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Author: Sarven Akçelyan
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
"A number of existing tall steel buildings in seismic regions may have potential deficiencies to seismic events with low probability of occurrence. It is understood that the seismic performance of such buildings should be evaluated thoroughly such that effective retrofit solutions can be proposed. In this thesis, the emphasis is on the implementation of supplemental damping devices, particularly, nonlinear viscous damper (NVDs), oil dampers with relief valves (ODs) and buckling-restrained braces (BRBs). In the context of performance based design there is an increased need to improve the reliability of state-of-art and simplified evaluation methods for tall buildings equipped with supplemental damping devices. This research presents enhanced models and algorithms for the numerical simulation of NVDs, ODs and BRBs within a nonlinear finite element program. Adaptive algorithms are implemented for computing high-precision solutions for NVDs and ODs that are typically represented mathematically with a nonlinear Maxwell model. Furthermore, a novel rate-dependent material model for BRBs and its calibration procedure with experimental data is developed. The applicability and computational efficiency of the numerical models is demonstrated through a number of validation examples with data that involve component experimentation as well as the utilization of full-scale shake table tests of a 5-story steel building equipped with supplemental damping devices. Based on a comparison of various engineering demand parameters with experimental data, it is shown that linear and nonlinear static procedures as per ASCE 41-13 may be unconservative for the evaluation of frame buildings with BRBs or NVDs, while the performance curves and P-Spectra methods provide more reliable predictions. In order to enhance current design methods for dampers in tall buildings, a practical multi-degree-of-freedom (MDF) performance curves tool is developed. The advantage of this tool over currently used methods is that the designer can directly obtain story-based EDPs for a range of design solutions, which do not contain typical errors due to transformation, (i.e. SDF idealization, higher modes, flexural deformations, irregular damping distribution) and linearization. A comprehensive study related to the seismic performance assessment of a benchmark existing 40-story steel building with moment-resisting frames that represents typical 1970s construction in North America is presented. Supplemental damping provided by ODs is utilized to design an efficient seismic retrofit system for the 40-story steel building under consideration. Multiple retrofit solutions are designed based on three damping levels. It is shown that the formation of local story collapse mechanisms can be prevented and the drift distribution can be controlled along the height of the building. The efficiency of vertical damping distribution methods varies with the level of the frame inelasticity." --
Author: Sarven Akçelyan
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
"A number of existing tall steel buildings in seismic regions may have potential deficiencies to seismic events with low probability of occurrence. It is understood that the seismic performance of such buildings should be evaluated thoroughly such that effective retrofit solutions can be proposed. In this thesis, the emphasis is on the implementation of supplemental damping devices, particularly, nonlinear viscous damper (NVDs), oil dampers with relief valves (ODs) and buckling-restrained braces (BRBs). In the context of performance based design there is an increased need to improve the reliability of state-of-art and simplified evaluation methods for tall buildings equipped with supplemental damping devices. This research presents enhanced models and algorithms for the numerical simulation of NVDs, ODs and BRBs within a nonlinear finite element program. Adaptive algorithms are implemented for computing high-precision solutions for NVDs and ODs that are typically represented mathematically with a nonlinear Maxwell model. Furthermore, a novel rate-dependent material model for BRBs and its calibration procedure with experimental data is developed. The applicability and computational efficiency of the numerical models is demonstrated through a number of validation examples with data that involve component experimentation as well as the utilization of full-scale shake table tests of a 5-story steel building equipped with supplemental damping devices. Based on a comparison of various engineering demand parameters with experimental data, it is shown that linear and nonlinear static procedures as per ASCE 41-13 may be unconservative for the evaluation of frame buildings with BRBs or NVDs, while the performance curves and P-Spectra methods provide more reliable predictions. In order to enhance current design methods for dampers in tall buildings, a practical multi-degree-of-freedom (MDF) performance curves tool is developed. The advantage of this tool over currently used methods is that the designer can directly obtain story-based EDPs for a range of design solutions, which do not contain typical errors due to transformation, (i.e. SDF idealization, higher modes, flexural deformations, irregular damping distribution) and linearization. A comprehensive study related to the seismic performance assessment of a benchmark existing 40-story steel building with moment-resisting frames that represents typical 1970s construction in North America is presented. Supplemental damping provided by ODs is utilized to design an efficient seismic retrofit system for the 40-story steel building under consideration. Multiple retrofit solutions are designed based on three damping levels. It is shown that the formation of local story collapse mechanisms can be prevented and the drift distribution can be controlled along the height of the building. The efficiency of vertical damping distribution methods varies with the level of the frame inelasticity." --
Author: Shanshan Wang
Publisher:
ISBN:
Category :
Languages : en
Pages : 283
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Book Description
This dissertation focuses on the use of supplemental energy-dissipation devices to improve the seismic performance of tall steel buildings. It is divided into two parts. Part 1 focuses on exploring cost-effective retrofit strategies to improve the seismic performance of an existing tall building. The selected building is a 35-story steel moment-resisting frame, with representative details from the early 1970s. Detailed seismic evaluations were conducted in the framework of Performance Based Earthquake Engineering (PBEE), using the scenario-based performance assessment methods. A three-dimensional numerical model capturing the mechanical properties of the most critical structural elements was generated using the program: Open System for Earthquake Engineering Simulation (OpenSees). Seismic evaluation of the selected building was done following ASCE 41-13, FEMA 351 and FEMA P-58, and two hazard levels: basic safety earthquake levels 1 and 2 (BSE-1E and BSE-2E) prescribed by ASCE 41 were used for the assessment. Results predicted that this building failed to meet the recommended performance objectives and had a variety of seismic vulnerabilities, and possible retrofits were needed. Therefore, a two-level retrofit approach was examined that focused on achieving the collapse prevention limit state under the BSE-2E hazard level. In Level-1, the brittle column splices were fixed everywhere in the building, and the massive concrete cladding was replaced with lightweight substitute in the exterior of the building. Level-2 strategies augmented the Level-1 methods by adding different supplemental energy-dissipation devices. Devices investigated include: fluid viscous dampers (FVDs), viscous wall dampers (VWDs) and buckling restrained braces (BRBs). Among these, the scheme that used FVDs was expected to be the most promising to upgrade the seismic performance of the case-study steel moment frame, and thus was examined first. In this approach, feasible damper locations and overall effective damping ratios were evaluated through a series of preliminary studies, and then a two-phase manual design method was used to refine the distribution and mechanical properties of the dampers. Thorough assessments of the refined design were carried out and the results indicated that the proposed retrofit method of using FVDs could achieve the retrofit goal and provide a cost-effective means of improving the structural behavior and reducing economic losses in a major seismic event for this case-study building. The study was extended to examine alternative measures to upgrade the case-study building by using either VWDs or BRBs, and compared their relative effectiveness and economy with the scheme using FVDs. The locations and effective damping ratios were kept the same for all three schemes to insure a valid comparison. Results indicated that the proposed schemes of VWDs and BRBs both failed to achieve the targeted performance goal for this structure under a BSE-2E event, and special design considerations were required. Part 2 of the dissertation focuses on developing an automated tool to streamline the design of FVDs in tall buildings. Aided by the high-performance computers and parallel processors, a large amount of complicated nonlinear response history analysis was conducted to facilitate the automate design procedure. The optimization problem was devised in a simplified PBEE framework under one hazard level each time. Basic optimization ingredients were selected to reflect the target performance goal, and several cases using different objective functions were evaluated. Two tall buildings: the existing steel moment frame examined before and a newly-designed mega-brace steel frame were selected to rely on the automated procedure to optimally design FVDs. In both cases, the automated procedure turned to be very efficient, help identify design parameters of dampers in selected locations and reduce a great amount of engineering efforts. With only limited number of iterations, optimal design patterns of FVDs in a tall building could be found, which were able to improve the structural performance under different hazard events. The suggested optimal design could meet retrofit goal for the existing tall building, as well as achieve enhanced performance goal for both existing and new tall buildings.
Author:
Publisher:
ISBN:
Category : Buildings, Reinforced concrete
Languages : en
Pages : 40
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Book Description
Author: Sachin Kuckian
Publisher: GRIN Verlag
ISBN: 3668992762
Category : Science
Languages : en
Pages : 90
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Book Description
Master's Thesis from the year 2015 in the subject Engineering - Geotechnology, grade: 9.44, , course: Masters (Structural Engineering), language: English, abstract: The present study investigates the seismic behavior of multi-story building using damping devices strategically located within the lateral load resisting elements. It concentrates on a retrofitting strategy with passive energy dissipation device known as Fluid Viscous Damper (FVD) which will be applicable to new design as well as retrofitting existing buildings to ensure seismic safety by fitting damping devices which can transform a wall panel into a damping element. The first study involves analysis of a nine-story model having cut-outs and the use of the dampers of different configuration in these structures. The second study involves the use the diagonal brace configuration dampers provided in the cutout sections of 2D 9, 18, 27 storey structures and 3D 27 storey with core wall structure at three consecutive story levels each. For the second study, the cut out locations is varied depending on their relative positions. The relative position is the ratio of the total height of the structure to the upper edge of the topmost cut-out. These structures were initially modeled and time history analysis was performed on the structure without FVD and the structure retrofitted with FVD. Three different ground motions were used for the analysis. Results of the un- retrofitted structures are then compared with a retrofitted structure in terms of peak story displacements, roof accelerations, and pseudo-spectral accelerations. Study shows that there has been a significant reduction in seismic demands for a structure retrofitted with FVD in terms of peak storey displacements, pseudo-spectral accelerations and roof accelerations when the dampers are placed at lower three cut outs i.e. with high relative position. It is also observed that damping coefficient value obtained is least for upper toggle-brace configuration out of the four different damper configurations and with maximum reduction compared to other configurations. For modeling and analysis purpose the software SAP2000® is used. Through the study it could be concluded that FVD significantly reduces the seismic demands of the structure in terms of peak storey displacements, pseudo-spectral accelerations and roof accelerations. This suggests that FVDs can be efficiently used in retrofitting. Also damping coefficient value obtained is least for upper toggle-brace configuration out of the four different damper configurations suggesting this is the most efficient configuration for retrofitting.
Author: Alberto Lago
Publisher: Butterworth-Heinemann
ISBN: 0128159642
Category : Technology & Engineering
Languages : en
Pages : 1124
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Book Description
Damping Technologies for Tall Buildings provides practical advice on the selection, design, installation and testing of damping systems. Richly illustrated with images and schematics, this book presents expert commentary on different damping systems, giving readers a way to accurately compare between different device categories and gain and understand the advantages and disadvantages of each. In addition, the book covers their economical and sustainability implications. Case studies are included to provide a direct understanding on the possible applications of each device category. Provides an expert guide on the selection and deployment of the various types of damping technologies Drawn from extensive contributions from international experts and research projects that represent the current state-of-the-art and design in damping technologies Includes 25+ real case studies collected with very detailed information on damping design, installation, testing and other building implications
Author:
Publisher:
ISBN:
Category : Juvenile Nonfiction
Languages : en
Pages : 74
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Book Description
This renamed version of the former Uniform code for building conservation guidelines for retrofitting unreinforced masonry bearing wall buildings, reinforced concrete and reinforced masonry buildings, wood frame residential buildings, and concrete with masonry infill buildings.
Author: Andrei M. Reinhorn
Publisher:
ISBN:
Category : Buildings
Languages : en
Pages :
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 32
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Book Description
The U.S. Army and Air Force have large inventories of concrete frame buildings built before the 1971 San Francisco earthquake, when seismic provisions in U.S. building codes were enhanced. Consequently, many of these buildings may not safely withstand the ground motions associated with large intensity earthquakes. The U.S. Army Construction Engineering Research Laboratories (USACERL) has developed a program to provide improved technologies for mitigating seismic hazards in older military buildings. This study investigated the effectiveness of a nonintrusive rehabilitation technique involving the addition of viscoelastic damping devices to a concrete structure. A one-third scale model of a concrete building was built and placed on the USACERL shaking table. The building was earthquake-tested using two sizes of dampers, and with no dampers in place. Preliminary observations showed that the model with dampers sustained only minimal damage. More detailed analysis continues.
Author: C. Li
Publisher:
ISBN:
Category : Building, Reinforced concrete
Languages : en
Pages : 0
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Author: C. Li
Publisher:
ISBN:
Category : Damping (Mechanics)
Languages : en
Pages :
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