Seismic Performance of Circular Elevated Water Tank: Rupachandra J. Aware, Dr. Vageesha S. Mathada
Seismic Performance of Circular Elevated Water Tank: Rupachandra J. Aware, Dr. Vageesha S. Mathada
Seismic Performance of Circular Elevated Water Tank: Rupachandra J. Aware, Dr. Vageesha S. Mathada
Abstract: Liquid storage tanks are used in industries for storing chemicals, petroleum products, and for storing water in public water
distribution systems. Behaviour of Cylindrical liquid storage tanks under earthquake loads has been studied as per Draft code Part II of
IS 1893:2002. A FEM based computer software (STAAD -PRO) used for seismic analysis of tanks which gives the earthquake induced
forces on tank systems. Draft code Part II of IS 1893:2002 which will contain provisions for all types of liquid storage tanks. Under
earthquake loads, a complicated pattern of stresses is generated in the tanks. Poorly designed tanks have leaked, buckled or even
collapsed during earthquakes. Common modes of failure are wall buckling, sloshing damage to roof, inlet/outlet pipe breaks and
implosion due to rapid loss of contents. Elevated water tanks should be competent of keeping the expected performance during and after
earthquake. It has large mass concentrated at the top of slender supporting structure hence extremely vulnerable against horizontal
forces due to earthquake. Staging is formed by a group of columns and horizontal braces provided at intermediate levels to reduce the
effective length of the column. In this research, a circular cylindrical elevated water tank is analysed by using finite modelling
techniques. This paper presents the study of seismic performance of the elevated water tanks for various heights and various seismic
zones of India. The effect of height of water tank, earthquake zones on Nodal displacement have been presented in this paper with the
help of analysis of 20 models for same parameters. Analysis is carried out by using finite element software STAAD-PRO.
Keywords: Elevated Circular Cylindrical Tank, Damages, Frame type staging, Nodal Displacement, Finite Element Software (STAAD-
PRO).
Staging acts like a lateral spring and one-third mass of For elevated tanks with moment resisting type frame
staging is considered based on classical result on effect of staging, the lateral stiffness can be evaluated by computer
spring mass on natural frequency of single degree of freedom analysis or by simple procedures or by established structural
system. analysis method.
The response of the two-degree of freedom system can be For elevated tanks with shaft type staging, in addition to the
obtained by elementary structural dynamics. However, for effect of flexural deformation, the effect of shear deformation
most elevated tanks it is observed that the two periods are may be included while calculating the lateral stiffness of
well separated. Hence, the system may be considered as two staging.
uncoupled single degree of freedom systems. This method
will be satisfactory for design purpose, if the ratio of the Lateral stiffness of the staging is the horizontal force required
period of the two uncoupled systems exceeds 2.514. If to be applied at the centre of gravity of the tank to cause a
impulsive and convective time periods are not well separated, corresponding unit horizontal displacement. The flexibility of
then coupled 2-DOF system will have to be solved using bracing beam shall be considered in calculating the lateral
elementary structural dynamics. In this context it shall be
Volume 4 Issue 12, December 2015
www.ijsr.net
Paper ID: NOV152347 1800
Licensed Under Creative Commons Attribution CC BY
International Journal of Science and Research (IJSR)
ISSN (Online): 2319-7064
Index Copernicus Value (2013): 6.14 | Impact Factor (2014): 5.611
stiffness, Ks of elevated moment resisting frame type tank supported on frame staging considering different height and
staging. zone and plotting the graphs as max. nodal displacement Vs
height and max. nodal displacement Vs zone.
4.2 The important factors that affect the magnitude of
earthquake forces are- 5.1 Capability of Staad- Pro software
(a) Seismic zone factor, Z STAAD.Pro.v8i is the most popular structural engineering
India has been divided into four seismic zones as per IS 1893 software product for 3D model generation, analysis and
(Part 1): 2002 for the Maximum Considered Earthquake multi-material design. It has an intuitive, user-friendly GUI,
(MCE) and service life of the structure in a zone. Different visualization tools, powerful analysis and design facilities
zone have different zone factor. Figure 3.3 shows seismic and seamless integration to several other modelling and
zone map of India. India is divided into four seismic zones. design software products. For static or dynamic analysis of
There are three types of soil considered by IS 1893 (Part 1): bridges, containment structures, embedded structures (tunnels
2002 i.e. soft medium and hard soil. and culverts), pipe racks, steel, concrete, aluminium or timber
buildings, transmission towers, stadiums or any other simple
or complex structure, STAAD.Pro has been the choice of
design professionals around the world for their specific
analysis needs.
For this study, water tanks with five different heights such as
5m, 10m, 15m, 20m and 25m are considered, and each water
tank is placed in Zone 2, 3, 4, and 5. The effect of heights of
tank and earthquake zones on nodal displacement is observed
with the help of analysis of 20 models having same
parameters.