Abstract
Abstract The behavior of the tuned liquid column damper (TLCD) is analyzed in the control of non-linear structures subjected to random seismic excitations. The structure is modeled as a system of one degree of freedom with incursion in the non-linear range. The Bouc-Wen hysteretic model is used to model the non-linear behavior of the structure. A stationary stochastic analysis is performed in the domain of the frequency. An equivalent statistical linearization was used for the analysis of the main system and the TLCD. The TLCD parameters considered for the optimization process were the frequency and the head loss coefficient. Two target functions were considered, (i) reduction of the main displacement of the system, (ii) reduction of the hysteretic energy. Two random processes were considered as seismic excitation, first a broad bandwidth process and secondly a narrow bandwidth process. The results show that for a broad bandwidth process, the TLCD tends to tune with the linear equivalent frequency of the system in the case without TLCD, while for the narrow bandwidth process, it tunes (TLCD) with the dominant frequency of the input. It is seen that the TLCD becomes detuned with regard to the frequency of the structure as the structure becomes more non-linear. It is also seen that the optimal tuning ratio of the TLCD is unsensitive to the mass ratio of the device and the main damping ratio of the system. It is also concluded that in case of flexible structures, the optimal head loss coefficient tends to be lower and increases with regard to its length ratio. It is seen that the effectiveness of the TLCD is greater for higher mass ratios of the device. In addition, it is found that the optimal TLCD becomes less effective as the structure enters the non-linear range, showing lower efficiency than what is seen in the literature for optimal TLCDs in linear structures.
Highlights
Gilda Espinoza et al Analysis of a tuned liquid column damper in non-linear structures subjected to seismic excitations where cs is the damping of the main system; ks is the rigidity of the main system; ms is the main mass of the system; Bh is the horizontal length of the tube; h is the height of the liquid column; üg is the acceleration of the ground; y is the displacement of the liquid within the column and x is the displacement of the main structure
The reductions correspond to the quotient between the standard displacement deviation of the system with tuned liquid column damper (TLCD) with regard to the standard deviation without TLCD and the hysteretic energy dissipated by inelastic inclusion of the system with an optimal TLCD and the hysteretic energy of the system without TLCD, respectively
It is concluded that the optimal tuning ratio of the TLCD is insensitive to the mass ratio and to the damping ratio of the main system
Summary
In order to provide functionality, serviceability and safety for the structures, new alternatives have arisen which allow to avoid the structural oversizing. Sakai & Takaeda (1989) introduces a device called tuned liquid column damper (TLCD), which consists of a “U” shaped container which contains liquid (typically water), which has an oscillation frequency and has an orifice in the horizontal part of the tube which causes head loss. Xu et al (1992) numerically show that with suitable parameters, the TLCD has an effectiveness that is similar to the tuned mass damper (TMD) in controlling the response of wind sensitive structures. Balendra et al (1995) studied the effectiveness of the TLCD in the control of vibrations for towers with a broad range of natural frequencies, concluding that the performance of the TLCD does not solely depend on the tuning ratio and on the opening ratio of the orifice. Battista et al (2008) and Souza (2003) propose a hybrid fluid-dynamic control system (HTLCD) for active/passive control of bending oscillations of tall and slender buildings under wind forces. Battista et al (2008) and Souza (2003) propose a hybrid fluid-dynamic control system (HTLCD) for active/passive control of bending oscillations of tall and slender buildings under wind forces. They conclude that when comparing uncontrolled and controlled responses of a tall and slender tower in terms of top horizontal displacement versus time and acceleration versus time, the HTLCD is more effective than two TLCD in orthogonal directions (DTLCD)
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