Development of Validated Omni-directional Models for Triple Friction Pendulum Bearings in Support of Performance-Based Seismic Engineering PDF Download
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Author: Henan Mao
Publisher:
ISBN:
Category :
Languages : en
Pages : 179
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Book Description
Seismic isolation systems are becoming more common in the construction of a variety of critical buildings/facilities, such as hospitals and data centers, that require more stringent seismic performance levels. The Triple Friction Pendulum (TFP) isolation bearing systems offer arguably the highest performance among seismic hazard mitigation devices/solutions. TFP bearings, which exhibit highly nonlinear and history-dependent responses, dissipate the seismic energy through friction. While there are numerous models available to simulate the cyclic responses of TFP bearings, most either lack several key features, such as coupled biaxial or triaxial reactions or account for these effects in a phenomenological manner. The present study tackles these issues by implementing a physics-based, extendable, and numerically robust model, which is packaged into a novel macroelement that can be used in nonlinear time-history analyses that are required for performance-based seismic assessment and design. The aforementioned macroelement model is based on a mechanically consistent multi-surface plasticity approach that can simulate the triaxial hysteretic responses of TFP bearings. The macroelement model is developed and implemented in ABAQUS as a User-defined ELement (UEL). It is validated using experimental data from component-scale laboratory and full-scale shake table tests carried out at the E-Defense facility. The experimentally validated biaxial and triaxial TFP models are then used in performance-based seismic assessment of a prototypical base-isolated braced frame building to examine the effects of modeling errors on the estimated seismic losses. While the scope of this case study was limited to one building, findings indicated that differences between the basic (i.e., uncoupled biaxial) and the more advanced (i.e., coupled biaxial and triaxial) approaches are non-negligible, warranting their use in practice as well as future studies.
Author: Henan Mao
Publisher:
ISBN:
Category :
Languages : en
Pages : 179
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Book Description
Seismic isolation systems are becoming more common in the construction of a variety of critical buildings/facilities, such as hospitals and data centers, that require more stringent seismic performance levels. The Triple Friction Pendulum (TFP) isolation bearing systems offer arguably the highest performance among seismic hazard mitigation devices/solutions. TFP bearings, which exhibit highly nonlinear and history-dependent responses, dissipate the seismic energy through friction. While there are numerous models available to simulate the cyclic responses of TFP bearings, most either lack several key features, such as coupled biaxial or triaxial reactions or account for these effects in a phenomenological manner. The present study tackles these issues by implementing a physics-based, extendable, and numerically robust model, which is packaged into a novel macroelement that can be used in nonlinear time-history analyses that are required for performance-based seismic assessment and design. The aforementioned macroelement model is based on a mechanically consistent multi-surface plasticity approach that can simulate the triaxial hysteretic responses of TFP bearings. The macroelement model is developed and implemented in ABAQUS as a User-defined ELement (UEL). It is validated using experimental data from component-scale laboratory and full-scale shake table tests carried out at the E-Defense facility. The experimentally validated biaxial and triaxial TFP models are then used in performance-based seismic assessment of a prototypical base-isolated braced frame building to examine the effects of modeling errors on the estimated seismic losses. While the scope of this case study was limited to one building, findings indicated that differences between the basic (i.e., uncoupled biaxial) and the more advanced (i.e., coupled biaxial and triaxial) approaches are non-negligible, warranting their use in practice as well as future studies.
Author: Tracy Celeste Becker
Publisher:
ISBN:
Category :
Languages : en
Pages : 298
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Book Description
Seismic isolators, and more specifically, triple friction pendulum (TFP) bearings are ideal earthquake protection technologies for use in performance-based design because they can be designed to achieve multiple performance objectives corresponding to different levels of ground shaking. TFP bearings can limit structure displacement during a design basis (or maximum considered) earthquake while the still effectively isolating the structure under the service level earthquake, reducing seismic demands on the structure and its non-structural components. Furthermore, TFP bearings allow for a gradual transfer of force to the superstructure at ultimate displacement. This dissertation presents an advanced bidirectional model for the TFP bearing that is based on the kinematic and compatibility relationships of the components of the bearing. To validate the model, experimental characterization tests were conducted on the shake table at the University of California, Berkeley. Two distinct types of experiments were conducted: (a) displacement-controlled tests in which the bearings were cycled through specified orbits and (b) unrestrained tests in which the table replicated ground motions recorded during earthquakes. The bidirectional displacement-controlled tests, which are the first of their kind, generated new knowledge to aid in the development and validation of TFP numerical models. The experimental results provided valuable insight into TFP bearing response and showed that the developed bidirectional model accurately captured the observed behavior of the TFP bearing. The advanced model, which includes translational and rotational degrees of freedom in both horizontal directions, tracks all component displacements as well as the change in bearing height during lateral displacements. The model is general so that no a priori conditions regarding bearing properties are required for the validity of the model. These properties make the advanced TFP model a valuable tool to explore the use TFP technology in novel applications. To further the use of seismic isolation in more standard applications, simplified methods are needed for design. This dissertation investigates the use of generalized modal response spectrum methods to approximate global responses of isolated buildings without the need for costly non-linear numerical simulations. The advanced nonlinear TFP model is used for evaluation of the simplified methods. Advanced isolation models are important and necessary for understanding the complex nonlinear dynamic behavior exhibited by seismically isolated structures, and to have confidence that performance goals are achieved under a wide variety of seismic hazards. Such models can, as shown in this dissertation, also be used to assess and improve simplified analysis methods suitable for use in routine design.
Author: Daniel M. Fenz
Publisher:
ISBN:
Category : Bearings (Machinery)
Languages : en
Pages : 279
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Book Description
Author: Ahmet Dindar (Mechanical engineer)
Publisher:
ISBN:
Category : Ball-bearings
Languages : en
Pages : 0
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Book Description
Although bearings provide low-friction interfaces between rotating components and their stationary housing, they are often responsible for a sizable portion of gearbox power losses. The current trends towards electrification of powertrains are likely to increase rotating speeds of drivetrains, making bearing performance even more critical. Physics-based modeling of a bearing that captures the coupling between its dynamic and tribological behaviors is required for simulation of bearing under such high-speed and high-load conditions. The main focus of this research is development and validation of such a model for deep-groove ball bearings. On the experimental side, a methodology to perform ball bearing power loss measurements under combined radial and axial loading conditions is developed. This methodology allows tight control of applied forces, bearing bulk and oil inlet temperatures, and rotational speed while measuring the torque loss precisely. A three-step procedure is devised to separate spin and mechanical components of power losses. Experimental parametric studies are performed to quantify the effects of various parameters on power losses. In the spin loss side, these parameters include speed, oil temperature (viscosity), oil flow rate, and bearing size. For mechanical losses, radial and axial force, speed and temperature are varied. Results of these parametric studies are compared to widely-used bearing power loss formulae available in the literature to assess their fidelity. Focusing first on the loading conditions causing the balls to stay loaded so that their individual motions are dictated by their race interfaces, a tribo-dynamic model of ball bearings operating at high speeds is developed by coupling a transient, point contact mixed EHL model into a singularity-free multi-body dynamic model. The model is employed to investigate mechanics of the ball-race contacts and ball motions, and to establish the sensitivity of the mechanical power loss to operating and lubrication conditions, and key design and manufacturing parameters. Its predictions are compared to measurements to demonstrate its accuracy within wide ranges of forces and speed. As the second phase of modeling effort, mostly radial loading conditions resulting in an unloaded zone are focused. As the balls lose contact with the races, various drag and hydrodynamic effects dictate the motions of the balls in the unloaded zone. Refined formulations for such effects are implemented in the earlier model to investigate complex ball and cage dynamic interactions. The model is then used to show such effects alter the mechanical power loss predictions only slightly such that the total power loss can practically be considered to be the sum of its spin and mechanical components.
Author: Earthquake Protection Systems, Inc
Publisher: Amer Society of Civil Engineers
ISBN: 9780784403709
Category : Technology & Engineering
Languages : en
Pages : 42
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Book Description
Presents the results of a detailed evaluation for one technology out of eleven that were evaluated. The evaluations were designed to test the performance of seismic isolators and dampers produced by several manufacturers.
Author: Tianye Yang
Publisher:
ISBN:
Category :
Languages : en
Pages : 162
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Book Description
Seismic isolation is effective in protecting both structural and non-structural elements during earthquakes. One of the most commonly used base-isolation systems is the friction pendulum system (FPS). It provides excellent re-centering and large energy dissipation capacities. Despite these benefits, FPSs are rarely used in the U.S. for several reasons. Out of many one may identify, the required peer review process and the conservativeness of the existing design guideline make the implementation of the technology somewhat less economically appealing. More critically, it is a well-known dilemma that FPS can only be designed to achieve optimal performance for one level of ground shaking. A possible answer to this challenge is to use "passive-adaptive" devices, including multiple friction pendulum systems and the recently proposed Variable Friction Systems (VFSs). While providing sufficient protection (usually life safety) during a maximum considered earthquake, these systems can still effectively isolate the structure during a service level earthquake, resulting in lower seismic demands on the supported structure and its non-structural components compared to a fixed-based building. However, the development of VFSs is still in early stage, and the performance of structures isolated with such systems is uncertain. Another recently identified challenge in designing isolation systems is the potential for large magnitude and long period earthquakes, in particular, the magnitude-9 (M9) earthquake in Cascadia Subduction Zone. The results obtained from recent numerical simulations indicated that this type of earthquake may be particularly detrimental for structures with fundamental periods of vibration of 1.0 second or larger. This finding may be particularly relevant for base-isolated structures, which tend to be characterized by large effective periods. However, such systems have not been included in the studies conducted thus far, and the effect of the simulated M9 earthquake on their performance remains unclear. To address the aforementioned knowledge gaps that are limiting the implementation of friction-type seismic isolation systems, this dissertation aims to: (i) develop an analysis, modeling, and design framework for structures isolated with VFSs; and (ii) evaluate how ground motions with different characteristics impact the performance and analysis of friction-type seismic isolation systems.
Author: Apostolos A. Sarlis
Publisher:
ISBN:
Category : Bearings (Machinery)
Languages : en
Pages : 267
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Book Description
This report presents a revised model of the behavior of the Triple Friction Pendulum bearing in which no assumptions are made on the location of the resultant forces at each sliding surface and no constraints on the values of the coefficient of friction are required, provided that all sliding surfaces are in full contact.
Author: Wei Song
Publisher: Frontiers Media SA
ISBN: 2889663809
Category : Technology & Engineering
Languages : en
Pages : 213
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Book Description
Author: U.S. Nuclear Regulatory Commission
Publisher:
ISBN:
Category : Nuclear energy
Languages : en
Pages : 48
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Book Description
Author:
Publisher: AASHTO
ISBN: 1560514566
Category : Technology & Engineering
Languages : en
Pages : 63
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Book Description
This edition is based on the work of NCHRP project 20-7, task 262 and updates the 2nd (1999) edition -- P. ix.
