Lead core heating in lead rubber bearings subjected to bidirectional ground motion excitations in various soil types

2013 ◽  
Vol 43 (2) ◽  
pp. 267-285 ◽  
Author(s):  
Gokhan Ozdemir
Keyword(s):  
Ground Motion ◽  
Soil Types ◽  
Lead Rubber Bearings ◽  
Rubber Bearings

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.

ON THE VARIATION OF MAXIMUM ISOLATOR DISPLACEMENTS DUE TO GROUND MOTION DIRECTIONALITY

2016 ◽  
Vol 3 (1) ◽  
Author(s):  
Gökhan Özdemir ◽  
Burak Erşeker ◽  
Özgür Avşar
Keyword(s):  
Ground Motion ◽  
Nonlinear Response ◽  
Ground Motions ◽  
Original Form ◽  
Motion Direction ◽  
Applied Loading ◽  
Lead Rubber Bearings ◽  
Motion Directionality ◽  
Rubber Bearings ◽  
Ground Motion Records

In most of the cases, code specifications dictate the use of nonlinear response history analyses (NRHA) to estimate maximum isolator displacements (MIDs) of a seismically isolated structure (SIS). For this purpose, a set of ground motion records with similar characteristics needs to be selected. Then, the structure is analyzed bidirectionally by considering both orthogonal horizontal components of these records. However, there is not any provision regarding the ground motion directionality effect in the codes but simply use of as-recorded motions is encouraged. This study investigates the effect of ground motion directionality on variation of MIDs in case of bidirectional NRHA. Thus, a typical SIS, where the isolator units are composed of lead rubber bearings (LRBs), is subjected to ground motions rotated from their as-recorded original form by increments of 10o up to 360o. Here, LRBs are modelled by a deteriorating hysteretic representation in which the strength of the isolator reduces gradually due to the applied loading. In the analyses, first, the original as-recorded ground motion is applied to the SIS and the corresponding MID is noted. Then, the same structure is subjected to rotated versions of the same motion and again the MIDs are noted. To quantify the variation in the isolator displacement, analytically obtained MIDs are compared. Results showed that there is an amplification in MIDs due to change in ground motion direction.

A new concept of isolation bearings for highway steel bridges using shape memory alloys

2005 ◽  
Vol 32 (5) ◽  
pp. 957-967 ◽  
Author(s):  
Eunsoo Choi ◽  
Tae-hyun Nam ◽  
Baik-Soon Cho
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Ground Motion ◽  
Residual Deformation ◽  
Steel Bridge ◽  
Ground Acceleration ◽  
Lead Rubber Bearings ◽  
Rubber Bearings ◽  
Isolation Device ◽  
Strong Ground

Conventional lead–rubber bearings (LRB) may have a problem of instability and unrecovered deformation with a strong ground motion. To improve the problems, this study proposed a new concept of an isolation device in which shape memory alloy wires were incorporated in an elastomeric bearing. This study illustrated the behavior of shape memory alloy in tension and discussed the variation of stiffness and stress on the hyteresis curves. A three-span continuous steel bridge was used for seismic analyses to compare the performance of lead–rubber bearings with the proposed bearings. This study showed that large residual deformation of LRB occurred even with a weak ground motion of peak ground acceleration (PGA) of 0.2g. The proposed bearings effectively limited the relative displacement of the deck when tested for the strong ground motions and almost recovered the original undeformed shape. However, the proposed bearing increases the demand on bridge columns compared with the LRB.Key words: shape memory alloy, lead–rubber bearings, seismic bridge analysis, isolation device, residual deformation.

An Investigation of Adaptive Rubber Bearings

2016 ◽  
Author(s):  
C. S. Tsai ◽  
Hui-Chen Su ◽  
Wen-Chun Huang
Keyword(s):  
Yield Strength ◽  
Lower Yield ◽  
Passive Devices ◽  
Major Benefit ◽  
Lead Rubber Bearings ◽  
Lower Yield Strength ◽  
Multiple Levels ◽  
Materials Used ◽  
Rubber Bearings ◽  
Stiffness And Damping

Proposed in this study are several innovative seismic isolators composed of rubber materials that are called adaptive rubber bearings based on their adaptive characteristics. The materials used in the proposed isolators are free of lead commonly found in lead rubber bearings. The lead material results in a heavy environmental burden as well as lower yield strength and damping due to rising temperature during earthquakes, and thus causes larger displacements than we would expect. The designed mechanisms in the proposed isolators enable these devices to be manufactured relatively easily. They also provide extremely high damping to bearings, which is strongly desired by engineers in practice. The proposed rubber bearings are completely passive devices yet possess adaptive stiffness and adaptive high damping. The change in stiffness and damping is predictable and can be calculated at specifiable and controllable displacement amplitudes. The major benefit of the adaptive characteristics of seismic isolators is that a given system can be optimized separately for multiple performance objects at multiple levels of earthquakes. In this study, mathematical formulations are derived to explain the mechanisms of the proposed devices. Experimental results of high velocity cyclical loadings are also provided to verify the advanced concepts of the proposed devices.

Effects of Heating on the Behavior of Lead-Rubber Bearings. I: Theory

2009 ◽  
Vol 135 (12) ◽  
pp. 1440-1449 ◽  
Author(s):  
Ioannis V. Kalpakidis ◽  
Michael C. Constantinou
Keyword(s):  
Lead Rubber Bearings ◽  
Rubber Bearings

Modeling of Lead Rubber Bearings under Large Cyclic Material Strains

2021 ◽  
Vol 147 (11) ◽  
pp. 04021170
Author(s):  
J. F. Marquez ◽  
G. Mosqueda ◽  
M. K. Kim
Keyword(s):  
Lead Rubber Bearings ◽  
Rubber Bearings

scholarly journals Predicting Maximum and Cumulative Response of A Base-isolated Building Using Pushover Analysis

Buildings ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 91
Author(s):  
Kenji Fujii ◽  
Yoshiyuki Mogi ◽  
Takumi Noguchi
Keyword(s):  
Seismic Design ◽  
Pushover Analysis ◽  
Analysis Method ◽  
Single Degree Of Freedom ◽  
Local Responses ◽  
Single Degree ◽  
Cumulative Response ◽  
Cumulative Strain ◽  
Lead Rubber Bearings ◽  
Rubber Bearings

The evaluation of the maximum and cumulative response is an important issue for the seismic design of new base-isolated buildings. This study predicts the maximum and cumulative response of a 14-story reinforced concrete base-isolated building using a set of pushover analyses. In the proposed pushover analysis method, the maximum and cumulative responses of the first and higher modes are evaluated from the nonlinear analysis of equivalent single-degree-of-freedom (SDOF) models. Then, the maximum local responses are predicted by enveloping the two pushover analysis results by referring to the contribution of the first and higher modal responses, while the cumulative strain energies of the lead-rubber bearings and steel dampers are predicted from the cumulative response of the first mode. The results reveal that the responses predicted by the proposed set of pushover analyses have satisfactory accuracy.

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