Site effect microzonation of Babol, Iran

Tavakoli, H.R.,Amiri, M. Talebzade,Abdollahzade, G.,Janalizade, A. Techno-Press 2016 Geomechanics & engineering Vol.11 No.6

Extensive researches on distribution of earthquake induced damages in different regions have shown that geological and geotechnical conditions of the local soils significantly influence behavior of alluvial areas under seismic loading. In this article, the site of Babol city which is formed up of saturated fine alluvial soils is considered as a case study. In order to reduce the uncertainties associated with earthquake resistant design of structures in this area (Babol city), the required design parameters have been evaluated with consideration of site's dynamic effects. The utilized methodology combines experimental ground ambient noise analysis, expressed in terms of horizontal to vertical (H/V) spectral ratio, with numerical one-dimensional response analysis of soil columns using DEEPSOIL software. The H/V spectral analysis was performed at 60 points, experimentally, for the region in order to estimate both the fundamental period and its corresponding amplification for the ground vibration. The investigation resulted in amplification ratios that were greater than one in all areas. A good agreement between the proposed ranges of natural periods and alluvial amplification ratios obtained through the analytical model and the experimental microtremor studies verifies the analytical model to provide a good engineering reflection of the subterraneous alluviums.

Bismuth ion-implanted solid-phase epitaxially grown shallow junction for metal-oxide-semiconductor field-effect transistors (3 pages)

Tavakoli, S. G.,Baek, S.,Chang, H. S.,Moon, D. W.,Hwang, H. AMERICAN INSTITUTE OF PHYSICS 2005 APPLIED PHYSICS LETTERS Vol.86 No.3

Optimal design of the floor panel for an automotive platform under uncertainty of the vehicle length

Lahijani, Abdolah Tavakoli,Shojaeefard, M.H.,Khalkhali, Abolfazl Techno-Press 2018 Geomechanics & engineering Vol.14 No.1

Length of a vehicle is an important variation to generate different variants of an automotive platform. This parameter is usually adjusted by embedding dimensional flexibility into different components of the Body in White (BIW) including the floor pan. Due to future uncertainties, it is not necessarily possible to define certain values of wheelbase for the future products of a platform. This work is performed to add flexibility into the design process of a length-variable floor pan. By means of this analysis, the cost and time consuming process of optimization is not necessary to be performed for designing the different variants of a product family. Stiffness and mass of the floor pan are two important functional requirements of this component which directly affect the occupant comfort, dynamic characteristics, fuel economy and environmental protection of the vehicle. A combination of Genetic algorithm, GMDH-type of artificial neural networks and TOPSIS methods is used to optimally design the floor pan associated with arbitrary length of the variant in the defined system range. The correlation between the optimal results shows that for a constant mass of the floor pan, the first natural frequency decreases by increasing the length of this component.

Comparing the generalized Hoek-Brown and Mohr-Coulomb failure criteria for stress analysis on the rocks failure plane

Mohammadi, M.,Tavakoli, H. Techno-Press 2015 Geomechanics & engineering Vol.9 No.1

Determination of mobilized shear strength parameters (that identify stresses on the failure plane) is required for analyzing the stability by limit equilibrium method. Generalized Hoek-Brown (GHB) and Mohr-Coulomb (MC) failure criteria are usually used for obtaining stresses on the plane of failure. In the present paper, the applicability of these criteria for determining the stresses on failure plane is investigated. The comparison is based on stresses on the real failure plane which are obtained from the Mohr stress circle. To do so, 18 sets of data (consist of principal stresses and angle of failure plane) presented in the literature are used. In addition, the values account for (VAF) and the root mean square error (RMSE) indices were calculated to check the determination performance of the obtained results. Values of VAF and RMSE for the normal stresses on the failure plane evaluated from MC are 49% and 31.5 where for GHB are 55% and 30.5, respectively. Also, for the shear stresses on failure plane, they are 74% and 36 for MC, 76% and 34.5 for GHB. Results show that the obtained stresses and angles of failure plane for each criterion differ from real ones, but GHB results are closer to the empirical results. Also, it is inferred that results are affected by the failure envelope not real failure plane. Therefore, obtained shear strength parameters are not mobilized. Finally, a multivariable regressed relation is presented for determining the stresses on the failure plane.

A new higher-order triangular plate bending element for the analysis of laminated composite and sandwich plates

Rezaiee-Pajand, M.,Shahabian, F.,Tavakoli, F.H. Techno-Press 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.43 No.2

To analyze the bending and transverse shear effects of laminated composite plates, a thirteen nodes triangular element will be presented. The suggested formulations consider a parabolic variation of the transverse shear strains through the thickness. As a result, there is no need to use shear correction coefficients in computing the shear stresses. The proposed element can model both thin and thick plates without any problems, such as shear locking and spurious modes. Moreover, the effectiveness of $w_{,n}$, as an independent degree of freedom, is concluded by the present study. To perform the accuracy tests, several examples will be solved. Numerical results for the orthotropic materials with different boundary conditions, shapes, number of layers, thickness ratios and fiber orientations will be presented. The suggested element calculates the deflections and stresses more accurate than those available in the literature.

Development of the Performance Based Plastic Design for Steel Moment Resistant Frame

M. Reza Banihashemi,A. R Mirzagoltabar,H. R Tavakoli 한국강구조학회 2015 International Journal of Steel Structures Vol.15 No.1

This paper presents the development of performance based plastic design (PBPD) method for steel moment frames withconsidering the gravity loads and P-Δ effects. In this method the design lateral forces are obtained from energy-work balanceequation by using pre-selected target drift and yield mechanism. For further improvement of PBPD method, some solutions arerepresented to precisely obtain the required moment of columns in order to prevent their yielding that leads to form undesirablemechanisms in the structure. In order to show more validity of PBPD method, two model frames, 5 and 10story, are designedbased on PBPD as well as elastic design method. The mentioned frames are evaluated by extensive nonlinear static pushoveranalysis and dynamic analysis. The results show that the frames designed by PBPD method reach the intended performanceobjectives in terms of yield mechanism and target drift levels. In contrast, the frame designed by Ed method experience largestory drifts due to flexural yielding of the columns. Since PBPD method is a direct design method, little or no evaluation areneeded after the initial design because the nonlinear behavior is built into the design process from the start.

REMARKS ON THE INNER POWER OF GRAPHS

S. JAFARI,A.R. ASHRAFI,G.H. FATH-TABAR,M. TAVAKOLI 한국전산응용수학회 2017 Journal of applied mathematics & informatics Vol.35 No.1

Let G be a graph and k is a positive integer. Hammack and Livesay in [The inner power of a graph, Ars Math. Contemp., 3 (2010), no. 2, 193{199] introduced a new graph operation G(k), called the kth inner power of G. In this paper, it is proved that if G is bipartite then G(2) has exactly three components such that one of them is bipartite and two others are isomorphic. As a consequence the edge frustration index of G(2) is computed based on the same values as for the original graph G. We also compute the rst and second Zagreb indices and coindices of G(2).

A new higher-order triangular plate bending element for the analysis of laminated composite and sandwich plates

M. Rezaiee-Pajand,F. Shahabian,F.H. Tavakoli 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.43 No.2

To analyze the bending and transverse shear effects of laminated composite plates, a thirteen nodes triangular element will be presented. The suggested formulations consider a parabolic variation of the transverse shear strains through the thickness. As a result, there is no need to use shear correction coefficients in computing the shear stresses. The proposed element can model both thin and thick plates without any problems, such as shear locking and spurious modes. Moreover, the effectiveness of w, n, as an independent degree of freedom, is concluded by the present study. To perform the accuracy tests, several examples will be solved. Numerical results for the orthotropic materials with different boundary conditions, shapes, number of layers, thickness ratios and fiber orientations will be presented. The suggested element calculates the deflections and stresses more accurate than those available in the literature.

REMARKS ON THE INNER POWER OF GRAPHS

JAFARI, S.,ASHRAFI, A.R.,FATH-TABAR, G.H.,TAVAKOLI, Mostafa The Korean Society for Computational and Applied M 2017 Journal of applied mathematics & informatics Vol.35 No.1

Let G be a graph and k is a positive integer. Hammack and Livesay in [The inner power of a graph, Ars Math. Contemp., 3 (2010), no. 2, 193-199] introduced a new graph operation $G^{(k)}$, called the $k^{th}$ inner power of G. In this paper, it is proved that if G is bipartite then $G^{(2)}$ has exactly three components such that one of them is bipartite and two others are isomorphic. As a consequence the edge frustration index of $G^{(2)}$ is computed based on the same values as for the original graph G. We also compute the first and second Zagreb indices and coindices of $G^{(2)}$.