scholarly journals Effect of Standard No. 2800 Rules for Moment Resisting Frames on the Elastic and Inelastic Behavior of Dual Steel Systems

2017 ◽  
Vol 7 (6) ◽  
pp. 2139-2146 ◽  
Author(s):  
H. Veladi ◽  
H. Najafi
Keyword(s):  
Steel Structures ◽  
Lateral Load ◽  
Nonlinear Static Analysis ◽  
Inelastic Behavior ◽  
Braced Frame ◽  
Moment Resisting Frames ◽  
Seismic Design Code ◽  
Moment Resisting ◽  
Bracing System ◽  
Steel Braced Frame

According to most valid Design Codes including the Iranian Seismic Design Code (Standard No. 2800), moment resisting frames in dual systems must have the ability of resisting the 25% of the total lateral load of the dual system independently. This study is conducted to investigate the implementation of this rule for dual steel structures with two types of steel braced frame. Also, its effect on the strength of the structure and the distribution of lateral load between the frames and the bracing system is evaluated. In order to investigate the effect of that rule, structural models with 5, 10 and 15 floors are modeled. Nonlinear static analysis is employed and results are discussed. Following the Standard No. 2008 seems to increase the structure’s lateral resistance and decrease the number of elements entered into the inelastic behavior stage. In general, the structure has a more desirable inelastic behavior.

scholarly journals Strengthening of the Panel Zone in Steel Moment Resisting Frames

2019 ◽  
Author(s):  
Masoud Abedini ◽  
Sudharshan N. Raman ◽  
Azrul A. Mutalib ◽  
Ebrahim Akhlaghi
Keyword(s):  
Structural Engineering ◽  
Steel Structures ◽  
Inelastic Behavior ◽  
Linear Deformation ◽  
Rigid Zone ◽  
Steel Moment Resisting Frames ◽  
Moment Resisting Frames ◽  
Panel Zone ◽  
Standard Design ◽  
Moment Resisting

Rehabilitation and retrofitting of structures designed in accordance to standard design codes is an essential practice in structural engineering and design. For steel structures, one of the challenges is to strengthen the panel zone as well as its analysis in moment-resisting frames. In this research, investigations were undertaken to analyze the influence of the panel zone in the response of structural frames through a computational approach using ETABS software. Moment-resisting frames of six stories were studied in supposition of real panel zone, different values of rigid zone factor, different thickness of double plates, and both double plates and rigid zone factor together. The frames were analyzed, designed and validated in accordance to Iranian steel building code. The results of drift values for six stories building models were plotted. After verifying and comparing the results, the findings showed that the rigidity lead to reduction in drifts of frames and also as a result, lower rigidity will be used for high rise building and higher rigidity will be used for low rise building. In frames with story drifts more than the permitted rate, where the frames are considered as the weaker panel zone area, the story drifts can be limited by strengthening the panel zone with double plates. It should be noted that higher thickness of double plates and higher rigidity of panel zone will result in enhancement of the non-linear deformation rates in beam elements. The resulting deformations of the panel zone due to this modification can have significant influence on the elastic and inelastic behavior of the frames.

scholarly journals A Comparative Study on the Behavior of Steel Moment-Resisting Frames with Different Bracing Systems Based on a Response-Based Damage Index

2018 ◽  
Vol 4 (6) ◽  
pp. 1354 ◽  
Author(s):  
Kamran Karsaz ◽  
Seyed Vahid Razavi Tosee
Keyword(s):  
Damage Index ◽  
Steel Structures ◽  
Braced Frames ◽  
Initial Stiffness ◽  
Concentrically Braced Frames ◽  
Braced Frame ◽  
Under Five ◽  
Seismic Rehabilitation ◽  
Moment Resisting Frames ◽  
Moment Resisting

Seismic rehabilitation of existing buildings is one of the most effective ways to reduce damages under destructive earthquakes. The use of bracings is one of techniques for seismic rehabilitation of steel structures. In this study we aimed to investigate the seismic performance of three 5, 10 and 15-storey steel structures with moment-resisting frames designed three dimensionally in ETABS 2015 application based on first edition of Iranian Standard 2800. Their damage under five ground motions was evaluated using response-based damage model proposed by Ghobara et al. (1999). Then, the structures were rehabilitated with different bracing systems (X, eccentric and concentric V and inverted-V) and, again, their damage under five earthquakes were evaluated and compared with those of moment resisting frames. The pushover analysis results indicated that X-braced frame was the least ductile system but had highest initial stiffness and yield stress. In low-rise building, X-braced frames showed better performance among studied bracing systems compared to moment resisting frames, while mid and high-rise buildings with eccentrically braced  frame (EBF) showed the best behavior against earthquakes with the least damage. Moreover, it was found out that EBFs’ performance increases by increasing storey height, but for concentrically braced frames (CBFs) it was decreased. We concluded that the use of response-based damage models can be a suitable procedure for estimating the vulnerability of steel structures rehabilitated with bracing system.

scholarly journals Seismic reliability analysis of steel moment-resisting frames retrofitted by vertical link elements using combined series–parallel system approach

2020 ◽  
Author(s):  
Vahid Mohsenian ◽  
Iman Hajirasouliha ◽  
Reza Filizadeh
Keyword(s):  
System Approach ◽  
Lateral Load ◽  
Parallel System ◽  
Performance Level ◽  
Analytical Models ◽  
Seismic Reliability ◽  
Steel Moment Resisting Frames ◽  
Moment Resisting Frames ◽  
Moment Resisting ◽  
Bracing System

AbstractThe eccentric bracing system equipped with vertical links is capable of providing high levels of stiffness, strength and ductility, and therefore, can be efficiently used for seismic retrofit of existing structures. This study aims to investigate the seismic reliability of steel moment-resisting frames retrofitted by this system using a novel combined series–parallel system approach. The seismic response of 4, 8 and 12-storey steel moment-resisting frames (MRFs) are evaluated under a set of design basis earthquakes (DBE) before and after retrofitting intervention. Adopting an engineering demand parameter approach (EDP-Based) for reliability assessment and development of analytical models for the frames using systems consisting of the series–parallel elements are the major distinctions between the present study and the other similar works. To estimate the global reliability of the frames, first, the reliability of each storey is individually derived based on various probable damage levels for the lateral-load resisting members. Then, the seismic reliability of the frame is globally obtained by combining the reliability of each storey for different damage levels in the lateral load-resisting subsystems. The results indicate significant impact of this type of bracing system on improvement of the performance level and load-carrying capacity of the frames along with reduction of the lateral displacements. It is shown that application of the vertical links can reduce the maximum inter-storey drifts by at least 60%, while it leads to at most 17% increase in the base shear. All retrofitted frames exhibited a performance level higher than the Life Safety (LS) when subjected to the DBE hazard level records (earthquakes with return period of 475 years). At the same level of earthquake intensity, in the cases when the drift corresponding to the LS performance level is used as the target, the reliability of the retrofitted frames was improved by more than 90% compared to the original frames for all damage states developed in the vertical links.

Earthquake Performance Analysis of Steel Structures with A3 Plan Irregularities

2021 ◽  
Vol 10 (12) ◽  
pp. 174-179
Author(s):  
Özlem Çavdar
Keyword(s):  
Earthquake Engineering ◽  
Design Method ◽  
Steel Structures ◽  
Nonlinear Static Analysis ◽  
Seismic Performance Evaluation ◽  
Moment Resisting Frame ◽  
Earthquake Effect ◽  
Steel Building ◽  
Moment Resisting ◽  
Earthquake Performance

In earthquake engineering, a performance-based design method is used to determine the level of the expected performance of the structures under the earthquake effect. The level of performance is related to the damage situation that could be occurred in the structure after the earthquake. In the performance-based structural design, it is predicted that more than one damage levels emerge under one certain earthquake effect. In this study, the seismic behavior of steel structures with plan irregularities in the Turkey Building Earthquake Code in the 2018 (TBEC-2018) is investigated by the nonlinear static analysis methods. The selected steel structures are located in İzmir, Turkey. The Turkey Earthquake Code in 2018 is considered for assessing seismic performance evaluation of the selected moment-resisting frame steel building. Four different A3 type irregularity was investigated. The steel building with no irregularity in its plan. was selected as the structure of the reference. The performance goals of the five different steel structures are evaluated by applying the pushover and procedures of the TBEC-2018. The steel structures were compared by obtaining pushover curves for both the X and Y directions. The results show that the effects of A3 type irregularity should be not considered in design and buildings without irregularities are safer.

scholarly journals Effect of the Bracing System on the Probability of Collapse of Steel Structures under Maximum Credible Earthquake

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Alireza Kianmehr
Keyword(s):  
Residential Buildings ◽  
Hazard Analysis ◽  
Fragility Curves ◽  
Steel Structures ◽  
Structural Members ◽  
Braced Frame ◽  
Ductile Behavior ◽  
Bracing System ◽  
Eccentric Bracing ◽  
Different Characteristics

Simple bracing frames can be divided into two types in terms of concentric or eccentric. Concentric bracing frames are frames that intersect with other structural members at one point in the structure along the bracing members. Otherwise, the braced frame will be eccentric. It is said empirically that due to this type of shaping, eccentric bracing frames exhibit more ductile behavior and concentric bracing frames exhibit more stiff behavior. This behavioral difference caused this study to be numerically computing for five frames, including unique concentric and eccentric bracing frames of 5 and 10 stories and an ordinary 5-story concentric bracing frame. Their tensions and drift ratios should be acceptable for the use of residential buildings. Using the primary two steps of the new PEER probabilistic framework, namely, probabilistic seismic hazard analysis and structural analysis, which leads to the drawing of fragility curves, the probability of collapse is obtained to compare the safety capability of these frames according to their different characteristics against earthquakes. The results show that increasing the ductility or increasing the number of floors or the height of these systems can reduce collapse. Also, according to the results of the probability of collapse obtained in frames with 5-story concentric bracing frames, it can be said that some of the current regulations, which work based on previous approaches of analysis, can lead to unsafe structures with a high probability of collapse.

scholarly journals Evaluation Of Response Modification Factor For Moment Resisting Frames

10.29007/q8wl ◽  
2018 ◽  
Author(s):  
Nirav K. Patel ◽  
Prutha Vyas
Keyword(s):  
Nonlinear Response ◽  
Seismic Analysis ◽  
Nonlinear Static Analysis ◽  
Elastic Response ◽  
Systematic Evaluation ◽  
Elastic Behaviour ◽  
Response Modification Factor ◽  
Moment Resisting Frames ◽  
Moment Resisting ◽  
Modification Factor

Conventional seismic analysis of structure incorporates only elastic response of the structure. To understand nonlinear response of the structure, Performance Based Design (PBD) approach is widely used. PBD includes Pushover analysis i.e. nonlinear static analysis, which shows the post-elastic behaviour of the structure. IS 1893-2002 incorporates the nonlinear response of a structure considering response reduction factor (R) so that a linear elastic force based approach can be used for design. The response modification factor plays a key role in the seismic design of new buildings. However, the Indian code does not provide information on the components of R factor. The values assigned to this factor is based on engineering judgment. The study includes the calculation of value R based on different components as per ATC-19 and compares values of R for Special Moment resisting frame (SMRF) and Ordinary Moment resisting frames (OMRF) for two different seismic zones. An improvement in the reliability of modern earthquake-resistant buildings will require the systematic evaluation of the building response characteristics, which mostly affects the values assigned to the factor.

Behaviour of dual eccentrically braced steel frames with short and long seismic links

2019 ◽  
Author(s):  
Ivan Lukačević ◽  
Tomislav Maleta ◽  
Darko Dujmovic
Keyword(s):  
Energy Dissipation ◽  
Plastic Hinge ◽  
Seismic Energy ◽  
High Strength ◽  
Elastic Behaviour ◽  
Braced Frame ◽  
Moment Resisting Frames ◽  
Collapse Mechanisms ◽  
Moment Resisting ◽  
Flexible Part

<p>Dual structures obtained by combining moment resisting frames with innovative bracing systems such as replaceable shear panels or seismic links have significant advantages among conventional solutions. The major advantages of such systems are energy dissipation in the specific locations and re-centring capability which significantly reduces repair costs. On the other hand, design of such systems is driven with specific requirements such as combining different steel grades to ensure elastic behaviour of the flexible part of the system. This paper deals with comparative behaviour analyses of two dual systems combining moment resisting multi-storey frames with eccentric bracing systems. The steel frame consists of three bays with central braced frame and two adjacent moment resisting frames. The bracing system contains either long or short seismic link. Seismic energy dissipation of these systems is completely different. Long seismic links are characterised with a classical plastic hinge in which energy is dissipated through bending while in case of short seismic links seismic energy is dissipated through shear. Multi-linear plastic diagrams for both links have been defined and pushover analyses are performed. The behaviour of the analysed systems based on collapse mechanisms, overstrength ratio, target displacement and possible solutions for re-centring capabilities are discussed. Analysed system with short seismic links despite more complicated modelling and requirements for high strength steel in MRFs, results in higher overstrength ratio regarding the system with long seismic links. It is also far easier to dismantle system with short seismic links, due to the bolted connection of links with the adjacent members.</p>

scholarly journals AN INVESTIGATION OF THE EFFECTIVENESS OF THE FRAMING SYSTEMS IN STEEL STRUCTURES SUBJECTED TO BLAST LOADING

2014 ◽  
Vol 20 (6) ◽  
pp. 767-777 ◽  
Author(s):  
Amy Coffield ◽  
Hojjat Adeli
Keyword(s):  
Failure Modes ◽  
Plastic Hinge ◽  
Blast Loading ◽  
Steel Structures ◽  
Response Analysis ◽  
Plastic Hinges ◽  
Braced Frame ◽  
Concentrically Braced Frame ◽  
Moment Resisting ◽  
Applied Element Method

The effectiveness of different framing systems for three seismically designed steel frame structures subjected to blast loading is investigated. The three faming systems considered are: a moment resisting frame (MRF), a concentrically braced frame (CBF) and an eccentrically braced frame (EBF). The blast loads are assumed to be unconfined, free air burst detonated 15 ft (4.572 m) from one of the center columns. The structures are modeled and analyzed using the Applied Element Method, which allows the structure to be evaluated during and through failure. Failure modes are investigated through a plastic hinge analysis and member failure comparison. Also, a global response analysis is observed through comparison of roof deflections and accelerations. A conclusion of this research is that braced frames provide a higher level of resistance to the blast loading scenario investigated in this research. Both the CBF and EBF had a smaller number of failed members and plastic hinges compared to the MRF. They also had smaller roof deflection and acceleration. The CBF yielded the fewest number of plastic hinges but the EBF had a slightly fewer number of failed members.

The Effects of Various Slippage Loads on the Response Modification Factor of Steel Structures Equipped with Frictional Dampers

2015 ◽  
Vol 15 (06) ◽  
pp. 1450080
Author(s):  
Hamid Rahmani Samani ◽  
Masoud Mirtaheri ◽  
Mojtaba Rafiee
Keyword(s):  
Structural Control ◽  
Steel Structures ◽  
Earthquake Excitation ◽  
Response Modification Factor ◽  
Steel Moment Resisting Frames ◽  
Optimum Energy ◽  
Seismic Design Code ◽  
Moment Resisting ◽  
Modification Factor ◽  
Code Procedure

A common and successful way of structural control is to dissipate the seismic kinetic energy via frictional dampers. Response of a friction damped frame during an earthquake excitation is heavily dependent to the slippage limit of the frictional dampers. Low values of slippage load may lead to excessive deformations while large slippage loads may prevent sliding. Therefore, selecting appropriate values for slippages loads of the dampers is very important in order to have optimum energy dissipating system. Utilizing a response modification factor, the standard seismic design code procedure can be applied to the frames equipped with frictional dampers to determine the value of slippage loads. In this investigation, the response modification factor of steel moment resisting frames equipped with frictional dampers is evaluated considering the effects of various slippage loads. The response modification factor is calculated for two bay widths of 5 m and 7 m in length. It is shown that the optimum slippage load that results in the maximum response modification factor is in the range of 8% to 20% of the total weight of the structure. The taller the structure is, the less the optimum slippage load will be. Finally, an equation is proposed for the response modification factor as a function of the slippage load.

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