Double Concave Friction Pendulum (DCFP) bearing is a new generation of Friction isolator that contains two separate concave sliding surfaces with different properties. Accommodating enhanced performance, compared to the Friction Pendulum System (FPS), is one of the most important benefits of DCFP. Herein, the seismic behavior of structures isolated by DCFP bearings is compared with the response of the same buildings using the FPS bearing. Accordingly, a series of nonlinear dynamic analyses are carried out under ensembles of ground motions at three different hazard levels (SLE, DBE and MCE). Moreover, the adaptive behavior of DCFP and its advantages in protecting secondary Systems is investigated. The probability of exceedance curves of peak roof acceleration, peak inter-story drift and peak isolator displacement is compared for two types of isolation System. The result supports the advantages of DCFP isolation Systems.

Objective: To investigate the Friction of rabbit’s knee joint with designed Pendulum Friction tester to diagnose and evaluate different pathological and therapeutic conditions following haemarthrosis, osteoarthritis, and other joint disorders. Materials and Methods: Friction coefficient of 10 adult male Albino rabbit’s joint (5 right and 5 left knees) weighted 1.59 ± 0.27 Kg, after designing and compiling the instrument and its processing software in the Physiotherapy department of Tarbiat Modares University were measured. Maximaum Pendulum rotation, number of oscillations to reach equilibrium, coefficient of Friction with Stanton’s equation, exponential and linear curve fitting, average logarithmic and linear decrement methods were measured. Results: Maximum rotation after Pendulum releasing in the left joints were higher than the right ones, P<0.001. Number of oscillations to reach equilibrium in the left knees were also greater than the right knees, P=0.005. All different Friction estimation methods had the same results and showed greater Friction in the right in comparison to the left side. Conclusion: The pattern of the joints amplitude decay did not have a linear behaviour and the rabbit’s knee joint coefficient of Friction with nonlinear estimations was less than linear ones. The findings revealed that selecting a separate control group in such investigation is essential and the contralateral limb could not be considered as control group. Pendulum Friction tester has the capability of evaluating changes in coefficient of Friction after application of different therapeutic methods. These changes have important role in diagnosis, evaluation of joint diseases and developing techniques for treating those pathologies.

When a structure's fundamental period lengthens, often shear and floor acceleration increases. The contribution of higher modes in the dynamic response of structural Systems with multiple degrees of freedom is significant in both the design of new structures and the evaluation of existing structures.Few research have looked at the impact of higher modes on base isolation Systems in structures. To investigate the effects of higher modes on a building with a Friction Pendulum base isolation, a study was conducted on four different types of buildings: one with an L-shaped plan with two, four, and six floors; another eccentricities of buildings 5%, 10%, 15%, and 20%; and two others with a building with an L-shaped plan, where the second floor is half the mass of the first floor and next S shape plan. Eight layouts of the Pendulum base isolation are considered for each building and their first mode, the second mode, and the mass participation rate of the first mode, the second mode, and higher modes are derived. Finally, in a linear time history analysis, the change in the maximum displacement of the base level is compared to the percentage of mass participation on the modes. The findings show that in four models, the percentage of first mode mass participation is decreased if the center of stiffness of the base isolation is aligned to the center of cumulative mass of the building, and the percentage of mass participation is increased in the second or third modes. The responses of the structure are thus determined by the second mode or higher modes. In general, the stiffness center of the base isolation must line up with the center of the base cumulative mass to produce the optimal design. And this Pendulum base isolation layout’s displacement of the base level is also reduced.

Recently, base isolation techniques are applied as a resisting System to protect the structures from seismic and dynamic loadings. Due to their importance, in this paper, an optimum arrangement of lead rubber bearing (LRB) and Friction Pendulum System (FPS) is investigated in irregular buildings and its performance is compared with a regular case. For this purpose, 3 types of irregularities have been adopted. Accordingly, 3, 7 and 10 story buildings have been performed and 12 possible combination have been applied for the isolators in each model. Afterwards, the numerical models have been analyzed using nonlinear time-history analysis and direct integration method and applying 7 earthquake records along the longitudinal and transverse directions of the building. The obtained results of the numerical study show that the application of FPS and LRB isolators in outer and inner columns respectively, led to a better performance compared to the other arrangements by reduction of the inter-story drifts as well as base shear and enhancement of the energy dissipation which is due to the characteristics of FPS isolators in balancing the applied forces with the building’ s mass and prevention of torsion occurrence in irregular structures. Unlike the irregular buildings, application of FPS and LRB isolators in inner and outer columns, result in a better performance by reducing the story drifts in regular structures.

One of the Systems that be used in order to prove efficiency of control methods with its easy structure, is inverted Pendulum System. The object of controlling this System is equilibrium of Pendulum with limited states. For this purpose, different methods are used. One of the best methods is fuzzy controller with defuzzy supervisory controller. In almost methods, limitation of initial conditions is important problem. In this paper for solving this problem, a new method is proposed. Because of similarity to back stepping method but its more applications than last method, we named this method to Generalized Back stepping Method.

Conventional seismic design and reinforcement methods are based on increasing the capacity of the structure. That is, the bearing capacity of the structure is increased by increasing its strength and ductility, which is not possible in the reinforcement of many structures. However, in seismic isolation, by reducing the seismic demand, by reducing the absolute acceleration of the structure and reducing the energy input to the structure, due to increasing the Period and damping in the level of isolation, the structure can be placed in safe areas. Therefore, in this study, the effect of seismic isolators and also the height of structures on different types of soils have been investigated. For this purpose, the effects of seismic isolators in two buildings of 5 and 8 floors in three types of soil S1, S2 and S3 are investigated and evaluated. After validation of the structure and base isolation, behavioral studies were performed, and it was found that the presence of base isolation reduces the maximum displacement of the roof by up to 20% and 80% of maximum base shear in the 5-storey building. Reduction of about 40% of the maximum sliding displacement of the base isolation in the 8-story structure compared to 5 floors has reduced the effect of the base isolation on the maximum displacement in the higher floors.

AbstractIn the present study, the evaluation of the seismic performance of steel framed buildings on two types of seismic isolation Systems under far-fault earthquakes has been investigated. The isolator used are lead rubber bearing and single arc Friction Pendulum System. In order to compare the behavior of these isolators, the effective time period is considered as one of the most important properties of the isolator. The effective time period of the isolators is 2.5, 3.5 and 4.5. Three types of steel framed buildings with special moment resistant steel frames of 3, 7 and 12 stories are placed on these isolators. These three buildings represent low-rise, mid-rise and high-rise buildings. The effect of these two types of seismic isolators has been investigated in reducing the acceleration response and the relative displacement(drift) of the floors. The results show that the efficiency of both types of lead rubber bearing and single arc Friction Pendulum System decreases with the increase in the height of the building. The efficiency of the single arc Friction Pendulum System is 14% lower than that of the lead rubber bearing. Increasing the target natural period (decreasing the stiffness of the isolator) in reducing the response of the buildings in the lead rubber bearing has an average of 27% better performance than the single arc Friction Pendulum System.

Sliding articulated isolators are well-known types of seismic control tools, that extensive observations have shown their effective role in reducing seismic damages in structures. Although this tool significantly improves the performance of the structure at different seismic levels, but the existence of uncertainties in the limited behavior of this isolator in earthquakes with long return periods has attracted the attention of researchers in recent years to model their ultimate behavior. When the isolator reaches its displacement capacity, the sliding parts strike the side edge of the sliding surfaces and the performance of the structure affects by this special condition. In this study, after implementing the equations governing the behavior of these isolators, we proceed to mathematically model their ultimate behavior and study its effects on the dynamic response of the superstructure. So, by designing and modeling a sample structure, we examine the superstructure dynamic response at different scales of several earthquake records. The results show that the average ground acceleration at the beginning of the contact behavior under the studied records, is about 1.25MCE, the elastic base shear is about 0.48 superstructure weight and the maximum elastic drift of the superstructure is about 0.0038. By increasing the level of acceleration, the amount of base shear increases to the levels that the superstructure shows the nonlinear behavior. Also, by performing analysis on models with and without ultimate behavior, converting ratio are presented for different PGA levels.

The triple Friction Pendulum isolator is adaptable and can exhibit variable stiffness and damping in response to different earthquakes. Therefore, the need to optimize the effective parameters of this isolator to achieve the desired performance is significant. In this research, the Covariance Matrix Adaptation Evolution Strategy (CMA-ES) algorithm is used to optimize the effective parameters of the triple Friction Pendulum isolator to minimize the maximum relative displacement between floors and the roof acceleration in two separate optimization processes. As optimizing complex models is computationally intensive and time-consuming, substituting the actual responses of the finite element model with cost-effective surrogate models results in significant time savings. In this article, structural analysis is performed using a nonlinear model implemented in OpenSees software, making the structural optimization process time-consuming and computationally expensive. To address this challenge, the Kriging model is employed as a surrogate to replace the finite element analysis computations necessary to calculate the responses, i. e., minimizing the maximum relative displacement between floors and the roof acceleration. The optimization results using the combination of the CMA-ES algorithm and the surrogate model are compared with optimization using the genetic algorithm. The findings reveal that utilizing the surrogate model for optimization reduces relative displacement between floors by 66. 39% and roof acceleration by 12. 28%. Additionally, computational costs are reduced by over 84%.

In this paper, attempts are made to compare the seismic fragility and the probability of failure of steel structures supported on different types of Friction Pendulum isolators. These isolators including single Friction, dual Friction Pendulum and triple Friction Pendulum are designed to have similar effective periods as a prominent characteristic of them. The designed bearings have 3-to 5-second effective period and supports 3-and 6-story moment framed steel structures. These two superstructures represent short-range and intermediate-order buildings based on HAZUS technical manual. Three-dimensional nonlinear models of the structures are idealized in a finite element framework and nonlinear time history analyses are performed. In order to compute the fragility of the structure, the probable uncertainty sources in an isolated building such as earthquake record, modeling, design, and properties of materials in a probabilistic framework are considered. Furthermore, incremental dynamic analysis (IDA) is performed and the fragility curves of the structure are obtained in slight, moderate, extensive and collapse damage states (DS). Calculating the failure probability according to FEMA P-695, it is showed that all the isolated structures have less than 10% collapse probability. In addition, it is revealed that the triple concave Friction Pendulum (TCFP) has greater collapse margin ratio (CMR) than other kind of Friction bearings. Growing the effective period of TCFP from 3 to 5 seconds, increases the CMR nearly 70 percent.