Design Development of a Four-Story Strongback Braced Frame

2018 ◽  
Vol 763 ◽  
pp. 1050-1057 ◽  
Author(s):  
Barbara Simpson ◽  
Stephen Mahin
Keyword(s):  
Design Space ◽  
Ground Motions ◽  
Design Development ◽  
Braced Frames ◽  
Braced Frame ◽  
Soft Story ◽  
Numerical Studies ◽  
Steel Truss ◽  
Uniform Drift ◽  
Large Earthquakes

Conventional braced frames tend to concentrate damage in one or a few stories during large earthquakes, indicative of “weak” or “soft” story behavior. To mitigate this behavior, several studies have proposed a modified braced frame, or “strongback”, that utilizes an essentially elastic vertical steel truss to impose a uniform drift distribution. While a subassemblage experimental test and past numerical studies have shown that the strongback system can successfully delay or prevent weak or soft story behavior, the dynamic behavior of this system has not been systematically assessed or evaluated. This study defines the design space for a four-story strongback system. The ability of the strongback to mitigate weak story behavior under a far-field suite of ground motions was assessed using the performance-based methodology in FEMA P695.

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.

Hybrid braced frame with buckling-restrained and strong braces to mitigate soft story

2021 ◽  
Vol 181 ◽  
pp. 106610
Author(s):  
Niloufar Mashhadiali ◽  
Siamak Saadati ◽  
Seyed Amir Mohammad Mohajerani ◽  
Parviz Ebadi
Keyword(s):  
Braced Frame ◽  
Soft Story

Development of a Hybrid Simulation Computational Model for Steel Braced Frames

2018 ◽  
Vol 763 ◽  
pp. 609-618
Author(s):  
Ali Imanpour ◽  
Robert Tremblay ◽  
Martin Leclerc ◽  
Romain Siguier
Keyword(s):  
Computational Model ◽  
Hybrid Simulation ◽  
Structural Testing ◽  
Frame Structure ◽  
Axial Stiffness ◽  
Braced Frames ◽  
Element Analysis ◽  
Braced Frame ◽  
Concentrically Braced Frame ◽  
Dynamic Hybrid

Hybrid simulation is an economical structural testing technique in which the critical part of the structure expected to respond in the inelastic range is tested physically whereas the rest of the structure is modelled numerically using a finite element analysis program. The article describes the development of a computational model for the hybrid simulation of the seismic collapse of a steel two-tiered braced frame structure due to column buckling. The column stability response in multi-tiered braced frames is first presented using a pure numerical model of the braced frame studied. The development of the hybrid simulation computational model is then discussed. Effects of initial out-of-straightness imperfections and axial stiffness, P-Delta analysis approach, and gravity analysis technique on the hybrid simulation results are evaluated using a numerical hybrid simulation model. Finally, the results of a continuous pseudo-dynamic hybrid simulation of the seismic response of the steel multi-tiered concentrically braced frame are presented. The test showed that failure of columns by instability is a possibility and can lead to collapse of multi-tiered braced frames, as was predicted by numerical analysis. Furthermore, suitable modeling methods are proposed for hybrid simulation of steel braced frame structures.

Efficient numerical modelling for the design of friction damped braced steel plane frames

1989 ◽  
Vol 16 (3) ◽  
pp. 211-218 ◽  
Author(s):  
A. Filiatrault ◽  
S. Cherry
Keyword(s):  
Numerical Modelling ◽  
Performance Index ◽  
Load Distribution ◽  
Structural Response ◽  
Computer Time ◽  
Numerical Approach ◽  
Braced Frames ◽  
Friction Damping ◽  
Braced Frame ◽  
Brake Lining

A novel friction damping system for the aseismic design of framed buildings has been proposed by Canadian researchers. The system has been shown experimentally to perform very well and is an exciting development in earthquake resistant design.The design of a building equipped with the friction damping system is achieved by determining the optimum slip load distribution to minimize structural response. The optimum slip load distribution is usually determined using the general nonlinear dynamic computer program DRAIN-2D, which requires extensive computer time and is not practical for most design offices.This paper describes a new, efficient, numerical modelling approach for the design of friction damped braced frames. The hysteretic properties of the friction devices are derived theoretically and included in a friction damped braced frame analysis program, which is adaptable to a microcomputer environment. The optimum slip load distribution is determined by minimizing a relative performance index derived from energy concepts. The new numerical approach is much more economical to use than DRAIN-2D and is of great value for the practical design of friction damped braced frames. Key words: braced frames, brake lining, performance index, damping, dynamics, earthquakes, energy, friction.

Earthquake Proof Efficiency of Sliding Base Isolator With Dog-Bone Type Damping

2005 ◽  
Author(s):  
C. S. Tsai ◽  
Tsu-Cheng Chiang ◽  
Bo-Jen Chen
Keyword(s):  
Ground Motions ◽  
Active Faults ◽  
Friction Behavior ◽  
Near Fault ◽  
The Past ◽  
Numerical Studies ◽  
Dog Bone ◽  
Base Isolator ◽  
Near Fault Earthquakes ◽  
Base Isolators

In recent years, there have been more and more seismic retrofit applications of using base isolators in seismic prone regions. In the past, the focuses of researches on the efficiency of various base isolators have been aimed at their behavior under earthquakes without long predominant periods. The doubts of efficiency of the base isolator nearby active faults or located at a soft deposit soil have been raised by researchers. It is revealed from previous studies that the seismic responses of the base isolated structure are significant due to the influence of resonance. In order to minimize the inherent shortcomings of base isolators, various base isolators with dog bone type of friction behavior have been proposed in this study. In the meanwhile, the exact solutions used to describe the behavior of the proposed isolators have also been derived in this study. The numerical studies show that the displacement responses of proposed isolators under near fault earthquakes and ground motions with long predominant periods are much lower than those of the traditional FPS and VCFPS devices. Hence, the required dimensions of proposed isolators can be smaller than those for the FPS and VCFPS isolators.

Earthquake resistant design of concentrically braced steel frames

1991 ◽  
Vol 18 (5) ◽  
pp. 839-850 ◽  
Author(s):  
R. G. Redwood ◽  
V. S. Channagiri
Keyword(s):  
Structural Engineering ◽  
Steel Structures ◽  
Braced Frames ◽  
Concentrically Braced Frames ◽  
Braced Frame ◽  
Earthquake Resistant Design ◽  
Earthquake Resistant ◽  
Concentrically Braced ◽  
Engineering Steel ◽  
The Impact

New provisions of the CSA standard for steel structures (CAN/CSA-S16.1-M89) dealing with detailing of concentrically braced frames for seismic design are described and related to requirements of the National Building Code of Canada. The basis of the new requirements is outlined, and an example eight-storey frame is used to outline a methodology for the design process for a ductile braced frame and to illustrate the impact of the provisions. Key words: design, structural engineering, steel, earthquakes, braced frame, standards.

Code provisions for seismic design for concentrically braced steel frames

1992 ◽  
Vol 19 (6) ◽  
pp. 1025-1031 ◽  
Author(s):  
R. G. Redwood ◽  
A. K. Jain
Keyword(s):  
Seismic Design ◽  
Structural Engineering ◽  
Steel Frames ◽  
Braced Frames ◽  
Concentrically Braced Frames ◽  
Braced Frame ◽  
Concentrically Braced ◽  
Interstorey Drift ◽  
Available Information ◽  
Steel Braced Frame

Extensive research into the inelastic seismic response of concentrically braced frames and their components has been carried out in the last two decades. This knowledge has now been incorporated into seismic design practice in several countries, notably the U.S.A., Canada, and New Zealand. In this paper, design specifications from these three countries, which derive largely from the same body of research, are compared. The basic design philosophy for concentrically braced steel frames, loading, and member detailing are examined. It is concluded that, in general, the Canadian specifications are in conformity with the available information and have many similar features to codes of the other countries. Significant differences exist in the classification of braced frames, between interstorey drift requirements, in the treatment of dual structural systems, and to a lesser extent in member detailing requirements. Some features of Canadian codes meriting review are identified. Key words: structural engineering, earthquakes, standards, steel, braced frame, ductility, concentric bracing, dual system.

Assessing the Collapse Probability of Base-Isolated Buildings considering Pounding to Moat Walls using the FEMA P695 Methodology

2015 ◽  
Vol 31 (4) ◽  
pp. 2069-2086 ◽  
Author(s):  
Armin Masroor ◽  
Gilberto Mosqueda
Keyword(s):  
Seismic Hazard ◽  
Ground Motions ◽  
Moment Frame ◽  
Isolation System ◽  
Braced Frame ◽  
Frame Model ◽  
Impact Forces ◽  
Collapse Probability ◽  
The Moment ◽  
The Impact

The collapse probability of two three story base-isolated buildings considering pounding to moat walls is examined using the methodology in FEMA P695. The superstructure models consist of a steel intermediate moment frame and a steel ordinary braced frame designed for the same seismic hazard. The behavior of these buildings under various ground motions is first examined, and it is found that the more rigid braced frame results in larger displacements demands on the isolation system, increasing the potential for impact. The collapse studies examine the effect of moat wall gap distance on the probability of collapse for these structures. These studies show that the flexibility and ductility of the moment frame model allow the superstructure to better absorb the impact forces. The braced frame superstructure tends to impact at lower shaking intensities and degrades in strength more rapidly due to the limited ductility that increases the risk of collapse.

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