Sharif Digital Repository

Predictions of soil behavior in response to dynamic loads require an understanding of dynamic properties of soil. Studies on dynamic properties of unsaturated soils at large-strains are quite limited, while some dynamic loadings, like earthquakes, are in the medium to large-strain ranges. A cyclic simple shear apparatus was developed to measure large-strain shear modulus and damping ratio under different matric suction or degree of saturation. Six cyclic tests, with referring to the soil-water retention curve, were conducted on clean medium sand. Results indicated that shear modulus slightly increases when suction varies from zero up to the air entry value. Approaching the residual value, a... 

This article investigates the influences of nonuniform imperfection on the dynamic amplitude and resonance frequency of the nanoshell reinforced with graphene nanoplatelet (GNP). The novelty of the current study is to consider the effects of porosity, thermal loading and graphene platelet reinforced composites on the dynamic behavior of the nanostructure. Three-length scale parameters (l0=5 h, l1=3 h, l2=5 h) in the modified strain gradient theory (MSGT) show a better agreement with MD simulation in comparison with other theories. Finally, the effects of different factors on the dynamic amplitude and resonance frequency of the porous nanostructure are examined in detail. © 2019, © 2019... 

In this paper the dynamic properties of Babolsar dry sand was investigated through one dimensional shaking table tests. 8 models of Babolsar loose dry sand under low confining pressures, were subjected to different harmonic and irregular dynamic loadings. The container was a laminar shear box having 24 layers each moving on the lower one. The dynamic properties including shear wave velocity, maximum shear modulus and damping ratio of the samples were addressed in this project. © 2006 Taylor & Francis Group, London  

On-demand resource provisioning and elasticity are two of the main characteristics of the cloud computing paradigm. As a result, the load on a cloud service provider (CSP) is not fixed and almost always a number of its physical resources are not used, called spare resources. As the CSPs typically don't want to be overprovisioned at any time, they procure physical resources in accordance to a pessimistic forecast of their loads and this leads to a large amount of spare resources most of the time. Some CSPs rent their spare resources with a lower price called the spot price, which varies over time with respect to the market or the internal state of the CSP. In this paper, we assume the spot... 

The dynamic behavior of a closure bolting system was predicted using a spring-mass-damper model. The loading was assumed to be an initially peaked, exponentially decaying internal pressure pulse acting on the closure. It was observed that optimal pre-stress values that minimized the peak bolt deformation and stress, existed for relatively high levels of applied force and low pre- stress  

This paper summarizes a research project in the field of design and manufacturing of a water brake dynamometer for power testing facilities. In the current study, the design process of a water brake with drilled rotor disks is presented. This process is examined against the development of a water brake for a 4MW gas turbine power measurement at 15,000 RPM speed. The proposed algorithm is based on vital assumptions such as; applying product designing issues and limited modular analysis that urges the disciplinary attitude and leads to the possibility of rapid development, easy maintenance and ease of access. The final scheme is divided into six disciplines with functional classification.... 

Structures of tapered geometry are customarily used in a variety of applications. The analysis of such structures is usually made through finite element method using traditional beam, shell or brick elements. In this paper, a new tapered superelement is presented that lends itself to modeling revolving geometries under lateral, axial and torsional loads. The presented tapered superelement has 16 nodes. The performance of this element under static and dynamic loading and in rotating condition is examined. It is shown that this element yields accurate results with higher computational efficiency compared to conventional elements. Furthermore, it is verified that a single tapered superelement... 

A new method, based on the concepts of matrix analysis as well as the learning capabilities of neural networks, for the analysis of nonlinear trusses under dynamic loading is presented. The method can be applied to static trusses too. While there have been attempts in the past to use neural networks to identify and model different structures based on data measured on structural response directly, the main feature and advantage of this new method is in its capability to model a nonlinear truss by assembling the data collected on the response of its members. The basics of the method are: (1) for each truss member, a neural network is trained to learn and simulate its loadresponse behavior, (2)... 

A large portion of the railway bridge stock in many countries is comprised of masonry arch bridges. During recent years, more attention has been paid to the maintenance of such structures. Rehabilitation and retrofitting methods have been proposed to enhance the performance of masonry arch bridges and extend their service life. Because a large portion of forces exerted on such structures comes from the railway track and passing trains, structural elements are added to the track to reduce the forces transmitted to bridges. One such element is the ballast mat, which, according to suppliers, has a positive impact on the structural performance of the track. This paper tries to assess the effects... 

In this paper, based on the modified couple stress theory, the size-dependent dynamic behavior of circular rings on elastic foundation is investigated. The ring is modeled by Euler-Bernoulli and Timoshenko beam theories, and Hamilton's principle is utilized to derive the equations of motion and boundary conditions. The formulation derived is a general form of the equation of motion of circular rings and can be reduced to the classical form by eliminating the size-dependent terms. On this basis, the size-dependent natural frequencies of a circular ring are calculated based on the non-classical Euler-Bernoulli and Timoshenko beam theories. The findings are compared with classical beam... 

This article investigates the influence of porosity on free and forced vibration characteristics of a nanoshell reinforced by graphene platelets (GPL). The material properties of piece-wise graphene-reinforced composites (GPLRCs) are assumed to be graded in the thickness direction of a cylindrical nanoshell and estimated using a nanomechanical model. In addition, because of imperfection of the current structure, three kinds of porosity distributions are considered. The nanostructure is modeled using modified strain gradient theory (MSGT) which is a size-dependent theory with three length scale parameters. The novelty of the current study is to consider the effects of porosity, GPLRC and MSGT... 

Bridge behavior under passing traffic loads has been studied for the past 50 years. This paper presents how to model congestion on bridges and how the maximum dynamic stress of bridges change during the passing of moving vehicles. Most current research is based on mid-span dynamic effects due to traffic load and most bridge codes define a factor called the dynamic load allowance (DLA), which is applied to the maximum static moment under static loading. This paper presents an algorithm to solve the governing equation of the bridge as well as the equations of motions of two real European trucks with different speeds, simultaneously. It will be shown, considering congestion in eight case...