The visco-elastic dampers can be economically designed for response reduction of dynamical systems. Recent developments in fractional calculus have affected the modeling of visco-elastic materials. The fractional models for visco-elastic dampers, which are parsimonious, require fewer parameters in comparison with other models. In this paper, we use the visco-elastic dampers for control of structural responses. The visco-elastic damper utilizes three important parameters including damping coefficient, stiffness, and fractional order. The dynamic model of the building with visco-elastic dampers can be acquired by a system of fractional differential equations, which includes both fractional and ordinary derivatives. We apply spline collocation methods for obtaining the numerical solution of this complex system. The collocation method is implemented in a graded mesh. The discrete data of earthquake are smoothed by spline interpolation of higher degree. The introduced method is used to simulate the response of a structure with active and passive controllers. A comparison of using different dampers is considered. Also, $H_{\infty }$ norm of the transform function is used for response analysis. The results of simulations for four-story and 10-story buildings show significant reductions in structural responses. Moreover, our analysis presents that the large variety of values can be used for parameters of the visco-elastic damper to provide flexibility in designing appropriate visco-elastic-dampers.

In this paper, a fuzzy-rule-based semi-active control of building frames using semi-active variable orifice dampers (VODs) is presented. Additionally, the consequences of well-known characteristics of near-fault ground motions, forward directivity and fling step, on the seismic response control is investigated. The membership functions and fuzzy rules of the fuzzy controller were optimized by genetic algorithm. To illustrate the efficiency of the proposed fuzzy controller strategy in application and effects of near-fault ground motions, numerical simulation for a 10-story building frame equipped with VODs is presented. The VODs are installed in all storeys to prevent damage to the structure from severe earthquakes. The controlled response of the frame was compared with results obtained by controlling the frame by the classical clipped-optimal control method based on linear quadratic regulator theory. Results revealed that the fuzzy logic controller is capable of improving the structural responses and VODs are promising for reducing seismic responses during near-fault earthquakes.

Active vibration control is one of the most efficient systems to mitigate excessive vibrations by providing significantly superior supplemental damping in civil engineering structures. One of the most challenging components of active control is development of an accurate analytical approach with minor computational expenses. Active mass damper (AMD) is one of the most commonly used active control devices, including a mass-spring-damper system with an actuator to increase the amount of damping in structures. Block pulse functions have been studied and applied frequently in recent years as a basic set of functions for signal characterizations in systems science and control. The purpose of this study is to establish an innovative method by using block pulse functions to minimize expenses of computations. Numerical simulations of earthquake-excited 10-story shear buildings equipped with an active mass damper are provided to verify the validity and feasibility of the proposed method. The proposed method's uncontrolled and controlled responses of structural system are compared with linear quadratic regulator method's results. The results reveal the proposed method can be beneficial in reducing seismic responses of structures with less computational expenses and high accuracy.

Composite Reinforced Concrete-Steel (RCS) frames which consist of Reinforced Concrete (RC) columns and Steel (S) beams were represented to combine the advantages of pure RC and steel frames. This system permits the primary steel beam to run continuous through the reinforced concrete column. This paper evaluates seismic performance of RCS frames based on FEMA-356, considering plastic rotations as acceptance criteria. The effect of joint deformations on overall behavior of RCS frames is studied through nonlinear static analysis (Pushover) that is performed in OpenSees software. It is concluded that the RCS joint behavior increases lateral load capacity of frame. Additionally, 3 RC frames are compared to RCS frames with columns similar to those of RC frames. The results show a great improvement on overall behavior since steel beams is used instead of RC beams.

Structural active control is one of the most efficient systems available to protect building structures from destructive effects of earthquakes. Active control efficiency is highly dependent on control algorithm. One of the most important and challenging components of structural control is the development of an accurate analytical approach having less computational expenses. Block pulse functions have been studied and applied frequently in recent years as a basic set of functions for signal characterizations in systems science and control. The proposed method evolves minimizing computational expenses of analytical approaches by a novel method to suppress the responses of the structure based on block pulse functions. To prove the validity and feasibility of the proposed control method, numerical simulations of earthquake-excited 10-story shear buildings with active tendons are performed, and comparative results are presented. The uncontrolled and controlled responses of structural system are obtained by using the proposed method and compared with linear quadratic regulator method. The results reveal that the proposed method can be beneficial in reducing seismic responses of structures with high accuracy and less computational expenses. Copyright © 2014 John Wiley & Sons, Ltd.