PERFORMANCE BASED EVALUATION OF … · water tank having different capacities ... (Pushover analysis) analysis in CSI SAP2000 Software. ... resting on ground or underground depending

International Journal of Recent Innovation in Engineering and Research

Scientific Journal Impact Factor - 3.605 by SJIF

e- ISSN: 2456 – 2084

@IJRIER-All rights Reserved -2018 Page 11

PERFORMANCE BASED EVALUATION OF RESPONSE

REDUCTION FACTOR FOR ELEVATED CIRCULAR WATER

TANK

Dr.H.J.Puttabasavegowda1, Shivaraj nayak

2 and Ramya H S

3 1Professor, Civil Engineering Department, P. E. S College of Engineering /VTU Belgaum ,India

2Assistant Professor, Civil Engineering Department, P. E. S College of Engineering /VTU Belgaum ,India

3Post Graduate student, Department of civil engineering. P.E. S College of Engineering /VTU Belgaum ,India

Absract- Earthquakes are one of the most dangerous natural hazards causing damage and collapse to

livelihood and they are the result of ground shaking caused by sudden release of energy in earth‟s

lithosphere. Due to Earthquake ground motions, there is heavy economic and life loss. Most of the

losses are due to collapse of structures such as buildings, bridges, water retaining structures.

Response reduction factor is defined as the factor by which the actual base shear force should be

reduced to obtain the design lateral force. It represents the ratio of the maximum lateral force VB

(Design seismic base shear) which would develop in a structure to the Design base shear calculated

using the approximate fundamental period Ta. To compare response reduction factor of elevated

water tank having different capacities (250m3, 500m3) for different seismic zones and also be

evaluation of strength factor ductility factor and redundancy factor for all various seismic zones.

Then evaluate the response reduction factor of elevated water tank for various capacities using non

linear static (Pushover analysis) analysis in CSI SAP2000 Software.

Keywords – Elevated storage reserviour,capacity of tank,Different staging height different zone

factor,Base shear,Over strength factor,Ductility factor,Redundancy factor,Non linear-static analysis

CSI SAP2000.

I. INTRODUCTION

1.1 GENERAL:

Water is considered as the source of every creation and is thus a very crucial element for

humans to live a healthy life. High demand of clean and safe drinking water is rising day by day as

one cannot live without water. It becomes necessary to store water. Water is stored generally in

concrete water tanks and later on it is pumped to different areas to serve the community. One of the

oldest known water tanks in kenya was built by the railway at makindu river in 1907. It appears the

tank was connected to a hydra pump that used the power of the flowing water in the river to push

water into the tank from where it was used by steam locomotives. Water tanks can be classified as

overhead, resting on ground or underground depending on their location. The tanks can be made of

steel or concrete. Tanks resting on ground are normally circular or rectangular in shape and are used

where large quantities of water need to be stored. Overhead water tanks are used to distribute water

directly through gravity flow and are normally of smaller capacity. As the overhead water tanks are

opening to public view, their shape is influenced by the aesthetic view in the surroundings.

1.2 NEED OF STUDY:

It is very important to consider earthquake load in design of elevated tank. Response

reduction factor (r) is very important to find out earthquake load. the response reduction factor

reflects the capacity of structure to dissipate energy by inelastic behaviour. The purpose of this paper

is to explore a methodology for evaluation of the response modification factor, r, of reinforced

concrete frame staging (supporting system) elevated tanks, which behave in a ductile manner under

seismic loads and expectedly fail in flexural mode instead of shear mode. The values of response

Volume: 03 Issue: 06 June – 2018 (IJRIER)

Available Online at: www.ijrier.com Page 12

reduction factor(r) of rc elevated water tank are given in is1893 draft code, which is calculated at

empirically based on engineering judgment.

1.3 OBJECTIVES:

The main objective of this study is to verify the r factor of most common designed elevated

intze tank through comparing the assumed r factor during design to actual r factor obtained from

non-linear analysis. the specific objectives of the study are to:

Conduct static non-linear (pushover) analysis and calculate r factor of elevated intze tank.

Compare the calculated r factor with the assumed r factor.

Evaluate ductility, redundancy and over strength factor of elevated circular water tank.

Study the effect of staging height and staging type on response reduction factor (r).

To study effect of zone factor on response reduction factor (r).

II. DESIGN METHODOLOGY

2.1 SPRING MASS MODELING TECHNIQUE: Two mass model for elevated tank has been used for modeling fluid, was proposed by

Houser, which is more appropriate and is being commonly used in most of the international codes

including Draft code for IS 1893 (Part-II). The pressure generated within the fluid due to the

dynamic motion of the tank can be separated into impulsive and convective parts. When a tank

containing liquid with a free surface is subjected to horizontal earthquake ground motion, tank wall

and liquid are subjected to horizontal acceleration. The liquid in the lower region of tank behaves

like a mass that is rigidly connected to tank wall. This mass is termed as impulsive liquid mass which

accelerates along with the wall and induces impulsive hydrodynamic pressure on tank wall and

similarly on base Liquid mass in the upper region of tank undergoes sloshing motion. This mass is

termed as convective liquid mass and it exerts convective hydrodynamic pressure on tank wall and

base. For representing these two masses and in order to include the effect of their hydrodynamic

pressure in analysis, spring mass model is adopted for ground-supported tanks and two- mass model

for elevated tanks as shown in Figure 1.

Figure.1: Two mass idealization for elevated tank

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In spring mass model convective mass (mc) is attached to the tank wall by the spring having

stiffness Kc, whereas impulsive mass (mi) is rigidly attached to tank wall. For elevated tanks two-

mass model is considered, which consists of two degrees of freedom system. Spring mass model can

also be applied on elevated tanks, but two - mass model idealization is closer to reality. The two -

mass model is shown in Fig. 1. where, mi, mc, Kc, hi, hc, hs, etc. are the parameters of spring mass

model and charts as well as empirical formulae are given for finding their values. The parameters of

this model depend on geometry of the tank and its flexibility.

2.2 Review of basic component about response reduction factor:

In the mid-1980s, data from experimental research at the University of California at Berkeley

were used to develop base shear-roof displacement relationships for steel braced frames and a draft

formulation for the response modification factor. The base shear-roof displacement relationships

were established using data acquired from the testing of two code-compliant braced steel frames; one

concentrically braced (Uang and Bertero, 1986) and one eccentrically braced (Whittaker et aI.,

1987). The force-displacement curves were developed by plotting the roof displacement at the time

corresponding to the maximum base shear force for each earthquake simulation and each model.

Response reduction factor is the factor by which the actual base shear force should be reduced, to

obtain the design lateral force. The response reduction factor reflects the capacity of structure to

dissipate energy by inelastic behaviour. This process is combined effect of over strength, redundancy

and ductility. Response reduction factor is also known as ratio of maximum elastic force to designed

force. Response reduction factor is depended on three factors. 1) Over strength factor

2) Ductility factor

3) Redundancy factor

R = Rs * RR * Rμ

The concept of r factor is based on the observations that well detailed seismic framing

systems can sustain large inelastic deformations without collapse and have excess of lateral strength

over design strength. Response reduction (r) factors are essential seismic design tools, which are

typically used to describe the level of inelasticity expected in lateral structural systems during an

earthquake. The response reduction factor (r) is depends on over strength (rs), ductility (rμ),

redundancy.

a) Estimation of strength factor:

The steps in the procedure are as follows: 1. using nonlinear static analysis, construct the base

shear-roof displacement relationship for the building. 2. At the roof displacement corresponding to




the limiting state of response, calculate the base shear force Vo in the building. The reserve strength

of the building is equal to the difference between the design base shear (Vd) and (Vo') . Calculate the

strength factor using the following expression:

1) Strength factor is the ratio of Maximum Base Shear (from pushover curve) VO to Design Base

shear (as per EQ calculation) Vd.

Rs = Vo / Vd

b) Estimation of ductility factor:

Equations for estimation of ductility factor is as below:

R μ = {(μ - 1 / Ф) + 1}

Ф for rock sites: = 1+ {1 / (10T -μT)}–{(1 / 2T)*e^ (-2(ln (T) – 0.6) ^2)}

Ф for alluvium sites: = 1+ {1 / (12T -μT)}–{(2 / 5T)*e^ (-2(ln (T) – 0.2) ^2)}

μ = Δm / Δy

Δm = Maximum drift capacity (0.004 H)

Δy = Yield drift (from pushover curve)

c) Estimation of redundancy factor:

The value of redundancy factor as suggested in ATC-19 is summaries in Table 3.

LINES OF VERTICAL SEISMIC

FRAMING

DRIFT REDUNDANCY FACTOR

2 0.71

3 0.86

4 1

2.3 Hinge formation:

The RC beams and columns are modeled as 3-D frame elements with centerline dimension.

Wall and domes are modeled as shell elements. Column foundations are assumed to be fixed. Default

hinges are considered for analysis Flexure moment (M3), axial biaxial moment (P-M2-M3) and axial

compressive shear force (V) hinges are assigned at the face of beam, column, and bracing

respectively using the static pushover analysis.

2.4 Static nonlinear analysis of tank:

SAP software is used to perform the nonlinear static pushover analysis. The RC beams and

columns are modeled as 3-D frame elements with centerline dimension. Wall and domes are

modeled as shell elements. Column foundations are assumed to be fixed. Default hinges are

considered for analysis Flexure moment (M3), axial biaxial moment (P-M2-M3) and axial

compressive shear force (V) hinges are assigned at the face of beam, column, and bracing

respectively using the static pushover analysis. Figure shows the procedure of pushover analysis.

Damping ratio is 0.5% considered.

2.5 PUSHOVER ANALYSIS PROCEDURE:

Following are the steps followed in the present study to carry out analysis, design and

performance study of RC frame

1. 3D model of RC frame was created.

2. Corresponding section and loads for the beam and column were assigned.

3. Analysis was carried out for both gravity and earthquake loads.

4. Design was carried out using CSI SAP2000, itself, as per IS: 456-2000 provision.

5. Default hinge properties at assumed potential points (near beginning and ending of the




element) were assigned.

6. For column PMM hinge property was assigned and for beam M3 hinge property was

assigned. These points have pre-defined properties as per ATC-40.

7. For non-linear/pushover cases, in which first case is force control and second case is

displacement control were defined.

8. For displacement control case, earthquake force is used to push the frame laterally upto

maximum displacement (4% of building height).

9. Run the non-linear static analysis to get pushover curve.

III. PROBLEM FORMULATION & ANALYSIS

3.1. General

The non-linear static procedure is a simple option for estimating the strength capacity in the

post-elastic range. The procedure consists of applying a predefined lateral load pattern to structure

model which is distributed along the structure height. The lateral forces are then monotonically

increase in constant proportion with a displacement control node of the building until a certain level

of deformation is reached. The applied base shear & the associated lateral displacement at each load

increment plotted. Based on the capacity curve, a target displacement which is an estimate of

displacement which is produced by design earthquake on the building is determined. At this target

displacement extent of damage experienced by the building is considered representative of the

damage experienced by the building when subjected to design level ground shaking

3.2 Modeling

Table 1:Description for water tank for 250 m3

Tank vessel property (m)

Tanks staging property (m)

Vessel Capacity

250 m3

No. of column

6 Nos

Cylinder diameter

8.6 m

Columns Diameter

0.65 m

Wall Height

3.7m

Columns height

12 m, 16m, 20m

Top Dome rise

1.75m

Staging diameter

5.78m

Conical dome rise

1.5m

Bracing Interval

4.00 m

Bottom dome rise

1.5m

Beams bracing

Size

0.3m × 0.6m

Top Ring Beam

0.25m × 0.3m

No of bracing per

level

6 Nos

Middle Ring Beam

0.5m × 0.3m

Bottom Ring Beam

0.5m × 0.6m

Seismic Data

Top Dome thickness

0.12 m

Zone

II, III, IV, V

Vessel thickness

0.20 m Response

Reduction Factor

2.5




Conical dome thickness

0.25 m Soil Type

Medium

Bottom Dome thickness

0.20 m

3D Modeling of water tank for 250 m3 with 12m height in zone II, III, IV, V



Table 2:Description for water tank for 500 m3:-

Tank vessel property (m)

Tanks staging property (m)

Vessel Capacity

500 m3

No. of column

6 Nos

Cylinder diameter 12 m Columns Diameter 0.65 m




Wall Height

3.7m

Columns height

12 m, 16m, 20m

Top Dome rise

1.75m

Staging diameter

7m

Conical dome rise

1.5m

Bracing Interval

4.00 m

Bottom dome rise

1.5m

Beams bracing Size

0.3m × 0.6m

Top Ring Beam

0.25m × 0.3m

No of bracing per

level

6 Nos

Middle Ring Beam

0.5m × 0.3m

Bottom Ring Beam

0.5m × 0.6m

Seismic Data

Top Dome thickness

0.12 m

Zone

II, III, IV, V

Vessel thickness

0.20 m Response Reduction

Factor

2.5

Conical dome thickness

0.25 m Soil Type

Medium

Bottom Dome thickness

0.20 m







IV. RESULTS AND DISCUSSIONS

RESULTS FOR 250m3 TANK:-

4.1 Result for250 m3 capacity of water tank with 12m staging height in Empty condition

Zone II III IV V

Time period 0.53 0.53 0.53 0.53

Base shear(KN) 126 202 303 454

Over strength factor(Rs) 6.3 3.8 2.51 1.65

Ductility factor(Rµ) 1.35 1.24 1.15 1.1

Redundancy factor(RR) 0.86 0.86 0.86 0.86

Response reduction factor(R) 7.3 4.1 2.48 1.6

4.2 Result for250 m3 capacity of water tank with 12m staging height in Full condition

Zone II III IV V

Time period 0.68 0.68 0.68 0.68

Base shear(KN) 247 360 480 590






Zone II III IV V

Time period 0.71 0.71 0.71 0.71

Base shear(KN) 131 210 315 473






Zone II III IV V

Time period 0.83 0.83 0.83 0.83

Base shear(KN) 252 372 490 609









Zone II III IV V

Time period 0.98 0.98 0.98 0.98

Base shear(KN) 136 216 326 490






Zone II III IV V

Time period 1.21 1.21 1.21 1.21

Base shear(KN) 257 385 510 620





4.7 BASE SHEAR FOR 250m3 TANK CAPACITY (Empty and Full)

Figure 1: graph of Base shear v/s seismic zones for different Tank condition


0

100

200

300

400

500

600

700

2 3 4 5

Empty

Full

0

100

200

300

400

500

600

700

2 3 4 5

Empty

Full

0

100

200

300

400

500

600

700

2 3 4 5

Empty

Full




4.8 RESPONSE REDUCTION FACTOR

(a) Variation of Response reduction factor for 250m3:

Figure 3: graph of R factor v/s seismic zones for different staging of water tank

Graph shows the comparison of staging height with three factors redundancy, ductility, and

over strength. Results are taken for 250m3 full and empty conditions. Results show that R factor

decrease with increase in staging height. Redundancy depends upon number of vertical framing, so

Redundancy factor is remaining same for all height. Over strength factor is decreasing by increasing

staging height. It shows that reserve strength of tank is decreasing by increasing height.

TANK EMPTY TANK FULL

Figure 4: graph of Factors v/s seismic zones for 12m staging of water tank

0

1

2

3

4

5

6

7

8

2 3 4 5

12 mStaging

16 mStaging

20 mStaging

0

1

2

3

4

5

6

7

2 3 4 5

12 mStaging

16 mStaging

20 mStaging

0

1

2

3

4

5

6

7

2 3 4 5

OVERSTRENGTHFACTOR

DUCTILITYFACTOR

REDUNDANCYFACTOR

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

2 3 4 5

OVERSTRENGTHFACTOR

DUCTILITYFACTOR

REDUNDANCYFACTOR






4.9 TIME PERIOD:

(a) Variation of Time Period for 250m3:

Figure 7: bar graph of Time period v/s different Staging for different zones and tank

condition of water tank

V. RESULTS FOR 500m3 TANK


Zone II III IV V

Time period 0.61 0.61 0.61 0.61

Base shear(KN) 172 275 413 550



0

1

2

3

4

5

2 3 4 5

OVERSTRENGTHFACTOR

DUCTILITYFACTOR

REDUNDANCYFACTOR 0

0.5

1

1.5

2

2.5

3

3.5

4

2 3 4 5

OVERSTRENGTHFACTOR

DUCTILITYFACTOR

REDUNDANCYFACTOR

0

0.5

1

1.5

2

2.5

3

3.5

2 3 4 5

OVERSTRENGHTHFACTOR

DUCTILITYFACTOR

REDUNDANCYFACTOR

0

1

2

3

4

2 3 4 5

OVERSTRENGTHFACTOR

DUCTILITYFACTOR

0

0.2

0.4

0.6

0.8

1

1.2

1.4

EMPTY FULL EMPTY FULL EMPTY FULL

12m 16m 20m

Zone 2

Zone 3

Zone 4

Zone 5







Zone II III IV V

Time period 0.72 0.72 0.72 0.72

Base shear(KN) 347 420 513 592




Response reduction factor(R) 5.4 32 2.01 1.8


Zone II III IV V

Time period 0.82 0.82 0.82 0.82

Base shear(KN) 177 283 425 568






Zone II III IV V

Time period 0.96 0.96 0.96 0.96

Base shear(KN) 352 432 544 613






Zone II III IV V

Time period 1.02 1.02 1.02 1.02

Base shear(KN) 182 291 437 582






Zone II III IV V

Time period 1.32 1.32 1.32 1.32

Base shear(KN) 357 451 582 646








5.7 BASE SHEAR FOR 250m3 TANK CAPACITY (Empty and Full)



5.8 RESPONSE REDUCTION FACTOR

(a) Variation of Response reduction factor for 250m3:

Figure 10: graph of R factor v/s seismic zones for different staging of water tank

0

100

200

300

400

500

600

700

2 3 4 5

Empty

Full

0

100

200

300

400

500

600

700

2 3 4 5

Empty

Full

0

100

200

300

400

500

600

700

2 3 4 5

Empty

Full

0

1

2

3

4

5

6

7

8

2 3 4 5

12 mStaging

16 mStaging

20 mStaging

0

1

2

3

4

5

6

7

2 3 4 5

12 mStaging

16 mStaging

20 mStaging




Graph shows the comparison of staging height with three factors redundancy, ductility, and

over strength. Results are taken for 250m3 full and empty condition. Results shows that R factor

decrease with increase in staging height. Redundancy depends upon number of vertical framing, so

Redundancy factor is remaining same for all height. Over strength factor is decreasing by increasing

staging height. It shows that reserve strength of tank is decreasing by increasing height.

TANK EMPTY TANK FULL




0

1

2

3

4

5

6

7

8

2 3 4 5

OVERSTRENGTHFACTOR

DUCTILITYFACTOR

REDUNDANCYFACTOR

0

1

2

3

4

5

6

2 3 4 5

OVERSTRENGTHFACTOR

DUCTILITYFACTOR

REDUNDANCY FACTOR

0

1

2

3

4

5

6

2 3 4 5

OVERSTRENGTHFACTOR

DUCTILITY FACTOR

REDUNDANCYFACTOR

0

0.5

1

1.5

2

2.5

3

3.5

4

2 3 4 5

OVERSTRENGTHFACTOR

DUCTILITYFACTOR

REDUNDANCY FACTOR

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

2 3 4 5

OVERSTRENGTHFACTOR

DUCTILITYFACTOR

REDUNDANCYFACTOR

0

0.5

1

1.5

2

2.5

3

2 3 4 5

OVERSTRENGTHFACTOR

DUCTILITYFACTOR

REDUNDANCYFACTOR




5.9 TIME PERIOD:-

(a) Variation of Time Period for 500m3:-

Figure 14: bar graph of Time period v/s different Staging for different zones and tank

condition of water tank

V. CONCLUSION

1. The response reduction factor is considerably affected by the staging height of water tank. It

reduces as the of water tank is increasing.

2. R factor is highly dependent on seismic zones. For various seismic zones R factor also changes.

3. Time period and Redundancy of elevated tank will remaining same for all zones of same height

of tank.

4. Base shear will increasing by changing the zone from II to V for the same height of elevated

tank.

5. The Time period is considerably affected by the staging height of water tanks. It increases as the

height of water tank is increasing.

6. Over strength factor of elevated tank is decreased by increasing zone factor. So, it shows that

reserved strength of water tank is decreasing by increasing the zone factor.

7. R factor is decreasing by changing the condition of water tank from full to empty.

8. Time period and base shear of elevated tank is also increased in full condition of tank.

REFERENCES

[1] ATC-19, „Structural response modification Factors‟, 1995

[2] ATC 40 (1996): “Seismic Evaluation and Retrofit of Concrete Buildings”, Volume1, ATC-40 Report, Applied

Technology Council, Redwood City, California

[3] IS 1893 (Part I) 2002, „Criteria for Earthquake Resistant Design of Structures

[4] Jinkoo Kim, Hyunhoon Choi., “Response modification factors of chevron-braced frames”Engineering Structures 27

(2005) 285–300(2004).

[5] Bhavin Patel and Dhara Shah., “Formulation of Response Reduction Factor for RCC Framed Staging of Elevated

Water Tank” Proceedings of the World Congress on Engineering 2010 Vol III WCE 2010, June 30 - July 2, 2010,

London, U.K.

[6] SoheilSoroushnia, TavousiTafreshi, Omidinasab SH, Beheshtian F, SajadSoroushnia N., “Seismic Performance of

RC Elevated Water Tanks with Frame Staging and Exhibition Damage Pattern” The Twelfth East Asia-Pacific

Conference on Structural Engineering and Construction(Procedia Engineering 14 (2011) 3076–3087).

[7] Moslemi M, Kianoush M R, Pogorzelski W., “Seismic response of liquid-filled elevated tanks” Engineering

Structures 33 (2011) 2074–2084 (2011)

[8] Estekanchi H E, Alembagheri M., “Seismic analysis of steel liquid storage tanks by Endurance Time method” Thin-

Walled Structures 50 (2012).

0

0.2

0.4

0.6

0.8

1

1.2

1.4

EMPTY FULL EMPTY FULL EMPTY FULL

12m 16m 20m

Zone 2

Zone 3

Zone 4

Zone 5


Documents

PERFORMANCE BASED EVALUATION OF … · water tank having different capacities ... (Pushover analysis) analysis in CSI SAP2000 Software. ... resting on ground or underground depending