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Investigation of Resilience of Eccentrically Braced Frames Equipped with Shape Memory Alloys

Pirmoghan Hamid, Khoshravi Hossein, Sadeghi Abbasali, Pouraminian Majid, Noroozinejad Farsangi Ehsan

Civil and Environmental Engineering Reports

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2022

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Vol. 32, no. 1

176--190

EN

Nowadays, the use of smart materials in structures is a major concern to structural engineers. The act of benefiting from numerous advantages of these materials is the main objective of researches and studies focused on seismic and structural engineering. In the present study, in addition to the development of finite element models of several steel frames using ABAQUS software, the effect of shape memory alloys (SMAs) on superelastic behavior and the various types of eccentric braces will be checked. Moreover, it was observed that the use of SMAs within various types of bracing systems of steel frames leads to a decrease in the reduction factor of the frames. Also, the eccentric bracing in which SMAs are utilized in the middle of bracing led to the highest effect on reduction of lateral drift of the frames and decrease of reduction factor. The obtained results indicated that the application of smart materials led to increasing of strain energy and base shear of the first plastic hinge, which is followed by a decrease in the reduction factor of the frame.

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Effect of Link Beam Length of the Eccentric Bracing System on Seismic Rehabilitation of Weak Reinforced Concrete Frames

Niknam Touraj, Saberi Hamid, Saberi Vahid, Sadeghi Abbasali, Noroozinejad Farsangi Ehsan

Civil and Environmental Engineering Reports

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2022

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Vol. 32, no. 1

152--175

EN

In this study, a reinforced concrete (RC) reference specimen with compressive strength of 250 kg/cm2 and the weak RC specimen for seismic rehabilitation with compressive strength of 150 kg/cm2 were examined in two types of structures with 6 and 12-stories. The link beam lengths of 50, 80, and 100 cm have been used in 6 and 12-stories prototypes under the effect of 7 earthquake records. The nonlinear dynamic analyses are performed. Then, The behavior of the link beam depends on its length. For short link beam lengths, shear behavior is serious, then for medium lengths, shear-flexural behavior is important, and finally, long lengths will have flexural behavior for the beam. In eccentrically braced frames, the details of the link beam and the fit of the other members must be done in such a way as to ensure its proper ductility. According to the obtained results, the performance of short link beams is much better than long link beams, and short link beams provide more energy dissipation and, at the same time, more ductility. Therefore, in the design of the link beam, mainly the shear of the link beam is considered as a ductile component. The axial force in the link beam, which is due to the application of lateral load to the structure, reduces both the bending capacity and the inelastic deformation capacity of the link beam, so it can be explained that in steel eccentric braces, the link beam is symmetrical between the two main components of the brace and it can affect the strength of the structure against lateral loads.

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Investigation of the Occurrence of Progressive Collapse in High-Rise Steel Buildings with Different Braced Configurations

Saberi Hamid, Saberi Vahid, Sadeghi Abbasali, Pooyasefat Abbas, Noroozinejad Farsangi Ehsan

Civil and Environmental Engineering Reports

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2021

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Vol. 31, no. 4

33--54

EN

The progressive collapse phenomenon refers to a chain of damages in a structure where all or a large part of the structure is destroyed by an initial local collapse in it, which can lead to very disastrous results. Therefore, the prevention of progressive collapse has become a necessary action in the design and analysis of buildings and it is vital to investigate this topic more accurately. This study aims to present a proposed pattern in the configuration of braces at the height of a high-rise steel building for reducing the probability of progressive collapse. In this regard, the vertical displacement of 18-story structure with four scenarios of column removal and five concentric bracing patterns including V, Inverted V, X, discontinuous X-bracing at height, and a combination of Xbracing in the side spans and discontinuous X-bracing at height in the middle spans are investigated and compared. In this study, the Alternative Path Method (APM) is used based on the GSA guideline for the analysis of progressive collapse. The results of this research showed that the use of X-bracing in the side spans and discontinuous X-bracing in the middle spans in nonlinear static and dynamic analyses performed better in reducing the probability of progressive collapse than other bracing configurations. Finally, it is recommended to use discontinuous X-bracing at the height that would place the bracings in one direction and providing alternative paths for force transferring in the structure.

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Finite Element Modeling of Self-Compacting Concrete Beams Under Shear

Hosseinimehrab lham, Sadeghi Abbasali, Noroozinejad Farsangi Ehsan

Civil and Environmental Engineering Reports

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2021

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Vol. 31, no. 4

1--16

EN

Development of self-compacting concrete (SCC) is a very desirable achievement in the reinforced concrete (RC) structures for overcoming issues associated with many problems such as congestions of steel reinforcement. This non-vibrating concrete is not affected by the skill of workers, and the shape and amount of reinforcing bar arrangement of a structure. Due to the high fluidity and resisting power of reinforcing of SCC, it can be pumped longer distances. In this study, the finite element (FE) modeling of three SCC beams in shear while taking into account, the flexural tensile strength of concrete is computed and the results are compared with the available experimental tested reinforced SCC beams. The stirrups are located at 75 mm apart from the end of beams up to the loading point. The electrical strain gauges (ESGs) have been embedded on the stirrups and their strain readings are taken for every step of load increment. For modeling longitudinal steel reinforcing bars and concrete, the 3-D elements with 2-node and 8-node, are used respectively. The comparison of results obtained by two methods is indicated that a good satisfactory agreement is achieved.