Performance of composite frame consisting of steel beams and concrete filled tubes under fire loading

Mahdi Shariati,Mohammad Grayeli,Ali Shariati,Morteza Naghipour 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.36 No.5

In recent years, the composite columns have been widely used in the structures. These columns are mainly used to construct the structures with a large span and high floor height. Concrete filled tubes (CFTs) are a type of composite column, which are popular nowadays due to their numerous benefits. The purpose of this study is to investigate such frames at elevated temperatures. The method used in this research is based on section 2.2 of Eurocode 4. First, for the verification purpose, a comparison was made between the experimental results and the numerical model of the concrete filled tube. Then a composite frame was analyzed under fire temperature with different parameters. The results showed that the failure time decreased with increasing the friction of different models. Moreover, investigation of the concrete moisture content revealed that an increase in the concrete moisture content from 3% to 10% led to extended failure time for different models. For instance, in the second frame model, the failure time has increased up to 8%.

Identification of the most influencing parameters on the properties of corroded concrete beams using an Adaptive Neuro-Fuzzy Inference System (ANFIS)

Mahdi Shariati,Mohammad Saeed Mafipour,James H. Haido,Salim T. Yousif,Ali Toghroli,Nguyen Thoi Trung,Ali Shariati 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.34 No.1

Different parameters potentially affect the properties of corroded reinforced concrete beams. However, the high number of these parameters and their dependence cause that the effectiveness of the parameters could not be simply identified. In this study, an adaptive neuro-fuzzy inference system (ANFIS) was employed to determine the most influencing parameters on the properties of the corrosion-damaged reinforced concrete beams. 207 ANFIS models were developed to analyze the collected data from 107 reinforced concrete (RC) beams. The impact of 23 input parameters on nine output factors was investigated. The results of the paper showed the order of influence of each input parameter on the outputs and revealed that the input parameters regarding the uncorroded properties of concrete beams are the most influencing factors on the corresponding corroded properties of the beams.

Application of Extreme Learning Machine (ELM) and Genetic Programming (GP) to design steel-concrete composite floor systems at elevated temperatures

Mahdi Shariati,Mohammad Saeed Mafipour,Peyman Mehrabi,Yousef Zandi,Davoud Dehghani,Alireza Bahadori,Ali Shariati,Nguyen Thoi Trung,Musab N.A. Salih,Shek Poi-Ngian 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.33 No.3

This study is aimed to predict the behaviour of channel shear connectors in composite floor systems at different temperatures. For this purpose, a soft computing approach is adopted. Two novel intelligence methods, including an Extreme Learning Machine (ELM) and a Genetic Programming (GP), are developed. In order to generate the required data for the intelligence methods, several push-out tests were conducted on various channel connectors at different temperatures. The dimension of the channel connectors, temperature, and slip are considered as the inputs of the models, and the strength of the connector is predicted as the output. Next, the performance of the ELM and GP is evaluated by developing an Artificial Neural Network (ANN). Finally, the performance of the ELM, GP, and ANN is compared with each other. Results show that ELM is capable of achieving superior performance indices in comparison with GP and ANN in the case of load prediction. Also, it is found that ELM is not only a very fast algorithm but also a more reliable model.

Evaluation of seismic performance factors for tension-only braced frames

Mahdi Shariati,Majid Lagzian,Shervin Maleki,Ali Shariati,Nguyen Thoi Trung 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.35 No.4

The tension-only braced frames (TOBFs) are widely used as a lateral force resisting system (LFRS) in low-rise steel buildings due to their simplicity and economic advantage. However, the system has poor seismic energy dissipation capacity and pinched hysteresis behavior caused by early buckling of slender bracing members. The main concern in utilizing the TOBF system is the determination of appropriate performance factors for seismic design. A formalized approach to quantify the seismic performance factor (SPF) based on determining an acceptable margin of safety against collapse is introduced by FEMA P695. The methodology is applied in this paper to assess the SPFs of the TOBF systems. For this purpose, a trial value of the R factor was first employed to design and model a set of TOBF archetype structures. Afterwards, the level of safety against collapse provided by the assumed R factor was investigated by using the non-linear analysis procedure of FEMA P695 comprising incremental dynamic analysis (IDA) under a set of prescribed ground motions. It was found that the R factor of 3.0 is appropriate for safe design of TOBFs. Also, the system overstrength factor (Ω0) was estimated as 2.0 by performing non-linear static analyses.

Experimental and numerical investigations on the ratcheting characteristics of cylindrical shell under cyclic axial loading

Shariati, M.,Hatami, H.,Torabi, H.,Epakchi, H.R. Techno-Press 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.44 No.6

The ratcheting characteristics of cylindrical shell under cyclic axial loading are investigated. The specimens are subjected to stress-controlled cycling with non-zero mean stress, which causes the accumulation of plastic strain or ratcheting behavior in continuous cycles. Also, cylindrical shell shows softening behavior under symmetric axial strain-controlled loading and due to the localized buckling, which occurs in the compressive stress-strain curve of the shell; it has more residual plastic strain in comparison to the tensile stress-strain hysteresis curve. The numerical analysis was carried out by ABAQUS software using hardening models. The nonlinear isotropic/kinematic hardening model accurately simulates the ratcheting behavior of shell. Although hardening models are incapable of simulating the softening behavior of the shell, this model analyzes the softening behavior well. Moreover, the model calculates the residual plastic strain close to the experimental data. Experimental tests were performed using an INSTRON 8802 servo-hydraulic machine. Simulations show good agreement between numerical and experimental results. The results reveal that the rate of plastic strain accumulation increases for the first few cycles and then reduces in the subsequent cycles. This reduction is more rapid for numerical results in comparison to experiments.

Investigation of microstructure and surface effects on vibrational characteristics of nanobeams based on nonlocal couple stress theory

Shariati, Ali,Barati, Mohammad Reza,Ebrahimi, Farzad,Toghroli, Ali Techno-Press 2020 Advances in nano research Vol.8 No.3

The article brings the study of nonlocal, surface and the couple stress together to apparent the frequency retaliation of FG nanobeams (Functionally graded). For the examination of frequency retaliation, the article considers the accurate spot of neutral axis. This article aims to enhance the coherence of proposed model to accurately encapsulate the significant effects of the nonlocal stress field, size effects together with material length scale parameters. These considered parameters are assimilated through what are referred to as modified couple stress as well as nonlocal elasticity theories, which encompasses the stiffness-hardening and softening influence on the nanobeams frequency characteristics. Power-law distribution is followed by the functional gradation of the material across the beam width in the considered structure of the article. Following the well-known Hamilton's principle, fundamental basic equations alongside their correlated boundary conditions are solved analytically. Validation of the study is also done with published result. Distinct parameters (such as surface energy, slenderness ratio, as nonlocal material length scale and power-law exponent) influence is depicted graphically following the boundary conditions on non-dimensional FG nanobeams frequency.

Investigating vibrational behavior of graphene sheets under linearly varying in-plane bending load based on the nonlocal strain gradient theory

Shariati, Ali,Barati, Mohammad Reza,Ebrahimi, Farzad,Singhal, Abhinav,Toghroli, Ali Techno-Press 2020 Advances in nano research Vol.8 No.4

A study that primarily focuses on nonlocal strain gradient plate model for the sole purpose of vibration examination, for graphene sheets under linearly variable in-plane mechanical loads. To study a better or more precise examination on graphene sheets, a new advance model was conducted which carries two scale parameters that happen to be related to the nonlocal as well as the strain gradient influences. Through the usage of two-variable shear deformation plate approach, that does not require the inclusion of shear correction factors, the graphene sheet is designed. Based on Hamilton's principle, fundamental expressions in regard to a nonlocal strain gradient graphene sheet on elastic half-space is originated. A Galerkin's technique is applied to resolve the fundamental expressions for distinct boundary conditions. Influence of distinct factors which can be in-plane loading, length scale parameter, load factor, elastic foundation, boundary conditions, and nonlocal parameter on vibration properties of the graphene sheets then undergo investigation.

Experimental investigation on the effect of cementitious materials on fresh and mechanical properties of self-consolidating concrete

Shariati, Mahdi,Rafie, Shervin,Zandi, Yousef,Fooladvand, Rouhollah,Gharehaghaj, Behnam,Mehrabi, Peyman,Shariat, Ali,Trung, Nguyen Thoi,Salih, Musab N.A.,Poi-Ngian, Shek Techno-Press 2019 Advances in concrete construction Vol.8 No.3

Although applying self-consolidating concrete (SCC) in many modern structures is an inevitable fact, the high consumption of cement in its mixing designs has led to increased production costs and adverse environmental effects. In order to find economically viable sources with environmentally friendly features, natural pozzolan pumice and blast furnace slag in 10-50% of replacement binary designs have been investigated for experiments on the properties of fresh concrete, mechanical properties, and durability. As a natural pozzolan, pumice does not require advanced equipment to prepare for consumption and only needs to be powdered. Pumice has been the main focus of this research because of simple preparation. Also to validate the results, in addition to the control specimens of each design, fly ash as a known powder has been evaluated. Moreover, ternary mixes of pumice and silica fume were investigated to enhance the obtained results of binary mixes. It was concluded that pumice and slag powders indicated favorable performance in the high percentage of replacement.

Optimal Trajectory Planning of a Mobile Robot with Spatial Manipulator For Obstacle Avoidance

Shariati Nia Mostafa,Ghayour Mostafa,Mosayebi Masoud 제어로봇시스템학회 2010 제어로봇시스템학회 국제학술대회 논문집 Vol.2010 No.10

Mobile robots consist of a mobile platform with one or many manipulators mounted on it are of great interest in a number of applications. Combination of platform and manipulator causes robot operates in extended work space. The analysis of these systems includes kinematics redundancy that makes more complicated problem. However, it gives more feasibility to robotic systems because of the existence of multiple solutions in a specified workspace. This paper presents a methodology in generating paths and trajectories for both the mobile platform and a 3DOF manipulator mounted on it, in the presence of obstacles. Obstacles add kinematics constraint into optimization problem. The method employs smooth and continuous functions such as polynomials. The proposed method includes obtaining time history of the mobile robot motion. It is supposed that the obstacles can be enclosed in cylinders. The platform has been used in this research is a differentially-driven platform. The core of the method is based on mapping the nonholonomic constraint to a space where it can be satisfied trivially. A suitable criterion can be used to solve an optimization problem to find the optimal solution. In this research, the problem of path planning with simultaneous optimization of kinematics and dynamic indices has been accomplished using genetic algorithm in order to find the global optimum solution. The validity of the methodology is demonstrated by using a differential-drive mobile manipulator system, various simulations of platform with a spatial 3-link manipulator are presented to show the effectiveness of the presented method.

On bending characteristics of smart magneto-electro-piezoelectric nanobeams system

Shariati, Ali,Ebrahimi, Farzad,Karimiasl, Mahsa,Selvamani, Rajendran,Toghroli, Ali Techno-Press 2020 Advances in nano research Vol.9 No.3

The content of this study focuses on bending of flexoelectric Magneto-Electro-Elastic (MEE) nanobeams inserted within the foundation of Winkler-Pasternak according to nonlocal elasticity theory. Applying Hamilton's principle, the nonlocal nanobeams' governing equations in the framework higher order refined beam theory are attained and resolved through adapting an analytical solution. A parametric research is demonstrated for studying the effects that magneto-electro-mechanical loadings, the nonlocal parameter, flexoelectric, as well as the aspect ratio all have on the deflection properties of nanobeams. A discovery lead to beam geometrical parameters, the boundary conditions, flexoelectricity and nonlocal parameter partake substantial effects on nanoscale beams' dimensionless deflection.