Optimization of modal load pattern for pushover analysis of building structures

Shayanfar, Mohsen Ali,Ashoory, Mansoor,Bakhshpoori, Taha,Farhadi, Basir Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.47 No.1

Nonlinear Static Procedures (NSPs) have been developed as a practical tool to estimate the seismic demand of structures. Several researches have accomplished to minimize errors of NSPs, namely pushover procedures, in the Nonlinear Time History Analysis (NTHA), as the most exact method. The most important issue in a typical pushover procedure is the pattern and technique of loading which are extracted based on structural dynamic fundamentals. In this paper, the coefficients of modal force combination is focused involving a meta-heuristic optimization algorithm to find the optimum load pattern which results in a response with minimum amount of errors in comparison to the NTHA counterpart. Other parameters of the problem are based on the FEMA recommendations for pushover analysis of building structures. The proposed approach is implemented on a high-rise 20 storey concrete moment resisting frame under three earthquake records. In order to demonstrate the effectiveness and robustness of the studied procedure the results are presented beside other well-known pushover methods such as MPA and the FEMA procedures, and the results show the efficiency of the proposed load patterns.

Optimization of modal load pattern for pushover analysis of building structures

Mohsen Ali Shayanfar,Mansoor Ashoory,Taha Bakhshpoori,Basir Farhadi 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.47 No.1

Nonlinear Static Procedures (NSPs) have been developed as a practical tool to estimate the seismic demand of structures. Several researches have accomplished to minimize errors of NSPs, namely pushover procedures, in the Nonlinear Time History Analysis (NTHA), as the most exact method. The most important issue in a typical pushover procedure is the pattern and technique of loading which are extracted based on structural dynamic fundamentals. In this paper, the coefficients of modal force combination is focused involving a meta-heuristic optimization algorithm to find the optimum load pattern which results in a response with minimum amount of errors in comparison to the NTHA counterpart. Other parameters of the problem are based on the FEMA recommendations for pushover analysis of building structures. The proposed approach is implemented on a high-rise 20 storey concrete moment resisting frame under three earthquake records. In order to demonstrate the effectiveness and robustness of the studied procedure the results are presented beside other well-known pushover methods such as MPA and the FEMA procedures, and the results show the efficiency of the proposed load patterns.

A new hybrid method for reliability-based optimal structural design with discrete and continuous variables

Ali Khodam,Mohammad Saeid Farajzadeh,Mohsenali Shayanfar 국제구조공학회 2023 Structural Engineering and Mechanics, An Int'l Jou Vol.85 No.3

Reliability-Based Design Optimization (RBDO) is an appropriate framework for obtaining optimal designs by taking uncertainties into account. Large-scale problems with implicit limit state functions and problems with discrete design variables are two significant challenges to traditional RBDO methods. To overcome these challenges, this paper proposes a hybrid method to perform RBDO of structures that links Firefly Algorithm (FA) as an optimization tool to advanced (finite element) reliability methods. Furthermore, the Genetic Algorithm (GA) and the FA are compared based on the design cost (objective function) they achieve. In the proposed method, Weighted Simulation Method (WSM) is utilized to assess reliability constraints in the RBDO problems with explicit limit state functions. WSM is selected to reduce computational costs. To performing RBDO of structures with finite element modeling and implicit limit state functions, a First-Order Reliability Method (FORM) based on the Direct Differentiation Method (DDM) is utilized. Four numerical examples are considered to assess the effectiveness of the proposed method. The findings illustrate that the proposed RBDO method is applicable and efficient for RBDO problems with discrete and continuous design variables and finite element modeling.

Reliability-based design optimization of structural systems using a hybrid genetic algorithm

Abbasnia, Reza,Shayanfar, Mohsenali,Khodam, Ali Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.52 No.6

In this paper, reliability-based design optimization (RBDO) of structures is addressed. For this purpose, the global search and optimization capabilities of genetic algorithm (GA) are combined with the efficiency and reasonable accuracy of an advanced moment-based finite element reliability method. For performing RBDO, three variants of GA including a real-coded, a binary-coded and an improved binary-coded GA are developed. In these methods, GA performs (finite element) reliability analyses to evaluate reliability constraints. For truss structures which include finite element modeling, reliability constraints are evaluated using finite element reliability analysis. Response sensitivity required for finite element reliability analysis is obtained by direct differentiation method (DDM) rather than finite difference method (FDM). The proposed methods are examined within four standard test examples and real-world design problems. The results illustrate the superiority and efficiency of the improved binary-coded GA. Results also illustrate that DDM significantly reduces the computational cost and improves the efficiency of the optimization procedure.

Solubility of celecoxib in N-methyl-2-pyrrolidone+water mixtures at various temperatures: Experimental data and thermodynamic analysis

Sarah Nozohouri,Ali Shayanfar,Zaira Johanna Cárdenas,Fleming Martinez,Abolghasem Jouyban 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.5

Solubility is one of the most significant physicochemical properties of drugs, and improving the solubility of drugs is still a challenging subject in pharmaceutical sciences due to requirements of enhancing their bioavailability. Celecoxib, according to the biopharmaceutics classification system (BCS), is a class 2 drug, possessing low water solubility (<5 μg·mL−1) and high permeability. Increasing the solubility of this group can lead to improved bioavailability, dose reduction and subsequently, increased efficiency and reduced side effects. In this study, celecoxib solubility was determined in binary mixtures of N-methyl-2-pyrrolidone (NMP)+water at 293.2, 298.2, 303.2, 308.2 and 313.2 K. The solubility of celecoxib is increased with the addition of NMP to the aqueous solutions and reaches a maximum value in neat NMP. In addition, increased temperature leads to enhanced solubility of celecoxib in a given solvent composition. The solubility data of celecoxib in NMP+water at different temperatures were correlated using different mathematical models including, the Jouyban-Acree model and a combination of the Jouyban-Acree and van’t Hoff models. Thermodynamic parameters, Gibbs energy, enthalpy and entropy of dissolution processes were performed based on Gibbs and van’t Hoff equations. Thermodynamic analysis allowed observing two main entropy or enthalpy-driven dissolution mechanisms, varying according to the composition of aqueous mixtures. Moreover, preferential solvation of celecoxib by water is observed in water-rich mixtures but preferential solvation by NMP was seen in mixtures with similar composition and also in NMP-rich mixtures.

Reliability-based design optimization of structural systems using a hybrid genetic algorithm

Reza Abbasnia,Mohsenali Shayanfar,Ali Khodam 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.52 No.6

In this paper, reliability-based design optimization (RBDO) of structures is addressed. For this purpose, the global search and optimization capabilities of genetic algorithm (GA) are combined with the efficiency and reasonable accuracy of an advanced moment-based finite element reliability method. For performing RBDO, three variants of GA including a real-coded, a binary-coded and an improved binarycoded GA are developed. In these methods, GA performs (finite element) reliability analyses to evaluate reliability constraints. For truss structures which include finite element modeling, reliability constraints are evaluated using finite element reliability analysis. Response sensitivity required for finite element reliability analysis is obtained by direct differentiation method (DDM) rather than finite difference method (FDM). The proposed methods are examined within four standard test examples and real-world design problems. The results illustrate the superiority and efficiency of the improved binary-coded GA. Results also illustrate that DDM significantly reduces the computational cost and improves the efficiency of the optimization procedure.

Durability of RC Structures against Carbonation-Induced Corrosion under the Impact of Climate-Change

Mohammad Ghanooni-Bagha,Mohammad Reza YekeFallah,Mohsen Ali Shayanfar 대한토목학회 2020 KSCE Journal of Civil Engineering Vol.24 No.1

The factors associated with concrete carbonation can be classified in three major categories of environmental factors, concrete’s internal-structural factors, and construction-operation conditions. Climate change is expected to cause gradual change in many primary environmental factors, which may accelerate reinforcement corrosion in reinforced concrete (RC) structures. Studies show that CO2 concentration in the atmosphere may rise from 379 ppm in 2005 to 1,000 ppm in 2100. Hence, adoption of suitable measures to protect exposed RC members against carbonation-induced corrosion is essential for countering the future environmental effects which, in turn, requires further investigation on the effect of critical structural factors, such as water-cement ratio and cement content in the concrete mix design, and construction-operation factors, such as concrete cover depth and surface protection, on the durability of RC members. In this study, these factors were investigated through Monte Carlo simulation. The results showed that slight adjustments in some structural and operational factors can significantly reduce the risk of corrosion initiation and ultimately improve the durability of concrete members against corrosion. The effect of each parameter on the probability of corrosion initiation during the design life of a RC structure was analyzed and interpreted using numerical examples.