Improved equivalent viscous damping model for base-isolated structures with lead rubber bearings

2014 ◽  
Vol 75 ◽  
pp. 340-352 ◽  
Author(s):  
Tobia Zordan ◽  
Tao Liu ◽  
Bruno Briseghella ◽  
Qilin Zhang
Keyword(s):  
Viscous Damping ◽  
Equivalent Viscous Damping ◽  
Lead Rubber Bearings ◽  
Isolated Structures ◽  
Rubber Bearings ◽  
Damping Model

scholarly journals Study on the Aging Time Variation Law of Mechanical Properties of the Laminated Rubber Bearing in Coastal Bridges considering Frictional Slip

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Yue Li ◽  
Chongming Gao ◽  
Chong Li ◽  
Qian Li
Keyword(s):  
Mechanical Properties ◽  
Aging Time ◽  
Damping Ratio ◽  
Viscous Damping ◽  
Equivalent Viscous Damping ◽  
Coastal Bridges ◽  
Shape Coefficient ◽  
Rubber Bearings ◽  
Frictional Slip ◽  
Equivalent Viscous Damping Ratio

As an important support member in the structural system of coastal bridges, the frictional slip and the rubber aging of laminated rubber bearings will affect the service safety of the overall structure in earthquakes. In order to investigate the mechanical properties aging law of the rubber bearings considering frictional slip in the coastal bridges, a frictional slip experiment was carried out on the laminated rubber bearings. Moreover, the influence of rubber aging on the mechanical properties of the bearings with various shape coefficients was analyzed by the finite element method during the 100 years of service life of bridges. The results indicate that (1) the horizontal and vertical stiffness of the bearing increase linearly with the aging time of the rubber. The amplification of the bearing stiffness also grows with the shape coefficient of the bearing. (2) The frictional slip initiation displacement of the bearing grows with the rubber aging time. Furthermore, the larger the shape coefficient of the bearing is, the more the frictional slip initiation displacement of the bearing increases. (3) With the increase of the aging time, the equivalent viscous damping ratio of the bearing continues to increase and more energy is consumed by frictional slip. For the bearing with the shape coefficient of 16.38, the equivalent viscous damping ratio at 100 years of rubber aging time is 1.17 times higher than that of the initial state of the bearing, and 33.21% more energy is consumed through frictional slip. Given that the marine environment accelerates rubber aging and changes the mechanical properties, the effects of the frictional slip and rubber aging properties of the laminated rubber bearings on the seismic dynamic response of bridges should be considered in the seismic design of coastal bridges.

scholarly journals Seismic Performance of Midstory Isolated Structures under Near-Field Pulse-Like Ground Motion and Limiting Deformation of Isolation Layers

2015 ◽  
Vol 2015 ◽  
pp. 1-17 ◽  
Author(s):  
Guiyun Yan ◽  
Fuquan Chen
Keyword(s):  
Ground Motion ◽  
Nonlinear Response ◽  
Near Field ◽  
Field Pulse ◽  
Isolation Layer ◽  
Protective System ◽  
Lead Rubber Bearings ◽  
Isolated Structures ◽  
Rubber Bearings ◽  
The Impact

Excessive deformation of the isolation layer in midstory isolated structures may occur under strong near-field pulse-like ground motion, which would result in the overturning collapse of the superstructure. The objective of the present research is to limit excessive deformation of the isolation layer and to reduce nonlinear response of midstory isolated structures. To this end, a protective system is presented to limit deformation of the isolation layer by soft pounding. Based on the Kelvin pounding model, a mechanical model is put forward for this protective system. In addition, a new method has been proposed that synthesizes artificial near-field pulse-like ground motion by combining the real near-field nonpulse ground motion with simple equivalent pulses. Also, the impact of artificial near-field pulse-like ground motion on the nonlinear response of midstory isolated structures and the deformation of the isolation layer has been investigated. The effectiveness of the midstory isolation with the protective system has been validated. The results show that the maximum deformation of the isolation layer significantly exceeds the allowable deformation of lead-rubber bearings when subjected to near-field pulse-like ground motion, and it causes the lead-rubber bearings destruction. The proposed protective system is effective in restricting the excessive deformation of the isolation layer and reducing nonlinear responses of the isolated structure, preventing collapse of the superstructure.

scholarly journals Rubber bearings in base-isolated structures

1991 ◽  
Vol 24 (3) ◽  
pp. 251-274 ◽  
Author(s):  
R. G. Tyler
Keyword(s):  
Load Capacity ◽  
Shear Stiffness ◽  
Vertical Deflection ◽  
Short Term ◽  
Traffic Loading ◽  
Rubber Layer ◽  
Tensile Forces ◽  
Lead Rubber Bearings ◽  
Isolated Structures ◽  
Rubber Bearings

The paper discusses the use of rubber bearings in base isolated structures. In Japan alone there are likely to be 100 base-isolated buildings completed by the end of 1994 all of which will be on rubber bearings [Ref 1.2]. A distinction is drawn between the use of rubber bearings in bridges where they are subject to both the fatigue of traffic loading and diurnal temperature movements throughout their life, and their use in buildings where the loading is comparatively static until severe earthquake shaking occurs, which at a particular location is not likely to occur more than about once a century. Vertical load capacity and characteristics of vertical deflection in relation to rubber layer thickness and instability are discussed. Shear stiffness and deflection characteristics are outlined together with methods used for providing damping, including damping in lead-rubber bearings. The design of the high-stability aseismic bearing for loads of 1 tonne upwards is discussed in relation to its stability characteristics. It is suggested that tensile forces should be permitted in the short-term loading induced by earthquakes and this is confirmed by current Japanese practice in using fully bonded bearings. The development of self-damping rubber bearings is discussed.

Crack Propagation Life Calculation of an Aircraft Compressor Blade due to Bird Ingestion

2014 ◽  
Author(s):  
Srinivasa R. Jammi ◽  
R. Rzadkowski
Keyword(s):  
Crack Propagation ◽  
Iterative Process ◽  
Reference Strain ◽  
Pressure Field ◽  
Nonlinear Damping ◽  
Compressor Blade ◽  
Viscous Damping ◽  
Equivalent Viscous Damping ◽  
The Given ◽  
Damping Model

Bird ingestion is simulated by blade passage blocks in the incoming flow and the pressure field is obtained from a CFD code. The alternating pressure field corresponding to the identified critical speed of the first stage rotor blade is obtained from an FFT. A nonlinear damping model is developed using Lazan’s hysteresis law; the equivalent viscous damping model is determined as a function of reference strain amplitude in the given mode of vibration at the rotational speed. An iterative process is developed with the nonlinear damping model and the resonant stress and location is determined. The Fracture Mechanics approach is used to estimate the crack propagation life of the blade.

Design and structural performance measurements of a novel multi-cantilever foil bearing

2014 ◽  
Vol 229 (10) ◽  
pp. 1830-1838 ◽  
Author(s):  
Kai Feng ◽  
Xueyuan Zhao ◽  
Zhiyang Guo
Keyword(s):  
Dynamic Characteristics ◽  
Dynamic Load ◽  
Dynamic Stiffness ◽  
Excitation Frequency ◽  
Viscous Damping ◽  
Equivalent Viscous Damping ◽  
Foil Bearing ◽  
Load Tests ◽  
Stiffness And Damping ◽  
Motion Amplitude

With increasing need for high-speed, high-temperature, and oil-free turbomachinery, gas foil bearings (GFBs) have been considered to be the best substitutes for traditional oil-lubricated bearings. A multi-cantilever foil bearing (MCFB), a novel GFB with multi-cantilever foil strips serving as the compliant underlying structure, was designed, fabricated, and tested. A series of static and dynamic load tests were conducted to measure the structural stiffness and equivalent viscous damping of the prototype MCFB. Experiments of static load versus deflection showed that the proposed bearing has a large mechanical energy dissipation capability and a pronounced nonlinear static stiffness that can prevents overly large motion amplitude of journal. Dynamic load tests evaluated the influence of motion amplitude, loading orientation and misalignment on the dynamic stiffness and equivalent viscous damping with respect to excitation frequency. The test results demonstrated that the dynamic stiffness and damping are strongly dependent on the excitation frequency. Three motion amplitudes were applied to the bearing housing to investigate the effects of motion amplitude on the dynamic characteristics. It is noted that the bearing dynamic stiffness and damping decreases with incrementally increasing motion amplitudes. A high level of misalignment can lead to larger static and dynamic bearing stiffness as well as to larger equivalent viscous damping. With dynamic loads applied to two orientations in the bearing midplane separately, the dynamic stiffness increases rapidly and the equivalent viscous damping declines slightly. These results indicate that the loading orientation is a non-negligible factor on the dynamic characteristics of MCFBs.

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