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Estimating failure probability of IBBC connection using direct coupling of reliability approach and finite element method

M Taherinasab, Ali A Aghakouchak
Journal PaperJournal of Building Engineering , Volume 38 , 2021 June 1, {Pages 102207 }


This paper aims to produce estimates of probabilities of exceeding specified structural performance thresholds for two types of I beam to box column (IBBC) connections used in steel moment resisting frames (SMRF), when subjected to earthquake ground motions, and to conduct sensitivity analysis of affecting parameters. This is done through coupling the finite element and reliability theory approaches, which allows the analyst to define all uncertainties associated with model parameters. In order to take into account, the record to record variability, incremental dynamic analysis was carried out and statistical properties of the random variable of seismic loading were obtained for the second story of a sample 12-story SMRF at the global colla

Experimental and numerical study on developed elastomeric layers based on natural and butyl matrix rubbers for viscoelastic dampers

Omid Ranaei, Ali Akbar Aghakouchak
Journal PaperMechanics of Time-Dependent Materials , 2021 February 1, {Pages 23-Jan }


Elastomeric layers, that serve as the base of a viscoelastic (VE) damping system in structures, dissipate energy through shear deformation and transform vibration energy into heat by internal friction between polymer chains. In this study, two compounds, based on natural rubber (NR) matrix and butyl rubber (IIR) matrix, were designed and manufactured. Then, the mechanical and dynamic properties of elastomeric layers were investigated. Dynamic loading tests were conducted on the elastomeric layers using a frequency range of 0.1–1.5 Hz and a shear strain range of 10–150% under harmonic loading in order to analyze their hysteretic behavior. The output of the experiments shows that the both of elastomeric layers have a large deformation cap

Cyclic behavior of moment frames with conventional or slit Infills

Zahra Ahmadi, Ali Akbar Aghakouchak, Seyyed Rasoul Mirghaderi
Journal PaperJournal of Constructional Steel Research , Volume 178 , 2021 March 1, {Pages 106494 }


This paper presents the results of a study to investigate the effects of conventional and slit shear infills on behavior, of steel frames when subjected to cyclic loading. Three structural specimens of steel moment frames with and without infill webs have been tested. The slits in slit shear wall specimen have had a new parabolic shape. Initiation of damage and fracture in these systems have also been studied. Ductile damage parameters of ISO S235 steel, used in the specimens, have been determined using tensile tests. Numerical models of tested specimens have confirmed the application of these damage parameters to simulate experimental results. Based on the results of experimental study, seismic characteristics of a conventional steel momen

Investigating the behaviour of steel framed-tube and moment-resisting frame systems exposed to fire

M Chaboki, M Heshmati, AA Aghakouchak
Journal Paper , , {Pages }


Design and numerical evaluation of two innovative moment-free beam-gusset-column connections for BRBFs

H Fatemi, AA Aghakouchak
Journal Paper , , {Pages }


Feasibility of reducing dynamic response of a fixed offshore platform using tuned liquid dampers

Ali Ghasemi Koohi Kheili, Ali Akbar Aghakouchak
Journal PaperShip Technology Research , 2020 May 19, {Pages 10-Jan }


Fixed offshore platforms are always subjected to dynamic loading. A potentially economical method to improve the dynamic behaviour of these platforms is using passive control devices. In this paper, the application of tuned liquid damper, TLD, in controlling the response of a fixed offshore platform located in the Persian Gulf against earthquake and wave loading was studied. Analysis of a 3D model of the structure equipped with TLDs was carried out using the finite element method, and the efficiency of TLDs was investigated. Also, the equivalent models of TLDs were constructed based on the lumped mass method, and linear wave theory and the results were compared to finite element modelling of TLD. Results showed good agreement between the fi

Application of slit link beam in eccentrically braced frames

Seyed Saeed Askariani, Sadegh Garivani, Ali Akbar Aghakouchak
Journal PaperJournal of Constructional Steel Research , Volume 170 , 2020 July 1, {Pages 106094 }


Slit dampers are a specific type of metallic yielding dampers, for which many studies have been conducted in recent years, to investigate their behavior and possible applications in structures. In this paper, by considering the behavior of this type of dampers, the use of slit link beam in eccentrically braced frames is proposed. A slit link beam is a link beam in which the beam web is divided into a number of vertical links using slits/openings. The geometry of the links is designed to ensure uniform distribution of normal stress along them. Analytical equations are developed to predict the behavior of the slit link beam and the eccentrically braced frame. The behavior of the proposed system is studied using verified numerical analyses in

Investigation of the behavior of mid–rise steel moment resisting frame with long spans exposed to fire and progressive collapse

Ali Akbar Aghakouchak
Journal PaperModares Civil Engineering journal , Volume 19 , Issue 6, 2020 February 10, {Pages 0-0 }


This paper investigates the behavior of a steel moment frame system with long spans subjected to compartment fires and progressive collapse scenarios due to girder drop and column removal. In this study, initially, a typical 15–story building with moment frame system with long spans and story height 3.2 (m) was designed using relevant chapters of national building code of Iran for conventional gravity and lateral loads. In order to perform thermal analyses, the most critical frame of this structure is modelled in finite element software OpenSees. Then the nonlinear behavior of the frame is studied at elevated temperatures under different fire scenarios and progressive collapse Scenarios due to girder drop and column removal. In this analy

Sensitivity analysis of the influence of ground motion intensity levels on the seismic behavior of steel frames in assessment of the target displacement considering near-fault?…

Alireza Esfahanian, Ali Akbar Aghakouchak
Journal PaperCanadian Journal of Civil Engineering , Volume 47 , Issue 4, 2020 January , {Pages 470-486 }


Nonlinear time-history analysis conducted as part of a performance-based seismic design approach often require that the ground motion records are selected and then scaled to a specified level of seismic intensity. In such analyses, besides an adequate structural model, a set of acceleration time-series is needed as the most realistic representation of the seismic action. In this paper, the effects of scaling procedure on seismic demands of steel frames are investigated. To this, two special steel moment-resisting frames with considerable higher mode effects, and two sets of ground motions, including near-fault and far-fault motions are considered. Moreover, three scaling procedures are introduced for performing nonlinear dynamic time-histor

An energy based method for seismic design of frame structures equipped with metallic yielding dampers considering uniform inter-story drift concept

Fatemeh Aliakbari, Sadegh Garivani, Ali Akbar Aghakouchak
Journal PaperEngineering Structures , Volume 205 , 2020 February 15, {Pages 110114 }


Application of passive control systems in earthquake-resistant structures has attracted much attention in recent decades. One of the most important obstacles to the widespread use of these systems is the lack of simple methods for analysis and design of these systems. Energy based approach is one of design methods that has been considered extensively in recent years. In this paper, an energy-based method is proposed for seismic design of the building structures equipped with metallic yielding dampers. Considering the concepts of energy balance in the structure, the required equations to determine the number of dampers in each story are developed so that uniform drift and ductility demands are achieved in different stories. A step-by-step de

Collapse analysis of regular and irregular tall steel moment frames under fire loading

Mahdi Heshmati, Ali Akbar Aghakouchak
Journal PaperThe Structural Design of Tall and Special Buildings , Volume 29 , Issue 3, 2020 February 25, {Pages e1696 }


This study is carried out to evaluate the progressive collapse of steel buildings under fire event. To this end, a 15‐story steel structure with moment‐resisting system and composite floors is considered. The effects of various parameters such as beam section size, gravity load ratio, vertical irregularity of resisting system, and location of fire compartments on collapse modes are investigated numerically. Different temperature‐time curves are defined across the composite floors according to the Eurocode 4. It is found that local collapse of the frames at the ground floor fire is triggered by the buckling of the interior heated columns at approximately 540?C. The redistributed loads by floors delay the global collapse at least 45?mi

Collapse of the 16-story Plasco Building in Tehran due to fire

MT Ahmadi, AA Aghakouchak, R Mirghaderi, S Tahouni, S Garivani, A Shahmari, S Epackachi
Journal PaperFire technology , Volume 56 , Issue 2, 2020 March , {Pages 769-799 }


On January 19, 2017 an accidental fire, which started by an electric shorting, resulted in the complete collapse of the 16-storey Plasco Building in Tehran. Twenty-two people including sixteen firefighters were killed in that incident. This paper reports the study carried out to investigate the most likely causes of the events and collapse of the structure. The information presented in this study was collected through gathering the limited amount of available information on the structure, generating as-built structural drawings, reviewing construction photographs, interviewing fire-fighters and other witnesses, frame-by-frame analysis of a number of available videotapes showing the structure during the fire as well as during the final stag

Parametric study on probabilistic local seismic demand of IBBC connection using finite element reliability method

Mohammad Taherinasab, Ali A Aghakouchak
Journal PaperSteel and Composite Structures , Volume 37 , Issue 2, 2020 January , {Pages 151-173 }


This paper aims to probabilistically evaluate performance of two types of I beam to box column (IBBC) connection. With the objective of considering the variability of seismic loading demand, statistical features of the inter-story drift ratio corresponding to the second, fifth and eleventh story of a 12-story steel special moment resisting frames are extracted through incremental dynamic analysis at global collapse state. Variability of geometrical variables and material strength are also taken into account. All of these random variables are exported as inputs to a probabilistic finite element model which simulates the connection. At the end, cumulative distribution functions of local seismic demand for each component of each connection are

Seismic design of structures with yielding dampers based on drift demands

Sadegh Garivani, Seyed Saeed Askariani, Ali Akbar Aghakouchak
Journal PaperStructures , Volume 28 , 2020 December 1, {Pages 1885-1899 }


Application of passive structural control using metallic yielding dampers (MYDs) in the design of buildings is considered more often in recent years. Design of a building structure equipped with dampers is more complicated compared to an ordinary structure; but recent design codes provide guidelines in this regard, which normally involve a trial and error process. In this paper, a fairly simple procedure for the design of structures incorporating MYDs is proposed. The aim of this procedure is to design a structure, which undergoes a uniform inter-story drift, when subjected to seismic excitation. The procedure is applied to design several low- and mid-rise structures and their behaviors are studied using nonlinear time history analysis. The

Collapse assessment and seismic performance factors in tall tube-in-tube diagrid buildings

Alireza Khatami, Mahdi Heshmati, Ali Akbar Aghakouchak
Journal PaperEarthquakes and Structures , Volume 19 , Issue 3, 2020 January , {Pages 197-214 }


Diagrid structures have been introduced as a fairly modern lateral load-resisting system in the design of high-rise buildings. In this paper, a novel diagrid system called tube-in-tube diagrid building is introduced and assessed through pushover and incremental dynamic analyses. The main objectives of this paper are to find the optimum angle of interior and exterior diagrid tube and evaluate the efficiency of diagrid core on the probability of collapse comparing to the conventional diagrid system. Finally, the seismic performance factors of the proposed system are validated according to the FEMA P695 methodology. To achieve these, 36-story diagrid buildings with various external and internal diagonal angles are designed and then 3-D nonline

Steel slit shear walls with an efficient geometry

Zahra Ahmadi, Ali Akbar Aghakouchak, Seyyed Rasoul Mirghaderi
Journal PaperThin-Walled Structures , 2020 November 24, {Pages 107296 }


This paper presents the results of a study to improve the seismic behavior of steel shear walls with vertical slits. In this system, the steel plate segments between the slits behave as a series of flexural links, which provide a fairly ductile response without the need for heavy stiffening. An efficient slit geometry is proposed, which assures simultaneous yielding of the plate along the vertical links and prevents strain localization. Experimental study and finite element modeling are used to verify the proposed steel slit shear wall and to study its nonlinear behavior under monotonic and cyclic loading. Out-of-plane buckling of the wall and the effects of buckling restraining clamps on this phenomenon is also studied. The results show sa

Structural investigation of the collapse of the 16‐story Plasco building due to fire

Ali Akbar Aghakouchak, Sadegh Garivani, Ali Shahmari, Mahdi Heshmati
Journal PaperThe Structural Design of Tall and Special Buildings , 2020 October 27, {Pages e1815 }


On January 19, 2017, the 16‐story Plasco tower located in Tehran, the capital city of Iran, collapsed in several stages, due to a fire lasting 3.5 h. This paper presents the results of numerical investigations on how the structure behaved during that incident. In this regard, initially, a part of floor system including main truss girders, secondary truss beams, tie beams, and reinforced concrete slab is simulated to study its deformed shape and collapse modes. Then 2D and 3D models of the building are developed to evaluate the global behavior of the structure under fire. The results show that at elevated temperatures, deflection of the floor system, main trusses, and out‐of‐plane bending of the beam‐to‐column gusset plates become

Sensitivity analysis of the influence of ground motion intensity levels on the seismic behavior of steel frames in assessment of the target displacement considering near-fault …

A Esfahanian, AA Aghakouchak
Journal Paper , , {Pages }


A new hybrid energy dissipation system with viscoelastic and flexural yielding strips dampers for multi-level vibration control

Omid Ranaei, Ali Akbar Aghakouchak
Journal PaperArchives of Civil and Mechanical Engineering , Volume 19 , Issue 2, 2019 March 1, {Pages 584-597 }


In this study, a new hybrid damper (HD) is introduced that consists of elastomeric layers, which act as a viscoelastic damper (VED), and metallic dampers (MDs). Metallic part is composed of flexural yielding strips. This HD not only removes the limitations of each of these two types of dampers, but also facilitates its application for multi-level vibration control. Based on operational mechanism and design objectives of the proposed HD, three specimens have been manufactured and tested under quasi-static cyclic loading to evaluate the functional objectives. Two types of elastomers and two types of metallic dampers are used in these specimens. Experimental results show stable hysteretic behavior and high energy dissipation capacity. Also, th

Development of design method for structures equipped with yielding metallic dampers based on performance objectives

Ali Akbar Aghakouchak, Mohammadhasan Ahmadi
Journal PaperModares Civil Engineering journal , Volume 18 , Issue 5, 2019 February 10, {Pages 17-Jan }


One of the effective ways to mitigate earthquake damage in structures is passive control of structures. Yielding metallic dampers economic passive control devices. Not only yielding metallic dampers are easy to erect, but they can also be used as a passive control systems easily. In this paper, the aim is to develop a design procedure for steel structures equipped with a combination of yielding metallic dampers so that, dampers will experience specific nonlinear behavior when subjected to various seismic hazard levels. For this purpose, the first step is providing seismic hazard spectra with different return periods for the intended site of construction. In this research, this step has been taken by using the Tehran probabilistic analysis h

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