2020-11-29T20:43:49Z
http://scientiairanica.sharif.edu/?_action=export&rf=summon&issue=1029
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2018
25
3
Coupling of energy and harmonic balance method for solving a conservative oscillator with strong odd-nonlinearity
M .
Abdur Razzak
In this paper, a new analytical technique, combining the energy balance method (EBM) with harmonic balance method (HBM), is presented to obtain higher-order approximations of a conservative oscillator with strong odd-nonlinearity. To show the accuracy of the present method, one nonlinear oscillator named as cubic-quintic Duffing oscillator is investigated. The results obtained in this paper are compared with those results determined by other methods and exact solutions. The results give high accuracy and also provide better result than other existing results for both small and large amplitudes of oscillation. The main advantage of the present paper is its simplicity, which contains a few harmonic terms with lower order terms and these terms make the solution quickly converges. The present technique can be used to other nonlinear oscillators.
Nonlinear oscillation
Odd-nonlinearity
Cubic-quintic Duffing oscillator
Energy balance method
Harmonic balance method
2018
06
01
991
998
http://scientiairanica.sharif.edu/article_4258_92b1e582cf94a2b0e7e938dc2484a145.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2018
25
3
A displacement finite volume formulation for the static and dynamic analysis of shear deformable circular curved beams
N.
Fallah
A.
Ghanbari
In this paper, a finite volume formulation is proposed for static and in-plane vibration analysis of curved beams in which the axis extensibility, shear deformation and rotary inertia are considered. A curved cell with three degrees of freedom is used in discretization. The unknowns and their derivatives on cell faces are approximated either by assuming a linear variation of unknowns between the two consecutive computational points or by using the moving least squares technique (MLS). The proposed method is validated through a series of benchmark comparisons where its capability in accurate predictions without shear and membrane locking deficiencies is revealed.
Curved beams
Finite volume
In-plane vibration
Membrane locking
Shear locking
Moving least squares
2018
06
01
999
1014
http://scientiairanica.sharif.edu/article_4259_1bb233d7a742a212ca6d6bb2ac1d2aca.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2018
25
3
Choice of Optimum Combination of Construction Machinery Using Modified Advanced Programmatic Risk Analysis and Management Model
Mehran
Zeynalian
Iman
Kalantari Dehaghi
Since the proper use of construction machinery in infrastructure projects is important, it is essential to employ an optimum selection of machinery in these projects. Advanced programmatic risk analysis and management model (APRAM) is one of recently developed methods that can be used for risk analysis and management purposes considering schedule, cost and quality, simultaneously. In this paper, first the APRAM method is introduced and then modified in order to consider environmental risks. This method can consider potential risks that might occur over the entire life cycle of the project, and can be employed as an efficient decision-support tool for construction managers selecting machinery for an infrastructure project where various alternatives might be technically feasible. A case study of three possible combinations of excavation machines is then discussed. All project risks related to cost, time, quality and environment are identified, considering the capital costs which should be spent on each combination. Finally, some graphs which are derived from the method are taken into account in order to decrease each combination’s risks and to optimize the selection of excavating machinery. The outcomes highlight the efficiency of the APRAM model for the optimal selection of machinery in construction projects.
Risk Management
Construction Management
Machinery Combination
Subway Project
Environmental impacts
2018
06
01
1015
1024
http://scientiairanica.sharif.edu/article_4197_bd39762216cba08effdfbc05ff293d74.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2018
25
3
Evaluation of PR steel frame connection with torsional plate and its optimal placement
Amin
Moghadam
H.
E. Estekanchi
M.
Yekrangnia
Characteristics of connections in steel moment-resisting frames are of utmost importance in determining the seismic performance of these structural systems. The results of several previous experimental studies have indicated that Partially-restrained (PR) connections possess excellent properties, which makes this connection a reliable substitution for Fully-restrained (FR) connections. These properties include needing less base shear, being more economic and in many cases, being able to absorb more energy. In this study, the behavior of two proposed PR connections with torsional plate is studied through finite element simulations. The results of the numerical studies regarding initial stiffness and maximum strength capacity of the proposed connections are calibrated against the results of solid mechanics formulations. Over 50 parametric studies are performed to determine the importance of various design variables of the proposed PR connections. A relation based on spring model is proposed to estimate the maximum strength capacity of the proposed connection. Seismic performance of the proposed connection is studied in a typical portal frame with various connection characteristics using nonlinear time-history analysis. The results explicitly show that using PR connections can considerably reduce the moment-rotation demands in the columns and as a result, higher performance levels can be achieved according to ASCE41.
PR connection
Torsional plate
Plastic rotation
Ultimate moment capacity
Stiffness of the connection
Nonlinear time-history analyses
Finite Element Method
2018
06
01
1025
1038
http://scientiairanica.sharif.edu/article_4196_f8fd47f113a22e13fb5458c345a994a7.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2018
25
3
Mode Choice and Number of Non-Work Stops during the Commute: Application of a Copula-Based Joint Model
arash
rasaizadi
Mohammad
Kermanshah
Commute mode choice and number of non-work stops during the commute are joint decisions that have interaction. If an individual chooses a vehicle for the commute, regarding restriction of that vehicle, could has some stops. On the other hand, if an individual need to has some stops, chooses a vehicle for commute regarding number of stops. In this study to consider the interaction between these decisions, we employed copula-based joint modeling framework. The data used in this study is drawn from origin-destination travels data of Shiraz-Iran conducted in 1997. The commute mode choice modeling is undertaken using a multinomial logit model and the number of non-work stops is modeled using an ordered response formulation. To capturing interactive between these decisions several copula functions have been used. Results approve that mode and number of none-work stop choices are interrelated choices by estimating commonly observed factors and dependence parameters with high statistical significance. By determining common effective factors, we can analyze the current situation in the community. also, we can use results for forecasting future travel demand and set some policies leading to promoting trip chaining.
joint model
Copula
mode choice
number of stops
trip chain
work trips
2018
06
01
1039
1047
http://scientiairanica.sharif.edu/article_4194_b77c78cddb19fcf81c93ff51d1d3b9fc.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2018
25
3
STREAMFLOW MAP OF THE EASTERN BLACK SEA REGION, TURKEY
Ebru
Eris
Necati
Agiralioglu
The purpose of this study is to generate a streamflow map for the coastal part of the Eastern Black Sea Region which is located in the north east of Turkey. The topographic structure of the region is an obstacle in terms of the number of observation gauges. In order to determine spatial variation of flow and to estimate flow on any ungauged points in the region, interpolation between gauged and ungauged points is applicable. For this purpose, any hydrological models which depend on a large number of meteorological dataset can be used. Instead, in this study, ordinary and universal kriging as geostatistical interpolation methods are used to interpolate mean annual flow depth over the study area, thus, flow values on ungauged points can be easily estimated. Kriging methods are compared to simple regression based on the relationship between flow data and basin area. Calibration results of observed and estimated flow depths for ordinary and universal kriging methods are satisfactory, the determination coefficients are found to be 0.84 and 0.87, respectively. Besides, the validation results show that the performance of kriging methods is superior compared to the regression model.
Streamflow map
ordinary kriging
universal kriging
simple regression
the Eastern Black Sea Region
2018
06
01
1048
1056
http://scientiairanica.sharif.edu/article_4261_17059a6610162b0f3df0d91031e4e6d4.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2018
25
3
STANDARD EQUATIONS FOR PREDICTING THE DISCHARGE COEFFICIENT OF A MODIFIED HIGH-PERFORMANCE SIDE WEIR
Amir Hossein
Zaji
Hossein
Bonakdari
Shahaboddin
Shamshirband
Side weirs are hydraulic structures that are used as discharge adjustments to divert the surplus water flowing from the main channel. Predicting the discharge coefficient is one of the most important parameters in the side weir design process. In practical situations, it is preferred to predict the discharge coefficient with simple equations. The goal of this study was to develop accurate standard equations for use in predicting the discharge coefficient of a high-performance, modified triangular side weir. The Particle Swarm Optimization (PSO) algorithm was used to optimize the parameters of the equations. Four different forms of the equations and two non-dimensional input combinations were used to develop the most appropriate model. The results obtained by our simple standard equations optimized by the PSO algorithm were compared with the results of complex nonlinear regression equations, and our equations were more accurate more accurate in modeling the discharge coefficient. Our method reduced the error in the results by as much as 43% compared to the regression methods, and its simplicity makes it useful in solving practical problems.
Discharge coefficient
Modified triangular side weir
Nonlinear regression
particle swarm optimization
Standard equation
2018
06
01
1057
1069
http://scientiairanica.sharif.edu/article_4198_8d2980e6689610705df19615b0e088cf.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2018
25
3
Modal data-based approach to structural damage identification by means of imperialist competitive optimization algorithm
H.
Dabbagh
G.
Ghodrati Amiri
Sh.
Shaabani
In this paper, an effective method for structural damage detection is put forth in which an objective function based on the natural frequencies and modal shapes of the structure is established to identify and detect structural damage. The problem is defined and solved as an optimization problem employing Imperialist Competition Algorithm (ICA). Moreover, four numerical examples are examined each of which has different damage scenarios in order that the applicability of the method would be clearly proved. The results show the efficiency of the method in detecting single and multiple damages in different structures. Afterwards, the effects of measurement noises are included in some of the examples so that the method can be more consistent with real situations. Besides, a comparison among several evolutionary optimization algorithms in the research is made to enlighten the accuracy, robustness and reliability of the method. All of the results lead to the conclusion that the suggested method of the paper is of good accuracy, and, therefore, can be both used and trusted in solving damage detection problems, even in cases that measurement noises are encountered.
structural damage detection
model updating
ICA
Modal assurance criterion
2018
06
01
1070
1082
http://scientiairanica.sharif.edu/article_4590_d4ea6b9bbfa43af2d58474d3a438b83d.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2018
25
3
Non-linear seismic ground response analysis considering two-dimensional topographic irregularities
Navid
Soltani
Mohammad Hossein
Bagheripour
In the event of an earthquake, local site conditions such as soil characteristics, dimension of topographic irregularities, seismic bedrock depth, etc. and also characteristics of incident wave have important effects on seismic ground response. In this study, Finite Element Method (FEM) coupled to Viscous Boundaries is used to evaluate the effect of empty two-dimensional valleys on amplification or attenuation of seismic waves. Parametric studies carry out and the effects of dimension of the topography, frequency of the incident wave and bedrock depth on the seismic ground response are considered using non-linear method in a time domain analysis. Results are shown by means of horizontal and vertical amplification ratio in valley span and its surrounding area. It is concluded that displacement variation on ground surface due to topographical effects is a considerable factor to select a site location or design structures in the valley mount and its surrounding area.
topographic irregularity
FEM
Viscous Boundary
non-linear method
2018
06
01
1083
1093
http://scientiairanica.sharif.edu/article_4257_40b0d4f9bf9a216d30e48b128b53caea.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2018
25
3
A hybrid WOA-CBO algorithm for construction site layout planning problem
A.
Kaveh
M.
Rastegar Moghaddam
The whale optimization algorithm (WOA) is a recently developed swarm-based optimization algorithm inspired by the hunting behavior of humpback whales. This study attempts to enhance the original formulation of the WOA by hybridizing it with some concepts of the colliding bodies optimization (CBO) in order to improve solution accuracy, reliability and convergence speed. The new method, called WOA-CBO algorithm, is applied to construction site layout planning problem. To show the efficiency and performance of the WOA and WOA-CBO in construction site layout problems, three case studies are selected. First case is a discrete and equal area facility layout problem that every facility could assign to any location. Second case is an unequal area version of discrete facility layout problem with more constraints and the last case is a continuous model of construction site layouts. These cases are studied by WOA, CBO and WOA-CBO, and the results are compared with each other.
optimization
Site layout problem
meta-heuristic algorithms
WOA algorithm
WOA-CBO algorithm
2018
06
01
1094
1104
http://scientiairanica.sharif.edu/article_4212_b841648df2860f1ae948e5c714a530ea.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2018
25
3
A node-based Smoothed Finite Element Method for Stability Analysis of Dual Square Tunnels in Cohesive-frictional Soils
Thien-M
Vo
An-N
Chau
Tam-M
Nguyen
Hoang-C
Nguyen
This paper presents an upper bound limit analysis procedure using the node-based smoothed finite element method (NS-FEM) and second order cone programming (SOCP) to evaluate the stability of dual square tunnels in cohesive-frictional soils subjected to surcharge loading. The displacement field of the tunnel problems is approximated by using NS-FEM triangular elements (NS-FEM-T3). Next, commercial software Mosek is employed to deal with optimization problems, which are formulated as second order cone. Collapse loads and failure mechanisms of dual square tunnels were performed by solving the optimization problems with a series of size-to-depth ratios and soil properties. For dual square tunnels, the distance between centers of two parallel tunnels is the major parameter used to determine the stability. In this study, surcharge loading is applied to the ground surface and drained conditions are considered. Numerical results are verified with those available to demonstrate the accuracy of the proposed method.
Limit analysis
dual square tunnels
stability
NS-FEM
SOCP
2018
06
01
1105
1121
http://scientiairanica.sharif.edu/article_20193_4d9579ce7ec4999d808b6c0c88713533.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2018
25
3
Employing nonlinear dynamic concepts for catchment classification using runoff response of catchments
H.
Delafrouz
A.
Ghaheri
M.A.
Ghorbani
Classification has been considered as a fundamental step towards improved science and management data. Introducing methods which describe the underlying dynamics of runoff could be a promising way for catchment classification. In this respect chaos theory and correlation dimension was applied to test its ability to construct a concept to introduce a catchment classification framework in this study. The correlation dimension, as an indicator, was calculated for the daily river flow of sixty grouping stations in different catchments in Iran, ranging in size from 8 to 36500 (km2). The results confirmed that applying this indicator to catchments in varied ranges, from low to high complexity, can also be classified. The results showed that Iran’s catchments can be classified into four groups based on the complexity degree of runoff time series. The group is as flows: low dimension (D2 D2 = 5) as group 2, high dimension (D2 => 6) as group 3 and unidentifiable as group 4.The spatial pattern classification of Iran's catchments indicates that catchments with different climate characteristics which are located at a far distance from each other might yield similar responses along with the same level of complexity.
Catchment Classification
Chaos theory
Correlation dimension
System Complexity
Streamflow variability
2018
06
01
1122
1131
http://scientiairanica.sharif.edu/article_4262_92fe77d01fb83d08d02f6dd2dc554c19.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2018
25
3
Optimization actions for irrigation by the Howell-Bunger valves
Ş.
Yurdagül KUMCU
In Bahçelik Dam, irrigation and drinking water is discharged from the bottom outlet to diversion channel when the reservoir water surface elevation is between1472 m-1500 m. It is planned that the flow discharge will be controlled by the valves automatically depending on the water demand. In this system; the valve type is characterized by opening, closing and regulating time of the valves for controlling system placed at the downstream of the main diversion channel. Howell-Bunger valves which are cavitation and water hammer resistant, velocity limitless, electronically controllable water control systems are selected. In the experimental study, four Howell-Bunger valves each having D=1400 mm and maximum discharge capacities Q=8.5 m3/s were placed at the upstream part of the main diversion channel and tested in various valve openings to obtain optimum operating conditions for all reservoir water levels in a 1/10 scaled model. It is found that, as the reservoir elevation is getting high, valve performance increases up to 75% of valve opening. In spite of the expected discharge capacity is 8.5 m3/s from a valve which woks in 100% open condition, this value is reached with two valves which work in 100% opening at the minimum reservoir operation level, i.e. H=1472 m.
ahçelik dam
Howell-Bunger valves
optimum valve operating systems
bottom outlet
free discharge valves
2018
06
01
1132
1139
http://scientiairanica.sharif.edu/article_4584_9ae0ca50e7ff31fcbf35530344fe5d51.pdf
Scientia Iranica
Scientia Iranica
1026-3098
1026-3098
2018
25
3
Evaluation the effects of stirrup spacing and buckling of steel reinforcing bars on the capacity of RC columns
Seyed Shaker
Hashemi
Mohammad
Vaghefi
Mehdi
Hemmat
The capacity of reinforced concrete sections highly depends on the interaction between reinforcing bars and surrounding concrete. The buckling of longitudinal steel bars have an important role in the nonlinear behavior of RC sections. In order to nonlinear analyzing of the bar’s buckling in RC columns, two types of column and joint elements are modeled and separate degrees of freedom are used for the reinforcing bars and concrete. Buckling effect is considered in the numerical modeling of bars and the ability and reliability of the numerical method is assessed through the verification of numerical and experimental results. The effect of stirrup spacing on the Axial-Force–Moment (P-M) interaction curve of the RC column is calculated using the nonlinear model of bar's buckling and compared with the ACI criteria. Results show that the numerical capacity in a RC section subject to pure axial compressive load and pure bending moment, with bar's buckling effect, are only about 6% and 9% lower than those obtained without buckling effect, respectively. Also, although ACI criteria does not takes bar's buckling effect into account in the estimation of ultimate strength capacity of RC section, the ultimate capacity recommended by ACI code is acceptable and conservatively enough.
buckling
Reinforced concrete column
Stirrup
Column Capacity
bond-slip effect
2018
06
01
1140
1151
http://scientiairanica.sharif.edu/article_4260_189baedafd388fdcc7741dee8a13d1ef.pdf