Determining behavior coefficient of cubic and cylinder concrete air tanks relies on bending frame using nonlinear analysis methods

Fathollah Sajedi¹ Farajollah Haseli²

1) Islamic Azad University of Ahvaz, Iran Email:
2) Islamic Azad University of Boroujerd, Iran Email:

IOI Code : XYCZ-AADZK
Publication : International Conference on Engineering and Applied Science(iceasconf.com)
Abstract :
    Requirements regarding the place of construction, importance of the structure, expected seismic response and acceptable surfaces of vulnerability can be determinative in designing earthquake resistance structures. Therefore, design codes reduce the required forces due to earthquake regarding to structural resisting systems and economic issues; hence, design codes permit the use of dissipation energy capacities due to non-elastic structural behavior. Therefore, structures can be designed for earthquake forces less than those obtained by the linear method. In the meantime, water air tanks are considered as high importance structures because of their important role after occurrence of an earthquake. Thus, analyzing the seismic performance and defining behavior coefficient is very important. Air tanks services after an earthquake must be continued because of the need for providing drinking water and controlling the fire arising from the earthquake. The formulation used is based on the FEMA 274 design code. In this study, two cylinder and cubic concrete air tanks designed for saving liquids were analyzed considering their geometric details including height, material properties, modeling the water inside each air tank, basic features of air tanks, type of soil and type of regional seismic. Calculating behavior coefficient using nonlinear statically analysis methods (push over) and nonlinear time history method is done for both air tanks. At first, the creation process of plastic joints is provided and then behavior coefficient of the two tanks under the same circumstances of San Fernando (USA), Kube (Japan) and Chi Chi (Taiwan) earthquakes are compared using the two mentioned methods. The most displacement and the most exerted force of the San Fernando earthquake were calculated as 56.48 and 52.08 mm and 201.75 and 289.21 tons, respectively for each of the cubic and cylinder air tanks relying on bending frame. The amount of behavior coefficient for cubic and cylinder air tanks are 1.92 and 2.41, respectively based on the push over analysis method. Eventually, the obtained results are compared with the Iran’s design code of 2800 and also the national management and planning magazine number 123.

Keywords : behavior coefficient air tanks nonlinear analysis methods plastic joints bending frame seismic performance