Leonid S. Lyakhovich, DSc, Professor, Department of Structural Engineering TSUAB, Academician of RAACS, Honoured Master of Sciences and Engineering of Russia, Honorary Constructor of Russia, lls@tsuab.ru, Tomsk.

Research interests include stability and oscillation analyses, system design of the lowest material consumption. The energy equivalence criterion proposed by Lyakhovich for the stability and oscillation analyses, underlies the development of the approximation theory when describing the behavior of structures, including the data processing of non-destructive testing. The proposed criterion of determination of the place of the predetermined number in a spectrum of critical forces and eigen-frequencies of elastic systems, clarifies and develops the theory of speculative analysis of the structure stability and oscillations. The energy equivalence criterion is also used for the kinematic analysis of buildings. It is adapted for the stability analysis of systems with unilateral and piecewise linear constraints. Based on the adapted criterion combined with the branch and bound method, Lyakhovich proposes the method of seeking for lower and upper critical loads in such systems. In the optimization theory, a method is proposed to simultaneously vary cross-sectional parameters of not only elements, but also constraints, additional or removed loads, and consider different heterogeneous limits. A series of properties is identified for systems with minimum material consumption. Among them are properties of buckling modes and eigen-frequencies at a reasonable arrangement of bonds for the optimal stiffness, and structural loading-unloading problems in the case of oscillations. Based on identified properties, the assessment criterion is formulated for the optimum solutions, and the synthesis method is suggested for optimum systems possessing properties known in advance. Lyakhovich is the author of more than a hundred scientific papers.