Showing papers by "Reza Attarnejad published in 2015"

Effects of forward directivity on the response of soil–structure systems

Abstract: The effects of input parameters of pulse-like ground motions on the response of soil–structure systems are investigated through employing an ensemble of 64 ground motions. The soil and superstructure are idealised as a semi-infinite cone and a non-linear multiple-degrees-of-freedom shear building, respectively. The results confirm that the location of the critical storey is significantly affected by the pulse inputs and interacting parameters. Also, the pulse period ranges in which the critical storey complies with upper storeys are influenced considerably by interacting parameters. Moreover, there is a trade-off between pulse period and amplitude to determine the seismic demands of the structure.

Numerical free vibration analysis of higher-order shear deformable beams resting on two-parameter elastic foundation

Abstract: Free vibration analysis of higher-order shear deformation beam resting on one- and two-parameter elasticfoundation is studied using differential transform method (DTM) as a part of a calculation procedure. First,the governing differential equations of beam are derived in a general form considering the shear-freeboundary conditions (zero shear stress conditions at the top and bottom of a beam). Using DTM the derivedequations governing beams, followed by higher-order shear deformation model, Timoshenko model andBernoulli-Euler model are transformed to algebraic forms and a set of recurrence formulae is then derived.Upon imposing the boundary conditions of the beam at hand, a set of algebraic equations are obtained andexpressed in matrix form. Finally, the transverse natural frequencies of the beam are calculated through aniterative procedure. Several numerical examples have been carried out to demonstrate the competency ofthe present method and the results obtained by DTM are in good agreement with those in the literature.Afterward, the free vibration of beams followed up by different models (i.e. Bernoulli-Euler, Timoshenkoand different higher-order models) are taken into consideration.

On the FEM Analysis of Higher-Order Shear Deformable Beams: Validation of an Efficient Element

Abstract: Since the accuracy of results obtained through displacement-based finite element method (FEM) considerably depends on the accuracy of shape functions used to interpolate the displacement field within an element, this paper aims at presenting a new efficient element for static and free vibration analysis of higher-order shear deformable beams using FEM with introducing basic displacement functions (BDFs). First, BDFs are introduced and computed. Afterward, new efficient shape functions are developed in terms of BDFs during the procedure based on the mechanical behavior of the element in which presented shape functions benefit generality and accuracy from stiffness and force method, respectively. Finally, deriving structural matrices of the beam with respect to new shape functions, static and free vibration behavior of the higher-order shear deformable beam is studied using FEM. The accuracy and economy of the method are demonstrated through several numerical examples.

3-node Basic Displacement Functions in Analysis of Non-Prismatic Beams

Abstract: Purpose– Analysis of non-prismatic beams has been focused of attention due to wide use in complex structures such as aircraft, turbine blades and space vehicles. Apart from aesthetic aspect, optimization of strength and weight is achieved in use of this type of structures. The purpose of this paper is to present new shape functions, namely 3-node Basic Displacement Functions (BDFs) for derivation of structural matrices for general non-prismatic Euler-Bernoulli beam elements. Design/methodology/approach– Static analysis and free transverse vibration of non-prismatic beams are extracted studied from a mechanical point of view. Following structural/mechanical principles, new static shape functions are in terms of BDFs, which are obtained using unit-dummy-load method. All types of cross-sections and cross-sectional dimensions of the beam element could be considered in this method. Findings– According to the outcome of static analysis, it is verified that exact results are obtained by applying one or a few elements. Furthermore, it is observed that results from both static and free transverse vibration analysis are in good agreement with the previous published once in the literature. Research limitations/implications– The method can be extended to structural analysis of curved and Timoshenko beams as well as plates and shells. Furthermore, exact dynamic shape functions can be derived using BDFs by solving the governing equation for transverse vibration of beams. Originality/value– The present investigation introduces new shape functions, namely 3-node Basic Displacement Functions (BDFs) extended from 2-node functions, and then compares its performance with previous element.