Evaluation of performance of intake tower dam for
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This document summarizes a study on evaluating the performance of intake tower dams in India during recent earthquakes. Intake towers are tall, hollow reinforced concrete structures that form the entrance to reservoir outlet works. The study aims to understand how parameters like depth of submergence, wall thickness, and slenderness ratio affect the dynamic behavior of intake towers during earthquakes. A simplified circular cylindrical tower model was analyzed in SAP2000 considering hydrodynamic added mass from surrounding and inside water. Dynamic analyses including modal and time history analyses were performed for different soil conditions and earthquakes in India from 2005-2013. The results show the effect of these parameters and soil conditions on the displacement and acceleration response of the intake towers.
![IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
__________________________________________________________________________________________
IC-RICE Conference Issue | Nov-2013, Available @ http://www.ijret.org 45
6 REFERENCES
[1] Goyal, A., and Chopra, A. K. (1989). "Hydrodynamic
and foundation interaction effects in dynamics of intake
towers: earthquake responses," / . Struct. Engrg.,
ASCE, 115(4), 1386-1395.
[2] Liaw, C-Y., and Chopra, A. K. (1974). "Dynamics of
towers surrounded by water." Int. J. of Earthquake
Engrg. and Struct. Dynamics, 3(1), 33-49.
[3] Liaw, C-Y., and Chopra, A. K. (1975). "Earthquake
analysis of axisymmetric towers partially submerged in
water." J. of Earthquake Engrg. and Struct. Dyn., 3(3),
233-248](https://image.slidesharecdn.com/evaluationofperformanceofintaketowerdamfor-140808015629-phpapp01/85/Evaluation-of-performance-of-intake-tower-dam-for-5-320.jpg)
Evaluation of performance of intake tower dam for
- 1. IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308 __________________________________________________________________________________________ IC-RICE Conference Issue | Nov-2013, Available @ http://www.ijret.org 41 EVALUATION OF PERFORMANCE OF INTAKE TOWER DAM FOR RECENT EARTHQUAKE IN INDIA Chethan kumar B1 , M.R Suresh2 , Ravikumar HS3 , B Sivakumara swamy4 1 Postgraduate student, Structural engineering, Dept of Civil engineering, Dr AIT Bangalore 2 Assistant professor, Geotechnical engineering, Dept of Civil engineering, Dr AIT Bangalore 3 Assistant professor, Structural engineering, Dept of Civil engineering MSRIT, Bangalore 4 Professor & Head of the Dept of Civil engineering, Dr AIT Bangalore [email protected] Abstract Intake towers are typically tall, hollow, reinforced concrete structures and form entrance to reservoir outlet works. A parametric study on dynamic behavior of circular cylindrical towers can be carried out to study the effect of depth of submergence, wall thickness and slenderness ratio, and also effect on tower considering dynamic analysis for time history function of different soil condition and by Goyal and Chopra accounting interaction effects of added hydrodynamic mass of surrounding and inside water in intake tower of dam Key words: Hydrodynamic mass, Depth of submergence, Reservoir, Time history analysis, ----------------------------------------------------------------------***----------------------------------------------------------------------- 1 INTRODUCTION Intake towers are typically tall, hollow reinforced concrete structures and form entrance to reservoir outlet works. They often house equipment for regulating the release of impounded water for vital public services such as water supply or generation of electricity, aid in emptying the reservoir in an emergency condition, and permit reservoir lowering for inspections and special repairs. Intake structures can be located within or attached to concrete gravity dams or located outside the dam. 1.1 Problem Description The dynamic response of an intake tower during an earthquake may present quite complex characteristics due to many factors. The water, inside and outside of the tower, plays an important role in the modification of the response of the structure. The behavior of the structure to the earthquake loading is very important considering the various benefits of the intake towers. Also IS codes does not provide any information for the dynamic analysis of the intake towers, so it is necessary to understand the dynamic behavior of these towers. Modeling and analysis of intake towers requires sound understanding of the behavior due to the complexities involved. The intake tower having axis symmetric geometry and being submerged in an unbounded reservoir necessitates a 3-dimensional model for accurate analysis. It is important to incorporate fluid-structure-interaction and the effect of unbounded reservoir condition while carrying out a seismic analysis. Thus it is necessary to investigate suitable method of analysis and modeling techniques to know the dynamic behavior intake towers. 1.2 Objective To study the different parameter that considerably affects the behavior of intake towers during the event of earthquake. The following parameters have been considered for the study 1. Depth of submergence( ⁄ ) 2. Outside radius( ) to height (H) of tower, i.e., ⁄ 3. Wall thickness (t) 4. Direction of ground motion on response of tower. Simplified model of a uniform and non-uniform intake tower is considered for the analysis in SAP 2000. Hydrodynamic effects were included in the analysis using the concept of hydrodynamic added masses (Goyal and Chopra 1989). 2 MODEL OF INTAKE TOWER A rectangular tower (Figure 1) of height of structure 61m, the depth of surrounding and inside water for all the models is taken equal to the height of the structure. Modal analysis is carried in SAP2000 to obtain the dynamic properties of the tower structure
- 2. IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308 __________________________________________________________________________________________ IC-RICE Conference Issue | Nov-2013, Available @ http://www.ijret.org 42 Figure 1 Typical intake tower 3 CALCULATION OF HYDRODYNAMIC MASS The fluid structure interaction is considered by calculating hydrodynamic mass of inside and outside water by the simplified procedure for evaluating the added hydrodynamic mass that is accurate enough for preliminary earthquake analysis of towers developed (Goyal and Chopra 1989) is mentioned below. According to this method, the mass of an intake tower m z having an arbitrary cross section with two axes of symmetry is replaced the by the virtual mass m z as: m z m z m z m z (3.1) Here, the added hydrodynamic masses m z and m z represent the effects of the outside and inside water, respectively, on the dynamic response of the tower. 4. DYNAMIC ANALYSIS 4.1 Model Analysis: Model analysis has been carried out by considering ritz vector because the Ritz vectors yield excellent results is that they are generated by taking into account the spatial distribution of the dynamic loading, whereas the direct use of the natural mode shapes neglects this very important information. By considering 12 natural modes and starting Load Vectors as acceleration in x direction model analysis of fully submerged, half submerged, quarter submerged & no water conditioned towers has been analyzed (figure 4) 4.2 Time History Analysis: Time history analysis of the intake tower has been carried by considering Time history function of recent earthquake India from 2005 to 2013 for different soil condition such as medium and hard soil condition of different seismic zones, which will give us critical response of the structure (figure 5) Figure 2 Calculation of surrounding water for equation 3.1 The above graphs has been plotted by considering concept given by Chopra and Goyal by using MATLAB program Figure 3 calculation of surrounding water for equation 3.1
- 3. IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308 __________________________________________________________________________________________ IC-RICE Conference Issue | Nov-2013, Available @ http://www.ijret.org 43 Figure 4 Model analysis in fully submerged condition of water Figure 5 time history function of Kohima Nagaland EQ
- 4. IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308 __________________________________________________________________________________________ IC-RICE Conference Issue | Nov-2013, Available @ http://www.ijret.org 44 5. RESULTS Figure 6 Plot of acceleration versus time of Kohima Nagaland EQ YEAR REGION STATION CODE MAGNITUDE Max. Acc DISPLACEMENT AT TOP CM/SEC^2 mm 2005 Chamoli-Uttarakhand CHM(E- W) 5.2 -63.48 -5.489 2007 DELHI-HARYANA HGR(E-W) 4.3 -117.605 -3.703 2007 DELHI-HARYANA HGR(N-S) 4.3 -91.026 -3.719 2007 DELHI-HARYANA GUR(N-S) 4.3 -41.023 -6.1 2008 SIKKIM-BORDER GTK(E-W) 4.4 48.168 4.080364 2008 SIKKIM-BORDER GTK(N-S) 4.4 -59.907 -2.273151 2008 SIKKIM-BORDER GTK(VET) 4.4 36.984 -1.867029 2008 Chamba CHA(N-S) 33.775 1.948 2008 DARRANG-ASSAM MNG(N-S) 4.2 -33.134 -2.867 2009 BHUTAN GOL(E-W) 6.2 41.862 5.076 2009 BHUTAN GOL(N-S) 6.2 -41.191 -5.07 2011 NEPAL-INDIA-BORDER- REGION PTH(N-S) 5.7 60.297 -3.657732 2011 NEPAL-INDIA-BORDER- REGION PTH(E-W) 5.7 60.489 4.341674 2011 NEPAL-INDIA-BORDER- REGION PTH(VET) 5.7 37.065 -3.962895 2011 NEPAL-INDIA-BORDER- REGION CHP(E-W) 5.7 -31.551 6.097132 2011 NEPAL-INDIA-BORDER- REGION DRC(E-W) 5.7 -131.811 5.949133 2011 NEPAL-INDIA-BORDER- REGION DRC(VET) 5.7 -56.222 4.572697 2011 NEPAL-INDIA-BORDER- REGION DRC(N-S) 5.7 131.634 5.84889 2011 Myanmar-India-Border JWI(E-W) 6.4 -35.119 4.344802 2011 Myanmar-India-Border NAU(VET) 6.4 32.113 2.536178 2012 Phek-Nagaland GOL(N-S) 5.8 36.742 -5.988978 2012 Phek-Nagaland JHR(E-W) 5.8 29.982 5.48057 2012 Kohima-Nagaland GOL(E-W) 5.5 37.142 4.749519 2012 Kohima-Nagaland JHR(E-W) 5.5 -37.763 5.12318
- 5. IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308 __________________________________________________________________________________________ IC-RICE Conference Issue | Nov-2013, Available @ http://www.ijret.org 45 6 REFERENCES [1] Goyal, A., and Chopra, A. K. (1989). "Hydrodynamic and foundation interaction effects in dynamics of intake towers: earthquake responses," / . Struct. Engrg., ASCE, 115(4), 1386-1395. [2] Liaw, C-Y., and Chopra, A. K. (1974). "Dynamics of towers surrounded by water." Int. J. of Earthquake Engrg. and Struct. Dynamics, 3(1), 33-49. [3] Liaw, C-Y., and Chopra, A. K. (1975). "Earthquake analysis of axisymmetric towers partially submerged in water." J. of Earthquake Engrg. and Struct. Dyn., 3(3), 233-248