Mid-story Isolation Research Articles

Damping performance and optimal design of mid-story isolation system with tuned inerter damper

Damping performance and optimal design of mid-story isolation system with tuned inerter damper

Analysis of shock absorption performance of a new staggered story isolation structure under far-field long-period ground motions

The new staggered story isolation (NSSI) is a new type of isolation method developed based on base isolation (BI) and mid-story isolation (MSI). Different from ordinary ground motions, far-field long-period ground motions have the characteristics of long period, long duration, and rich low-frequency components, which will have adverse effects on structures with relatively large periods of isolation, which need to be discussed in depth. Based on this, this paper establishes a 16-story frame core tube structure, under rare earthquakes, adopts NSSI, and inputs 7 ordinary ground motions (OGM), 7 far-field anharmonic-like ground motions (FAGM), and 7 far-field harmonic-like ground motions (FHGM), the latter two are collectively referred to as far-field long-period ground motions (FLGM). The seismic response results are obtained through simulation, and the shock absorption performance is compared with non-isolated, BI, and MSI. Combined isolation is proposed, and its displacement-limiting effect under FLGM is discussed. The results show that the seismic responses of various structures under FLGM are much larger than those of OGM; the NSSI structure has better overall shock absorption performance and better safety performance under FLGM; The Combined isolation has a good displacement limiting effect under various ground motions, especially for FHGM, the displacement limiting effect is the best.

Study on Shock-Absorbing Effect of a Double-Story Isolation Structure Considering Soil–Structure Interaction

The double-story isolation structure is a novel development based on the mid-story isolation structure. To accurately reflect the seismic response of the double-story isolation structure, this study considers a dynamic elastoplastic analysis model that incorporates soil–structure interaction (SSI). Comparative models of a base-fixed structure and a mid-story isolation structure are also established. The results indicate that the double-story isolation structure has a longer structural period compared to the mid-story isolation structure. Furthermore, the structural period increases as the soil softens and the structure becomes more flexible. When considering SSI on hard soil versus not considering SSI, the double-story isolation structure exhibits smaller base shear, story force, inter-story displacement, maximum acceleration of the top floor, and displacement of the upper isolation layer, indicating the significant shock-absorbing effect of the double-story isolation structure. However, when SSI is considered on soft soil, the shock-absorbing effect of the isolation structure diminishes, and the effectiveness of the double-story isolation structure may not necessarily surpass that of the mid-story isolation structure. In all three soil conditions, the compressive stresses of the isolation bearings in the upper isolation layer of the double-story isolation structure were lower than those in the isolation bearings of the base isolation layer. Additionally, the double-story isolation structure demonstrates reduced compressive stress in the isolation bearings, fewer plastic hinges in the frame, and less stress damage compared to the mid-story isolation structure. Consequently, the risk of overturning damage in the double-story isolation structure is significantly reduced compared to the mid-story isolation structure. The effect of soft ground on structures can be highly detrimental, which should be paid more attention to during the design process. This study offers valuable insights for future research on double-story isolation systems and serves as a reference for the development of high-performance building structures in the future.

Research on irregular plane mid story isolation structures in castor earthquake prone areas considering SSI effect

The rock composition of karst area is mainly limestone, which is easy to be eroded and dissolved by water, forming a complex and fragile tectonics. Under the action of earthquake, the instability of stratum is aggravated. The mid story isolation structure is a new type of isolation structure developed from the basic isolation structure, and irregular mid story isolation buildings are highly susceptible to adverse seismic conditions. Previous studies have mostly adopted the assumption of rigid foundations, neglecting the influence of soil on irregular structures. In order to study the seismic response of isolated structures in irregular planes in karst earthquake prone areas considering soil structure interaction, a finite element model of isolated structures in irregular planes considering soil component interaction was established, and the seismic response of the structure under rigid foundation was calculated. Soft and hard soil foundations were studied, and compared with structures without considering SSI effect. Research shows that when considering the SSI effect, the seismic response of the structure increases and the damage to the structure intensifies; When considering SSI, the seismic response of soft soil is greater than that of hard soil, and the softer the soil, the more obvious it becomes; After considering the SSI effect, the torsional effect caused by the irregularity of the plane increases; The design of building structures should fully consider the adverse effects of soil layers on the seismic response of structures under plane interlayer seismic irregularities. In the design of building structures, it is necessary to fully consider the adverse effects of irregular planes on the seismic response of the structure. This consideration is particularly important in the design of soft soil high-rise buildings in karst earthquake areas to prevent unsafe designs and consider the SSI effect in actual seismic resistance.

Simple Soil Effect Analysis in a Base and Mid-Story Isolated 15 Story Building

In this study the effect of soil-structure interaction on seismic performance is investigated considering a 15 story building incorporating base and mid-story seismic isolation. The cases that are taken into account are; fixed base model, base isolated model and base and mid-story isolated model. All three models are analyzed by excluding and including soil-structure interaction. Three different earthquakes are used for the time-history analysis. It is concluded that the seismic performance is enhanced by the implementation of base and mid-story isolation to the structure. In addition, it is observed that soil-structure interaction had a small effect on seismic performance of the structure depending on the base soil type.

Development of a Control Algorithm for a Semi-Active Mid-Story Isolation System Using Reinforcement Learning

The semi-active control system is widely used to reduce the seismic response of building structures. Its control performance mainly depends on the applied control algorithms. Various semi-active control algorithms have been developed to date. Recently, machine learning has been applied to various engineering fields and provided successful results. Because reinforcement learning (RL) has shown good performance for real-time decision-making problems, structural control engineers have become interested in RL. In this study, RL was applied to the development of a semi-active control algorithm. Among various RL methods, a Deep Q-network (DQN) was selected because of its successful application to many control problems. A sample building structure was constructed by using a semi-active mid-story isolation system (SMIS) with a magnetorheological damper. Artificial ground motions were generated for numerical simulation. In this study, the sample building structure and seismic excitation were used to make the RL environment. The reward of RL was designed to reduce the peak story drift and the isolation story drift. Skyhook and groundhook control algorithms were applied for comparative study. Based on numerical results, this paper shows that the proposed control algorithm can effectively reduce the seismic responses of building structures with a SMIS.

Soil-structure interaction in a base and mid-story seismically isolated building

The main goal of this study is to analyze the performance of seismic isolation systems by implementing isolation to the base and inter-story of the buildings together, in order to reduce the earthquake impact in multi-story buildings. In addition the soil-structure interaction for these cases are taken into consideration. An example building model was composed to observe the effect of base isolation and mid-story isolation numerically. Analyses were performed by using SAP2000 software. A five story building was used as an example structure. Investigations were carried out for six different combinations that are: fixed base buildings, buildings with soil-structure interaction, buildings incorporating single base isolation system with and without consideration of soil-structure interaction, buildings with base and mid story isolation system with and without consideration of soil-structure interaction. Two different earthquake motions were selected for time-history analysis. The results obtained from time-history analysis were discussed comparatively, for all the base-isolation cases including and excluding soil-structure interaction. It has been concluded that the seismic isolation application of the base and mid-story improves the seismic performance of the building. In addition, it has been observed that the soil-structure interaction affects the building seismic performances according to the reference ground type.

Optimal Design of Semi-Active Mid-Story Isolation System using Supervised Learning and Reinforcement Learning

Optimal Design of Semi-Active Mid-Story Isolation System using Supervised Learning and Reinforcement Learning

Evaluation of the Modal Coupling Effect in Midstory Isolation Systems Based on Random Vibration Analysis

At present, the midstory isolation (MSI) technology has great potential for application in historical buildings’ retrofitting and multifunction buildings. The coupling effect due to the variability of the location of the isolation layer may amplify the structural seismic response and is required for in-depth analysis. This paper aims to evaluate the magnitude of the coupling effect and delimitate the region of the coupling effect to be considered. Based on the complex mode superposition method, the explicit formulas for calculating the random response of the simplified model are deduced. The root-mean-square (RMS) ratio of the shear force coefficient of the upper isolation system is adopted as the performance indicator to evaluate the coupling amplification effect of the MSI system. Parameter analysis indicates that the coupling region is closely related to the mass ratio and frequency ratio of the upper and lower structures to the isolation layer. In general, the region of the coupling effect to be considered can be divided into two parts according to parameters of frequency ratios, depending on the thresholds of the performance indicator. As the mass ratio of the upper isolation system to the entire system increases, one of the coupling regions shrinks and eventually disappears, indicating that the coupling amplification effect in this region can be neglected under certain conditions. Finally, the time-domain analysis of three representative numerical cases of MSI buildings was performed to verify the reliability of the results obtained from the frequency-domain analysis. The research results can provide technical guidance for the preliminary design of the MSI buildings.

Stability Analysis and Verification of Real-Time Hybrid Simulation Using a Shake Table for Building Mass Damper Systems

The building mass damper (BMD) system, which incorporates the concept of a tuned mass damper into a mid-story isolation system, has been demonstrated as an effective system for suppressing structural vibration due to earthquakes. The BMD system separates a building into a substructure, a control layer and a superstructure. By applying well-design parameters, the seismic responses of the superstructure and substructure of a building can be mitigated simultaneously. However, merely limited design parameters have been verified by shaking table testing because it is difficult to construct several sets of specimens with limited research funding. Therefore, real-time hybrid simulation (RTHS) may become an alternative to conduct parametric studies of the BMD system efficiently and economically. In this study, the BMD system is separated into a numerical substructure and an experimental substructure. The experimental substructure includes the control layer and the superstructure of the BMD system installed on a seismic shake table while the substructure is numerically simulated. Then, substructuring method of the BMD system is derived and the stability analysis considering the dynamics of the shake table is performed to realize the potential feasibility of RTHS for BMD systems. The stability margin is represented as an allowable mass ratio of the experimental substructure to the entire BMD system. Finally, RTHS of a simplified BMD system has been conducted to verify the stability margin in the laboratory. Phase-lead compensation and force correction are applied to RTHS in order to improve the accuracy of RTHS for the simplified BMD system.

Development of Seismic Response Simulation Model for Building Structures with Semi-Active Control Devices Using Recurrent Neural Network

A structural analysis model to represent the dynamic behavior of building structure is required to develop a semi-active seismic response control system. Although the finite element method (FEM) is the most widely used method for seismic response analysis, when the FEM is applied to the dynamic analysis of building structures with nonlinear semi-active control devices, the computational effort required for the simulation for optimal design of the semi-active control system can be considerable. To solve this problem, this paper used recurrent neural network (RNN) to make a time history response simulation model for building structures with a semi-active control system. Example structures were selected of an 11-story building structure with a semi-active tuned mass damper (TMD), and a 27-story building having a semi-active mid-story isolation system. A magnetorheological damper was used as the semi-active control device. Five historical earthquakes and five artificial ground motions were used as ground excitations to train the RNN model. Two artificial ground motions and one historical earthquake, which were not used for training, were used to verify the developed the RNN model. Compared to the FEM model, the developed RNN model could effectively provide very accurate seismic responses, with significantly reduced computational cost.

Insights into inter-story isolation design through the analysis of two case studies

Inter-story isolation system (IIS, also appointed as mid-story isolation), is currently spreading and gaining significant popularity, mainly in Japan. However, while more than sixty applications have been realized in nearly twenty years, the conceptual framework for dealing with the design problem of IIS is not well established, since the IIS combines isolation and mass damping control strategies.In this paper two case studies of real inter-story isolated buildings are in depth examined for interpreting the latest design practice in the light of approaches and indications coming from the world of research. The two buildings, very different from each other, cover the wide applicability of IIS. One of them is a paradigmatic example of ideal IIS, with dynamic characteristics commonly adopted in the scientific community, i.e. a very rigid superstructure, and frequencies of the two structural parts well separated from the isolation frequency. The other building is a non-typical case of IIS, with the upper structures less rigid than the lower one, and both structural portions quite flexible. Modal and frequency response analyses are carried out on simplified two- or three- degree-of-freedom models, representing the reduced-order models utilized in the inherent scientific literature for grasping the influence of the main design parameters governing the dynamic problem. Modal and non-linear time history analyses are then carried out on multi degree-of-freedom models, for the seismic assessment of the buildings. The main results are reported and design implications are discussed.

Control Performance Evaluation of Smart Mid-story Isolation System with RNN Model

Control Performance Evaluation of Smart Mid-story Isolation System with RNN Model

Design of an active mass damper to simultaneously mitigate seismic acceleration in superstructures and substructures of a mid-story isolation building

Design of an active mass damper to simultaneously mitigate seismic acceleration in superstructures and substructures of a mid-story isolation building

Seismic Response Analysis According to the Height of Substructure of the Dome Structure Using Mid-Story Isolation System

Seismic Response Analysis According to the Height of Substructure of the Dome Structure Using Mid-Story Isolation System

Simultaneous Optimization of Hybrid Mid-Story Isolation System and Building Structure

Simultaneous Optimization of Hybrid Mid-Story Isolation System and Building Structure

Control Performance Evaluation of Mid-Story Isolation System for Residence-Commerce Complex Building

Control Performance Evaluation of Mid-Story Isolation System for Residence-Commerce Complex Building

Optimal Design of Smart Mid-Story Isolated Control System for a High-Rise Building

Mid-story isolation systems have previously been studied for decrease of the earthquake induced responses of high-rise buildings. The systems have been successfully applied to several buildings in Korea and Japan. Structural designers usually have to ensure that both the peak story and isolator drifts are within permissible limits. However, these two objectives conflict with each other. To solve this problem, a smart mid-story isolation system can be used for tall buildings. The system is composed of rubber bearings and magnetorheological (MR) dampers. The system was employed for an existing structure to reduce both the isolator and story drift. The control efficiency of smart mid-story isolator was evaluated based on a passive system. An artificial seismic load was made for numerical analyses for both systems. A fuzzy soft-computing technique with a multi-objective optimization was adopted to make control algorithm for decrease of both the inter-story and isolator drift. A numerical analysis results presents that the proposed method can effectively decrease the seismic-induced inter-story and isolator drift in the example of a tall building.

Shaking table test and numerical analysis of mid-story isolation eccentric structure with tower–podium

Mid-story isolation eccentric structures with tower–podium are examples of vertically irregular structures. Its seismic performance and the related mechanisms, however, have not been experimentally examined. In this study, a representative model of a practical mid-story isolation eccentric structure with a large podium was fabricated, tested, and simulated to investigate its seismic response under different earthquakes. The results were then compared to those of an anti-seismic model without the isolation layer. The results show that (a) the mid-story isolation eccentric structure with tower–podium has the similar characteristics of seismic performance with the regular story isolation structure; (b) as the peak acceleration value increases, the podium could quickly enter the elastoplastic state and reach the medium damage level. The damage extent in the second layer of the podium is larger than that in its first layer. It is thus recommended that the structural components of the podium be strengthened, and the elastoplastic displacement angle limit of the podium be increased. The modeling results also indicate the torsional effects of such eccentric structure are effectively inhibited. Our study enhances the understanding of the mid-story isolation eccentric structure with tower–podium and pioneers a guide to the seismic design of such a structure.

Vibration Control Performance Evaluation of Hybrid Mid-Story Isolation System for a Tall Building

Vibration Control Performance Evaluation of Hybrid Mid-Story Isolation System for a Tall Building