Sharif Digital Repository

In this paper, a new analytical method is presented that can be used to determine the behavior of particular steel beam-to-column extended end plate connection in linear and nonlinear regions. A common means of forming a rigid joint between a universal beam and column is to weld an end plate to the beam end and then to bolt it to the column. A physically based analytical method that can predict the behavior of bolted and extended end plate eave connections, using the connection dimensions as input, is presented. This article demonstrates an analytical procedure for the establishment of elastic and plastic parts of the M-χ curve of this form of connection. An analytical method is proposed for... 

In this paper, the numerical modeling of powder-forming process is simulated by a finite element analysis using a density-dependent endochronic plasticity model. Endochronic constitutive model based on large strain plasticity is presented. The elastic response is stated in terms of hypoelastic model and the endochronic plasticity constitutive equations are developed in unrotated frame of reference. Constitutive equations of the endochronic theory in large strain state and their numerical integrations are established. The algorithmic modulus consistent with the numerical integration algorithm of constitutive equations is extracted. Finally, the numerical schemes are examined for efficiency in... 

In this paper, the numerical modelling of powder forming process is simulated by a finite element analysis using an endochronic plasticity model. A general algorithm for the endochronic theory from the viewpoint of efficient numerical modelling is presented. Constitutive equations are established based on coupling between deviatoric and hydrostatic behaviour to the endochronic theory. Finally, the numerical schemes are examined for efficiency in the modelling of a rotational flanged-component. It is shown how the endochronic plasticity describes the behaviour of powder material from the initial stage of compaction to final stage, in which material behaves as solid metals. © 2003 John Wiley... 

In this paper, a new rate type endochronic constitutive model is introduced to describe deformations in the finite strain range. A new material dependent objective rate of Cauchy stress is suggested based on the general form of spin tensors, defining objective stress rates. The endochronic constitutive equations are extended using the concept of corotational stress rates and additive decomposition of deformation rate. The constitutive relations are specialized for thin-walled tubes under torsion and a procedure for solving the ordinary differential equations for cases of simple and pure torsion is developed. The axial effects for various materials, subjected to simple and pure torsion, are... 

This paper is concerned with objective stress update algorithm for elasto-plastic and elasto-viscoplastic endochronic theory within the framework of additive plasticity. The elastic response is stated in terms of hypoelastic model and endochronic constitutive equations are stated in unrotated frame of reference. A trivially incrementally objective integration scheme for rate constitutive equations is established. Algorithmic modulus consistent with numerical integration algorithm of constitutive equations is extracted. The implementation is validated by means of a set of simple deformation paths (simple shear, extension and rotation), two benchmark test in nonlinear mechanics (the necking of... 

In this paper, an endochronic plasticity model is developed based on a large strain plasticity to describe the behavior of powder material in cold compaction process. The elastic response is stated in terms of hypoelastic model and endochronic plasticity constitutive equations are stated in unrotated frame of reference. A trivially incrementally objective integration scheme for rate constitutive equations is established. Algorithmic modulus consistent with numerical integration algorithm of constitutive equations is extracted. Finally, the numerical schemes are examined for efficacy in the modeling of a plain bush and a rotational-flanged powder compaction component. It is shown how the... 

In this paper, a density-dependent endochronic plasticity is presented for modelling the isothermal deformation behaviour of metal powder at low homologous temperature. As large deformation is observed in powder compaction process, a hypoelastic-plastic formulation is developed in the context of finite deformation plasticity. Constitutive equations are stated in unrotated frame of reference that greatly simplifies endochronic constitutive relation for finite plasticity. The material parameters in the constitutive model are calibrated for a tip shape component by fitting the model to reproduce data from true triaxial compression experiments. Numerical algorithm for accurate and stable... 

This work presents the details of a finite element-based numerical method to analyse general contact/impact problems, called united elements method (UEM). In contrast to usual methods, that is Lagrange Multipliers and Penalty Function, this method is conceptual, suitable for computer programming, and free from inherent deficiencies of those methods. The key points of this procedure are elimination of the normal degree of freedom of the contactor node from the system energy potential functional in terms of target surface motion, and proper calculation of target element unbalanced forces, to incorporate the contact constraints. After a review on classic formulations, the mathematical and... 

This technical note addresses the free vibration problem of an elastically restrained Euler–Bernoulli beam with rotational spring-lumped rotary inertia system at its mid-span hinge. The governing differential equations and the boundary conditions of the beam are presented. Special attention is directed toward the conditions of the intermediate spring-mass system which plays a key role in the solution. Sample frequency parameters of the beam system are solved and tabulated. Mode shapes of the beam are also plotted for some spring stiffnesses  

An analytical approach is employed to investigate the transient and steady-state stresses in an isotropic, homogeneous half-space subjected to moving concentrated loads with subsonic speeds. Applying the Stokes-Helmholtz resolution to the Navier's equation of motion for the half-space results in a system of wavetype partial differential equations. Based on the new moving coordinate system, a modified system of partial differential equations is obtained. Applying a concurrent two-sided and one-sided Laplace transformation, this system is modified to a system of ordinary differential equations, the solutions of which are obtained with respect to boundary conditions. The transformed transient... 

In this article, the dynamic responses of a Timoshenko beam subjected to a moving mass, and a moving sprung mass are analyzed. By making recourse to Hamilton's principle, governing differential equations for beam vibration are derived. By using the modal superposition method, the partial differential equations of the system are transformed into a set of Ordinary Differential Equations (ODEs). The resulted set of ODEs is represented in state-space form, and solved by means of a numerical technique. The accuracy of the results has been ascertained through comparing the results of our approach with those available from previous studies; moreover, a reasonable agreement has been obtained. The... 

Rectangular plates on distributed elastic foundations are widely employed in footings and raft foundations of variety of structures. In particular, mounted columns and single footings may partially occupy the rectangular plate of any kind. This study deals with free vibration problem of thin rectangular plates on Winkler and Pasternak elastic foundation model which is distributed over a particular arbitrary area of the plate. Closed form solutions are developed through solving the governing differential equations of plates. Moreover, a novel mathematical approach is proposed to find the exact analytical solution of free vibration of plates with mixed or fully-clamped boundary conditions.... 

The dynamic response of a homogeneous, isotropic elastic half-space under a moving time-varying inertial load with subsonic speed is investigated. The surface of the half-space, which is under the action of the moving load, is a thin frictionless layer. In order to study the influences of the inertia of loads, the problem was first solved for a moving load and, then, the procedure was extended to include the inertial effects. The Navier equations of motion for the two-dimensional half-space were transformed to a system of wave-type partial differential equations using the Stokes-Helmholtz resolution. A new moving coordinate system was used and a modified system of equation was derived. The... 

Bolted Column Base Plate (BCBP) connections are widely used to connect steel columns to the concrete foundations. This paper conducts a parametric study on the initial stiffness of bolted base plate with Square Hollow Section (SHS) column connection, through an extended 3-D Finite Element Modeling (FEM). Different features of the connection such as material behavior, geometric details, typical contact phenomena and large displacements are also considered in the modeling. A comparison between experimental test and FEM is carried out to illustrate the ability of the numerical method to simulate the connection behavior. An analytical explanation on the initial stiffness of the connection is... 

Modeling the water flow in cohesive fracture is a fundamental issue in the crack growth simulation of cracked concrete gravity dams and hydraulic fracture problems. In this paper, a mathematical model is presented for the analysis of fracture propagation in the semi-saturated porous media. The solid behavior incorporates a discrete cohesive fracture model, coupled with the flow in porous media through the fracture network. The double-nodded zero-thickness cohesive interface element is employed for the mixed mode fracture behavior in tension and contact behavior in compression. The modified crack permeability is applied in fracture propagation based on the data obtained from experimental... 

In this paper, a mathematical model is presented for the analysis of dynamic fracture propagation in the saturated porous media. The solid behavior incorporates a discrete cohesive fracture model, coupled with the flow in porous media through the fracture network. The double-nodded zero-thickness cohesive interface element is employed for the mixed mode fracture behavior in tension and contact behavior in compression. The crack is automatically detected and propagated perpendicular to the maximum effective stress. The spatial discretization is continuously updated during the crack propagation. Numerical examples from the hydraulic fracturing test and the concrete gravity dam show the... 

This technical note addresses the free vibration problem of an elastically restrained Euler-Bernoulli beam with rotational spring-lumped rotary inertia system at its mid-span hinge. The governing differential equations and the boundary conditions of the beam are presented. Special attention is directed toward the conditions of the intermediate spring-mass system which plays a key role in the solution. Sample frequency parameters of the beam system are solved and tabulated. Mode shapes of the beam are also plotted for some spring stiffnesses  

In this paper, the project earthquake occurrence risk coefficient is determined for each construction project that is located in one of Iran's twenty seismic regions. This coefficient is allocated, regardless of the current situation of the project, being in the plan or execution phase or even completed. This coefficient indicates the possibility of an earthquake occurrence during a project's life time. To find this coefficient, the Gutenberg-Richter linear relationship has been applied, in conjunction with the Poisson distribution. The Gutenberg-Richter linear equation expresses the relationship between the magnitude of an earthquake and the number of occurrences, during a fixed time, of... 

An exact solution is established pertaining to the dynamic response of an Euler–Bernoulli beam resting on a Winkler foundation with variable subgrade modulus. The solution is performed by employing the infinite power series method. Moreover, using the Frobenius theorem, the proposed method is extended in order to solve the problems wherein the variation of the modulus is not an analytic function. The solution procedure is demonstrated through several illustrative examples, and the correctness of the results has been ascertained through comparison with recognized solutions in the literature. Finally, it is shown that the proposed method of solution is directly applicable to the more general... 

In the free vibration analysis of beams, the inclusion of an intermediate sliding connection with an attached mass-spring system has not been yet treated. The present paper studies the free vibrations of uniform Euler-Bernoulli beams with an intermediate sliding connection and joined by a mass-spring system. Two different types of beams are considered. The Type 1 is attached with a single-degree-of-freedom mass-spring system and the Type 2 is attached with a two-degree-of-freedom mass-spring system. The ends of both beams are elastically restrained against rotation and translation. First, the eigenvalue problems including differential equations and boundary conditions are introduced. Then,...