Alternate tank staging configurations with reduced torsional vulnerability
详细信息 查看全文
- 作者：Dutta ; S.C. ; Jain ; S.K. ; Murty ; C.V.R.
- 关键词：Earthquake analysis ; Elevated water tanks ; Staging ; Reinforced concrete ; Seismic design ; Torsional effect
- 刊名：Soil Dynamics and Earthquake Engineering
- 出版年：2000
- 出版时间：April, 2000
- 年：2000
- 卷：19
- 期：3
- 页码：199-215
- 全文大小：1.01 M
文摘
The companion paper [Dutta SC, Jain SK, Murty CVR. Assessing the seismic torsional vulnerability of elevated tanks with RC frame-type staging. Soil Dynamics and Earthquake Engineering 2000;19(3):183–97] shows that many of the currently designed reinforced concrete elevated water tanks supported on frame-type stagings have the ratio of torsional and lateral natural periods, τ, in the critical range of 0.7–1.25. This may amplify the effect of small accidental eccentricity and cause large torsional vibration during translational ground shaking in earthquakes [Dutta SC. Torsional behaviour of elevated water tanks with reinforced concrete frame-type stagings during earthquakes. PhD thesis. Department of Civil Engineering, Indian Institute of Technology Kanpur, Kanpur 208 016, India. 1995 and Dutta SC, Murty CVR, Jain SK. Torsional failure of elevated water tanks: the problems and some solutions. Paper No. 287. Eleventh World Conference on Earthquake Engineering. Acapulco, Mexico, 1996 June 23–28: Elsevier, Amsterdam, 1996]. It was seen that the period ratio (τ) of the frame-type stagings cannot be changed appreciably by adjusting properties of the basic configuration, e.g. number of panels Np, number of columns Nc, and the parameter Kr related to the relative stiffness of columns and beams. Hence, alternate structural configurations are needed for such stagings so that τ lies outside the critical region. In this paper, approximate closed-form expressions are derived for lateral and torsional stiffnesses for a few alternate configurations. These expressions are used for studying the natural period ratio (τ) for those alternate configurations. The alternate configurations are made by adding to the basic configuration (a) radial beams, (b) radial beams and a central column, (c) another concentric row of columns connected through radial and circumferential beams, and (d) diagonal braces. First three of these configurations have higher value of τ while the fourth configuration has a lower τ when compared with that of the basic configuration. The paper presents a limited parametric study to evaluate the effectiveness of each of these configurations in changing τ. A systematic stepwise approach is proposed for checking torsional vulnerability of the tanks and choosing a suitable configuration. Since the magnitude and direction of eccentricity for elevated water tanks is often not known, configuration-based solution may be preferable to the conventional increased strength design.