PART 1 DEALS WITH THE DYNAMIC ASPECTS OF THE SUBJECT: MATHEMATICAL ANALYSIS OF SYSTEMS SUBJECTED TO INDEPENDENT VIBRATIONS BY MEANS OF MATHEMATICAL MODELS. THE ANALYTICAL SYSTEMS USED ARE NON-LINEAR SYSTEMS, HYDRODYNAMICS AND NUMERICAL METHODS. PART 2 EXAMINES SEISMIC MOVEMENTS, THE DYNAMIC BEHAVIOUR OF STRUCTURES AND THE BASIC CONCEPTS OF THE SEISMIC DESIGN OF STRUCTURES.

Fundamentals of earthquake engineering

It is 100 years since the well-know Mohr-Coulomb strength theory was established in 1900. A considerable amount of theoretical and experimental research on strength theory of materials under complex stress state was done in the 20th Century. This review article presents a survey of the advances in strength theory (yield criteria, failure criterion, etc) of materials (including matellic materials, rock, soil, concrete, ice, iron, polymers, energetic material, etc) under complex stress, discusses the relationship among various criteria, and gives a method of choosing a reasonable failure criterion for applications in research and engineering. Three series of strength theories, the unified yield criterion, the unified strength theory, and others are summarized. This review article contains 1163 references regarding the strength theories. This review also includes a biref discussion of the computational implementation of the strength theories and multi-axial fatigue.

Advances in strength theories for materials under complex stress state in the 20th Century

A review on static and dynamic shape control of structures by piezoelectric actuation

Tuned liquid column dampers in offshore wind turbines for structural control

Review: A review of active structural control: challenges for engineering informatics

1. Kinematics.- 2. Statics, Systems of Forces, Hydrostatics.- 3. Mechanical Work, Power, Potential Energy.- 4. Constitutive Equations.- 5. Principle of Virtual Work.- 6. Selected Topics of Elastostatics.- 7. Dynamics of Solids and Fluids, Conservation of Momentum of Material and Control Volumes.- 8 First Integrals of the Equations of Motion, Kinetic Energy.- 9. Stability Problems.- 10. D'Alember's Principle and Lagrange Equations of Motion.- 11. Some Approximation Methods of Dynamics and Statics.- 12. Impact.- 13. Elementary Supplements of Fluid Dynamics.- 14. Selected Problems.- Table A. Some Average Values of Mechanical Material Parameters.- Table B. U.S. (Basic) Customary Units and Their SI Equivalents.

Mechanics of solids and fluids

Sealed liquid column damper (TLCD) are tuned in the low-frequency range of application (say below 5 Hz) with respect to a selected natural frequency of the main structure by means of a geometrical transformation in analogy to the classical tuned mass damper (TMD). To improve the performance in MDOF buildings even further, the influence of neighboring modes is taken into account by fine-tuning in state space, rendering the optimal parameters modified. Final adjustments are easily made in the course of in situ testing. The passive sealed TLCD making use of the gas-spring effect and, since turbulent damping of assigned strength is present, is perfectly suited to counteract steady-state vibrations. Reduction of transient vibration peaks, observed within the initial period of the strong motion phase of earthquakes, requires active control, realized by controlled pressure input into the gas volume. The TLCD is commonly sufficiently damped and the vertical component of the seismic excitation does not cause parametric resonance. A sufficient condition based on the cut-off damping must be checked. Computer simulations and small scale experimental testing under time-harmonic-, single seismogram- and random- forcing confirmed the excellent performance and robustness of the TLCD. Optimal solutions for benchmark MDOF structures with multiple TLCD are presented when excited either by wind gusts or by earthquakes. A base-isolated structure is considered with the effective damping supplied by a TLCD in the basement. Copyright © 2005 John Wiley & Sons, Ltd.

Control of tall building vibrations by sealed tuned liquid column dampers

Technische Mechanik der festen und flüssigen Körper

Sealed tuned liquid column dampers, with a gas-spring effect taken into account are ideally suited to increase the effective structural damping of bridges vibrating in the low-frequency band, up to about 5 Hz. Modal tuning in analogy to the classical mechanical damper followed by fine-tuning in state space, render the parameter optimal and the control more robust. Sufficient conditions to prevent parametric resonance of vertical motions of the TLCD and to avoid the synchronization effect of densely walking pedestrians on the lateral bridge vibrations are presented. Numerical simulations are experimentally checked for a novel laboratory model. Effective structural damping of the Millennium Bridge by five TLCD and of the Toda Park Bridge by a single TLCD are worked out in detail. Copyright © 2005 John Wiley & Sons, Ltd.

Control of pedestrian-induced vibrations of long-span bridges

The present contribution explores two fundamental aspects of eigenstrain analysis in three-dimensional bodies. At first, distributions of eigenstrain are derived that do not cause stresses, so-called stress-free or impotent eigenstrains. We consider bodies of finite extent with geometric surface constraints, such as imposed by immovable supports or rigidly clamped boundaries. Within the setting of anisotropic linear elastic bodies, it is verified that a field of eigenstrains that is equal to the field of strains produced by external forces is a stress-free one and that the deformations caused by these eigenstrains and the deformations caused by the forces are equal. Hence, the stress-free eigenstrain load represents an exact solution for the static shape control problem of bodies acted upon by forces. Additionally, nonuniqueness of this shape control problem is demonstrated, and three-dimensional eigenstrains responsible for that nonuniqueness are identified. This is performed by showing that incompatible distributions of eigenstrain and the strains generated by these fields, when applied as a compatible distribution of eigenstrain, result in identical deformations and stresses. Deformation-free fields then result by applying the difference between those fields of eigenstrain.

Franz Ziegler

Papers

Mechanics of solids and fluids

Control of tall building vibrations by sealed tuned liquid column dampers

Technische Mechanik der festen und flüssigen Körper

Control of pedestrian-induced vibrations of long-span bridges

Eigenstrain Without Stress and Static Shape Control of Structures