scholarly journals IMPACT OF INTRODUCING SEMI-RIGID MOMENT FRAMES ON SEISMIC RESPONSE OF BRACED FRAMES

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Mahmoud Faytarouni ◽  
Onur Seker ◽  
Bulent Akbas ◽  
Jay Shen
Keyword(s):  
Braced Frames ◽  
Seismic Evaluation ◽  
Moment Frames ◽  
Moment Frame ◽  
Braced Frame ◽  
Shear Connections ◽  
Seismic Force ◽  
Steel Building ◽  
Story Drift ◽  
Moment Resisting

Maximum seismic inelastic drift demand in a steel building with braced frames as primary seismic-force-resisting (SFR) system tends to concentrate in few stories without considering inherent participation of designed gravity-force-resisting (GFR) system in actual structural stiffness and strength. The influence of GFR system on stiffness and strength can be taken into account by considering the composite action in beam-to-column shear connections that exist in modern steel building construction to form actual semi-rigid moment-resisting frames. Therefore, modeling semi-rigid moment frames as an equivalent to the GFR system in braced frame buildings could be utilized as a representative to the strength provided by gravity frames. This paper presents a seismic evaluation of a six-story chevron braced frame, with and without semi-rigid moment frame. Four different cases are investigated under a set of ground motions and results are discussed in terms of story drift distribution along the height. The results pointed out that the current findings lay a foundation to conduct further investigation on the seismic performance of braced frames as designed SFR system together with GFR system.

scholarly journals Inelastic dynamic analysis of steel structures

1975 ◽  
Vol 8 (4) ◽  
pp. 273-277
Author(s):  
J. Lord ◽  
J. B. Hoerner ◽  
M. Zayed
Keyword(s):  
Bending Moment ◽  
Steel Structures ◽  
Braced Frames ◽  
Moment Frames ◽  
Moment Frame ◽  
Braced Frame ◽  
Panel Zone ◽  
Aspect Ratios ◽  
Linear Behaviour ◽  
Zone Deformation

This paper updates a previously described analytical approach (1,2) using computer technology to investigate the time-dependent material non-linear behaviour of two dimensional moment-frame, truss-frame, and braced-frame steel structures during significant excursions into the post-elastic range. The approach includes considerations for energy analysis; element buckling; stable or unstable mechanism formation; yield capacity reduction resulting from interaction of axial load and bending moment; stiffness degradation; P-δ effects; viscous damping; joint panel zone deformation; and also incorporates a suitable element load-deformation relationship. The computer program NLDYN2 which incorporates this approach has been implemented successfully on many steel structures ranging from 60-story moment frames to braced frames having aspect ratios of up to 10.

scholarly journals Improving resilience of moment frames using steel pipe dampers

2018 ◽  
Vol 195 ◽  
pp. 02014
Author(s):  
Junaedi Utomo ◽  
Antonius
Keyword(s):  
Numerical Study ◽  
Steel Pipe ◽  
Frame Structures ◽  
Earthquake Risk ◽  
Moment Frames ◽  
Moment Frame ◽  
Story Drift ◽  
Moment Resisting ◽  
Lateral Displacements ◽  
The Moment

Earthquake resiliency of moment resisting frames, either new or existing ones, are important for maintaining community functionality. Improving earthquake resiliency needs a strong initiative in reducing earthquake risk. Steel pipe dampers can be used to increase earthquake resiliency. Steel pipe dampers, when installed at strategic locations in the moment frame structures, dissipate most of the earthquake energy in structures through inelastic deformation so that other components of the structure are protected. Steel pipe dampers control vibration in moment frame structures and are a disposable component in structures so that the damaged dampers can be replaced easily. Steel pipe dampers are cheap and require low workmanship, therefore the recovery time after disasters is short and the cost of recovery is low. Utilizing steel pipe dampers in passive energy dissipation systems help maintain community functionality during and after disasters. Lateral displacements were quantified and used as performance indicators. Significant drift and inter story drift reduction were achieved during a numerical study. All structural components, except the steel pipe dampers, remain elastic, indicating the effectiveness of the dampers in reducing the losses due to earthquakes.

Code-Oriented Methodology for the Seismic Design of Regular Steel Moment-Resisting Braced Frames

2014 ◽  
Vol 30 (4) ◽  
pp. 1683-1709 ◽  
Author(s):  
Edgar Tapia-Hernández ◽  
Arturo Tena-Colunga
Keyword(s):  
Seismic Design ◽  
Time History ◽  
Federal District ◽  
Design Parameters ◽  
Braced Frames ◽  
Steel Buildings ◽  
Moment Frames ◽  
Concentrically Braced Frames ◽  
Design Spectrum ◽  
Moment Resisting

In order to help improve the seismic design of regular steel buildings structured with ductile moment-resisting concentrically braced frames (MRCBFs) using the general design methodology of Mexico's Federal District Code (MFDC-04), suitable design parameters were first assessed using the results of pushover analyses of 13 regular MRCBFs. In order to insure collapse mechanisms consistent with the assumptions implicit in a code-based design (strong-column/weak-beam/weaker-brace), it is proposed to relate the minimum strength ratio for the resisting columns of the moment frames and the bracing system. Improved equations are proposed for a more realistic assessment of ductility and overstrength factors. In a second stage, the effectiveness of the improved methodology was assessed with the design of six regular steel buildings with MRCBFs. Buildings were evaluated by performing both pushover and nonlinear time-history analyses under ten selected artificial ground motions related to the corresponding design spectrum.

scholarly journals Experimental Study on the Seismic Performance of Steel H-Shaped Beam-to-Column Connections

2020 ◽  
Vol 20 (5) ◽  
pp. 1-9
Author(s):  
Seongyeon Seo
Keyword(s):  
Seismic Performance ◽  
Steel Structures ◽  
Initial Stiffness ◽  
Moment Frame ◽  
Shaped Beam ◽  
Shear Connections ◽  
Story Drift ◽  
Frame System ◽  
The Moment ◽  
Plastic Rotation Capacity

In terms of the moment frame system of steel structures, early brittle fractures developed in the H-shaped beam-to-column connection during the Northridge and Kobe earthquakes, thereby indicating insufficient seismic performance of these components. In this study, experiments were conducted on two-side shear connections of web and rib plate reinforcements of the flanges on an H-shaped beam-to-column connection. According to the test results, the H-shaped beam-to-column connections with two-side shear connections of beam web and rib plate reinforcements of the flanges were superior to the existing connections in terms of initial stiffness, energy dissipation capacity, and plastic rotational capacity. The test values exceeded 4.2%, 0.027 rad, and 125% in terms of story drift ratio, total plastic rotation capacity, and full plastic moment of the beam, respectively. Accordingly, the proposed H-shaped beam-to-column connection showed better performance than that of the intermediate moment frame regarding seismic design.

Shake Table Testing of a Low Damage Steel Building with Asymmetric Friction Connections (AFC)

2018 ◽  
Vol 763 ◽  
pp. 400-405
Author(s):  
Ali A. Rad ◽  
Gregory A. MacRae ◽  
Nikoo K. Hazaveh ◽  
Quincy T. Ma
Keyword(s):  
Shaking Table ◽  
Shake Table ◽  
Moment Frame ◽  
Shake Table Testing ◽  
Steel Moment Frame ◽  
Residual Drift ◽  
Steel Building ◽  
Story Drift ◽  
Column Bases

The paper describes the shaking table performance of a half-scale two-story steel moment frame with asymmetric friction connections (AFCs) at the column bases and at the beam ends. The results showed that the beam ends and the base-column joints exhibited bilinear and trilinear response respectively. Residual drifts were less than 0.2% for shake table trials up to 3% peak inter-story drift. Even at a peak inter-story drift of 6.5%, the residual drift response was still only 0.7%.

scholarly journals The effect of number and position of braced frames on column behavior of the dual steel structural system (MRF and EBF) (With a view on amplified seismic load)

2015 ◽  
Vol 37 ◽  
pp. 277
Author(s):  
Sajjad Mohammadi ◽  
Abd-ol-Reza Sarvghad Moghaddam ◽  
Alireza Faroughi
Keyword(s):  
Seismic Design ◽  
Structural Model ◽  
Seismic Load ◽  
Structural System ◽  
Braced Frames ◽  
Moment Frame ◽  
Moment Capacity ◽  
Moment Resisting Frame ◽  
Moment Resisting

In seismic design of structures, determination of number and position of braced frames, considering the architectural scheme of projects, is usually confronted by obstacles. Due to this fact, in some cases, selecting the best location and number of braced bays has led to mistakes in determination of their adjacent members (columns) design loads. One of the seismic design requirements of lateral resisting system is to control the columns adjacent to braced bays for load combinations of amplified seismic load, which is a function of over-strength factor of the structure. This research aims to present and introduce the best structural model of number and position of braced frames in a structural system, such as steel moment resisting frame and eccentric braces dual system; because in 3rd revision of Iranian 2800 standard of seismic provision, there are statements and criteria provided only for capacity of moment frame, not for braces. Though the amplified seismic load function is controlled in models which columns are connected to braces in 2 directions, and seismic loads are applied in those 2 directions, number of damage hinges (Exceeding CP) is significantly increased in comparison to the models with straggly braces. As the increase in axial force of these columns leads to decrease in their moment capacity (despite controlling the amplified seismic load provision), columns in dual systems that resist flexure, would be damaged and exceed the collapse threshold much sooner than other columns. This important fact is not presented in Iranian or even American codes and provisions.

Braced Frame Symmetrical and Asymmetrical Friction Connection Performance

2018 ◽  
Vol 763 ◽  
pp. 216-223 ◽  
Author(s):  
Robin Xie ◽  
Jose Chanchi Golondrino ◽  
Gregory A. MacRae ◽  
George Charles Clifton
Keyword(s):  
Energy Dissipation ◽  
Coefficient Of Friction ◽  
Large Displacements ◽  
Effective Coefficient ◽  
Sliding Surface ◽  
Moment Frame ◽  
Braced Frame ◽  
Static Testing ◽  
Moment Resisting ◽  
The Moment

This paper describes quasi-static testing of Asymmetrical Friction Connection (AFC) and Symmetrical Friction Connections (SFC) in steel braces. It is shown that stable energy dissipation mechanisms have been achieved in braces using Bisalloy 500 shims on the sliding surface. When incorporated into a moment frame, the braces and the moment resisting frames underwent large displacements without significant frame yielding. The effective coefficient of friction is shown to be dependent on prying.

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 Damage Concentration Effect of Multistory Buckling-Restrained Braced Frames

2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Hanqin Wang ◽  
Yulong Feng ◽  
Jing Wu ◽  
Qing Jiang ◽  
Xun Chong
Keyword(s):  
Statistical Correlation ◽  
Concentration Effect ◽  
Braced Frames ◽  
Braced Frame ◽  
Factors Affecting ◽  
Residual Drift ◽  
Moment Resisting ◽  
Distribution Parameters ◽  
Buckling Restrained Braced Frames ◽  
Parametric Analyses

Due to the low postyield stiffness of buckling-restrained braces (BRBs), multistory buckling-restrained braced frames (BRBFs) subjected to earthquakes are prone to lateral deformations and damage concentrations at certain stories, which is deemed a damage concentration effect (DCE). A series of nonlinear pushover analyses and response history analyses are conducted to investigate the key factors affecting the DCE of BRBFs. Two comparisons of the DCE are performed for different types of structures and different beam-to-column connections in the main frame (MF). These comparisons show that BRBFs equipped with BRBs as the main earthquake resistance system have a more serious DCE than the traditional moment-resisting frame or conventional braced frame and that the MF stiffness significantly affects the structural residual displacement and DCE. Then, parametric analyses are performed to investigate the influence of two stiffness distribution parameters (in the horizontal and vertical directions) on the DCE of a 6-story BRBF dual system designed according to the Chinese seismic code. The results show that increasing the MF stiffness and avoiding abrupt changes in the BRB stiffness between stories can effectively mitigate the DCE of BRBFs. Finally, the correlations between various damage performance indices are analyzed. A low statistical correlation between the peak and residual drift responses can be observed in BRBFs. Therefore, it is recommended that the DCE be considered in BRBF design.

New Directions in Structural Seismic Designs

1993 ◽  
Vol 9 (4) ◽  
pp. 845-875 ◽  
Author(s):  
Egor P. Popov ◽  
Tzong-Shuoh Yang ◽  
Carl E. Grigorian
Keyword(s):  
Point Of View ◽  
Braced Frames ◽  
Eccentrically Braced Frames ◽  
Displacement Ductility ◽  
Steel Moment Resisting Frames ◽  
Structural Resistance ◽  
Seismic Force ◽  
New Directions ◽  
Moment Resisting ◽  
Ductile Behavior

The code stipulated seismic force requirements for buildings from the historical point of view are described first. This is followed by examples of the emerging criteria of inelastic seismic spectra for displacement ductility, and number of yield reversals as a function of building period and strength. Novel spatial representations of seismic input energy and hysteresis energy, interpreted as damage energy, are given next. The available structural resistance countering the imposed seismic demand is illustrated by the ductile behavior of steel moment resisting frames (MRFs) and eccentrically braced frames (EBFs). A discussion of a practical and versatile frictional energy dissipating connection is given at the end.

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