@article { author = {Morovvat, M. and Zarrati, A. R. and Jalili Ghazizadeh, M. R.}, title = {A study on the accuracy of finite volume numerical models with non-rectangular mesh}, journal = {Scientia Iranica}, volume = {28}, number = {4}, pages = {1963-1972}, year = {2021}, publisher = {Sharif University of Technology}, issn = {1026-3098}, eissn = {2345-3605}, doi = {10.24200/sci.2021.52017.2484}, abstract = {During numerical simulation of complex geometries and flow depth variations, non-rectangular computational cells are to be generated. However, application of this kind of mesh cause numerical errors. A 3-D model, which was verified and validated before, was used to illustrate the problem in a simple open channel flow. A zigzag computational mesh was used to study the effect of non-rectangular cells on the accuracy of the model. Results showed that water surface and velocity profiles oscillated around the correct answer. Investigating the reason for this oscillation showed that assuming constant velocity at non-rectangular computational cell surfaces, which is a usual practice in all numerical schemes, cause this error. Variation of velocity at mesh surfaces was then added to the computation model and as a result, the oscillations in velocity profiles and water surface were eliminated. Further analysis showed that this is a general problem in any finite volume model with non-rectangular mesh.}, keywords = {Non-rectangular mesh,Complex geometry,Numerical error,Finite volume method,Velocity oscillation,Discretization assumptions,Differential Advection}, url = {https://scientiairanica.sharif.edu/article_22204.html}, eprint = {https://scientiairanica.sharif.edu/article_22204_d11a8ca5a148c7768bdf3e1bbabfd325.pdf} } @article { author = {Shahrouzi, M. and Salehi, A.}, title = {Enhanced imperialist competitive algorithm for optimal structural design}, journal = {Scientia Iranica}, volume = {28}, number = {4}, pages = {1973-1993}, year = {2021}, publisher = {Sharif University of Technology}, issn = {1026-3098}, eissn = {2345-3605}, doi = {10.24200/sci.2020.53827.3441}, abstract = {Solution of complex engineering problems by meta-heuristics, requires powerful operators to maintain sufficient diversification as well as proper intensification during the search. Standard Imperialist Competitive Algorithm, ICA, delays the search intensification by propagating it via a number of artificial empires that compete each other until one concurs the others. An Enhanced Imperialist Competitive Algorithm is developed here by adding an evolutionary operator to the standard ICA followed by greedy replacement; in order to improve its effectiveness. The new operator introduces a walk step directed from the less fit to the fitter individual in each pair of the search agents together with a random scaling and pick up scheme. EICA performance is then compared with ICA as well as GA, PSO, DE, CBO, TLBO, SOS; first in a set of fifteen test functions. Second, a variety of continuous and discrete engineering benchmarks and structural sizing problems are solved to evaluate EICA in constrained optimization. In this regard, a diversity index is traced as well as the other convergence metrics. The results exhibit considerable improvement of the algorithm by the proposed features of EICA and its competitive performance with respect to the other treated methods.}, keywords = {Enhanced Imperialist Competitive Algorithm,hybrid optimization method,diversity index,constrained problem,structural sizing design}, url = {https://scientiairanica.sharif.edu/article_22087.html}, eprint = {https://scientiairanica.sharif.edu/article_22087_24a61df8ae4c86a64f05eb0c872f2ab5.pdf} } @article { author = {Vosough, S. and Samimi, A.}, title = {Disability effects on daily activity type and duration}, journal = {Scientia Iranica}, volume = {28}, number = {4}, pages = {1994-2009}, year = {2021}, publisher = {Sharif University of Technology}, issn = {1026-3098}, eissn = {2345-3605}, doi = {10.24200/sci.2020.54103.3590}, abstract = {Equity concerns of urban planners and policy-makers could not be addressed unless disability effects on daily activities are disentangled. The findings, however, strongly depend on how disability is incorporated into the model. Two MDCEV models for analyzing disability effects on daily activity type and duration are discussed and compared in this paper. In the “classic” approach, an independent dummy variable is used to distinguish disability. While, in the “separate” approach, the dataset is divided into disabled and non-disabled groups, and then a separate model is calibrated for the disabled group. The two approaches result in different coefficients and elasticity values, evidencing that model specification matters for policy assessments. Three transferability metrics are adopted to evidence that the separate approach outperforms the classic approach in explaining travel pattern of persons with disabilities. Finally, three policies that have been practiced across the globe to prevent social exclusion of disabled people are discussed in terms of the effects of model specification on the policy assessment outcomes. This assessment offers managerial insights for policy-makers to develop appropriate infrastructure and accessibility strategies to the disabled people.}, keywords = {Disability,MDCEV model,Activity type,activity duration,Model specification}, url = {https://scientiairanica.sharif.edu/article_22101.html}, eprint = {https://scientiairanica.sharif.edu/article_22101_d64caa4a208ab04d19200d29dd99f50e.pdf} } @article { author = {Maddahi, M. and Gerami, M. and Naderpour, H.}, title = {Effect of structural uncertainties on seismic performance of moment frame rehabilitated with steel shear wall}, journal = {Scientia Iranica}, volume = {28}, number = {4}, pages = {2010-2022}, year = {2021}, publisher = {Sharif University of Technology}, issn = {1026-3098}, eissn = {2345-3605}, doi = {10.24200/sci.2020.54252.3668}, abstract = {In performance-based engineering, conservatism in acceptance criteria at structural performance levels has increased the cost of retrofitting. When simulating structure response in the presence of uncertainties, seismic demand and structural capacity cannot be expressed certainly, though the possible range of these can be predicted. In the seismic rehabilitation of structures, uncertainties have been studied on existing structures and rehabilitation guidelines have been implemented on these uncertainties by reliability index. Adding a secondary system to rehabilitate existing structure may increase uncertainties and may be effective for results of reliability. Therefore, in this study, reliability of rehabilitated a structure with steel shear wall has been discussed with the aim of quantifying uncertainties. Also, the parametric study of reliability index has been performed on probabilistic variables considered for steel shear wall. The selected structure is a three-storey structure of SAC steel moment frame, which was rehabilitated by steel shear wall. For modeling and analyzing the structure, OpenSees software was used. The structure was subject to incremental dynamic analysis before and after of rehabilitation, with probabilistic variables considered for steel shear wall.}, keywords = {Rehabilitation,uncertainty,Reliability,IDA analysis,Steel shear wall}, url = {https://scientiairanica.sharif.edu/article_22102.html}, eprint = {https://scientiairanica.sharif.edu/article_22102_d697acd77d2f6af3814f799e5be6079e.pdf} } @article { author = {Huang, Z. and Wei, B. and Chen, Y. and Zhang, J. and Liu, Y.}, title = {Experimental study on the ultrasonic nonlinear damage characteristics of expansive soil during constant amplitude dry-wet cycles}, journal = {Scientia Iranica}, volume = {28}, number = {4}, pages = {2023-2036}, year = {2021}, publisher = {Sharif University of Technology}, issn = {1026-3098}, eissn = {2345-3605}, doi = {10.24200/sci.2021.55447.4225}, abstract = {Dry-wet cycles can cause fatigue damage to expansive soil, and various control parameters of the dry-wet cycles (initial moisture content, number of dry-wet cycles, cycle amplitude, etc.) can affect the development of soil damage. Therefore, it is important to study the fatigue damage characteristics of expansive soil under dry-wet cycles of constant amplitude. This paper considers expansive soil from Baise in Guangxi, China, as the research object. Based on tests of the P-wave velocity and low-stress shear strength of expansive soil under 0-6 constant amplitude dry-wet cycles, the attenuation laws for the P-wave velocity were analysed, the damage variable of expansive soil was characterized by P-wave velocity, and the rationality of this damage variable was verified by measuring the low-stress shear strength values of expansive soil specimens. Based on the experimental P-wave velocity results, a nonlinear empirical model of fatigue damage for expansive soil was constructed. The results illustrate that the P-wave velocity of an expansive soil sample decreases nonlinearly with an increasing number of dry-wet cycles and that the damage degree increases nonlinearly with an increasing number of cycles. The P-wave velocity can be successfully used to define a representative damage variable for expansive soil.}, keywords = {Expansive soil,dry-wet cycles,fatigue damage,Wave velocity,low-stress shear strength}, url = {https://scientiairanica.sharif.edu/article_22252.html}, eprint = {https://scientiairanica.sharif.edu/article_22252_349c4d37a8c6850d697a3fff47e36f5d.pdf} } @article { author = {Jafari Shahdani, F. and Rasaizadi, A. and Seyedabrishami, S.}, title = {The interaction between activity choice and duration: Application of copula-based and nested-logit models}, journal = {Scientia Iranica}, volume = {28}, number = {4}, pages = {2037-2052}, year = {2021}, publisher = {Sharif University of Technology}, issn = {1026-3098}, eissn = {2345-3605}, doi = {10.24200/sci.2020.55424.4232}, abstract = {There is a relationship between choosing an activity and duration of that activity, especially for non-mandatory ones. Some previous studies have analyzed the decisions about an activity type and duration independently, though some others have used joint models. This paper contributes to the body of knowledge through using Nested-logit and Copula-based models for assessing the existence of interdependency or a hierarchy between non-mandatory activity choice and the relative duration. In the Nested-logit model, it is assumed that error terms of these decisions are interrelated, though one is influenced by another. In contrast, the Copula-based model can accommodate spatial error correlation across observational units without imposing a restrictive distribution assumption on the dependency structures between the error components. The data from Qazvin, a city in Iran, are used for estimating both Nested-logit and Copula-based models and the best variables explaining both choices for each model have been selected. The final models were compared in terms of log-likelihood at convergence and adjusted likelihood ratio index. The results indicated that there are some common influential observed and unobserved factors between these decisions. Also, Copula-based joint model with ρ_0^2 equals to 0.134 outperforms Nested-logit models and provides a better explanatory power.}, keywords = {non-mandatory activities,joint model,activity choice,activity duration,Copula,Nested-logit}, url = {https://scientiairanica.sharif.edu/article_22017.html}, eprint = {https://scientiairanica.sharif.edu/article_22017_b9e68c87d983a9af0b485debdf686d36.pdf} } @article { author = {Farahani, S. and Fathi, M. and Nazarimofrad, E.}, title = {The effect of buckling and post-buckling behavior of laminated composite plates with rotationally restrained and Pasternak foundation on stacking sequence optimization}, journal = {Scientia Iranica}, volume = {28}, number = {4}, pages = {2053-2069}, year = {2021}, publisher = {Sharif University of Technology}, issn = {1026-3098}, eissn = {2345-3605}, doi = {10.24200/sci.2020.55883.4453}, abstract = {This paper presents a stacking sequence optimization for maximizing the buckling load of rotationally restrained laminated composite rectangular plates with different boundary conditions resting on an elastic Pasternak foundation subjected to uniaxial and biaxial in-plane static loads. The Mindlin Plate Theory (MPT), which considers the first-order shear deformation effect, is used to extract the characteristic equations of the plates under in-plane loading, including plate-foundation interaction. The buckling problem of the laminated plates is analyzed by the Rayleigh–Ritz method. The aim of optimization is to maximize the buckling load and post-buckling load capacity by using the Genetic Algorithm (GA) method, and the design variable is the ply orientation. The results showed that the optimal orientation, θ, of the laminated square plate under biaxial in-plane loading with various conditions is 〖45〗^∘ approximately. The existence of a foundation, clamped boundary conditions, and high aspect ratio lead to increase the optimal orientation.}, keywords = {Stacking sequence optimization,buckling and post-buckling behavior,Rotationally restrained laminated composite plates,Pasternak Foundation,Mindlin plate theory}, url = {https://scientiairanica.sharif.edu/article_22111.html}, eprint = {https://scientiairanica.sharif.edu/article_22111_4d294397fc0452db40737884c46cdf48.pdf} } @article { author = {Johari, A. and Amjadi, A. H. and Heidari, A.}, title = {Stochastic nonlinear ground response analysis: A case study site in Shiraz, Iran}, journal = {Scientia Iranica}, volume = {28}, number = {4}, pages = {2070-2086}, year = {2021}, publisher = {Sharif University of Technology}, issn = {1026-3098}, eissn = {2345-3605}, doi = {10.24200/sci.2021.55997.4507}, abstract = {This study attempts to investigate the influence of the dynamic soil properties uncertainties on ground response analysis via a case study site. For this purpose, nonlinear time-domain ground response analysis and uncertainties in soil parameters are coupled simultaneously using a coded program in MATLAB. To take full advantage of the real data, two investigation boreholes are drilled in the site. The analysis is performed deterministically and then extended to the stochastic context in order to take into consideration the variability of Plastic Index, shear wave velocity, and unit weight of the soil. In a part of this study, the capability of the three different methods for predicting the stochastic fundamental period of the site including modal analysis, approximate method, and nonlinear method, is investigated. To achieve the advantage of the stochastic analysis, the maximum Coefficient of Variation (COV) of the peak ground motion parameters, fundamental period, response spectrum, and amplification factor are calculated. The results demonstrate that the heterogeneity of the soil parameters has a significant effect on the variation of the surface Peak Ground Displacement (PGD). Among the other stochastic responses, the fundamental period has received the least effect from soil parameters’ uncertainty.}, keywords = {Nonlinear ground response analysis,Soil parameters uncertainties,Borehole data,stochastic analysis,Fundamental period}, url = {https://scientiairanica.sharif.edu/article_22130.html}, eprint = {https://scientiairanica.sharif.edu/article_22130_77198ba46377a18c9b124af6b01ac475.pdf} } @article { author = {Etebari Ghasbeh, M. A. and Ghoddousi, P. and Shirzadi Javid, A. A.}, title = {Modeling concrete thermal expansion based on packing density theory}, journal = {Scientia Iranica}, volume = {28}, number = {4}, pages = {2087-2100}, year = {2021}, publisher = {Sharif University of Technology}, issn = {1026-3098}, eissn = {2345-3605}, doi = {10.24200/sci.2021.56121.4558}, abstract = {In this study, the effects of supplementary cementitious materials with changes in the structure of the concrete pores have been examined on the coefficient of thermal expansion (CTE) at different ages. The results indicated a descending trend for the CTE of the reference concrete up to 60 days (diminishing by about 12%), after which it remained constant. In contrast, an opposite trend was observed for the slag-containing concrete, i.e., the descending trend started after 60 days, and its CTE declined by 10% up to 120 days. In the following, two equations are presented for the concrete to estimate the CTE of the concrete during its lifetime based on its CTE at the age of seven days. Across all the concretes, the reduction of CTE was associated with lowered porosity. Moreover, evaluating the distribution of the pore size showed that when the pore diameter decreased, the CTE decreased as well, indicating a strong relationship between the median diameter of the pores and the CTE. Considering the fact that the concrete’s CTE depends on aggregates and the cement paste, a model was presented based on the CTE of the cement paste and its packing density to estimate the CTE of the concrete.}, keywords = {coefficient of thermal expansion (CTE),supplementary cementitious materials,packing density,Prediction}, url = {https://scientiairanica.sharif.edu/article_22132.html}, eprint = {https://scientiairanica.sharif.edu/article_22132_88399d66535229f11207fc532c8de6ba.pdf} } @article { author = {Ramezani, M. and Bahar, O.}, title = {Indirect structure damage identification with the information of the vertical and rotational mode shapes}, journal = {Scientia Iranica}, volume = {28}, number = {4}, pages = {2101-2118}, year = {2021}, publisher = {Sharif University of Technology}, issn = {1026-3098}, eissn = {2345-3605}, doi = {10.24200/sci.2021.56842.4939}, abstract = {In this paper, a robust method is proposed to detect damage extent and location of structural elements focusing on data type and acquisition method and aiming to the promotion of model updating tools. The novelty of this method is rotational mode shape acquisition, which provides valuable information on the damage. In this method, the damaged elements are indirectly identified by detecting the healthy elements and eliminating them from searching space. This method requires to minimize the modal strain energy difference between the damaged model and numerical model via an optimization algorithm, then an improved genetic algorithm (IGA) is used. In this study, four numerical and two experimental damage scenarios are applied on a simply supported beam to examine the performance of the proposed method. Modal data acquisitions have been made by vision-based method and accelerometer sensors. The results demonstrate that this method could accurately figure out the location and severity of damage using just the first mode shape since rotational mode shapes are more sensitive than vertical mode shapes in damage detection.}, keywords = {Indirect damage detection,Rotational mode shapes,Genetic Algorithm,model updating,Modal strain energy}, url = {https://scientiairanica.sharif.edu/article_22247.html}, eprint = {https://scientiairanica.sharif.edu/article_22247_28814428c7b76e9b2b2550219750bccc.pdf} } @article { author = {Aydin, A. C. and Bayrak, B and Maali, M. and Mete, E. and Cebi, K. and Kilic, M.}, title = {The shear and flexural behavior of cold-formed steel composite I and U beams}, journal = {Scientia Iranica}, volume = {28}, number = {4}, pages = {2119-2132}, year = {2021}, publisher = {Sharif University of Technology}, issn = {1026-3098}, eissn = {2345-3605}, doi = {10.24200/sci.2021.57157.5092}, abstract = {The recycling and re-usability of the waste materials are of great importance and meaning when evaluated in terms of ecological order. Furthermore, cold formed steel has great importance, nowadays. The aim of this study is to investigate the bending and shear behavior of the composite formed by pouring the waste polymer into the cold formed I and U profile melds after homogenous pulping. The best results in shear and bending strengths were obtained with melted polypropylene. The enhanced adherence between the steel and molted PP increased the shear and bending capacity, both. Moreover, it is reinforced with carbon fiber reinforced polymer and glass fiber reinforced polymer bars to increase the bending and shear behavior of I and U profiles filled with melted waste polymer. Changing the cross-sectional area in I and U beams under bending moment has an effect on the load at yielding, ultimate strength, displacement values corresponding to these loads, ductility and energy dissipation capacity. The addition of CFRP in I beams significantly increased the displacement capacity in the free end region under the shear force. The addition of GFRP bars with higher elongation capacity in I and U beams caused ductile behavior than CFRP bars.}, keywords = {cold-formed steel,polypropylene,flexural and shear behavior,waste,Plastic waste}, url = {https://scientiairanica.sharif.edu/article_22203.html}, eprint = {https://scientiairanica.sharif.edu/article_22203_16b31949501332274fd70890229f5c4d.pdf} }