scholarly journals Verification of a Stiffness-Variable Control System with Feed-Forward Predictive Earthquake Energy Analysis

Sensors ◽  
2021 ◽  
Vol 21 (22) ◽  
pp. 7764
Author(s):  
Tzu-Kang Lin ◽  
Tappiti Chandrasekhara ◽  
Zheng-Jia Liu ◽  
Ko-Yi Chen
Keyword(s):  
Energy Analysis ◽  
Seismic Velocity ◽  
Shaking Table ◽  
Velocity Spectrum ◽  
Far Field ◽  
Feed Forward ◽  
Earthquake Energy ◽  
Isolation Layer ◽  
Near Fault ◽  
Structural Responses

Semi-active isolation systems with controllable stiffness have been widely developed in the field of seismic mitigation. Most systems with controllable stiffness perform more robustly and effectively for far-field earthquakes than for near-fault earthquakes. Consequently, a comprehensive system that provides comparable reductions in seismic responses to both near-fault and far-field excitations is required. In this regard, a new algorithm called Feed-Forward Predictive Earthquake Energy Analysis (FPEEA) is proposed to identify the ground motion characteristics of and reduce the structural responses to earthquakes. The energy distribution of the seismic velocity spectrum is considered, and the balance between the kinetic energy and potential energy is optimized to reduce the seismic energy. To demonstrate the performance of the FPEEA algorithm, a two-degree-of-freedom structure was used as the benchmark in the numerical simulation. The peak structural responses under two near-fault and far-field earthquakes of different earthquake intensities were simulated. The isolation layer displacement was suppressed most by the FPEEA, which outperformed the other three control methods. Moreover, superior control on superstructure acceleration was also supported by the FPEEA. Experimental verification was then conducted with shaking table test, and the satisfactory performance of the FPEEA on both isolation layer displacement and superstructure acceleration was demonstrated again. In summary, the proposed FPEEA has potential for practical application to unexpected near-fault and far-field earthquakes.

Seismic Performance of Guideway Sliding Isolator with Gap Springs for Precision Machinery

2008 ◽  
Vol 11 (5) ◽  
pp. 511-524
Author(s):  
George C. Yao ◽  
Wen-Chun Huang ◽  
Fan-Ru Lin
Keyword(s):  
Shaking Table Test ◽  
Model Simulation ◽  
Shaking Table ◽  
Viscous Damping ◽  
Far Field ◽  
Seismic Excitations ◽  
Isolation System ◽  
Near Fault ◽  
Seismic Motion ◽  
Nonlinear Performance

The performance of gap springs in a guideway sliding isolator (GSI) system developed to protect precision machinery against seismic motion has been studied. A spring is initially distanced from the system by a gap, causing the isolation system to exhibit nonlinear performance once the gap is closed, reducing the chance of resonance. A full-scale shaking table test of a 22-ton specimen and a numerical model simulation in SAP2000 have been performed. The study shows that springs possessing the appropriate gaps are more effective in controlling relative displacements than is a pure friction system. The optimal gap for a system subjected to far-field earthquakes was found to be 5mm. In addition, supplemental viscous damping of less than 15% of the critical damping had no significant effect on the GSI system far-field seismic response, but it did reduce the relative displacements of the system for near-fault seismic excitations.

scholarly journals Dynamic Response of a Combined Isolation Based Mega-Substructure under Bidirectional Near-Fault Ground Motions

2018 ◽  
Vol 2018 ◽  
pp. 1-15
Author(s):  
Xueyuan Yan ◽  
Weihong Chen ◽  
Shen Shi ◽  
Xuan Wang
Keyword(s):  
Seismic Response ◽  
Seismic Isolation ◽  
Control Method ◽  
Ground Motions ◽  
Vibration Reduction ◽  
Shaking Table ◽  
Main Body ◽  
Isolation Layer ◽  
Near Fault ◽  
Model Structures

A typical megaframe structure has a high lateral stiffness and is excellent for high-rise structures. However, this high stiffness can lead to poor seismic response of a structure. Seismic isolation technology is a mature and cheap vibration control method that is used for vibration reduction in megaframes. This paper introduces a megaframe structure based on substructure combined isolation. The structure consists of two parts. The main body is a megaframe, and the substructure is the subframe with the combined isolation layer arranged at the bottom of the subframe. The seismic performance of this structure system was evaluated by performing shaking table tests of two megaframe model structures. The responses of the deformation, acceleration, and shear of the structure were measured. The dynamic behaviors of the structure with or without the combined isolation layer when exposed to single and bidirectional near-fault and far-fault ground motions with different peak values were investigated. The results showed that the combined isolation layer can reduce the bidirectional seismic response of the main frame and subframe. The acceleration, base shear, and displacement responses had similar vibration reduction trends for the two model structures, and the structural responses under bidirectional earthquake were generally greater than that under a single directional earthquake. The near-fault pulse effect increased the seismic response of the structure. The increase of the predominant period of ground motion also increased the seismic response of the structure.

Impact and Energy Analysis of Deformation-Limited Base-Isolated Structure in Shaking Table Test

2014 ◽  
Vol 638-640 ◽  
pp. 1811-1817 ◽  
Author(s):  
Hong Kai Du ◽  
Miao Han
Keyword(s):  
High Frequency ◽  
Energy Analysis ◽  
Shaking Table Test ◽  
Retaining Wall ◽  
Shaking Table ◽  
Original Design ◽  
Isolation Layer ◽  
Study Find ◽  
Total Energy Input ◽  
Limited Base

The deformation of isolation layer in base-isolated building can exceed original design during strong earthquake excitations, which will cause poundings between structure and surrounding retaining wall. Spring limiter installed in base-isolated building can protect the structure. Shaking table test of base-isolated model pounding with spring limiters were performed. The study find the deformation of isolation layer can be effectively reduced by spring limiters, and the deformation of the superstructure will increase slightly. Pounding between structure and spring limiters can arouse high frequency acceleration of building, but had little effect on velocity.Increasing the spring limiters will not change seismic total energy input on the structure, and most of the energy dissipate by the damping. Impact energy dissipation increases with reducing in the gap between structure and spring limiters.

scholarly journals Seismic Response of RC Frames with a Soft First Story Retrofitted with Hysteretic Dampers under Near-Fault Earthquakes

2021 ◽  
Vol 11 (3) ◽  
pp. 1290
Author(s):  
Santiago Mota-Páez ◽  
David Escolano-Margarit ◽  
Amadeo Benavent-Climent
Keyword(s):  
Cost Effective ◽  
Far Field ◽  
Soft Story ◽  
Near Fault ◽  
Rc Frames ◽  
Story Drift ◽  
Number Of Cycles ◽  
Rc Frame Structures ◽  
Near Fault Earthquakes ◽  
Hysteretic Dampers

Reinforced concrete (RC) frame structures with open first stories and masonry infill walls at the upper stories are very common in seismic areas. Under strong earthquakes, most of the energy dissipation demand imposed by the earthquake concentrates in the first story, and this eventually leads the building to collapse. A very efficient and cost-effective solution for the seismic upgrading of this type of structure consists of installing hysteretic dampers in the first story. This paper investigates the response of RC soft-story frames retrofitted with hysteretic dampers subjected to near-fault ground motions in terms of maximum displacements and lateral seismic forces and compares them with those obtained by far-field earthquakes. It is found that for similar levels of total seismic input energy, the maximum displacements in the first story caused by near-fault earthquakes are about 1.3 times larger than those under far-field earthquakes, while the maximum inter-story drift in the upper stories and the distribution and values of the lateral forces are scarcely affected. It is concluded that the maximum displacements can be easily predicted from the energy balance of the structure by using appropriate values for the parameter that reflects the influence of the impulsivity of the ground motion: the so-called equivalent number of cycles.

scholarly journals Structural and Acoustic Responses of a Submerged Stiffened Conical Shell

2014 ◽  
Vol 2014 ◽  
pp. 1-14 ◽  
Author(s):  
Meixia Chen ◽  
Cong Zhang ◽  
Xiangfan Tao ◽  
Naiqi Deng
Keyword(s):  
Conical Shell ◽  
Element Model ◽  
Analytical Models ◽  
Superposition Method ◽  
Far Field ◽  
Fluid Loading ◽  
Low Frequencies ◽  
Structural Responses ◽  
The Individual ◽  
Field Sound

This paper studies the vibrational behavior and far-field sound radiation of a submerged stiffened conical shell at low frequencies. The solution for the dynamic response of the conical shell is presented in the form of a power series. A smeared approach is used to model the ring stiffeners. Fluid loading is taken into account by dividing the conical shell into narrow strips which are considered to be local cylindrical shells. The far-field sound pressure is solved by the Element Radiation Superposition Method. Excitations in two directions are considered to simulate the loading on the surface of the conical shell. These excitations are applied along the generator and normal to the surface of the conical shell. The contributions from the individual circumferential modes on the structural responses of the conical shell are studied. The effects of the external fluid loading and stiffeners are discussed. The results from the analytical models are validated by numerical results from a fully coupled finite element/boundary element model.

Shaking Table Test Study on Mid-Story Isolation Structures

2012 ◽  
Vol 446-449 ◽  
pp. 378-381
Author(s):  
Jian Min Jin ◽  
Ping Tan ◽  
Fu Lin Zhou ◽  
Yu Hong Ma ◽  
Chao Yong Shen
Keyword(s):  
Seismic Response ◽  
Seismic Isolation ◽  
Shaking Table Test ◽  
Base Isolation ◽  
Shaking Table ◽  
Natural Period ◽  
Isolation System ◽  
Isolation Layer ◽  
Lead Rubber Bearing ◽  
Complex Structural

Mid-story isolation structure is developing from base isolation structures. As a complex structural system, the work mechanism of base isolation structure is not entirely appropriate for mid-story isolation structure, and the prolonging of structural natural period may not be able to decrease the seismic response of substructure and superstructure simultaneously. In this paper, for a four-story steel frame model, whose prototype first natural period is about 1s without seismic isolation design, the seismic responses and isolation effectiveness of mid-story isolation system with lead rubber bearing are studied experimentally by changing the location of isolation layer. Respectively, the locations of isolation layer are set at bottom of the first story, top of the first story, top of the second story and top of the third story. The results show that mid-story isolation can reduce seismic response in general, and substructure acceleration may be amplified.

scholarly journals Seismic Fragility Analysis of Mid-Story Isolation Buildings

2021 ◽  
Keyword(s):  
Fragility Curves ◽  
Ground Motions ◽  
Near Field ◽  
Fragility Analysis ◽  
Seismic Fragility ◽  
Plastic State ◽  
Far Field ◽  
Analysis Method ◽  
Isolation System ◽  
Isolation Layer

Abstract. Seismic fragility analysis is essential for seismic risk assessment of structures. This study focuses on the damage probability assessment of the mid-story isolation buildings with different locations of the isolation system. To this end, the performance-based fragility analysis method of the mid-story isolation system is proposed, adopting the maximum story drifts of structures above and below the isolation layer and displacement of the isolation layer as performance indicators. Then, the entire process of the mid-story isolation system, from the initial elastic state to the elastic-plastic state, then to the limit state, is simulated on the basis of the incremental dynamic analysis method. Seismic fragility curves are obtained for mid-story isolation buildings with different locations of the isolation layer, each with fragility curves for near-field and far-field ground motions, respectively. The results indicate that the seismic fragility probability subjected to the near-field ground motions is much greater than those subjected to the far-field ground motions. In addition, with the increase of the location of the isolation layer, the dominant components for the failure of mid-story isolated structures change from superstructure and isolation system to substructure and isolation system.

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