scholarly journals Optimum parameters of a five-story building supported by lead-rubber bearings under near-fault ground motions

2019 ◽  
Vol 39 (1) ◽  
pp. 98-113 ◽  
Author(s):  
Qiang Rong
Keyword(s):  
Ground Motions ◽  
Isolation System ◽  
Optimum Yield ◽  
Shear Coefficient ◽  
Near Fault ◽  
Optimum Parameters ◽  
Yield Displacement ◽  
Lead Rubber Bearings ◽  
Rubber Bearings ◽  
Isolation Period

Seismic response of five-story frame structure supported by lead-rubber bearings isolation system is investigated subjected to near-fault ground motions. The main structure is modeled as a simple linear multi-degrees-of-freedom vibration system with lumped masses, excited by near-fault ground motions in the horizontal direction. The variation curves of peak top floor acceleration and peak bearing displacement of isolated building are plotted under different yield shear coefficient. The objective function selected for optimality is to maximize the seismic energy dissipated by the lead-rubber bearings. The main constraint conditions selected for optimality are the minimization of both peak bearing displacement and peak top floor acceleration. Optimum parameters of lead-rubber bearing isolation system are investigated and found that optimum yield shear coefficient of lead-rubber bearings is found to be in the range of 0.10–0.14 under near-fault ground motions. Optimum yield shear coefficient decreases with the increase of second isolation period. Optimum yield shear coefficient of lead-rubber bearings with higher yield displacement is larger than that of lead-rubber bearings with low yield displacement. Optimum ratio of pre-yield stiffness to post-yield stiffness of lead-rubber bearings is found to be in the range of 16–35. Optimum stiffness ratio increases proportionally with the decrease of yield displacement. Optimum stiffness ratio increases slightly with the increase of yield shear coefficient. Excluding the effect of pre-yield stiffness, the optimum second isolation period is recommended to be in the range of 4–6 s.

Performance of bi-directional elliptical rolling rods for base isolation of buildings under near-fault earthquakes

2017 ◽  
Vol 21 (5) ◽  
pp. 675-693 ◽  
Author(s):  
Aruna Rawat ◽  
Naseef Ummer ◽  
Vasant Matsagar
Keyword(s):  
Base Isolation ◽  
Ground Motions ◽  
Frictional Resistance ◽  
Curved Surface ◽  
Isolation System ◽  
Near Fault ◽  
Earthquake Ground Motions ◽  
Base Isolation System ◽  
Near Fault Earthquakes ◽  
Storey Building

Rolling base isolation system provides effective isolation to the structures from seismic base excitations by virtue of its low frictional resistance. Herein, dynamic analysis of flexible-shear type multi-storey building mounted on orthogonally placed elliptical rolling rod base isolation systems subjected to bi-directional components of near-fault earthquake ground motions is presented. The orthogonally placed rods would make it possible to resist the earthquake forces induced in the structure in both the horizontal directions. The curved surface of these elliptical rods has a self-restoring capability due to which the magnitude of peak isolator displacement and residual displacement is reduced. The roughness of the tempered curved surface of the rollers dissipates energy in motion due to frictional damping. The seismic performance of the multi-storey building mounted on the elliptical rolling rod base isolation system is compared with that mounted on the sliding pure-friction and cylindrical rolling rod systems. Parametric studies are conducted to examine the behavior of the building for different superstructure flexibilities, eccentricities of the elliptical rod, and coefficients of friction. It is concluded that the elliptical rolling rod base isolation system is effective in mitigation of damaging effects of the near-fault earthquake ground motions in the multi-storey buildings. Even under the near-fault earthquake ground motions, the base-isolated building mounted on the elliptical rolling rods shows considerable reduction in seismic response. The isolator displacement with the elliptical rolling rod base isolation system is less in comparison to the pure-friction and cylindrical rolling rod systems.

Parametric study of stochastic seismic responses of base-isolated liquid storage tanks under near-fault and far-fault ground motions

2016 ◽  
Vol 24 (24) ◽  
pp. 5747-5764 ◽  
Author(s):  
Sina Safari ◽  
Reza Tarinejad
Keyword(s):  
Base Isolation ◽  
Seismic Analysis ◽  
Ground Motions ◽  
Characteristic Parameter ◽  
Statistical Linearization ◽  
Storage Tanks ◽  
Earthquake Excitation ◽  
Isolation System ◽  
Near Fault ◽  
Liquid Storage

Seismic response of base isolated steel liquid storage tanks is investigated in this study by a stochastic approach in frequency domain. For the purpose of evaluating different frequency contents of seismic events on the responses of fixed and isolated tanks, the earthquake excitation is characterized by power spectral density function. Since earthquake is a random process, stochastic seismic analysis is used and root mean square response predicts behavior of system properly. Two types of isolation system are assumed and nonlinear behavior of base isolation systems are developed by an iterative statistical linearization scheme. The study demonstrates the influence of each characteristic parameter of the storage tanks and isolation system and also excitation features. It is confirmed that near-fault earthquake excitations amplify the overall response of the system. Base isolation is known as an effective technique to reduce responses appropriately. It is demonstrated that the sloshing responses of the tanks is significantly reduced by sliding bearing. Further, excitation parameters, PGV/PGA ratio of records and pulse period in near-fault ground motions, that represent differences in two sets of earthquakes are defined to recognize variation of responses.

Longitudinal seismic response control of long-span cable-stayed bridges using shape memory alloy wire-based lead rubber bearings under near-fault records

2017 ◽  
Vol 29 (5) ◽  
pp. 703-728 ◽  
Author(s):  
Shuai Li ◽  
Farshad Hedayati Dezfuli ◽  
Jing-quan Wang ◽  
M Shahria Alam
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Shape Memory Alloy Wire ◽  
Base Shear ◽  
Alloy Wire ◽  
Near Fault ◽  
Long Span ◽  
Lead Rubber Bearing ◽  
Lead Rubber Bearings ◽  
Rubber Bearings

This article investigates the efficiency of a new generation smart isolation system, namely shape memory alloy wire-based lead rubber bearing, for the seismic response control of long-span cable-stayed bridge systems under near-fault ground motions. The constitutive model of shape memory alloy wire-based lead rubber bearings is coded and implemented into OpenSees as a new user element. This user element can accurately predict the re-centering capability and energy dissipation capacity of shape memory alloy wire-based lead rubber bearing under different excitations. The Sutong cable-stayed bridge in China, with a main span of 1088 m, is taken as an example. Results reveal that implementing shape memory alloy wires into lead rubber bearings can effectively increase the self-centering property and, as a result, reduce the residual deformation in shape memory alloy wire-based lead rubber bearings under near-fault ground motions. Shape memory alloy wires lead to an increase in the horizontal stiffness and energy dissipation capacity of shape memory alloy wire-based lead rubber bearings. The deck displacement is restricted effectively, and a superior structural performance is achieved in terms of the deck acceleration. Shape memory alloy wire-based lead rubber bearings can effectively reduce the base shear and base moment of the towers. However, it is observed that an increase in the shape memory alloy wire diameter may have negligible effect on the deck acceleration, tower base shear and moment, and in some cases, on the pier base shear and moment.

scholarly journals Seismic Response of a Base Isolated Cable-Stayed Bridge Under Near-Fault Ground Motion Excitations

2018 ◽  
Vol 15 (1) ◽  
pp. 1-14
Author(s):  
Ahad Javanmardi ◽  
Zainab Ibrahim ◽  
Khaled Gheadi ◽  
Mohammed Jameel ◽  
Usman Hanif ◽  
...  
Keyword(s):  
Ground Motion ◽  
Ground Motions ◽  
Nonlinear Dynamic Analysis ◽  
Dynamic Responses ◽  
Base Shear ◽  
Seismic Behaviour ◽  
Isolation System ◽  
Near Fault ◽  
Cable Stayed Bridge ◽  
Near Fault Ground Motion

Nowadays, development of cable-stayed bridges is increasing around the world. The mitigation of seismic forces to these bridges are obligatory to prevent damages or failure of its structural members. Herein, this paper aimed to determine the near-fault ground motion effect on an existing cablestayed bridge equipped with lead-rubber bearing. In this context, Shipshaw cable-stayed bridge is selected as the case study. The selected bridge has a span of 183.2 m composite deck and 43 m height of steel tower. 2D finite element models of the non-isolated and base isolated bridges are modelled by using SAP2000. Three different near-fault ground motions which are Tabas 1978, Cape Mendocino 1992 and Kobe 1995 were subjected to the 2D FEM models in order to determine the seismic behaviour of the bridge. The near-fault ground motions were applied to the bridge in the longitudinal direction. Nonlinear dynamic analysis was performed to determine the dynamic responses of the bridge. Comparison of dynamic response of nonisolated and base isolated bridge under three different near-fault ground motions were conducted. The results obtained from numerical analyses of the bridge showed that the isolation system lengthened the period of bridge and minimised deck displacement, base shear and base moment of the bridge. It is concluded that the isolation system significantly reduced the destructive effects of near-fault ground motions on the bridge.

Investigations on a mega–sub isolation system under near-fault ground motions

2021 ◽  
pp. 136943322110262
Author(s):  
Xiangxiu Li ◽  
Ping Tan ◽  
Aiwen Liu ◽  
Xiaojun Li
Keyword(s):  
Failure Mechanism ◽  
Ground Motion ◽  
Failure Probability ◽  
Structural Parameters ◽  
Ground Motions ◽  
Damping Ratio ◽  
Correlation Coefficients ◽  
Isolation System ◽  
Isolation Layer ◽  
Near Fault

The failure mechanism of the mega–sub isolation system under near-fault ground motions is studied in this article. 90 suites of near-fault ground motions collected from 23 earthquakes are adopted to investigate the ground motion intensity indices applicable for the mega–sub isolation system. Then, the sensitivities of the stochastic responses to the structural parameters are analyzed to determine the representative random structural parameters. Furthermore, considering the uncertainties of ground motion characteristics and structural parameters, the seismic fragility is analyzed by the response surface method in order to obtain the failure mechanism of this system under near-fault ground motions. Results show that different intensity indices have various correlation coefficients with the peak responses of the mega–sub isolation system. The correlations of acceleration-related intensity indices are the worst, whereas the correlations of displacement-related intensity indices show high linearity. The sensitivities of the structural responses are weaker to the sub-structure story stiffness but more sensitive to the sub-structure story mass and the stiffness and damping ratio of the isolation layer. The failure probability of the sub-structure is higher than that of the mega-structure under near-fault ground motion. While in the collapse state, the failure probability of the isolation layer is greater than that of the sub-structure.

The Behavior of Bearings Used for Seismic Isolation under Rotation and Axial Load

1999 ◽  
Vol 15 (2) ◽  
pp. 225-244 ◽  
Author(s):  
Atsushi Mori ◽  
Peter J. Moss ◽  
Nigel Cooke ◽  
Athol J. Carr
Keyword(s):  
Seismic Isolation ◽  
Axial Loads ◽  
Isolation System ◽  
Elastomeric Bearings ◽  
Lead Rubber Bearings ◽  
Combined Action ◽  
Lift Off ◽  
Rubber Bearings ◽  
Bearing Behavior ◽  
Angle Of Rotation

The investigation described in this paper looked at both laminated elastomeric bearings and lead-rubber bearings in order to obtain a better understanding of the real bearing behavior under the combined action of rotation and axial loads when used in a seismic-isolation system. In particular, the investigation focused on the distributions of vertical pressure on the bearing faces and the degree of lift-off of the edges of the bearings as the angle of rotation increased.

Influence of Isolation Gap Size on the Collapse Performance of Seismically Base-Isolated Buildings

2013 ◽  
Vol 29 (4) ◽  
pp. 1477-1494 ◽  
Author(s):  
Zhe Qu ◽  
Shoichi Kishiki ◽  
Toshiyuki Nakazawa
Keyword(s):  
Seismic Performance ◽  
Potential Risk ◽  
Ground Motions ◽  
Retaining Walls ◽  
Incremental Dynamic Analysis ◽  
Far Field ◽  
Gap Size ◽  
Near Fault ◽  
Earthquake Ground Motions ◽  
Isolation Period

The pounding of retaining walls forms a potential risk of degrading the performance of seismically base-isolated buildings subjected to strong, especially near-fault, earthquake ground motions. Incremental dynamic analysis is employed to generate the so-called gap graph, in which two characteristic gap sizes of a base-isolated building are related with the isolation period of the building and the strengthof the superstructure. Thegapgraph canbe usedto evaluate the required gap size for a base-isolated building to have certain collapse performance. By means of gap graphs, the interdependent relations of gap size with other important factors that influence the seismic performance of the base-isolated building are examined. In particular, the results show that near-fault pulse-like ground motions are likely to impose much higher demand for the isolation gap than far-field ones.

Research on Isolated Strengthening of Erose School Buildings

2011 ◽  
Vol 94-96 ◽  
pp. 1298-1303
Author(s):  
Xi Sen Fan ◽  
Shu Zhen Ren
Keyword(s):  
Seismic Response ◽  
Masonry Structure ◽  
School Buildings ◽  
Isolation System ◽  
Torsional Response ◽  
Rubber Bearing ◽  
Lead Rubber Bearing ◽  
Lead Rubber Bearings ◽  
Rubber Bearings ◽  
Strengthening Technique

The aseismatic strengthening technique for masonry structure was researched in this paper. The seismic response of a L-type school building with and without isolation system were computed by using software SAP2000. The isolation system were made up of lead rubber bearings or combined Isolation system. The results showed that base-isolated strengthening can reduce not only the translational response but also the torsional response with earthquake. The combined Isolation system was more effetive in decreasing translational response than the lead rubber bearing, but inferior to in decreasing torsion response.

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