A.P.Leschenko has offered a completely new approach to structural mechanics, which allowed for a unique technique for structural engineering to be developed. This new method is based on the following three discoveries made by the author:

--- Phenomenon of separating torsional strains of elastic bars;

--- Specific law of analogy in stability and oscillation of elastic systems;

--- Principle of force factors pairing in structural mechanics.

All actual approaches and theories of structural mechanics widely employ such an abstract concept as generalized force, neglecting, however, a definite and practical concept of external force factor. In author's opinion, this breaks the interrelations between the external and internal forces acting on structures and the strains occurring in the structures, which leads to an implicit violation of the classical mechanics laws, namely the law of energy conservation, the Lagrange principle, and Newton's laws. It should be stressed that Leschenko does not suggest that one concept should be simply replaced by the other, but interrelates the external action with other forces and factors concurrently acting on the structure.

Thus, the author has proposed to consider any elastic system as based on three permanently acting factors: 1) external forces; 2) internal forces; and 3) elastic strains; and indicated the principles linking the effects of these factors. Leschenko has developed a graphical scheme (the so-called *triad*) for an analysis of elastic systems. The *triad* analysis of elastic systems has enabled to reveal great contradictions in the available structural calculations of plates, shells and bars. On the other hand, the new method has allowed for an adequate model of stress-and-strain state of constructions to be developed, which, for the first time ever, has made it possible to predict with a high accuracy the moment of structural failure.

As main advantages of the new method we can list comparatively quick calculations of all types of structures, the examination and verification of design solutions, and`the detection of critical loads and weak points of constructions. All these result in a considerable saving of materials, which is accompanied by improving the safety of constructions.

Introduction and a brief historical review |

Conventional symbols used in the book |

Chapter I. | Description of the author's invention |

| 1.1. | Calculation method to control catastrophic destruction |

| 1.2. | Description of invention |

| | 1.2.1. | Object -- phenomenon |

| | 1.2.2. | Introduction |

| | 1.2.3. | Justification of invention |

| | 1.2.4. | Formula of invention |

| 1.3. | Description of invention |

| | 1.3.1. | Object -- law |

| | 1.3.2. | Introduction |

| | 1.3.3. | Justification of invention |

| | 1.3.4. | Formula of invention |

| 1.4. | Description of invention |

| | 1.4.1. | Object -- law |

| | 1.4.2. | Introduction |

| | 1.4.3. | Justification of invention |

| | 1.4.4. | Formula of invention |

Chapter II. | The method of analogy in stability of thin walled constructions (a general linear theory of stability) |

| 2.1. | Setting of the problem on stability of eccentrically compressed bar and ways of its solution |

| 2.2. | Loss of stability "in small" and "in big" |

| 2.3. | Possible forms of stability loss "in big". Solution of differential equation of the form |

| 2.4. | Classification of load combination in stability. A concept of analogy |

| 2.5. | The theorem on analogy in stability |

| 2.6. | The analogy method in calculations on stability of centrally and eccentrically compressed thin walled bars. Calculation of the examples was performed using a computer |

| 2.7. | Experimental grounding of the analogy method and correction provided by the experiment for the calculations on normative technique |

| 2.8. | The analogy method in calculations on stability of the beam loaded with a concentrated load in the middle of the span |

| 2.9. | The analogy method in calculations on stability of the beam loaded with the load evenly distributed by the length |

| 2.10. | The analogy method in calculations on stability of the beam loaded with concentrated moments at bearings |

| 2.11. | Method of analogy in calculations on stability of thin plates and gentle cylindrical shells |

Chapter III. | Application of the method of analogy in calculation on stability of construction elements of bridges and flying apparatus |

| 3.1. | Introduction |

| 3.2. | Solution of the sets of differential equations of stability of the analogy method for thin walled bars with rigidity variable by the length |

| 3.3. | The qualitative method of solution of some equations on stability of bars |

| 3.4. | General informations about frame/beam bridges and description of their constructions |

| 3.5. | Calculation on stability of the span structure of the frame/beam bridge |

| 3.6. | The computer programs at calculation of the bridge's girder on stability |

| 3.7. | The forces effecting for carrier rocket in flight |

| 3.8. | The forces effecting an aircraft in flight |

| 3.9. | On selection of the design model of construction elements of flying apparatus at calculation on stability |

| 3.10. | The calculation on stability of a carrier rocket |

| 3.11. | Calculation on stability of construction elements of the aircraft |

Chapter IV. | Corrections provided by new concepts on state of the problems on strength, stability and dynamics of thin-walled constructions |

| 4.1. | LaGrange-Castiliano's principle in the theory of elasticity |

| 4.2. | A variational method in construction mechanics |

| 4.3. | The corrections provided by new concepts to a state of the problem on strength of thin walled constructions |

| 4.4. | The corrections provided by new concepts to the state of a problem on stability and oscillations of thin walled constructions |

Conclusion |

References |

Introduction and a brief historical review

The second part of the XX century was characterized by the rapid
process of scientific/technical revolution which embraced all
the spheres of human activity.

The actual task for theory as well as for practice is the
scientific understanding and maximum application of
scientific/technical achievements born by scientific/technical
revolution.

Development of the new branches of engineering as cosmonautics,
rocket construction, the study of hydrosphere depth sets the
more complicated tasks on calculation of constructions on
stability and oscillations before engineers and designers.
Accidents and catastrophes of different constructions that still
take place in practice testify that the existing methods of
calculation of constructions do not take into account all the
variety of factors effecting their durability and stability.

In many researches of late the cases of discrepancy between the
existing methods of calculation of constructions on stability
and practice of designing and experiments were indicated.

The investigators were faced with a need of immediate search of
new ways of solving this problem caused by these discrepancies.

To exclude these discrepancies from practice, to explain all the
paradoxes in the field of elastic systems' stability, to create
a complete theory of constructions' stability -- is the main
purpose of investigations.

The author has involved to some extent in solving these problems
for thin walled constructions.

Over 200 years ago Leonard Eiler for the first time considered
the problem on buckling of prism bar.

These results have not been used for about one hundred years and
only in the second part of the XIX century Eiler's research
attracted attention.

During this period which was characterized by a rapid growth of
industry and construction engineering, the engineering
constructions of primary importance which had been built without
strict theoretical basis and calculations have appeared. It was
the reason of many accidents and catastrophies. Desriptions of
some of them already appeared at the end of the XIX century on
the pages of technical journals.

V.L.Kirpichev in his book "The course on strength of
materials" gives interesting informations that 251 bridges had
collapsed in the period from 1875 to 1888 in the USA. Bridges
are the most important engineering constructions. All this
required development of science of construction mechanics and in
particular the part of construction's stability. When accidents
of the bridges had been investigated rich material was
accumulated which have impulses to development of engineering
ideas and construction mechanics.

Thus, after the catastrophy of the bridge across the Kevda river
(1875) at Syzran -- Morshansk railway F.S.Yassinsky developed
the calculation technique of the trusses' compressed belts.

As the result of the analysis of the Tei Bridge wreckage (1879)
an effort of wind load at calculation on stability against
turning over was taken into account.

After the Quebeck bridge across St.Laurentis river (Canada,
1907) has collapsed, stability of the compressed elements of
composed section was considered.

The absence of calculation technique for stability of compressed
elements is also the main reason of the bridge wreck across the
river Birs at the village of Menhenstein (Switzerland, 1891),
the author of which was famous engineer Eifel.

The fields of developing technique as shipbuilding, machine
building etc also required strict theoretical grounding. The
fact that a field of stability of thin walled constructions and
plates had not been studied caused a wreck of the ship
"Machchi" at the Spain coast in the seventies of the last
century. The elements of the body's covering lost stability at
a comparatively small wave and the ship has broken in two. It all
happened at the edge of XIX and XX centuries and it pushed
forward new problems and profound studies in the field of
stability.

Thus, S.P.Timoshenko in 1905 first set the problem on
stability of a flat form of i-beam bar.

Russian scientists I.G.Bubnov, S.P.Timoshenko,
B.G.Galerkin, P.F.Papkovich, A.N.Krylov, L.S.Leibenson,
V.Z.Vlassov and others played the great part in development of
theory and calculation technique of constructions.

I.G.Bubnov in his capital paper "Construction mechanics of
a ship" solved many particular problems and for the first time
completely solved one of the most difficult task -- the problem
of a plate buckling loaded evenly with distributed load.

In B.G.Galerkin's book "Elastic plates" (1933) the method of
a differential equation integration of a plate buckling was
proposed.

P.F.Papkovich, the Soviet engineer and the scientist brought
invaluable contribution to research in the field of stability of
constructions. His eleven theorems on stability of elastic
systems are fundamental in this field. Brilliantly combining
engineering intuition and analysis of a scientist he stepped far
forward. The vast monograph by P.F.Papkovich on building
mechanics of a ship is the text book for scientists and
engineers.

A merit of the Soviet scientist V.Z.Vlassov should be noted in
particular. In 1935 he formulated the law of section areas which
he proposed as a basis of practical method of calculation of
ribbed arches-shells, general theory of strength and stability
of thin walled bars of an open profile.

The author of the present book had to encounter not once with
practical aspects of the construction operation.

Thus, analysing the catastrophy at Savinsk concrete plant in
Archangelsk region (1970) I established that the designers
accepted wrong concepts at calculation of pressed bent elements
of columns of raw materials storage. Designed according to
generally accepted technique the columns did not endure
overloads from the cover of the workshop and became unstable
which resulted in the storage collapse. The State suffered great
loss. This experiment set by the life made the author to
critically observe some aspects of the theory of bars'
stability. The analysis of the catastrophy may be seen in
Fig. 2.1.

Conclusion: since as at *e* --> 0,
*N*_{pred} == *N*_{э}, then introducing off-center *e* > 0 into
calculation scheme the conditions of the construction operation
get worse and, consequently it should be
*N*_{pred} < *N*_{э}. There is an error admitted in the
Inquiry Book [14, p.246, R. 17.7] as *N*_{pred} > *N*_{э}.

After the catastrophy the practical question arises: what
expenses, time and force will be required to restore the
workshop? Simultaneously, an idea occurred: what forces are
needed to be applied and what operation they will perform in
order to straighten the columns' elements that lost their
stability and put them back into the previous position? It
appeared that to "uncoil" the columns' twisted elements to the
previous position it is necessary to apply a load of
a diametrical compression (draft) which could cause a torsion form
of stability loss. When the problem was set up the area of
elastic and plastic deformations was not limited, but the
problem on a load character capable to put the elements into the
previous position was set up. In the considered case a load
character was of interest but not a fact if this load was real
which could take place in practice or unreal, fictitious load.
According to loads' classification by P.F.Papkovich, the load
of a diametrical compression is a specific one and it
corresponds totally to a torsion form of stability loss. Thus,
the problem occurred on stability of a diametrically compressed
bar.

The further analysis demonstrated that this is a purely
bifurcation problem and at certain value, the forces of cross
compression may cause purely a torsion form of stability loss
the same as according to Eiler, the force of central compression
may cause a longitudinal curve of a bar.

Revealing of the new type of a load and the search of the ways
of its realization in stability problems made the author to turn
to the theorems by P.F.Papkovich, to his classification of
loads.

In development of P.F.Papkovich's ideas and in relation the
introduction of new types of load into consideration a more
general classification of loads combinations in stability is
given in the second chapter of the present book, the concept
"analogy" is introduced and a new theorem and a corollary to
it are formulated and proved.

For a consistent and argumented realization of new concepts it
was necessary to carry out the profound analysis of the existing
methods of calculation of stability in practice. In the previous
book such analysis for thin walled bars is given, contradictions
have been revealed in V.Z.Vlassov's theory, the new hypothesis
on division of a torsion angle has been proposed and
experimental basis of this hypothesis in a theory of stability
of thin walled bars has been given.

In order to ground new concepts in the theory of stability
a series of experiments on testing eccentrically compressed thin
walled bars had been conducted in the laboratories of Leningrad
Engineering/Construction Institute which produced positive
results and allowed to develop calculation technique of thin
walled constructions based on analogy in stability- an analogy
method.

Taking part in construction of Kalinin Nuclear Power Plant, the
author introduced the analogy method into the practice of
construction. Thus, bearing elements of the columns of machinery
hall of NPP and the Club of construction workers in t. Udomla,
Kalinin region had been recalculated according to the new
technique. It produced economical effect of 10 thousand roubles.

A further development of the analogy method allowed to the
author to elaborate an oscillation theory and flutter of thin
walled constructions.

Prof. Alexander Petrovich Leschenko was born in 1939. He has got PhD degree
in Civil Engineering.

Prof. Leschenko has 3 Certificates on his discoveries in the field of
Structural Mechanics:

1) Certificate DO N 000008 on discovery Principle of pairing of force
factors;

2) Certificate DO N 000006 on discovery Phenomena of separating
torsional strains of elastic bars;

3) Certificate DO N 000007 on discovery Specific analogy law in
stability and oscillation of an elastic system;

and 2 patents on his inventions:

1) Patent N 2150098 of 27.05.2000 on invention Testing method for
buckling failure of metal constructions;

2) Patent N 542435 of 21.09.1978 on invention Breakdown controller of
pile driver.

His current research concerns various aspects of Civil Engeneering and
Structural Mechanics.

The publication list comprises the following books:

-- Structural mechanics of thin-walled structures (in Russian),
Moscow, Stroyizdat, 1989;

-- New principles in structural mechanics of thin-walled
structures (in Russian), Moscow, Stroyizdat, 1995;

-- Fundamental structural mechanics of elastic systems (in
Russian), Taganrog, Sphinx, 2003.