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Author: Er Mao Gong Publisher: ISBN: Category : Damping (Mechanics) Languages : en Pages : 0
Book Description
In previous investigations [Chopra and Goel, 2001], the Modal Pushover Analysis (MPA) procedure was demonstrated to be accurate enough in estimating floor displacements and story drifts, and identifying locations of most plastic hinges for Moment Resistant Frame (MRF) systems. The principal objective of this investigation is to implement MPA procedure to analyze Friction Damped Braced Frame (FDBF) Systems. The comparisons of the seismic responses of the FDBF determined by MPA with Nonlinear Response History Analysis (NL-RHA) procedure illustrate that for a FDBF system, the MPA procedure is probably accepted in estimating floor displacements, but for the story drift of the structure, the accuracy of the MPA is too poor to be accepted. This leads to the introduction of an improved modal pushover analysis (IMPA) procedure. Comparing the seismic demands determined by IMPA procedure, FEMA-273 pushover analysis [Building Seismic Safety Council, 1997], and NL-RHA, it is demonstrated that the IMPA procedure is also better than FEMA-273 pushover analysis in determining the floor displacement, story drifts and the plastic slip of the friction damped bracing. (Abstract shortened by UMI.).
Author: Er Mao Gong Publisher: ISBN: Category : Damping (Mechanics) Languages : en Pages : 0
Book Description
In previous investigations [Chopra and Goel, 2001], the Modal Pushover Analysis (MPA) procedure was demonstrated to be accurate enough in estimating floor displacements and story drifts, and identifying locations of most plastic hinges for Moment Resistant Frame (MRF) systems. The principal objective of this investigation is to implement MPA procedure to analyze Friction Damped Braced Frame (FDBF) Systems. The comparisons of the seismic responses of the FDBF determined by MPA with Nonlinear Response History Analysis (NL-RHA) procedure illustrate that for a FDBF system, the MPA procedure is probably accepted in estimating floor displacements, but for the story drift of the structure, the accuracy of the MPA is too poor to be accepted. This leads to the introduction of an improved modal pushover analysis (IMPA) procedure. Comparing the seismic demands determined by IMPA procedure, FEMA-273 pushover analysis [Building Seismic Safety Council, 1997], and NL-RHA, it is demonstrated that the IMPA procedure is also better than FEMA-273 pushover analysis in determining the floor displacement, story drifts and the plastic slip of the friction damped bracing. (Abstract shortened by UMI.).
Author: Felix C. Blebo Publisher: ISBN: Category : Civil engineering Languages : en Pages : 135
Book Description
Conventional braced frame systems have limited drift capacity before brace buckling and related damage leads to deterioration in strength and stiffness. A friction-damped braced frame (FDBF) system is being developed to provide significant drift capacity while limiting damage and residual drift. The FDBF system consists of beams, columns, and braces branching off a central column. Friction at lateral-load bearings that transfer inertia forces from the floor diaphragms to the FDBF is used to dissipate energy, to reduce the overall seismic response of the FDBF system, and to provide overturning moment resistance. Vertically oriented post-tensioning bars provide additional overturning moment resistance and help to reduce residual drift. The thesis introduces a preliminary design approach for FDBF systems. Several FDBF systems are designed, and pushover and dynamic nonlinear analysis results are presented. Dynamic analysis results confirm the expected drift capacity and behavior of the system.
Author: Mona Rais Esmaili Publisher: ISBN: Category : Languages : en Pages : 148
Book Description
Eccentrically braced frames (EBFs) are very effective lateral load resisting systems against earthquakes because of their hybrid behavior that includes great stiffness corresponding to the bracing actions, and considerable ductility owing to the inelastic activity of a small part of the floor beam called link. Current capacity design approach of EBFs is to confine the inelastic behavior of the frame primarily to the link such that other members remain essentially in elastic range. Limited research works are available in the literature studying the behavior of multi-storey EBFs designed according to the current Canadian seismic provisions. This thesis was aimed to study seismic performance of EBFs through nonlinear time history analysis (NLTHA) of three 4-, 8- and 14-storey chevron eccentrically braced frames. The selected EBFs were subjected to real and artificial ground motion records scaled to match the response spectrum of Vancouver. All the EBFs, designed according to current capacity design provisions, exhibited excellent seismic performance in terms of stiffness, strength, and ductility. It was observed that the inelastic link rotations of all EBFs were lower than the design limit of 0.08 rad, except for the two upper floors in 14-storey EBF where the link rotation slightly exceeded the limit. Seismic analysis also showed that maximum inelastic link shear forces exceeded the values recommended in design for many earthquake records. Although NLTHA can precisely estimate structural seismic responses, it requires high computational demands making it impractical for engineering design offices. On the other hand, the conventional pushover analysis does not consider contributions of higher modes to the structural responses and thus it often does not provide good estimation of seismic responses for taller buildings. Capacity-Spectrum Method (CSM) and modal pushover analysis (MPA) are two simple nonlinear static methods that have been proposed and recently used for seismic performance evaluation of few lateral load-resisting systems. This research further studies the application of CSM and MPA as alternatives for rigorous NLTHA to estimate seismic performance parameters of EBFs. The three selected EBFs were analyzed using MPA and CSM and the results were compared with nonlinear seismic analysis results. It was observed that both CSM and MPA predicted the peak top displacements of EBFs with sufficient accuracy.
Author: Xiaoming Zhao Publisher: ISBN: Category : Computer-aided engineering Languages : en Pages : 0
Book Description
A 20-storey all-steel office building and a 10-storey reinforced concrete office building are used as application examples, to evaluate the effectiveness of the computer program as a tool for assisting engineers in seismic design of the frames.
Author: Felix C. Blebo Publisher: ISBN: Category : Damping (Mechanics) Languages : en Pages : 172
Book Description
Conventional concentrically braced frame (CBF) systems have limited drift capacity prior to brace buckling, and related damage leads to deterioration in strength and stiffness. CBFs are also susceptible to weak story failure. A pin- supported self-centering friction-damped braced frame system with buckling-restrained columns (FDBF-BRC) is being developed to provide significant drift capacity while limiting damage due to residual drift and soft-story mechanisms. The FDBF-BRC system consists of beams, columns, and braces branching off a central column, with buckling restrained columns (BRCs) incorporated into the system at the first story external column positions. The BRCs and friction generated at lateral-load bearings at each floor level are used to dissipate energy to minimize the overall seismic response of the FDBF-BRC system. Vertically aligned post-tensioning bars provide additional overturning moment resistance and aid in self-centering the system to eliminate residual drift. The pin support condition and the lateral stiffness of the system enable it to exhibit a nearly uniform inter-story drift distribution. In this study, a suite of 44 DBE-level ground motions used in FEMA P695 is numerically applied to several FDBF- BRCs to demonstrate the seismic performance of the system. The results show that the FDBF-BRC system has a nearly uniform inter-story drift response, high ductility, and a high energy dissipation capacity, and is an effective seismic-resistant system.
Author: Chibuike Anozie Publisher: ISBN: Category : Buildings Languages : en Pages : 172
Book Description
The friction-damped braced frame system with buckling restrained columns (FDBF-BRC) is being developed to provide significant drift capacity while limiting damage due to residual drift and soft-story mechanisms. BRCs will be on both ends of the frame, where they will experience tension and compression due to conditioned earthquake simulations on OPENSEES. This research is a continuation of previous work by Dr. David A. Roke's previous graduate student, Dr. Felix C. Blebo, for multiple stories, based on the established design recommendations. This study includes buildings with 4, 6, and 8 stories, with application of recommended frame hardening factor and BRC hardening factor. This system consists of beams, columns, braces interlocking at a central column, a pinned support condition, and BRCs at both external columns of first story. Energy dissipation to minimize overall seismic response on each floor level are products of the incorporated BRCs and friction generated at the lateral-load bearings. A suite of 20 DBE, 20 MCE, and 20 FOE-level ground motions is numerically applied to several FDBF-BRCs. Based on dynamic analysis results, the FDBF-BRC still proves to be an effective seismic-resistant system. The system's performance shows a nearly uniform inter-story drift response, high ductility, and high energy dissipation capacity.
Author: Hani Mohamed Akkari Publisher: ISBN: Category : Earthquake resistant design Languages : en Pages : 342
Book Description
Concentrically braced steel frames (CBFs) are efficient and commonly used steel systems for resisting seismic loads through a complete truss action. In strong earthquake events, multi-storey concentrically braced steel frames (CBFs) are prone to form a storey-collapse mechanism after buckling and yielding of the braces in a storey. This thesis evaluates the seismic performance of steel concentrically braced frames (CBFs) in Abu Dhabi, UAE. The aim of this study is to assess the overall lateral capacity of multi-storey buildings and the associated sequence of formation of plastic hinges using inelastic pushover analysis technique. The time history analysis approach is employed to assess the local and global seismic performance of braced frame structures under various earthquake records representing the potential seismic loading scenarios. In addition, the adequacy of using inelastic pushover analysis as a simplified means to examine the seismic integrity of braced frame structures and to predict the sequence of development of plastic hinges within the system is evaluated. This study shows that under the expected level of Abu Dhabi's seismicity the designed concentrically braced steel frames (CBFs) perform in an excellent manner by suffering of repairable damages with no life safety threatening. This study puts a step forward in the effort of spreading the knowledge of using the concentrically braced steel frames as lateral force resisting system in Abu Dhabi for mid and high rise buildings.
Author: Er Mao Gong
Author: Er Mao Gong
Author: André Filiatrault
Author: Felix C. Blebo
Author: Mona Rais Esmaili
Author: Xiao Ming Zhao
Author: Xiaoming Zhao
Author: André Filiatrault
Author: Felix C. Blebo
Author: Chibuike Anozie
Author: Hani Mohamed Akkari