Resumo em Inglês:

The environment prevalent in ocean necessitates the piles supporting offshore structures to be designed against lateral cyclic loading initiated by wave action. Such quasi-static load reversal induces deterioration in the strength and stiffness of the soil-pile system introducing progressive reduction in the bearing capacity as well as the pile head displacement. To understand the effect of lateral cyclic load on lateral capacity of pile group in soft clay, a series of laboratory experiments were performed on model piles in soft cohesive soil. This paper presents the experimental observations made and the relevant conclusions drawn there from.

Resumo em Inglês:

This paper presents the study of the vibratory behavior of rotating composite shafts. The composite shaft contains isotropic rigid disks and is supported by bearings that are modeled as springs and viscous dampers. An hp-version of the Finite Element Method (FEM) is used to model the structure. A hierarchical finite element of beam type with six degrees of freedom per node is developed. The assembly is made by the standard version of the finite element method for several elements. A theoretical study allows the establishment of the kinetic energy and the strain energy of the system (shaft, disk and bearings) necessary to the result of the equations of motion. In this study the transverse shear deformation, rotary inertia and gyroscopic effects, as well as the coupling effect due to the lamination of composite layers have been incorporated. A program is elaborate for the calculation of the eigen-frequencies and critical speeds of the system. The results obtained compared with those available in the literature show the speed of convergence, the exactitude and the effectiveness of the method used. Several examples are treated, and a discussion is established to determine the influence of the various parameters and boundary conditions.

Resumo em Inglês:

An elastic damage model for concrete has been proposed considering damage-induced bimodularity. A scalar damage parameter has been chosen to quantify the damage. Expressions for the material compliance tensor components have been derived from the assumed strain and complementary energy functions stated in terms of the principal stresses and strains. Incremental constitutive equations have been derived incorporating the elastic behavior due to stress increments as well as stiffness degradation. Within the current damage surface, the stiffness of the material with constant damage varies with applied stress variations. During loading beyond the current damage surface, the material experiences stiffness degradation due to increase in extent of damage suffered by it. Using the proposed elastic damage model, the material response has been predicted for different load histories.

Resumo em Inglês:

A technique for enhancement of buckling loads of composite plates is proposed. The technique relies on using stress stiffening to create a non-zero tensile force acting along the plate plane which ultimately permits the application of higher external compressive forces that lead to traditional buckling instabilities. The idea is to completely restrain the plate movements in its plane direction, at all edges, and to apply voltages to pairs of symmetrically bonded piezoelectric patches. This voltage is applied such that the piezoelectric patches contract resulting in a uniform tensile force over the plate plane.

Resumo em Inglês:

The resonance characteristics of a two-span continuous beam traversed by moving high speed trains at a constant velocity is investigated, in which the continuous beam has uniform span length. Each span of the continuous beam is modeled as a Bernoulli-Euler beam and the moving trains are represented as a series of two degrees-of-freedom mass-springdamper systems at the axle locations. A method of modal analysis is proposed in this paper to investigate the vibration of two-span continuous beam. The effects of different influencing parameters, such as the velocities of moving trains, the damping ratios and the span lengths of the beam, on the dynamic response of the continuous beam are examined. The two-span continuous beam has two critical velocities causing two resonance responses, which is different from simple supported beam. The resonance condition of the two-span continuous beam is put forward which depends on the first and second natural frequency of the beam and the moving velocity.

Resumo em Inglês:

In this study, mixed finite element models of plate bending are developed to include other variables (e.g., the membrane forces and shear forces) in addition to the generalized displacements to investigate their effect on nonlinear response. Various finite element models are developed using the weighted-residual statements of suitable equations. The classical plate theory and the first-order shear deformation plate theory are used in this study and the von Karman nonlinear strains are accounted for. Each newly developed model is examined and compared with displacement finite element models to evaluate their performance. Numerical results show that the new mixed models developed herein show better accuracy than existing displacement based models.