Mechanical Marvels, Invention in the 

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14 APPENDIX 

F stn 

 

F stn 

 

The Unloading Point Method (UPM) 

Step I) Determination of static resistance from 

unloading point 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

M 

 

F soil 

 

 

F a 

Assumption: 

The long duration Statnamic load F stn allows modelling of the pile as a 

concentrated mass (M) and springs 

F stn = Statnamic force (measured and known) 

u = displacement (measured and known) 

v = du\dt = velocity 

(known) 

a = d 2 u/dt 2 = acceleration (known) 

F soil = F u + F v 

F u = static resistance (unknown) 

F v = C.v = damping force 

(unknown) 

C = damping factor 

(unknown) 

Load F stn 

STATNAMIC SIGNALS 

F a = M.a 

(known) 

Equilibrium: 

F unl 

F stn = F soil + F a 

Displacement u 

Time 

F stn = F u + F v + F a 

F u = F stn - C v - M.a 

At maximum displacement (Unloading Point) 

v = 0 → u = maximum, t = t umax 

F unl = F stn(t umax) , a unl = a(t umax) 

u unl 

Velocity 

v 

Time 

F u(t umax) = F unl - M.a unl 

(known) 

Static resistance F u is known at u unl 

v = 0, t = t umax 

F u(t umax) , u unl is a static point 

Acceleration a 

Time 

Step II) Construction of static load-displacement 

Assumption: 

diagram 

The soil is yielding over range F stn(max) to F unl 

So F u = F unl 

a unl 

Time 

Over this range the following equation is valid 

F v = F stn - F unl - F a 

Load 

F stn 

with F v = C.v 

C = (F stn - F unl - F a) / v 

Calculate mean damping factor C mean for above range. 

F stn 

Now static resistance Fu can be calculated at all points 

F u 

F stn(max) 

F u = F stn - C mean .v - F a 

Draw static load-displacement diagram with F u and u 

F unl, u unl 

F a 

Displacement u 

Load displacement diagrams

Bermingham

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