Optimization of Staging Height of RCC Overhead Water Tank in High Seismic Zones Using P-Delta Analysis

Abstract

This study investigates the P-delta effect, which is a secondary effect or a geometric non-linear effect in the analysis of a circular overhead water tank with a capacity of 100 KL using STAAD software in high seismic zones, i.e., Zone IV & Zone V with a focus on optimization of staging height and to quantify the effect of P-Delta. Initially, a linear static analysis was performed without considering the P-Delta effect to determine the shear forces, bending moments and lateral displacements due to all possible loads including seismic and wind loads acting on RCC overhead water tanks. Subsequently, the P-Delta effect has been considered to assess the structural behaviour of the RCC overhead water tank with varying staging heights. To optimize the staging height, the maximum lateral displacement has been considered as the governing criteria. Based on the analysis, the optimum staging heights can be observed at 30 m. and 33 m. in Seismic Zone V and Zone IV respectively.

Introduction

I. INTRODUCTION

Rapid urban growth and population growth requires the development of a reliable water supply, especially in earthquake-prone regions where the risk of damage from earthquakes is high. An important part of this system is reinforced concrete (RCC) waterworks, which must be designed to withstand seismic forces while ensuring proper water distribution. The water distribution area will increase as the above water tank's staging height rises.

The P-Delta effect plays a crucial role in the analysis of structures when they encounter with lateral forces. When a tall structure or structural component is subjected to lateral forces or significant lateral displacement, it leads to additional moments, and/or axial force distribution at the base of the structure. In the P-Delta analysis initially structural response under the imposed loads, conduct a linear static analysis without considering the P-Delta effect, later that The P-Delta effect is to be taken into account in this analysis either geometric nonlinear analysis or iterative process or both.

In this study to assess and quantify the structural performance parameters like axial force, shear force, bending moment of the overhead water tank with and without P-Delta effect in accordance with IS codal provisions, subsequently to optimize the staging height of the 100 KL circular RCC overhead water tank in high seismic zones.

II. NUMERICAL MODELLING

A circular flat bottom RC overhead water tank has modelled in Bentley Staad pro software. The columns, brace/tie beams and ring beams are considered as beam elements and tank walls, top and bottom slabs are considered as plate elements with the following input parameters

Table I - Input Parameters for tank Model

V. DISCUSSIONS

1. The P Delta effect has a greater impact from the corresponding parameters, such as displacements, axial shear, shear force, and bending moment, as the staging height increases.
2. The earthquake load is the predominant force up to 21 meters of staging height; after that, the wind load is the predominant for determining the maximum lateral displacement.
3. Moving from Seismic Zone IV to Seismic Zone V for a common staging height result in increases in displacement, shear force, and bending moments.
4. As a result, the maximum lateral displacement in Seismic Zone V exceeding the allowable limit at a staging height of 33 meters, hence the analysis in Zone IV is performed from a staging height of 27 meters.

VI. FUTURE SCOPE

The current investigations can be extended by considering the following parameters

1. The tank's storage capacity can be increased in various soil conditions, more research can be done.
2. In this study, only simple bracing was performed; additionally, because the type of bracing varies, the outcomes may also vary.
3. Since the current study focused on seismic zones IV and V, additional seismic zones might be taken into consideration as well, which could lead to more generalised outcomes.

Conclusion

The following conclusions have been shown after the analysis of a circular overhead water tank in high seismic zones i.e., Zone IV & V with the aforementioned parametric study as outlined below: 1) The maximum axial force for a certain staging height for a given zone is shown to have an average increment of 1.8% in tank full condition and 1.3% in tank empty condition which takes the P-Delta effect into account. 2) The maximum shear force for a certain staging height for a given zone is shown to have an average increment of 2.5% in tank full condition and 2.05% in tank empty condition which takes the P-Delta effect into account. 3) The maximum Bending Moment for a certain staging height for a given zone is shown to have an average increment of 3.3% in tank full condition and 2.15% in tank empty condition which takes the P-Delta effect into account. 4) The optimum staging height of 30m. has been arrived in seismic zone V by considering the exceedance of maximum lateral displacement i.e., Hs/500 for the cases with & without P-Delta and tank full & empty conditions. 5) The optimum staging height of 33m. has been arrived in seismic zone IV by considering the exceedance of maximum lateral displacement i.e., Hs/500 for the cases with & without P-Delta and tank full & empty conditions.

References

[1] IS: 456-2000 - Code of Practice for Plain and Reinforced Concrete. [1] [2] IS:875- 2015(Part-III) - Code of Practice for Wind Loads. [3] IS:1893-2016 (Part-I)- Criteria for Earthquake Resistant Design of structures- General Provisions and Buildings. [4] IS:1893-2014 (Part-II) Criteria for Earthquake Resistant Design of structures- Liquid Retaining Tanks [5] IS:3370-2021 (Part I) - code of practice Concrete Structures for the storage of liquids. [6] IS:3370-2021 (Part II) - code of practice Concrete Structures for the storage of liquids (RCS). [7] IS 13920-2016 Ductile Detailing of RCS subjected to seismic forces [8] IS:11682-1985 - Criteria for Design of RCC Staging for Overhead Water Tanks [9] IITK-GSDMA Guidelines for Seismic Design of Liquid storage tanks 2007. [10] Hemishkumar Patel, Prof. Jayeshkumar Pitroda, Dr. K.B.Parikh (2014) “Analysis Of Circular And Rectangular Overhead Water tank”, National Conference on: “Trends and Challenges of Civil Engineering in Today’s Transforming World”,2014 [11] P.S.Nemade, Prof. D. G. Agrawal, Dr. A. M. Pande, (2016) “Parametric Studies In Design Of Staging Configuration For Elevated Service Reservoir For Seismic Consideration”, International Journal of Science Technology & Engineering, pp.756-763,2016. [12] Arbaj Khan Demrot (2017) “First Order Analysis of Elevated Water Tanks During Seismic Activity Using Staad. Pro v8i”, International Research Journal of Engineering and Technology, pp.743-747,2017. [13] Santosh Rathod, Prof. M. B. Ishwaragol (2018) “Analysis of Overhead Water Tank with Different Staging Height and Base Width”, International Research Journal of Engineering and Technology, pp.471-474,2018. [14] Mareddy Arun Kumar, O.Sriramulu, N. Venkateswarlu (2018) “Planning, Analysis And Design Of A Over Head Circular Water Tank In N.B.K.R.I.S.T Using Staad Pro Software”, Journal of Emerging Technologies and Innovative Research, pp.851-858,2018. [15] Himanshu Dwivedi, Dr. M.K. Gupta, (2019) “Analysis and Design of Water Tank Employing Staad. Pro For Cost Optimization”, International Journal of Scientific Research and Engineering Development, pp.597-606,2019. [16] Abdul Qayyum Ansari, Jitesh Chourasia, Prof. Manoj Deosarkar, Prof Arya Geetha, Rishab Gupta, Shahid Shaikh, (2020) “Design Calculation of Overhead Water Tank Using Manual Method” International Journal of All Research Writings, pp.27-36,2020. [17] Diwakar Yadav, Vinayak Mishra (2021) “Elevated Water Tank Design and Seismic Study in Various Zones” International Research Journal of Engineering and Technology, pp.588-595,2021. [18] Siddhnath Verma, Ganesh Jaiswal (2021) “Seismic Analysis of Circular Water Tank Designed by Indian Standard Code and Euro Code” International Journal for Research in Applied Science & Engineering Technology, pp.635-638,2021. [19] Sagar Chinchghare, Prof. Rahul Hinge (2022) “Literature Review on Design of Overhead Water Tank and Compare It with Conventional Approach”, Journal of Emerging Technologies and Innovative Research, pp.c519-c521,2022. [20] Prakash Mahdewa, Kirti Sahu Tirpude (2022) “Design the Circular Water Tank by Using the Staad Pro Software”, International Journal for Research in Applied Science & Engineering Technology, pp.1678-1692,2022. [21] Shubam Kumar Balmiki, Himmi Gupta (2022) “Analytical Approach to Evaluate the Behavior of Overhead Tank With P-Delta Analysis”, Journal of Emerging Technologies and Innovative Research, pp. c531-c544,2022. [22] L.K. Jain, Consulting Engineer (2023) “Information Series on Liquid Retaining Concrete Structures P Delta Effect in staging of Elevated Tanks & Stiffness of Members” ICI Journal Vol. 23 January – March 2023 No.4 ISSN 0972-2998

Copyright

Copyright © 2024 Bandari Murali Krishna, Himmi Gupta. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.