On the Solution to Pre- Buckling of a Thin Rectangular Plate Subjected to a Thick Strip in-plane Loading

The current paper deals with the problem of the simply supported thin rectangular plate subjected to the intermediate strip in-plane loading. Based on the strain energy method (Fourier ansatz), the critical (minimum value) of buckling stress occurrence was determined in a general form dependent only on the strip thickness, strip location, plate width and stress magnitude. Compatible with the classical columns Euler method it was found that the plate stability is decreased with the increasing of the plate width due to larger induced stresses. Also, strip location relative to the support region was found to influence the buckling (same analogy to the Euler buckling theory; consider the strip as a both sides pressed rod). Additionally, the strip width parameter increase is likely to cause larger buckling stress. Moreover, expressions that includes both axial and transverse loads for different extended cases configurations were also derived and examined based on the strain energy method alongside explanation for possible applications (thin aluminum plate welding). In a general view, it was found that the cases of combined axial and perpendicular loading action are less stabilized than cases where only one kind of loading configuration is participated. Finally, the buckling stress was found to agree qualitatively with the cited literature.

Damping Estimation of an Eight-Story Steel Building Equipped with Oil Dampers

The damping estimation of an eight-story steel building equipped with oil dampers is examined, carried out by adopting a proposed framework, which consists of an enhanced strain-energy method and an improved direct method for model updating. The building is located at Tohoku Institute of Technology and is equipped with a structural monitoring system that measures its seismic response, including floor acceleration and displacement and force of oil dampers. The enhanced strain-energy method is first developed and employed to assess the supplemental damping and stiffness provided by oil dampers, herein quantified in the form of equivalent damping ratios and natural frequencies. Then, modal characteristics extracted from the earthquake measurements are modified accordingly and utilized for the building model updating, in which mass and stiffness matrices are corrected by the improved direct method. The updated model accurately reproduces the target modal data, especially measured mode participation factors, and is further used for the building response predictions. Through prediction validations, the precision of the modified modal parameters is verified. Finally, a large earthquake event is chosen to demonstrate the effectiveness of the proposed framework for the damping estimation of the investigated building.

Strain energy method for solving wave problems of a flexible thread

The paper considers the behavior of a flexible deformable thread when longitudinal and transverse waves pass through it. The processes occurring in a thread during the passage of a wave perturbation through it are analyzed under the assumption that the wave front zone is limited comparing with the length of the thread but not assuming this quantity to be of infinite smallness. In contrast to other similar works, no assumptions were made in advance about the shape of the thread in the zone of the wave perturbation passage (the fracture of the thread) and the dependence of the tension force on its elongation. The only requirement is the implementation of the general theorems of dynamics. Formulas for the relation of the thread speed before and after the passage of the wave with a change in the angle of thread inclination are obtained making possible solving wave propagation problems in a new way. The method is illustrated by new solutions to known problems, which allows comparing the obtained results with known solutions and verifying the advantages of the proposed method.