Stochastic analysis of elastic wave and second sound propagation in media with Gaussian uncertainty in mechanical properties using a stochastic hybrid mesh-free method

Hosseini, Seyed Mahmoud,Shahabian, Farzad Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.49 No.1

The main objective of this article is the exploitation of a stochastic hybrid mesh-free method based on stochastic generalized finite difference (SGFD), Newmark finite difference (NFD) methods and Monte Carlo simulation for thermoelastic wave propagation and coupled thermoelasticity analysis based on GN theory (without energy dissipation). A thick hollow cylinder with Gaussian uncertainty in mechanical properties is considered as an analyzed domain for the problem. The effects of uncertainty in mechanical properties with various coefficients of variations on thermo-elastic wave propagation are studied in details. Also, the time histories and distribution on thickness of cylinder of maximum, mean and variance values of temperature and radial displacement are studied for various coefficients of variations (COVs).

Exact closed-form equations for internal forces functions of bridge-type structures

Mahmoud-Reza Hosseini-Tabatabaei,Mahmoud Reza Mollaeinia 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.80 No.2

Influence lines and internal forces functions are vital tools for designing and monitoring engineering structures. This research explored a static method to derive exact closed-form equations for internal forces functions of bridge-type structures, continuous beams, and bridge frames, considering the bending flexibility. For this aim, first, we achieved member-end moment functions by applying the moment-rotation relationships in conjunction with the rotation propagation method. Then, substituting these functions into the static equilibrium equations provided the desired functions in terms of both the unit load and intended cross-section positions all over the structure, subjected to concentrated loads. Finally, the authors solved three illustrative examples to clarify the dominance of their suggested method for constructing both influence line and internal forces diagrams of statically indeterminate structures.

Bridge-type structures analysis using RMP concept considering shear and bending flexibility

Mahmoud-Reza Hosseini-Tabatabaei,Mohmmad Rezaiee-Pajand,Mahmoud R. Mollaeinia 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.74 No.2

Researchers have elaborated several accurate methods to calculate member-end rotations or moments, directly, for bridge-type structures. Recently, the concept of rotation and moment propagation (RMP) has been presented considering bending flexibility, only. Through which, in spite of moment distribution method, all joints are free resulting in rotation and moment emit throughout the structure similar to wave motion. This paper proposes a new set of closed-form equations to calculate member-end rotation or moment, directly, comprising both shear and bending flexibility. Furthermore, the authors program the algorithm of Timoshenko beam theory cooperated with the finite element. Several numerical examples, conducted on the procedures, show that the method is superior in not only the dominant algorithm but also the preciseness of results.

The Beneficial Effects of Olibanum on Memory Deficit Induced by Hypothyroidism in Adult Rats Tested in Morris Water Maze

Mahmoud Hosseini,Mosa Al-Reza Hadjzadeh,Mohammad Derakhshan,Shahrzad Havakhah,Fatemeh Behnam Rassouli,Hassan Rakhshandeh,Fatema Saffarzadeh 대한약학회 2010 Archives of Pharmacal Research Vol.33 No.3

Functional consequences of hypothyroidism include impaired learning and memory and inability to produce long-term potentiation (LTP) in hippocampus. Olibanum has been used for variety of therapeutic purposes. In traditional medicine, oilbanum is used to enhance learning and memory. In the present study the effect of olibanum on memory deficit in hypothyroid rats was investigated. Male wistar rats were divided into four groups and treated for 180 days. Group 1 received tap drinking water while in group 2, 0.03% methimazol was added to drinking water. Group 3 and 4 were treated with 0.03% methimazole as well as 100 and 500 mg/kg olibanum respectively. The animals were tested in Morris water maze. The swimming speed was significantly lower and the distance and time latency were higher in group 2 compared with group 1. In groups 3 and 4 the swimming speed was significantly higher while, the length of the swim path and time latency were significantly lower in comparison with group 2. It is concluded that methimazole-induced hypothyroidism impairs learning and memory in adult rats which could be prevented by using olibanum.

Stochastic analysis of elastic wave and second sound propagation in media with Gaussian uncertainty in mechanical properties using a stochastic hybrid mesh-free method

Seyed Mahmoud Hosseini,Farzad Shahabian 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.49 No.1

The main objective of this article is the exploitation of a stochastic hybrid mesh-free method based on stochastic generalized finite difference (SGFD), Newmark finite difference (NFD) methods and Monte Carlo simulation for thermoelastic wave propagation and coupled thermoelasticity analysis based on GN theory (without energy dissipation). A thick hollow cylinder with Gaussian uncertainty in mechanical properties is considered as an analyzed domain for the problem. The effects of uncertainty in mechanical properties with various coefficients of variations on thermo-elastic wave propagation are studied in details. Also, the time histories and distribution on thickness of cylinder of maximum, mean and variance values of temperature and radial displacement are studied for various coefficients of variations (COVs).

Elastodynamic and wave propagation analysis in a FG graphene platelets-reinforced nanocomposite cylinder using a modified nonlinear micromechanical model

Seyed Mahmoud Hosseini,Chuanzeng Zhang 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.27 No.3

This paper deals with the transient dynamic analysis and elastic wave propagation in a functionally graded graphene platelets (FGGPLs)-reinforced composite thick hollow cylinder, which is subjected to shock loading. A micromechanical model based on the Halpin-Tsai model and rule of mixture is modified for nonlinear functionally graded distributions of graphene platelets (GPLs) in polymer matrix of composites. The governing equations are derived for an axisymmetric FGGPLs-reinforced composite cylinder with a finite length and then solved using a hybrid meshless method based on the generalized finite difference (GFD) and Newmark finite difference methods. A numerical time discretization is performed for the dynamic problem using the Newmark method. The dynamic behaviors of the displacements and stresses are obtained and discussed in detail using the modified micromechanical model and meshless GFD method. The effects of the reinforcement of the composite cylinder by GPLs on the elastic wave propagations in both displacement and stress fields are obtained for various parameters. It is concluded that the proposed micromechanical model and also the meshless GFD method have a high capability to simulate the composite structures under shock loadings, which are reinforced by FGGPLs. It is shown that the modified micromechanical model and solution technique based on the meshless GFD method are accurate. Also, the time histories of the field variables are shown for various parameters.

Stochastic hybrid numerical method for transient analysis of stress field in functionally graded thick hollow cylinders subjected to shock loading

Seyed Mahmoud Hosseini,Farzad Shahabian 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.5

This investigation aims to study the random stresses in a functionally graded (FG) thick hollow cylinder with uncertain material properties subjected to mechanical shock loading using a hybrid numerical method. The mechanical properties are considered to vary across thickness of FG cylinder as a nonlinear power function of radius. The stresses are obtained by solving Navier equation and using Galerkin finite element and Newmark finite difference methods. The Monte Carlo simulation is used to generate the random mechanical properties for the problem. The failure probabilities and time history analysis of stresses are determined for various coefficient of variation considering various grading patterns of mechanical properties. The presented hybrid numerical method is effective, with high capability for stochastic analysis of dynamic and transient analysis of FG structures with various boundary conditions.

A GN-based modified model for size-dependent coupled thermoelasticity analysis in nano scale, considering nonlocality in heat conduction and elasticity: An analytical solution for a nano beam with energy dissipation

Seyed Mahmoud Hosseini 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.73 No.3

This investigation deals with a size-dependent coupled thermoelasticity analysis based on Green-Naghdi (GN) theory in nano scale using a new modified nonlocal model of heat conduction, which is based on the GN theory and nonlocal Eringen theory of elasticity. In the analysis based on the proposed model, the nonlocality is taken into account in both heat conduction and elasticity. The governing equations including the equations of motion and the energy balance equation are derived using the proposed model in a nano beam resonator. An analytical solution is proposed for the problem using the Laplace transform technique and Talbot technique for inversion to time domain. It is assumed that the nano beam is subjected to sinusoidal thermal shock loading, which is applied on the one of beam ends. The transient behaviors of fields’ quantities such as lateral deflection and temperature are studied in detail. Also, the effects of small scale parameter on the dynamic behaviors of lateral deflection and temperature are obtained and assessed for the problem. The proposed GN-based model, analytical solution and data are verified and also compared with reported data obtained from GN coupled thermoelasticity analysis without considering the nonlocality in heat conduction in a nano beam.

Generalized coupled non-Fickian/non-Fourierian diffusion- thermoelasticity analysis subjected to shock loading using analytical method

Seyed Amin Hosseini,Mohammad Hossein Abolbashari,Seyed Mahmoud Hosseini 국제구조공학회 2016 Structural Engineering and Mechanics, An Int'l Jou Vol.60 No.3

In this article, the generalized coupled non-Fickian diffusion-thermoelasticity analysis is carried out using an analytical method. The transient behaviors of field variables, including mass concentration, temperature and displacement are studied in a strip, which is subjected to shock loading. The governing equations are derived using generalized coupled non-Fickian diffusion-thermoelasticity theory, which is based on Lord-Shulman theory of coupled thermoelasticity. The governing equations are transferred to the frequency domain using Laplace transform technique and then the field variables are obtained in analytical forms using the presented method. The field variables are eventually determined in time domain by employing the Talbot technique. The dynamic behaviors of mass concentration, temperature and displacement are studied in details. It is concluded that the presented analytical method has a high capability for simulating the wave propagation with finite speed in mass concentration field as well as for tracking thermoelastic waves. Furthermore, the obtained results are more realistic than that of others.

Proposing a multi-mushroom structural system for enhanced seismic performance in large-plan low-rise reinforced concrete buildings

Mahmoud Alhashash,Ahed Habib,Mahmood Hosseini 국제구조공학회 2024 Structural Engineering and Mechanics, An Int'l Jou Vol.91 No.5

This study introduces a novel ‘multi-mushroom’ structural system designed to improve seismic performance in lowrise buildings. Traditional low-rise structures tend to favor sliding over rocking due to their smaller aspect ratios despite the rocking system’s superior seismic response reduction. Rocking designs allow structures to pivot at their base during seismic events, reducing damage by dissipating energy. The proposed multi-mushroom system divides the building into four equal sections with small gaps in between, each capable of independent rocking. Numerical analyses are conducted using scaled earthquake records from far- and near-source events to evaluate this system’s performance. The results indicated that the multimushroom system significantly reduces plastic hinge formation compared to conventional designs. The system also demonstrated enhanced beam performance and a robust base girder, contributing to reduced collapse vulnerability. The 3-story model exhibited the most favorable behavior, effectively mitigating peak roof drift values, where the rocking system achieved a 21% reduction in mean roof displacement for near-field records and 15% for far-field records. However, the 5-story configuration showed increased roof displacement, and the 7-story model recorded higher incidences of collapse prevention (CP) hinges, indicating areas for further optimization. Overall, the multi-mushroom system enhances seismic resilience by minimizing plastic hinge formation and improving structural integrity. While the system shows significant promise for low-rise buildings, challenges related to roof displacement and inter-story drift ratio in taller structures necessitate further research. These findings suggest that the multi-mushroom system offers a viable solution for seismic risk reduction, contributing to safer and more sustainable urban development in earthquake-prone areas.