Behaviour of the water tank staging with aluminum and steel X-plate damper.

: - Many water tanks are pull-down during post-earthquake due to failure of water tank staging and this occurs because of the dynamic behaviour of the water tank staging that leads to collapse of water tank. These are important elements during post-earthquake that must be in service. In this study to reduce the damage of water tank staging by installation of additional dissipation devices known as dampers made up of X-plate steel and aluminum and these are effective in reduction of damage of structures, gives the additional damping and additional stiffness to the structure. For this study water tank staging’s with different heights are modeled in SAP-2000 and performed nonlinear dynamic analysis under four real ground motions with and without damper. After the analysis the results obtained is, Displacement, shear force, amount of energy dissipation, maximum axial force and bending moment compared with and without damper and significantly reduced.


Introduction:
Earthquake is an unexpected tragic event that produces some energy in the form of waves due to this ground starts shaking. The structure existing on the ground behaves like a dynamic loading on the structure. If any inelastic behaviour of the structures gets damaged.
In general water is an essential for every human beings life. For that the storage of water tanks are constructing, that may be ground supported, underground and elevated water tanks. In this paper describing about elevated water tanks, these tanks plays an important role in municipality services. The tanks may be shaft supported and frame supported apart from this frame supported tanks are efficient in retrofitting purpose. Many water tanks are week against seismic forces but rapid growth of population the importance of water tanks increases day by day.
During post-earthquake elevated water tanks plays main role in water distribution purpose and should be in service. But many water tanks are pull down during earthquake for example Bhuj earthquake (2001), the forces from the earthquake to the structure is dynamic and the structure starts moves horizontally, behaves like nonlinear inelastic. This may be the reason for the damage of the structure. Reduction of seismic damage by retrofitting is tough task and requires expertise work man ship. It can be reduced by introducing effective technique that may be the dissipation of seismic energy. Dissipation of energy can be attained by introducing control device. Now days there is different types of dampers are available. In this paper displacement control dampers are used which controls the displacement, gives the additional stiffness to the structure and dissipates the seismic energy.
According many authors studied the effectiveness of dampers on water tanks. Studied the performance of double variable frequency pendulum isolators of four different combinations, different geometry and coefficient of friction on liquid storage slender and broad tanks. it`s concluded initial stiffness was more on top sliding surfaces compared to bottom sliding surfaces, Soni.et.al [1]. Seismic performance of the liquid storage steel tank isolated with variable friction pendulum system as compared with conventional friction pendulum investigated under trigonometric cycloidal pulses Panchal and Jangid [2]. The behaviour of the water tanks isolated with curved surface sliding bearings and it is affective in reduction of responsive quantity of base shear Abali and Uckan [3]. Water tank is designed according to Eurocode 8, performed response spectra analysis and observed the responsive quantities. Malhotra.et.al [4]. The performance of the water tank is isolated with fluid structure interaction by Housner; this isolation is effective in small capacity tank in reduction of responsive quantities Shenton.et.al [5]. Frame staging of frame members are decided is based on the ductility factor and response reduction factors Lakhade.et.al. [6]. Some of the authors worked on the various dampers, seismic response RC structure and effectiveness of the damper when equipped with X-plate damper and it is effective in reducing the responsive quantities. Manchalwar and Bakre [7]. The behaviour of the fluid viscous damper and steel yielding devices discussed by Terenzi.et.al [8]. To determine the seismic response of the structure five advanced placement methods were used Williams. Et.al [9}Study the behaviour of the two types of metallic dampers that is X-plate and accordion metallic dampers and discussed about optimal placement of damper by Manchalwar and Bakre [10]. Effectiveness of X-plate damper equipped in elevated water tank staging discussed by Nirmala.G.et.al [11]. In this paper damage states were determined by using Ang and park indices Kumar.R.et.al [12]. The behaviour of the structure when subjected to tuned metallic damper at top base of the storey and the damper is effective in minimize the seismic response of the structure Manchalwar and Bakre [13].

X-plate damper:-
XPD is used to resist the displacement of the inelastic behaviour of the select structure gives the additional stiffness to the structure and dissipates the input seismic energy of the structure. The configuration of the damper is X so it is called as X-plate damper, the size of the single X-plate damper is these are made up of steel and aluminum. The numerous authors investigated on the X-plate damper and observed the performance of the damper. Manchalwar and Bakre [7] worked on the two metallic dampers steel and aluminum and many numbers of tests were performed in BARK and IIT in Mumbai. Where, a is height of the damper, b is the width of the damper and t is the thickness of the damper,40, 60 and 4mm respectively. F Y is the yield force and σ y young's modulus and yield stress of the damper;

Problem statement:-
To determine the seismic response of the structure with steel and aluminum damper for this study 12 column 20m staging height and 24 column 24m staging height has been considered and As per Indian standards the grade of the concrete and yield strength of the steel M20 and Fe500 has been considered respectively. The size of the frame members has been considered based on the elastic flexibility criteria as shown in table -2, dead load live load for design taken as per IS 875-1983 of part 1&2 respectively.

Shear, Axial and Bending moment comparison:-
From the experimental analysis the responsive quantities of shear, axial and bending moment of two elevated water tank staging as shown in table 3&4.From the results it is noted that axial force gradually increases and shear force and bending moment significantly reduces as compared without damper case.

Displacement comparison:-
From the Fig.4 it is noted that 32-35% of the displacement gradually decreases Al-6063 as compared with no damper case. Fig.5 shows the steel damper 35-38% displacement decreases as compared to the without damper case for the 12 column 20m staging.

Hysteresis loop:-
To control the vibration of elevated water tank many devices are available to dissipate the seismic energy in early ages. X-plate damper is belonging to this category. Hysteresis loop is a Displacement Vs force relationship represents the energy disig.11sipation Fig.8 &.9 shows the dissipation of both Al-6063 and Steel damper have been same for the 12 column 20m staging. Fig.10 & Fig.11 represents the hysteresis loop of 24 column 24m staging of Al-6063 & steel damper respectively. Two dampers have same capacity significantly in dissipation of energy.

Conclusion:-
In this study seismic response of the structure is analysed by using steel and Al-6063 damper. For this study 12 column 20m staging and 24 column 20m staging is modeled and performed time history analysis under four time histories in SAP2000.The resultant quantities Displacement, Axial force, Shear force, bending moment and energy dissipation observed.
1. Dampers are effective in increase the axial force, decrease the shear force and bending moment significantly in models. 2. In 12 column 20m staging top story displacement is reduced by 30-35% in two dampers. 3. 30-40% top storey displacement reduction is observed in 24 column 24m staging in both Al-6063 and steel damper. 4. From the results dissipation of energy is same in Al-6063 and steel damper.
From the responsive parameters it is concluded that geometry of the structure and dampers decides their effectiveness.