Probabilistic study on buildings with MTMD system in different seismic performance levels

Sadegh Etedali 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.81 No.4

A probabilistic assessment of the seismic-excited buildings with a multiple-tuned-mass-damper (MTMD) system is carried out in the presence of uncertainties of the structural model, MTMD system, and the stochastic model of the seismic excitations. A free search optimization procedure of the individual mass, stiffness and, damping parameters of the MTMD system based on the snap-drift cuckoo search (SDCS) optimization algorithm is proposed for the optimal design of the MTMD system. Considering a 10-story structure in three cases equipped with single tuned mass damper (STMS), 5-TMD and 10-TMD, sensitivity analyses are carried out using Sobol’ indices based on the Monte Carlo simulation (MCS) method. Considering different seismic performance levels, the reliability analyses are done using MCS and kriging-based MCS methods. The results show the maximum structural responses are more affected by changes in the PGA and the stiffness coefficients of the structural floors and TMDs. The results indicate the kriging-based MCS method can estimate the accurate amount of failure probability by spending less time than the MCS. The results also show the MTMD gives a significant reduction in the structural failure probability. The effect of the MTMD on the reduction of the failure probability is remarkable in the performance levels of life safety and collapse prevention. The maximum drift of floors may be reduced for the nominal structural system by increasing the TMDs, however, the complexity of the MTMD model and increasing its corresponding uncertainty sources can be caused a slight increase in the failure probability of the structure.

A Proposed Approach to Mitigate the Torsional Amplifications of Asymmetric Base-isolated Buildings During Earthquakes

Sadegh Etedali,Mohammad Reza Sohrabi 대한토목학회 2016 KSCE JOURNAL OF CIVIL ENGINEERING Vol.20 No.2

In this paper, the rotational behavior of asymmetric base-isolated buildings is compared with the similar asymmetric fixed-base buildings. A vast range of lead rubber bearings with different periods is considered to evaluate the effect of the isolation degree on seismic responses of the structures. The simulation results confirm that the base isolators are able to reduce rotation of stories. However, this reduction is negligible in large eccentricities. The numerical simulations show that increasing period of isolators results in large displacement at bearings located on the flexible edge of the isolation system. This paper proposes practical solutions to reduce torsional responses of the base-isolated structures. In order to investigate the effectiveness of the proposed solutions, four structural models are defined. Considering three earthquake excitations, the simulation results of these models indicate that increase in stiffness of flexible edge of isolation system can reduce torsional responses of asymmetric 3-story base isolated structure. Furthermore, the simultaneous increase in stiffness of flexible edge of isolation system and superstructure lead to a suitable reduction of torsional responses in asymmetric 8-story base-isolated structure.

A control scheme for AMD in the presence of time-delays and SSI effects for tall buildings

Sadegh Etedali,Mohammad Shahi 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.79 No.2

The present study addresses the issue of seismic control of active mass damper (AMD) devices in the presence of time-delay for the tall buildings taking into account soil-structure interaction (SSI) effects. Considering the simultaneous effects of the time-delay and SSI, a control scheme of linear quadratic regulator (LQR) controller with a new form of the weighting matrices is proposed. Then, a design procedure based on a particle swarm optimization (PSO) algorithm is proposed to find the optimal weighting matrices of the controller. The numerical studies are conducted on a benchmark tall building. The validity of the proposed LQR controller is demonstrated for the structure subjected to 44 well-known earthquakes. It is concluded that ignoring the SSI and time-delay effects may give an incorrect estimation of the seismic demands of the building. By increasing the soil softness, the structural responses are often increased. Furthermore, it is found that the proposed controller gives a worthy performance in mitigation of maximum top floor displacement for different soil conditions in the presence of time-delays. However, in the presence of long time-delay, a significant increment may achieve for maximum floor acceleration, especially for the soft and medium soils. However, the maximum drifts of the floors remain within the allowed ranges.

Failure probability of tall buildings with TMD in the presence of structural, seismic, and soil uncertainties

Sadegh Etedali,Mohammad Seifi,Morteza Akbari 국제구조공학회 2023 Structural Engineering and Mechanics, An Int'l Jou Vol.85 No.3

The seismic performance of the tall building equipped with a tuned mass damper (TMD) considering soil-structure interaction (SSI) effects is well studied in the literature. However, these studies are performed on the nominal model of the seismic-excited structural system with SSI. Hence, the outcomes of the studies may not valid for the actual structural system. To address the study gap, the reliability theory as a useful and powerful method is utilized in the paper. The present study aims to carry out reliability analyses on tall buildings equipped with TMD under near‐field pulse-like (NFPL) ground motions considering SSI effects using a subset simulation (SS) method. In the presence of uncertainties of the structural model, TMD device, foundation, soil, and near‐field pulse-like ground motions, the numerical studies are performed on a benchmark 40-story building and the failure probabilities of the structures with and without TMD are evaluated. Three types of soils (dense, medium, and soft soils), different earthquake magnitudes ( = 7,0. 7,25. 7,5 ), different nearest fault distances ( = 5. 10 and 15 km), and three seismic performance levels of immediate occupancy (IO), life safety (LS), and collapse prevention (CP) are considered in this study. The results show that tall buildings built near faults and on soft soils are more affected by uncertainties of the structural and ground motion models. Hence, ignoring these uncertainties may result in an inaccurate estimation of the maximum seismic responses. Also, it is found the TMD is not able to reduce the failure probabilities of the structure in the IO seismic performance level, especially for high earthquake magnitudes and structures built near the fault. However, TMD is significantly effective in the reduction of failure probability for the LS and CP performance levels. For weak earthquakes and long fault distances, the failure probabilities of both structures with and without TMD are near zero, and the efficiency of the TMD in the reduction of failure probabilities is reduced by increasing earthquake magnitudes and the reduction of fault distance. As soil softness increases, the failure probability of structures both with and without TMD often increases, especially for severe near-fault earthquake motion.

A new control approach for seismic control of buildings equipped with active mass damper: Optimal fractional-order brain emotional learning-based intelligent controller

Abbas-Ali Zamani,Sadegh Etedali 국제구조공학회 2023 Structural Engineering and Mechanics, An Int'l Jou Vol.87 No.4

The idea of the combination of the fractional-order operators with the brain emotional learning-based intelligent controller (BELBIC) is developed for implementation in seismic-excited structures equipped with active mass damper (AMD). For this purpose, a new design framework of the mentioned combination namely fractional-order BEBIC (FOBELBIC) is proposed based on a modified-teaching-learning-based optimization (MTLBO) algorithm. The seismic performance of the proposed controller is then evaluated for a 15-story building equipped with AMD subjected to two far-field and two near-field earthquakes. An optimal BELBIC based on the MTLBO algorithm is also introduced for comparison purposes. In comparison with the structure equipped with a passive tuned mass damper (TMD), an average reduction of 44.7% and 42.8% are obtained in terms of the maximum absolute and RMS top floor displacement for FOBELBIC, while these reductions are obtained as 30.4% and 30.1% for the optimal BELBIC, respectively. Similarly, the optimal FOBELBIC results in an average reduction of 42.6% and 39.4% in terms of the maximum absolute and RMS top floor acceleration, while these reductions are given as 37.9% and 30.5%, for the optimal BELBIC, respectively. Consequently, the superiority of the FOBELBIC over the BELBIC is concluded in the reduction of maximum and RMS seismic responses.

SSI effects on seismic behavior of smart base-isolated structures

Shourestani, Saeed,Soltani, Fazlollah,Ghasemi, Mojtaba,Etedali, Sadegh Techno-Press 2018 Geomechanics & engineering Vol.14 No.2

The present study investigates the soil-structure interaction (SSI) effects on the seismic performance of smart base-isolated structures. The adopted control algorithm for tuning the control force plays a key role in successful implementation of such structures; however, in most studied carried out in the literature, these algorithms are designed without considering the SSI effect. Considering the SSI effects, a linear quadratic regulator (LQR) controller is employed to seismic control of a smart base-isolated structure. A particle swarm optimization (PSO) algorithm is used to tune the gain matrix of the controller in both cases without and with SSI effects. In order to conduct a parametric study, three types of soil, three well-known earthquakes and a vast range of period of the superstructure are considered for assessment the SSI effects on seismic control process of the smart-base isolated structure. The adopted controller is able to make a significant reduction in base displacement. However, any attempt to decrease the maximum base displacement results in slight increasing in superstructure accelerations. The maximum and RMS base displacements of the smart base-isolated structures in the case of considering SSI effects are more than the corresponding responses in the case of ignoring SSI effects. Overall, it is also observed that the maximum and RMS base displacements of the structure are increased by increasing the natural period of the superstructure. Furthermore, it can be concluded that the maximum and RMS superstructure accelerations are significant influenced by the frequency content of earthquake excitations and the natural frequency of the superstructure. The results show that the design of the controller is very influenced by the SSI effects. In addition, the simulation results demonstrate that the ignoring the SSI effect provides an unfavorable control system, which may lead to decline in the seismic performance of the smart-base isolated structure including the SSI effects.