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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: 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: Robert D. Hanson
Publisher:
ISBN:
Category : Technology & Engineering
Languages : en
Pages : 160
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Book Description
The purpose of this monograph is to impart basic concepts of the supplemental energy dissipation technology to design engineers, architects, and building officials so they can understand its benefits and limitations in structural applications. The approach is introductory. References are cited throughout the monograph for readers who wish to study the subject in more depth.Supplemental energy dissipation systems are recent innovations to improve earthquake building performance. Research has led to a better understanding of the effects of supplemental energy dissipation on the earthquake response of buildings. Over the last 20 years, significant progress has been made in developing manufactured systems. They are being reliably designed and installed in new as well as existing buildings.Development of design codes and standards for energy dissipation systems has progressed slowly. This monograph summarizes information on their use in designing new earthquake-resistant buildings and upgrading the seismic performance of existing buildings. The following areas are covered:? The physical consequences of adding energy dissipation systems to a structure for various types of input motion? Summary of generic energy dissipation device characteristics? Summary of pros and cons of specific device characteristics in meeting selected design objectives? Seismic design limits for selecting energy dissipation systems? Design approaches for the limits of elastic or inelastic response
Author: Xiang-Lin Gu
Publisher: Springer Nature
ISBN: 9819933625
Category : Technology & Engineering
Languages : en
Pages : 962
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Book Description
This book is a compilation of selected papers from the 6th International Conference on Smart Monitoring, Assessment and Rehabilitation of Civil Structures (SMAR 2022). The work focuses on the state-of-the-practice and recent advances in testing and monitoring technology, in structural modeling and assessment methods, and in the application of advanced materials for structural rehabilitation. The contents make valuable contributions to international professors, research scientists, professional engineers, postdoctoral fellows and postgraduate students.
Author: Paolo Castaldo
Publisher: Springer Science & Business Media
ISBN: 3319026151
Category : Technology & Engineering
Languages : en
Pages : 226
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Book Description
The structural optimization procedure presented in this book makes it possible to achieve seismic protection through integrated structural/control system design. In particular, it is explained how slender structural systems with a high seismic performance can be achieved through inclusion of viscous and viscoelastic dampers as an integral part of the system. Readers are provided with essential introductory information on passive structural control and passive energy dissipation systems. Dynamic analyses of both single and multiple degree of freedom systems are performed in order to verify the achievement of pre-assigned performance targets, and it is explained how the optimal integrated design methodology, also relevant to retrofitting of existing buildings, should be applied. The book illustrates how structural control research is opening up new possibilities in structural forms and configurations without compromising structural performance.
Author: Ramin Golesorkhi
Publisher:
ISBN: 9780939493562
Category : Buildings
Languages : en
Pages : 116
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Book Description
Performance-Based Seismic Design (PBSD) is a structural design methodology that has become more common in urban centers around the world, particularly for the design of high-rise buildings. The primary benefit of PBSD is that it substantiates exceptions to prescribed code requirements, such as height limits applied to specific structural systems, and allows project teams to demonstrate higher performance levels for structures during a seismic event.However, the methodology also involves significantly more effort in the analysis and design stages, with verification of building performance required at multiple seismic demand levels using Nonlinear Response History Analysis (NRHA). The design process also requires substantial knowledge of overall building performance and analytical modeling, in order to proportion and detail structural systems to meet specific performance objectives.This CTBUH Technical Guide provides structural engineers, developers, and contractors with a general understanding of the PBSD process by presenting case studies that demonstrate the issues commonly encountered when using the methodology, along with their corresponding solutions. The guide also provides references to the latest industry guidelines, as applied in the western United States, with the goal of disseminating these methods to an international audience for the advancement and expansion of PBSD principles worldwide.
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: Wang Xi
Publisher:
ISBN:
Category :
Languages : en
Pages : 215
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Book Description
In order to improve the seismic performance of structures and to reduce the total cost (both direct and indirect) due to earthquake damages, structural control through seismic protective devices in either passive or semi-active forms is essential to achieve the desired performance goals. This research intends to develop optimal design and placement of seismic protective devices for improving structural performance of buildings and bridges. This is accomplished by deriving (a) optimal nonlinear damping for inelastic structures, (b) hybrid numerical simulation framework to facilitate nonlinear structural control analysis and (c) efficient seismic protective scheme for bridges using base isolation, nonlinear supplemental damping and semi-active MR dampers. Supplemental energy dissipation in the form of nonlinear viscous dampers is often used to improve the performance of structures. The effect of nonlinear damping is a function of structural properties, ground motion characteristics and performance objectives. In order to quantify the optimal amount of nonlinear damping needed for inelastic structures, a novel dimensionless nonlinear damping ratio is first proposed through dimensional analysis of inelastic SDOF structures. Subsequently, an equivalent SDOF inelastic system is derived to represent the general MDOF inelastic structures. Based on this equivalency and the help of the nonlinear damping ratio definition, the optimal damping and damper placement for MDOF inelastic structures are developed using genetic algorithms. It's demonstrated that the added nonlinear damping is not always beneficial for inelastic structures, i.e. resulting in the increase of total acceleration response under certain ground motions. A critical structure-to-input frequency ratio exists, upon which an optimal nonlinear damping is needed to balance between the increase of total acceleration and the reduction of structural drift. Secondly, to facilitate the nonlinear control simulation of complex structures, an existing hybrid testing framework (UI_SimCor) is adopted and modified to enable the dynamic analysis of nonlinear structures equipped with seismic protective devices, including nonlinear viscous dampers, base isolators and MR dampers. Under this framework, inelastic structures can be modeled realistically in general FEM platform (e.g. OpenSees) while the seismic protective devices can be modeled numerically in a different software (e.g. Matlab). Furthermore, control algorithms can also be implemented easily under this hybrid simulation scheme. To validate the hybrid simulation approach, an experimental program is implemented on a scaled 3-story steel frame structure controlled by a semi-active MR damper. Both real-time hybrid simulation and shake table tests were performed and compared. The good agreement between them verifies the accuracy and efficiency of the hybrid simulation scheme. In addition, for application to bridges, special scheme to incorporate multi-support input earthquake motions is also developed so that the significant soil-structure interaction effects on bridges can be simulated. Finally, the efficient seismic protective scheme for bridges is explored using the hybrid simulation scheme developed. A real highway bridge, the Painter Street Bridge (PSB) is modeled realistically in OpenSees including soil-structure interaction effects while the seismic protective devices and control algorithm are implemented separately in Matlab. Clipped-optimal control algorithm based on LQG regulator and Kalman filter is adopted to derive the optimal structural response of PSB with base isolation and semi-active controlled MR dampers. Eventually, an equivalent passive form of MR dampers is developed, which can mimic the effects of semi-active control to achieve the optimal design of seismic protective devices for highway bridge applications.
Author: Yi Peng
Publisher:
ISBN:
Category :
Languages : en
Pages : 213
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Book Description
Significant structural damages (even collapses) have been observed in past earthquakes. Seismic protective devices and innovative structural systems can be used to improve the responses and post-earthquake serviceability. This study aims to derive the optimal design of protective devices for structures and evaluate the promises of rocking components to effectively improve the structural performance and mitigate the earthquake hazards. First, the hybrid simulation framework is adapted and validated to enable nonlinear structural control of inelastic structures with protective devices. The structure is modeled in OpenSees while the protective devices and control algorithms are modeled in MATLAB. Subsequently, guided by the actively controlled responses, the study provides different optimization procedures to identify the optimal design parameters of equivalent passive protective devices. Demonstrated by an eight-story inelastic building, the equivalent passive design yields much improved structural performance, comparable to actively controlled response. Second, the hybrid simulation scheme is further modified to incorporate multi-support excitations, often observed in bridges due to significant soil-structure interaction effects. The methodology is applied to a benchmark highway bridge where base isolation and supplemental energy dissipation are used. Active control algorithms (either linear or nonlinear) are implemented and optimal parameters for base isolators and damping devices are derived to mimic the actively controlled responses. The robustness of active controls and optimal passive controls is further demonstrated by comparing various control schemes under different bridge systems and motion inputs. Third, rocking components are evaluated as an innovative structural system that can be incorporated along with conventional lateral force resisting systems. Several numerical models are evaluated and improved to account for complex dynamic behavior of rocking components in flexible structures. A probabilistic seismic demand model (PSDM) is also proposed as an alternative way to capture the uncertainties in predicting individual rocking responses. A new finite element-based rocking model is implemented in OpenSees, which consists of a zero-length rocking element with a Dirac-delta type impact model. Finally, a nine-story rocking wall-frame building is designed and analyzed. Nonlinear time history analysis results demonstrated that both strength and deformation demands are reduced, and the structural damage is controlled when rocking motion is activated.
Author: Mehmet Halis Günel
Publisher: Routledge
ISBN: 1317690729
Category : Technology & Engineering
Languages : en
Pages : 214
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Book Description
The structural challenges of building 800 metres into the sky are substantial, and include several factors which do not affect low-rise construction. This book focusses on these areas specifically to provide the architectural and structural knowledge which must be taken into account in order to design tall buildings successfully. In presenting examples of steel, reinforced concrete, and composite structural systems for such buildings, it is shown that wind load has a very important effect on the architectural and structural design. The aerodynamic approach to tall buildings is considered in this context, as is earthquake induced lateral loading. Case studies of some of the world’s most iconic buildings, illustrated with full colour photographs, structural plans and axonometrics, will bring to life the design challenges which they presented to architects and structural engineers. The Empire State Building, the Burj Khalifa, Taipei 101 and the HSB Turning Torso are just a few examples of the buildings whose real-life specifications are used to explain and illustrate core design principles, and their subsequent effect on the finished structure.
Author: Michalakis C. Constantinou
Publisher:
ISBN: 9780965668217
Category : Force and energy
Languages : en
Pages : 299
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Book Description
