scholarly journals Collapse Probability of Immediate and Special Moment Frames in Tehran under MCE

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Alireza Kianmehr
Keyword(s):  
Residential Buildings ◽  
Steel Structures ◽  
Moment Frames ◽  
Steel Moment Frames ◽  
Strong Earthquakes ◽  
Collapse Probability ◽  
Probabilistic Evaluation ◽  
Special Moment Frames ◽  
The Face ◽  
Human Losses

Residential buildings in most cities, which make up the most significant percentage of buildings, generally contain the most financial and human losses in the face of strong earthquakes. The purpose of this study is to investigate the possibility of the collapse of intermediate and unique steel moment frames against maximum ground excitations. In this study, through the first two steps of PEER methodology, using four steel structural frames with intermediate and unique moment frames, after designing according to the codes of national building regulations of Iran and standard 2800, this probabilistic evaluation was used to ensure their safety against collapse. In the next step, to deepen the results, 7 other sites from Tehran were selected. Their hazard spectrum was used to calculate the probability of collapse. In the end, it was observed that, with the reduction of the number of structural floors, the IDA curves at the lower IM level become horizontal in this project. The results showed that some of the 5-story steel structures under study in some parts of Tehran have a higher probability of collapse than acceptable.

Seismic characterization of steel special moment frames subjected to megathrust earthquakes

2020 ◽  
Vol 36 (4) ◽  
pp. 2033-2057
Author(s):  
Miguel Medalla ◽  
Diego Lopez-Garcia ◽  
Farzin Zareian
Keyword(s):  
Seismic Design ◽  
Ground Motions ◽  
Steel Structures ◽  
Moment Frames ◽  
Risk Levels ◽  
Megathrust Earthquakes ◽  
Crustal Earthquakes ◽  
Special Moment Frames ◽  
Seismic Characterization ◽  
Design Requirements

Current seismic design requirements were established considering mainly (almost exclusively) ground motions caused by shallow crustal earthquakes, hence they might lead to different-from-intended risk levels when applied at locations prone to large-magnitude subduction (i.e. megathrust) earthquakes. In this study, the seismic behavior of 40 modern steel special moment frames (SSMFs) subjected to both megathrust and crustal ground motions is evaluated. Three analyses are performed: (1) a hazard-consistent analysis; (2) a comparative collapse risk evaluation; and (3) a performance evaluation following the approach indicated in Federal Emergency Management Agency (FEMA) P695. Results indicate that the collapse probability of mid- and high-rise SSMFs subjected to megathrust ground motions is indeed larger than that under crustal ground motions. Modifications to the current design criteria are then suggested, intended not only for United States but also for countries, such as Ecuador, where the US seismic design requirements for steel structures were adopted and seismic ground motions are actually caused by megathrust earthquakes.

Design by Qualification Testing of Reduced Beam Section Welded Connections

2015 ◽  
Vol 1111 ◽  
pp. 229-234
Author(s):  
Florea Dinu ◽  
Dan Dubină ◽  
Cristian Vulcu ◽  
Calin Neagu
Keyword(s):  
Numerical Models ◽  
Shear Stresses ◽  
Moment Frames ◽  
Steel Moment Frames ◽  
Reduced Beam Section ◽  
The Face ◽  
Qualification Testing ◽  
Low Stiffness ◽  
Beam Section ◽  
Seismic Applications

Steel moment frames are common systems in multi-storey buildings. Even the relatively low stiffness of the system limits the applicability, they remain popular in seismic applications due to the good dissipation capacity. Considered deemed-to-comply in seismic applications, welded beam to column connections experienced serious damages and even failures during strong seismic earthquakes. These failures included fractures of the beam flange-to-column flange groove welds, cracks in beam flanges, and cracks through the column section. To reduce the risk of brittle failure of welded connections, beam weakening near the ends became popular. To assure the desired behavior, i.e. the development of plastic deformations in the reduced beam section zones rather than at the face of the column, proper detailing and sizing is necessary. Today design provisions are limited to long beams, where the effect of shear stresses may be neglected. The application of the same rules for short beams might be non-conservative, and therefore qualification testing is necessary. The study presents the qualification testing of reduced beam sections welded connections of short beams. Both monotonic and cyclic tests were performed and numerical models were validated based on the test data.

scholarly journals Improvement of Seismic Performance of Beam-column Connection With Replaceable Drilled Attachment Parts

2020 ◽  
Author(s):  
Mehdi Vajdian ◽  
Ali Parvari ◽  
Mohammad Afzali
Keyword(s):  
Plastic Hinge ◽  
Steel Structures ◽  
Moment Frames ◽  
Steel Moment Frames ◽  
Flange Connection ◽  
Reduced Beam Section ◽  
Steel Connections ◽  
Advantages And Disadvantages ◽  
Variable Diameter ◽  
And Performance

Since beam-column connection plays a prominent role in steel structures, by designing and constructing it properly, the structure will behave better and safer. Numerous researches are carried out on steel connections, like Reduced Beam Section (RBS) and Drilled Flange Connection (DFC). Each connection has advantages and disadvantages. This study evaluates the effect of different connections on behavior of steel moment frames. The connections evaluated in this study are as follows: Connection with drilled attachment part, drilled connection with identical and variable diameter, beam connection with reduced flange. This connection contains one or two replaceable drilled parts that are mounted in connection place. The connection is modeled using the ABAQUS software. Finally, Finite Elements Modeling (FEM) is utilized to calculate the stiffness of each connection. According to the results of the newly introduced connection in terms of energy absorption and ductility is the best example and among the drilled models investigated in this study, drilled connection with variable diameter (proportional to diamond shape) which performed better in terms of behavior and performance than the other perforated models. Also, reduced flange connection ranks third in performance. In proposed connection the plastic hinge is formed at the attachment part of the connection that is replaceable, also there is little damage to the beams and columns, which is one of the main benefits of this connection.

scholarly journals Seismic Performance of Steel Moment Frames Containing Concentric Bracing Equipped with Shape Memory Alloys

2019 ◽  
Vol 13 (1) ◽  
pp. 189-200
Author(s):  
Hamed Jabbari ◽  
Reza Vahdani ◽  
Mohsen Gerami ◽  
Hossein Naderpour
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Steel Structures ◽  
Relative Displacement ◽  
Design Element ◽  
Moment Frames ◽  
Steel Moment Frames ◽  
Moment Frame ◽  
Maximum Displacement ◽  
Finite Element Software

Background: A building’s stability is a critical design element that structural engineers must understand. And, utilization of Shape Memory Alloys (SMAs) in steel structures can importantly diminish seismic residual deformations, which will facilitate postseismic retrofitting. Objective: The aim of the present study was to evaluate the seismic behavior of 7-story and 15-story steel frames with moment frame system having chevron concentric brace equipped with Shape Memory Alloys (SMAs). Braces containing various amount of alloy (including 20%, 40%, 60%, 80% and 100%) applied to study SMAs effect on structural performance. Relatively persistent displacement of the structure as well as its relative maximum displacement under the earthquake imposing on frame models were investigated using non-linear dynamic analysis by OpenSees finite element software. The earthquakes were in near- fault nine accelerographs, which involved various maximum accelerations. Results: Results indicated a reduction in relatively persistent displacement using 20% SMAs in braces. Addition more amount of alloy resulted in less relative displacement as compared to steel one braces. Conclusion: Applying SMAs brace showed a reduction in persistent structural displacement in any types of frames. Furthermore, adding more than 20% SMAs to the brace, resulted in a decrease in structural displacement.

Multi-Hazard Risk Mitigation through Application of Seismic Design Rules

2018 ◽  
Vol 763 ◽  
pp. 1139-1146 ◽  
Author(s):  
Dan Dubină ◽  
Florea Dinu ◽  
Ioan Marginean
Keyword(s):  
Seismic Design ◽  
Risk Mitigation ◽  
Progressive Collapse ◽  
Steel Structures ◽  
Lateral Force ◽  
Moment Frames ◽  
Steel Moment Frames ◽  
Design Concepts ◽  
Collapse Resistance ◽  
Extreme Hazards

Multi-story buildings often use steel moment frames as lateral force resisting systems, because such systems would allow architectural flexibility, while providing the strength, stiffness, and ductility required to resist the gravity, wind, and seismic loads. Steel moment frames on which capacity design concepts are applied to resist earthquake induced forces, are generally considered robust structures, with adequate resistance against collapse for other extreme hazards, for example blast or impact. Starting from this point, the present paper summarizes the results of some recent studies carried out in the Department of Steel Structures and Structural Mechanics and CEMSIG Research Center from Politehnica University Timisoara, aiming to evaluate the influence of beam-to-column joints, designed to satisfy seismic design requirements, on the progressive collapse resistance of multi-story steel frame buildings.

Effects of Fling Step and Forward Directivity on Seismic Response of Buildings

2006 ◽  
Vol 22 (2) ◽  
pp. 367-390 ◽  
Author(s):  
Erol Kalkan ◽  
Sashi K. Kunnath
Keyword(s):  
Seismic Response ◽  
Ground Motions ◽  
High Amplitude ◽  
Moment Frames ◽  
Steel Moment Frames ◽  
Damage Potential ◽  
Near Fault ◽  
Forward Directivity ◽  
Fling Step ◽  
Far Fault

This paper investigates the consequences of well-known characteristics of near-fault ground motions on the seismic response of steel moment frames. Additionally, idealized pulses are utilized in a separate study to gain further insight into the effects of high-amplitude pulses on structural demands. Simple input pulses were also synthesized to simulate artificial fling-step effects in ground motions originally having forward directivity. Findings from the study reveal that median maximum demands and the dispersion in the peak values were higher for near-fault records than far-fault motions. The arrival of the velocity pulse in a near-fault record causes the structure to dissipate considerable input energy in relatively few plastic cycles, whereas cumulative effects from increased cyclic demands are more pronounced in far-fault records. For pulse-type input, the maximum demand is a function of the ratio of the pulse period to the fundamental period of the structure. Records with fling effects were found to excite systems primarily in their fundamental mode while waveforms with forward directivity in the absence of fling caused higher modes to be activated. It is concluded that the acceleration and velocity spectra, when examined collectively, can be utilized to reasonably assess the damage potential of near-fault records.

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