scholarly journals Effect of a Near Fault on the Seismic Response of a Base-Isolated Structure with a Soft Storey

2017 ◽  
Vol 25 (4) ◽  
pp. 34-46
Author(s):  
B. Athamnia ◽  
A. Ounis ◽  
M. Abdeddaim
Keyword(s):  
Seismic Isolation ◽  
Seismic Analysis ◽  
Time History ◽  
Nonlinear Time History Analysis ◽  
Base Shear ◽  
Rc Structures ◽  
Soft Storey ◽  
Near Fault ◽  
Nonlinear Time History ◽  
Far Fault

AbstractThis study focuses on the soft-storey behavior of RC structures with lead core rubber bearing (LRB) isolation systems under near and far-fault motions. Under near-fault ground motions, seismic isolation devices might perform poorly because of large isolator displacements caused by large velocity and displacement pulses associated with such strong motions. In this study, four different structural models have been designed to study the effect of soft-storey behavior under near-fault and far-fault motions. The seismic analysis for isolated reinforced concrete buildings is carried out using a nonlinear time history analysis method. Inter-story drifts, absolute acceleration, displacement, base shear forces, hysteretic loops and the distribution of plastic hinges are examined as a result of the analysis. These results show that the performance of a base isolated RC structure is more affected by increasing the height of a story under nearfault motion than under far-fault motion.

scholarly journals Comparison and analysis of seismic isolation, energy dissipation structure and traditional seismic structure

2021 ◽  
Vol 248 ◽  
pp. 01001
Author(s):  
Shu-jiang Jiang ◽  
Shun-zhong Yao ◽  
De-wen Liu
Keyword(s):  
Seismic Isolation ◽  
Time History ◽  
Nonlinear Time History Analysis ◽  
Seismic Structure ◽  
Base Shear ◽  
Finite Element Software ◽  
History Analysis ◽  
Rare Earthquake ◽  
Nonlinear Time History ◽  
The Impact

This paper uses SAP2000 finite element software to perform nonlinear time history analysis of nine structural systems, and compares the period, total floor displacement, base shear force, vertex displacement, and top acceleration of the structure under the action of an 8-degree rare earthquake. The research results show that seismic isolation and damping technology can effectively reduce the impact of earthquakes on structures.

Sensitivity analysis of the influence of ground motion intensity levels on the seismic behavior of steel frames in assessment of the target displacement considering near-fault effects

2020 ◽  
Vol 47 (4) ◽  
pp. 470-486
Author(s):  
Alireza Esfahanian ◽  
Ali Akbar Aghakouchak
Keyword(s):  
Ground Motions ◽  
Steel Frames ◽  
Time History ◽  
Time History Analysis ◽  
Nonlinear Time History Analysis ◽  
Seismic Demands ◽  
Near Fault ◽  
History Analysis ◽  
Nonlinear Time History ◽  
Far Fault

Nonlinear time-history analysis conducted as part of a performance-based seismic design approach often require that the ground motion records are selected and then scaled to a specified level of seismic intensity. In such analyses, besides an adequate structural model, a set of acceleration time-series is needed as the most realistic representation of the seismic action. In this paper, the effects of scaling procedure on seismic demands of steel frames are investigated. To this, two special steel moment-resisting frames with considerable higher mode effects, and two sets of ground motions, including near-fault and far-fault motions are considered. Moreover, three scaling procedures are introduced for performing nonlinear dynamic time-history analysis of structures. Among different demands, lateral roof displacement and interstory drift are selected as seismic demands. The height-wise distribution of demands shows that the inelastic seismic demands of the near-fault pulse-like ground motions differ considerably from those of far-fault ones. These results show that the story drifts are mostly larger for far-fault motions in the upper story levels in comparison to near-fault records and in the lower floors, the reverse is true. Thus, the scaling procedures directly affect the results of seismic demands and choosing different methods would result in varying responses. Moreover, a low-cost and fairly effective procedure is proposed to estimate the target displacement demands of buildings from response-spectrum analyses, considering near-fault effects. The precision of this method is verified by nonlinear time-history analysis results, as the benchmark solution, and acceptable improvements have been achieved.

scholarly journals FRP Composite in Mitigating Seismic Risk of RC Structures in Near-Fault Regions with/without Aftershocks

2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Vui Van Cao ◽  
Son Quang Pham
Keyword(s):  
Plastic Hinge ◽  
Time History ◽  
Damage State ◽  
Rc Structures ◽  
Seismic Sequences ◽  
Near Fault ◽  
Damage Indices ◽  
Aftershock Sequences ◽  
Nonlinear Time History ◽  
Original Frame

The literature related to earthquakes and fibre reinforced polymer (FRP) retrofitting can be divided into two main categories: (1) the applications of FRP to retrofit structures subjected to single traditional earthquakes and (2) the effects of mainshock-aftershock sequences on original structures (without FRP retrofitting). Research on using FRP to mitigate the risk of pulse-type mainshock-aftershock sequences for reinforced concrete (RC) structures located in near-fault regions is hardly found in the literature and is thus the aim of this study. To achieve this aim, a four-storey RC frame, near-fault mainshocks, and seismic sequences were selected. The frame was retrofitted using FRP wraps at plastic hinge locations. Nonlinear time history and damage analyses of the original and FRP-retrofitted frames subjected to these near-fault mainshocks and seismic sequences were conducted. The results showed that aftershocks significantly increase the damage indices of the frames, shifting the damage state of the original frame from severe damage to collapse and the damage state of the FRP-retrofitted frame from light damage to moderate damage. FRP retrofitting successfully reduced the risk of seismic sequences by reducing the damage two levels, shifting the damage state of the original frame from collapse to moderate damage.

The Longitudinal Seismic Analysis of Single-Story and Single-Span Gabled Frame Structures

2015 ◽  
Vol 744-746 ◽  
pp. 335-339
Author(s):  
Hong Dong Ran ◽  
Le Chen ◽  
Yun Mei Ma
Keyword(s):  
Seismic Analysis ◽  
Time History ◽  
Steel Structure ◽  
National Standard ◽  
Nonlinear Time History Analysis ◽  
Frame Structures ◽  
Seismic Action ◽  
Light Weight ◽  
Standard Design ◽  
Nonlinear Time History

Four single-story single-span Gabled Frame Structures (GFSs) which included in China national Standard Design Drawing of Light-weight Steel Structure with Gabled Frame (02SG518-1) were studied and their longitudinal seismic performances were evaluated through extensive nonlinear time-history analysis using eight ground motions representing the Frequent Earthquake, DBE and the MCE hazard levels, the load-bearing performances, deformation capacities and the curves of displacement were studied. The analysis results showed that the longitudinal seismic action of all GFSs considered in this study is very little, the displacement at the top of the column can satisfy the demands of the Technical Specificationfor Steel Structure of Light-weight Building with Gabled Frames even in MCE. The GFSs designed followed the Specificaiton have the excellent longitudinal seismic performance.

Seismic Isolation Retrofit of an Office Building Using Friction Pendulum System

2014 ◽  
Vol 578-579 ◽  
pp. 1361-1365
Author(s):  
Lin Liu ◽  
Xuan Min Li ◽  
Wei Tian
Keyword(s):  
Seismic Isolation ◽  
Base Isolation ◽  
Time History ◽  
Nonlinear Behavior ◽  
Office Building ◽  
Nonlinear Time History Analysis ◽  
Isolation System ◽  
Pendulum System ◽  
Nonlinear Time History ◽  
Friction Pendulum

Friction Pendulum Systems have been used as base isolation systems for both new construction and retrofit around the world. This paper presented its implementation in an office building located in Shanghai. To evaluate its impact on seismic performance of the retrofitted structure, models are needed to capture the intricate nonlinear behavior of both structural components and isolator elements. Nonlinear time history analysis of the building for the original and retrofitted cases was conducted to assess the efficiency of the isolation system at the high earthquake level. The numerical results indicate that the retrofitted structure experiences significantly less damage and less deformation due to the shake isolation and energy dissipation through the isolators.

scholarly journals Isolating system using U Shaped steel damper

2021 ◽  
Vol 309 ◽  
pp. 01136
Author(s):  
Siripuram Vamshisheela ◽  
Atulkumar Manchalwar
Keyword(s):  
Base Isolation ◽  
Ground Motions ◽  
Time History ◽  
Nonlinear Time History Analysis ◽  
Base Shear ◽  
Energy Device ◽  
History Analysis ◽  
Structural Responses ◽  
Nonlinear Time History ◽  
Story Building

In this work the performance of U-Shaped Steel Isolator is evaluated for a 5-story building subjected to seismic and blast vibrations. The structure is analysed using SAP 2000 software and a nonlinear time history analysis is carried out. The effectiveness of using base isolation is studied by comparing the structural responses of the building with isolator and without isolator and noticeable difference was observed. As the U-Shaped isolator absorbs the energy in all directions, it effectively controls the structural responses. In this study, the building is subjected to four different seismic and four different blast induced ground motions. It was observed that by the use of supplementary energy device there is reduction in top story acceleration, base shear and less deformation in the structure. This study concludes that the use of isolator has been effective in minimizing structural responses.

Study on Methods for HCLPF Value of Nonlinear Supports System of Steam Generator

2018 ◽  
Author(s):  
Feng-chun Cai ◽  
Xian-hui Ye ◽  
Qian Huang ◽  
Wenzheng Zhang
Keyword(s):  
Steam Generator ◽  
Nonlinear Model ◽  
Seismic Analysis ◽  
Time History ◽  
Nonlinear Time History Analysis ◽  
Cost Calculation ◽  
Seismic Capacity ◽  
Ground Acceleration ◽  
Reactor Building ◽  
Nonlinear Time History

High confidence of low probability of failure (HCLPF) values of equipment, representing the seismic capacities of the equipment, are the fundamental ingredient in seismic probability safety assessment (SPSA) and seismic margin analyses (SMA). In this paper, two methods for calculating the HCLPF values of equipment were investigated, fragility analysis, and conservative deterministic failure margin (CDFM). These methods are linear methods. Based on these methods, HCLPF value of equipment can be computed conveniently by scaling the results of the existing seismic analysis. For a nonlinear systems, the HCLPF values based on these linear scaling methods are unrealistic. For a complicated nonlinear equipment or structure, a detail nonlinear model was used to derive the seismic capacity. The results by this method are realistic, but cost calculation time. In this paper, a nonlinear model of reactor coolant system coupled reactor building was built. This model includes the steam generator and considers the nonlinear factors of steam generator such as gap in the supports, plasticity of hot leg and cold leg. Forced motion was applied to the base of reactor building. And seismic response of the steam generator was calculated iteratively by scaling the ground motion level step by step. Based on these calculations, a curve of load on the supports VS peak ground acceleration (PGA) can be obtained. Then based on these curves and allowable load of supports of steam generator, which derived from stress analysis on support of steam generator, seismic capacity of the supports of steam generator was determined. Then the HCLPF Value of the supports of steam generator was obtained by this nonlinear time history analysis and was compared with the results based on the CDFM. The two results were different. Therefore, the HCLPF seismic capacity of equipment with nonlinearity, such as gap nonlinearity, should be calculated by nonlinear time history method.

scholarly journals Seismic Design of Bridges against Near-Fault Ground Motions Using Combined Seismic Isolation and Restraining Systems of LRBs and CDRs

2019 ◽  
Vol 2019 ◽  
pp. 1-11
Author(s):  
Xiaoli Li ◽  
Yan Shi
Keyword(s):  
Control System ◽  
Seismic Design ◽  
High Intensity ◽  
Seismic Isolation ◽  
Ground Motions ◽  
Time History ◽  
Nonlinear Time History Analysis ◽  
Near Fault ◽  
Combined Control ◽  
Quantitative Design

This paper focuses on the seismic isolation design of near-fault bridges under the seismic excitations of near-fault ground motions in high-intensity earthquake zones and proposes a combined control system using lead rubber bearings (LRBs) and cable displacement restrainers (CDRs) along with ductility seismic resistance for the reinforced concrete piers. As part of the performance-based seismic design framework, this study provides the quantitative design criteria for multilevel performance-based objectives of a combined control system under conditions of frequent earthquake (E1), design earthquake (medium earthquake), and rare earthquake (E2). Moreover, in this study, a preliminary performance-based seismic isolation design for a near-fault actual highway bridge in high-intensity earthquake zones (basic peak of ground acceleration 0.4 g) was developed. Using nonlinear time-history analysis of the actual bridge under near-fault ground motions, the feasibility of a performance-based design method was validated. Furthermore, to ensure the predicted performance of the isolated bridges during a strong earthquake, a relatively quantitative design in structural details derived from the stirrup ratio of piers, expansion joints gap, supported length of capping beams, and limited vertical displacement response was obtained.

scholarly journals Mitigation of Seismic Risks to Soft-Storey Structures Using Toggle-Brace-Damper Systems

2012 ◽  
Vol 238 ◽  
pp. 833-837 ◽  
Author(s):  
Ricky W.K. Chan ◽  
Zhe Fei Zhao
Keyword(s):  
Time History ◽  
Ground Level ◽  
Nonlinear Time History Analysis ◽  
Lateral Stiffness ◽  
Governing Equations ◽  
Magnification Factor ◽  
Soft Storey ◽  
History Analysis ◽  
Nonlinear Time History ◽  
Sudden Reduction

Soft-storey mechanism is characterized by a sudden reduction of lateral stiffness in one or more levels of a structure. Soft-storey is often observed in the ground level due to the absence of wall or cladding. With recent develop of energy dissipation systems, soft-storey mechanism can be corrected by addition of a damper-brace assembly. In particular, this paper investigates the effect of toggle-damper-brace systems on such situations. Governing equations including the magnification factor and lateral stiffness contributed by a toggle-damper-brace are formulated. It was found that a toggle-damper-brace system, if proportioned correctly, will significantly increase the travel in the damper and overall stiffness of structure can be enhanced. An illustrative example is presented using nonlinear time history analysis implemented on MATLAB.

Evaluation of Seismic Behavior on Steel Frames with TSW Semi-Rigid Connections under the Nonlinear Time History Analysis

2012 ◽  
Vol 166-169 ◽  
pp. 2083-2087
Author(s):  
Miaad Najdian ◽  
Mohsen Izadinia
Keyword(s):  
Time History ◽  
High Energy ◽  
Time History Analysis ◽  
Nonlinear Time History Analysis ◽  
Near Fault ◽  
Good Ability ◽  
History Analysis ◽  
Ductile Behavior ◽  
Near Fault Earthquakes ◽  
Nonlinear Time History

Movements of pulse shape and the high energy applied in short duration by the near fault earthquake, causes brittle fracture in rigid connections that during the Northridge 1994 and Kobe 1995 earthquakes was frequently seen. Rigid connections, which are generally welded due to lack of ductility, have low energy absorption capability. On the other hand semi-rigid connections have a ductile behavior and have a good ability to absorb energy. The purpose of this paper is analysis and compares the behaviors of “rigid” and “TSW semi-rigid” connections under the near fault earthquakes with nonlinear time history analysis by perform 3D software.

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