Effect of Beam-Column Connection Fixity on Collapse Performance of a Six-Storey Special Concentrically Braced Frame

2018 ◽  
Vol 763 ◽  
pp. 157-164
Author(s):  
Vahid Mohsenzadeh ◽  
Lydell D.A. Wiebe
Keyword(s):  
Large Earthquake ◽  
Lateral Force ◽  
Concentrically Braced Frames ◽  
Gusset Plate ◽  
Braced Frame ◽  
Soft Storey ◽  
Concentrically Braced Frame ◽  
Seismic Force ◽  
Concentrically Braced ◽  
Strength And Stiffness

Concentrically braced frames are one of the most common seismic force resisting systems because of their high strength and stiffness. In current practice, the gusset plates that connect the brace to the adjacent beams and columns can increase the strength and stiffness of the connection significantly. This strength and stiffness can provide a reserve of lateral force resisting capacity during a large earthquake, which may play a role in the seismic collapse behaviour of the braced frame. An alternative connection has recently been proposed as a means of ensuring that brace buckling occurs only in-plane, that no field welding is required, and that all damage is confined to a replaceable brace module. However, the proposed connection does not include a gusset plate that can provide a similar stiffness and reserve capacity. In order to investigate the potential influence of the range of possible beam-column-gusset plate designs, this paper assesses the effect of the fixity of these connections on the behavior of a six-storey special concentrically braced frame. Nonlinear dynamic analyses have been conducted to determine the seismic performance of the frame with this connection modelled using three different assumptions (pinned, shear tab and fixed), and the collapse risk is assessed using the FEMA P695 methodology. The results show that when the gravity framing is not modelled, the fixity of the beam-column connections is important in avoiding the formation of a soft storey under extreme earthquakes, thereby reducing the probability of collapse of the building.

Seismic evaluation of single-storey steel buildings

1999 ◽  
Vol 26 (4) ◽  
pp. 379-394 ◽  
Author(s):  
M S Medhekar ◽  
DJL Kennedy
Keyword(s):  
Seismic Performance ◽  
Response Spectrum ◽  
Time History ◽  
Analytical Models ◽  
Steel Buildings ◽  
Concentrically Braced Frames ◽  
Braced Frame ◽  
Seismic Zones ◽  
Concentrically Braced Frame ◽  
Concentrically Braced

The seismic performance of single-storey steel buildings, with concentrically braced frames and a roof diaphragm that acts structurally, is evaluated. The buildings are designed in accordance with the National Building Code of Canada 1995 and CSA Standard S16.1-94 for five seismic zones in western Canada with seismicities ranging from low to high. Only frames designed with a force modification factor of 1.5 are considered. Analytical models of the building are developed, which consider the nonlinear seismic behaviour of the concentrically braced frame, the strength and stiffness contributions of the cladding, and the flexibility, strength, and distributed mass of the roof diaphragm. The seismic response of the models is assessed by means of a linear static analysis, a response spectrum analysis, a nonlinear static or "pushover" analysis, and nonlinear dynamic time history analyses. The results indicate that current design procedures provide a reasonable estimate of the drift and brace ductility demand, but do not ensure that yielding is restricted to the braces. Moreover, in moderate and high seismic zones, the roof diaphragm responds inelastically and brace connections are overloaded. Recommendations are made to improve the seismic performance of such buildings.Key words: analyses, concentrically braced frame, dynamic, earthquake, flexible diaphragm, low-rise, nonlinear, seismic design, steel.

scholarly journals The Effect of Local Fuse on Behavior of Concentrically Braced Frame by a Numerical Study

2018 ◽  
Vol 4 (3) ◽  
pp. 655 ◽  
Author(s):  
Ali Kachooee ◽  
Mohammad Ali Kafi ◽  
Mohsen Gerami
Keyword(s):  
Seismic Response ◽  
Numerical Study ◽  
Numerical Models ◽  
Compressive Loading ◽  
Braced Frames ◽  
Concentrically Braced Frames ◽  
Reduced Cross Section ◽  
Braced Frame ◽  
Concentrically Braced Frame ◽  
Concentrically Braced

The concentrically braced frames (CBFs) are one of the most widely used lateral load-resisting systems. Seismic performance of these structures has a weakness that is due to the brace buckling at a lower loading than the ultimate compressive loading capacity. In this paper, attempt is made to enhance the seismic response of CBFs through utilizing a local fuse. For this purpose, first the formulation of fuse area and length are presented. Then based on this formulation, several numerical models have been built and analyzed to examine the effect of implementing this fuse on seismic response of CBFs. From the analyses results, it is found that if the reduced cross-section fuse (RCF) is properly designed and also the end of brace is fixed, the CBFs with equal energy dissipation capacity, that are equipped with this fuse exhibit a better ductility than the customary CBFs.

Seismic response of two-storey buildings with concentrically braced steel frames

1999 ◽  
Vol 26 (4) ◽  
pp. 497-509 ◽  
Author(s):  
M S Medhekar ◽  
DJL Kennedy
Keyword(s):  
Seismic Response ◽  
Response Spectrum ◽  
Time History ◽  
Steel Buildings ◽  
Capacity Design ◽  
Concentrically Braced Frames ◽  
Braced Frame ◽  
Seismic Zones ◽  
Concentrically Braced Frame ◽  
Concentrically Braced

The seismic performance of two-storey steel buildings with concentrically braced frames as the lateral load resisting system is evaluated. The buildings are designed in accordance with the National Building Code of Canada (1995) and CSA Standard S16.1-94 for five seismic zones in western Canada. Only frames designed with a force modification factor of 1.5 are considered. Analytical models of the buildings are developed, which consider the nonlinear seismic behaviour of the concentrically braced frame, the shear strength of the roof diaphragm, and the stiffness and strength contributions of the nonstructural partitions. The seismic response is estimated with nonlinear static and dynamic time history analyses. Roof diaphragm flexibility does not influence the dynamic behaviour significantly. The distribution of lateral forces from response spectrum analysis agrees well with that specified. Current design procedures provide reasonable estimates of the lateral drift in low and moderate seismic zones. Brace ductility demands are reasonable and may be limited due to the contributions of nonstructural partitions. However, in moderate and high seismic zones, the connections, beams, columns, and roof diaphragm are overloaded. The capacity design procedure is recommended to provide adequate resistance to the overloaded components.Key words: analyses, capacity design, concentrically braced frame, diaphragm, dynamic, earthquake, low-rise, nonlinear, seismic design, steel.

Deep learning-based brace damage detection for concentrically braced frame structures under seismic loadings

2019 ◽  
Vol 22 (16) ◽  
pp. 3473-3486 ◽  
Author(s):  
Heng Liu ◽  
Yunfeng Zhang
Keyword(s):  
Deep Learning ◽  
Damage Detection ◽  
Learning Model ◽  
Frame Structures ◽  
Braced Frame ◽  
Concentrically Braced Frame ◽  
Seismic Force ◽  
Concentrically Braced ◽  
Deep Learning Model

Automated and robust damage detection tool is needed to enhance the resilience of civil infrastructures. In this article, a deep learning-based damage detection procedure using acceleration data is proposed as an automated post-hazard inspection tool for rapid structural condition assessment. The procedure is investigated with a focus on application in concentrically braced frame structure, a commonly used seismic force-resisting structural system with bracing as fuse members. A case study of six-story concentrically braced frame building was selected to numerically validate and demonstrate the proposed method. The deep learning model, a convolutional neural network, was trained and tested using numerically generated dataset from over 2000 sets of nonlinear seismic simulation, and an accuracy of over 90% was observed for bracing buckling damage detection in this case study. The results of the deep learning model were also discussed and extended to define other damage feature indices. This study shows that the proposed procedure is promising for rapid bracing condition inspection in concentrically braced frame structures after earthquakes.

Application of low yield strength steel on controlled plastification ductile concentrically braced frames

2001 ◽  
Vol 28 (5) ◽  
pp. 823-836 ◽  
Author(s):  
Cheng-Cheng Chen ◽  
Shyh-Yeang Chen ◽  
Jiunn-Jye Liaw
Keyword(s):  
Yield Strength ◽  
Steel Structures ◽  
Lateral Force ◽  
Force Distribution ◽  
Test Results ◽  
Braced Frames ◽  
Concentrically Braced Frames ◽  
Concentrically Braced Frame ◽  
Concentrically Braced ◽  
Distribution Requirement

The hysteretic behavior of buckling inhibited braces (BIBs) (or unbonded braces) made of low yield strength steel is investigated experimentally. Test results from four large-scale specimens showed that the BIB is able to prevent early buckling and cracking that occur in conventional braces and develop to the full capacity the strength, ductility, and energy-dissipation capacity of the steel used. In addition, the use of low yield strength steel results in small yield deformation and dramatic strain hardening of the BIB. Earthquake simulation tests of a 0.4-scale three-storey ductile concentrically braced frame (DCBF), which employed low yield strength steel BIBs as concentric braces, were carried out. Test results verified the applicability of the BIB and the high seismic performance of the DCBF. The idea of controlled plastification worked well. In addition, both the 70% lateral-force distribution requirement of the Uniform Building Code and the 30% lateral-force distribution requirement of CAN/CSA-S16.1-94 seem unnecessary for a DCBF system.Key words: concentrically braced frames, earthquake-resistant structures, braces, steel structures.

Rehabilitation of steel concentrically braced frames with rocking cores for improved performance under near-fault ground motions

2016 ◽  
Vol 20 (6) ◽  
pp. 940-952 ◽  
Author(s):  
Bing Qu ◽  
Francisco Sanchez-Zamora ◽  
Michael Pollino ◽  
Hetao Hou
Keyword(s):  
Ground Motions ◽  
Braced Frames ◽  
Concentrically Braced Frames ◽  
Braced Frame ◽  
Near Fault ◽  
Modal Properties ◽  
Concentrically Braced Frame ◽  
Core Technology ◽  
Concentrically Braced ◽  
Near Fault Earthquakes

This article focuses on evaluating the adequacy of a seismic rehabilitation technology which adds rocking cores to deficient steel concentrically braced frames in near-fault regions. Two demonstration buildings were rehabilitated with the technology. Seismic performance of the rehabilitated buildings was evaluated through numerical simulations. Analysis results suggest that the code-compliant concentrically braced frames may be vulnerable to collapse under the fault-normal components of the near-fault ground motions, approximately having a probability of exceedance of 10% in 50 years. It is found that the Rocking Core technology is effective in reducing the inter-story drift responses of the demonstration buildings under near-fault earthquakes. The rehabilitated systems can further benefit from the use of hysteretic energy dissipating links between the rocking cores and existing concentrically braced frames. This article also addresses the influence of the rocking cores on modal properties of the rehabilitated buildings. It is found that the rocking core with moderate stiffness does not significantly alter the modal properties of a rehabilitated concentrically braced frame.

Cyclic Performance of Braces with Different Support Connections in Special Concentrically Braced Frames

2018 ◽  
Vol 763 ◽  
pp. 694-701 ◽  
Author(s):  
Pratik Patra ◽  
P.C. Ashwin Kumar ◽  
Dipti Ranjan Sahoo
Keyword(s):  
Cyclic Behavior ◽  
Cyclic Performance ◽  
Braced Frames ◽  
Concentrically Braced Frames ◽  
Gusset Plates ◽  
Gusset Plate ◽  
Concentrically Braced Frame ◽  
Concentrically Braced ◽  
Out Of Plane ◽  
Plate Connections

Gusset plate connections between the steel braces and the supporting frame members play an important role in the performance of special concentrically braced frames (SCBFs) under earthquake loading conditions. Extensive studies have been conducted on SCBFs in which the gusset plate connections are designed to ensure the out-of-plane buckling of steel braces. However, research on the cyclic behavior of gusset plate connections allowing the in-plane buckling of braces is very limited. An experimental investigation has been carried out in this study to investigate the cyclic performance of the in-plane buckling of gusset-brace assemblies. Tests showed that the gusset plate connections detailed for in-plane buckling of braces provided performance at par with those detailed for the out-of-plane deformation arrangement. A numerical comparative study on three types of connection arrangements has also been conducted, namely, a) out-of-plane buckling of braces using gusset plates, b) in-plane buckling of braces using knife plates, and c) direct connection of braces without using any gusset plates. Braces made of hollow steel sections having constant slenderness ratio and width-to-thickness ratio are used in all the numerical models. The main parameters compared are the energy dissipation capacity, displacement ductility, patterns of failure, and the sequence of yielding in the components. Both test and analysis results are used to quantify the performances of gusset plate connections in order to achieve an efficient and reliable concentrically braced frame systems.

Cyclic Behaviors of Steel Braces in Concentrically Braced Frames

2016 ◽  
Vol 847 ◽  
pp. 128-134
Author(s):  
Zhi Hao Zhou ◽  
Camillo Nuti ◽  
Davide Lavorato ◽  
Alessandro Vittorio Bergami
Keyword(s):  
Experimental Data ◽  
Plastic Hinge ◽  
Material Model ◽  
Braced Frames ◽  
Concentrically Braced Frames ◽  
Braced Frame ◽  
New Model ◽  
Concentrically Braced Frame ◽  
Concentrically Braced ◽  
Different Types

In this paper, a new model named as “brace01” for steel brace is presented on the basis of experimental data on different types of steel struts. This model shows a peasant capability in the structural analysis of Concentrically Braced Frames. A brace is idealized as a pin-ended member with a plastic hinge located at its midspan. This expression of the model is proposed by combining the mechanical properties and the phenomenological characters. The model for steel brace is implemented in an effective way in OpenSees. The calibration of the material model is done by comparing the numerical curves generated by the numerical model with the experimental curves of pin-ended steel braces. The new model is proved applicable to practical Concentrically Braced Frame.

scholarly journals Evaluation of Seismic Performance of Improved Rocking Concentrically Braced-frames with Zipper Columns

2020 ◽  
Author(s):  
Nasim Irani Sarand ◽  
Abdolrahim Jalali
Keyword(s):  
Time History ◽  
Nonlinear Time History Analysis ◽  
Braced Frames ◽  
Concentrically Braced Frames ◽  
Restoring Force ◽  
Braced Frame ◽  
Concentrically Braced Frame ◽  
Concentrically Braced ◽  
Rocking Behavior ◽  
Post Tensioned

Concentrically braced frames (CBFs) as one of well-known stiff and common lateral force resisting systems often show limited ductility capacity under severe earthquakes. This study proposes rocking zipper braced frame (RZBF) to improve the drift capacity of CBFs which is based on combination of rocking behavior and zipper columns. In the RZBF system, rocking behavior permit the braced frame to uplift during the earthquake and then restoring force induced through post-tensioned bars self-center the frame to its initial state. Also, zipper columns can decrease the concentration of damage by distributing the unbalance force at the mid bay over the frame’s height. To assess the performance of RZBF, a comparison study is carried out considering CBF, rocking concentrically braced frame, zipper braced frame and RZBF. For this purpose, some frames structures are designed and nonlinear time history analysis conduct under a set of earthquake records. Seismic responses such as roof drift ratio, gap opening at the column-base interface, forces of top story braces and post-tensioned bars are taken into consideration. The results show that the proposed RZBF has better performance among the others and zipper columns can improve the behavior of rocking systems.

Seismic Design of Gusset Plate Connections in Concentrically Braced Frames

2018 ◽  
Vol 763 ◽  
pp. 141-148
Author(s):  
Yao Cui ◽  
Wei Zhang ◽  
Jia Chen Zhang ◽  
Qi Tang
Keyword(s):  
Seismic Design ◽  
Axial Load ◽  
Finite Element Models ◽  
Braced Frames ◽  
Concentrically Braced Frames ◽  
Gusset Plates ◽  
Gusset Plate ◽  
Braced Frame ◽  
Concentrically Braced ◽  
Plate Connections

In concentrically braced frames (CBF), gusset plates as the connected members are subjected to forces not only from brace but also from frame action. When the braced frame is deformed, the beam-column connection will deform, and the deformation of beam-column connection either “open” or “close” as the brace under “compression” or “tension”. Therefore, the design of gusset plate should consider the effect of such frame action, in addition of the brace axial load. Six finite element models were developed using ABAQUS to investigate the force distribution of gusset plate under the two actions. It is noted that force in gusset plate can be divided into two parts and frame action is so small that can be neglected during brace buckling.

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