STABILITY ANALYSIS OF CONCRETE GRAVITY DAM USING … · STAAD Foundation to provide engineers...

STABILITY ANALYSIS OF CONCRETE GRAVITY DAM

USING STAAD PRO

Mr. Manoj Nallanathel [1], Mr. B. Ramesh [2], AB. Pavan Kumar Raju [3]

Associate Professor [1], Professor [2], Bachelor of Engineering [3]

Department of Civil Engineering, Saveetha School of engineering,

Saveetha Institute of Medical and Technological Sciences, Chennai-602105, TN, INDIA.

[email protected] [1], [email protected] [2], [email protected] [3]

Abstract:

A gravity dam is a solid structure, made of

concrete or masonry, built throughout a river to

create a reservoir on its upstream. The segment of

the gravity dam is approximately triangular in

shape, with its apex at its pinnacle and most width

at backside. The phase is so proportioned that it

resists the numerous forces acting on it by using

its very own weight. In this paper analysis of dam

is achieved the use of STAAD.pro software

program. STAAD.pro is extensively used for

multi-storied homes with beam and columns. But

STAAD.pro can examine any form of element

which include, plate, shell or strong further to

beam individuals. So, in the software with

appropriate facts, dam is modelled with stable

factors. Result of stresses and pressure contours

are defined on the end of paper. The goal of paper

is to have a course of analysis of dam thinking

about solid elements using STAAD.pro and

conventional methods. STAAD.pro is computer

software, which is used for stability and stress

analysis of structures. Dam is such a massive

structure; to evaluate such structure manually is

very tedious and long timing process so it’s easy

to evaluate the dam stability STAAD.pro.

Key words: Gravity dam, concrete, moments,

frictional force, stability, STAAD Pro v8i

Introduction:

The gravity dam is constructed with the concrete

or masonry. The purpose of the dam is to store,

hold water and to control the floods, to supply

water to households, irrigation, energy

generation, livestock water supplies, pollution

control etc..,. The dam are classified according to

the type of material used in construction, the way

dam resist the loads, type of the structure etc..,.

The materials used for construction of dams

include earth, rock, tailings from mining or

milling, concrete, masonry, steel, timber,

miscellaneous materials and any combination of

all these materials. The following are the different

dams as their shape, size and use of it.

Embankment dams

International Journal of Pure and Applied MathematicsVolume 119 No. 17 2018, 297-310ISSN: 1314-3395 (on-line version)url: http://www.acadpubl.eu/hub/Special Issue http://www.acadpubl.eu/hub/

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Gravity dams

Buttress dams

Arch dams.

Coffer dams.

Essentially a gravity dam should fulfill the

subsequent standards:

1. It will be secure in opposition to overturning

at any horizontal role in the dam at the touch

with the inspiration or inside the basis.

2. It have to be secure towards sliding at any

horizontal plane within the dam, at the contact

with the inspiration or alongside any geological

feature within the foundation.

3. The segment need to be so proportional that the

allowable stresses in each the concrete and the

foundation must no longer exceed.

Objectives:-

The main objective is to determine the stability of

the concrete gravity dam with different load

conditions by varying the water level. The

stability of concrete gravity dam is analyzed by

using STAAD Pro. With the three different

conditions are

When the reservoir is empty.

When the reservoir is half fill.

When the reservoir is fully fill.

About STAAD.pro: -

STAAD Pro is a structural analysis and design

computer program originally developed by

Research Engineers International at Yorba Linda,

CA in 1997. In late 2005, Research Engineers

International was bought by Bentley Systems. An

older version called STAAD-III for Windows is

used by Iowa State University for educational

purposes for civil and structural engineers. The

commercial version, STAAD Pro, is one of the

most widely used structural analysis and design

software products worldwide. It supports several

steel, concrete and timber design codes. It can

make use of various forms of analysis from the

traditional 1st order static analysis, 2nd order p-

delta analysis, geometric non-linear analysis,

Pushover analysis (Static-Non Linear Analysis)

or a buckling analysis. It can also make use of

various forms of dynamic analysis from modal

extraction to time history and response spectrum

analysis. In recent years it has become part of

integrated structural analysis and design solutions

mainly using an exposed API called Open

STAAD pro to access and drive the program

using a Visual Basic macro system included in

the application or by including Open STAAD

functionality in applications that themselves

include suitable programmable macro systems.

Additionally, STAAD Pro has added direct links

to applications such as RAM Connection and

STAAD Foundation to provide engineers

working with those applications which handle

design post processing not handled by STAAD

Pro itself. Another form of integration supported

by the STAAD Pro is the analysis schema of the

CIM steel Integration Standard, version 2

International Journal of Pure and Applied Mathematics Special Issue

298

commonly known as CIS/2 and used by a number

modeling and analysis applications.

Forces on the concrete gravity dam

1. Water pressure: -

Water Pressure (p) is the most major external

force acting on such a dam. The horizontal water

pressure, exerted by the weight of the water

stored on the upstream side of the dam can be

estimated from rule of hydrostatic pressure

distribution. This is the largest external force

acting on the dam. It has the largest capacity for

disturbing the stability of the dam. It is a

horizontal force which acts at the C.G. of the

pressure distribution diagram, due to water. The

pressure distribution diagram is always triangular

with zero value at surface of the water and

increasing linearly to maximum at the base of the

dam. The value of maximum horizontal pressure

at base of the dam is w.h where w is the density

of water in kg/m3 and h the depth of water in

meters. Since pressure distribution diagram due

to water is triangular, the value of the total

horizontal pressure (P) due to water will be area

of the triangle.

2. Earthquake Forces: - The effect of

earthquake is equivalent to acceleration to the

foundation of the dam in the direction in which

the wave is travelling at the moment. Earthquake

wave may move in any direction and for design

purposes, it is resolved into the vertical and

horizontal directions. On an average, a value of

0.1 to 0.15g (where g = acceleration due to

gravity) is generally sufficient for high dams in

seismic zones. In extremely seismic regions and

in conservative designs, even a value of 0.3g may

sometimes by adopt. Vertical acceleration

reduces the unit weight of the dam material and

that of water is to(1-kv) times the original unit

weight, where kv is the value of g accounted

against earthquake forces, i.e. 0.1 when 0.1g is

accounted for earthquake forces. The horizontal

acceleration acting towards the reservoir causes a

momentary increase in water pressure and the

foundation and dam accelerate towards the

reservoir and the water resists the movement

owing to its inertia. The extra pressure exerted by

this process is known as hydrodynamic pressure.

3. Silt Pressure: -

If h is the height of silt deposited, then the forces

exerted by this silt in addition to the external

water pressure, can be represented by Rankin’s

formula psilt =12γgh2ka acting at h/3 from the

base. Where, ka = coefficient of active earth

pressure of silt = 1−𝑠𝑖𝑛∅1+𝑠𝑖𝑛∅ ∅ = angle of

internal friction of soil, cohesion neglected.

γs= submerged unit weight of silt material. h =

height of silt deposited.

4. Wave Pressure: - Waves are generated on the

surface of the reservoir by the blowing winds,

which exert a pressure on the downstream side.

Wave pressure depends upon wave height which

is given by the equation

hw =0.32√𝑝𝑣+0.763-0.271×F1/4 for F < 32 km,

and hw =0.32√𝑝𝑣 for F > 32 km Where hw is the


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height of water from the top of crest to bottom of

trough in meters

5. Ice Pressure: - The ice which may be formed

on the water surface of the reservoir in cold

countries may sometimes melt and expand. The

dam face is subjected to the thrust and exerted by

the expanding ice. This force acts linearly along

the length of the dam and at the reservoir level.

The magnitude of this force varies from 250 to

1500 KN/m2 depending upon the temperature

variations. On an average, a value 500 KN/m2

may be taken under ordinary circumstances.

6. Weight of dam: - The weight of dam and its

foundation is a major resisting force

Methodology:-

A studies offers the primary functions and

corporation of STAADPRO, a software that has

been advanced for the static and seismic stability

opinions of concrete gravity dams. STAADPRO

is primarily based at the gravity approach the

usage of rigid frame equilibrium and beam idea

to carry out pressure analyses, compute crack

lengths, and protection elements. Seismic

analyses can be executed the usage of both the

pseudo-static and a simplified response spectrum

approach. The Curtain Wall is designed the usage

of STAADPRO to face up to and manage all of

the imposed masses on it in addition to preserve

air and water from penetrating within the

constructing. The masses imposed at the curtain

wall are transferred to the constructing structure

thru structural interface (i.e. Brackets) which

attaches the mullions to the constructing

Design steps in STAAD.pro

Step - 1: Creation of nodal points. Based on the

positioning of plan we entered the node points

into the STAAD file

Step - 2: Representation of plates. By using, add

plate command we had drawn the plates between

the corresponding node points.

Step - 3: 3D view of structure. Here we have used

the Transitional repeat command in Y direction

get the 3D view of structure.

Step - 4: Supports and property assigning. After

the creation of structure, the supports at the base

of structure are specified as fixed. In addition, the

Materials were specified and cross section of

plate members was assigned.

Step - 5: 3D rendering view. After assigning the

property the 3d rendering view of the structure

can be shown

Step - 6: Assigning of wind loads. Wind loads are

defined as per IS 875 PART 3 based on intensity

calculated and exposure factor. Then loads are

added in load case details in +X,-X, +Z,-Z

directions.

Step - 7: Assigning of dead loads.

Step -8 :- Assigning of load combinations

DL+LL, DL+LL+UPL,DL+LL+UPL+WL


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multiple factor of 1,1.5& wind load having

different directions of X+ ,X- ,Z+ ,Z-

Step-9:- Concrete Design by using STAAD.pro

software for analysis part and assign all required

parameters also. The code books are IS 456: 2000

& SP 16:2000.

Step-10:- save and run the file for analysis print.

Check how many errors for dam from this

process, if not getting any results so can we

modified & find out where did we mistaken.

Finally post processing & print out of analysis

can be taken out.

Step-11:- After analysis part of entire gravity

dam only applicable to start STAAD. Foundation

v8i for entire building design separately. We can

design based upon our requirements types of

foundations, depth of footings.

Calculations:-

Case 1 :-when the reservoir is empty

Self-weight-

W= l x b x h x γcon

W1= 4.6mx47mx100mx24x9.81

=509021.28kN

W2=1/2x30.4x40x2.4x9.81x100

=1431475.2kN

Case 2:- when the reservoir is maximum level

Self-weight-

W1=509021.28kN

W2=1431475.2Kn

Water pressure:-

PW=ρgh

=1000x9.81x40mts

PW=392400N/m

=392.4KN/m2

Water pressure=1/2x40x392.4

=7848kN

Acts on 40/30=13.34mts from the base

Uplift pressure:-

At heel

P’=γh

=1000x9.81x40

=392400N/m =392.4kN/m

At toe

P’’=γh’

=1000x9.8x10

=98100N/m =98.1kN/m

Over turning moment:-

Moment over toe

Stabilizing moments

M1=w1x32.7

=509021.28x32.7 =16644995.86kNm

M2=w2x20.26mts

=1431475.2x20.26 =29001687.55kNm

M1+m2=45646683.41kNm

Opposing moments:-

Mw1=784800x13.34

=10469232 KN.m

Mup1=490506x20.26m

=9937530kNm

Mw1 +mup1 =10469232 + 9937530 KN.m

Factor of safety=45646683/20406762

=2.24 >2 safe

Sliding:-

Friction ff=μ.N

=0.7(509021.28 + 1431475.2


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1358347.536

Wp=784800

F.o.s =1358347.536/784800

=1.73 >1.5

Safe

Case 3:-

When the reservoir is half fill

W1=509021.28kN

W2=1431475.2kN

Water pressure:-

W1=ρgh

=1000x9.81x20m

=196200N/m =196.2kN/m2

Wp1=1/2x20x196.2

=1962kN

Acts on20/3=6.67mts

Uplift pressure:-

At heel

up1=γwxh

=1000x9.81x20

=196.2kN/m

At toe

Up2=γwxh

=1000x9.81x10

=98100N/m

=98.1kN/m

Over turning moment

Stabilizing moment

Mw1=16644995.86kNm

Mw2=29001687.55kNm

Mw1+Mw2=45646683.41

Opposing moment

Mw1’=196200x6.67

=108654kNm

Mup’=257512.5x2026

=521720.25

Mw1’+ Mup’=6525857.25

Factor of safety=4564668.41/6525857.25

=6.9972

Safe

Sliding force:-

Friction

Ff=μn

=0.7(509021.28+1431475.2

=1358347.536 kN

Wp =196200kN

Factor of safety=1358347.536/196200

=6.9 > 1.5

Safe

Tables and Results:-

Case 2

Sl.no force Horizontal force Vertical force

1 Self-weight

M1 509021.28

M2 1431475.2

2 Water pressure W

748400

3 Uplift

pressure, at heel

-396.2

At toe -98.1

4 Silt pressure -180

Table 1

Sl.no force Horizontal force Vertical force

1 Self-weight

M1 509021.28

M2 1431475.2

2 Water pressure W

196200


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3 Uplift

pressure, at heel

-196.2

At toe -98.1

4 Silt pressure -180

Table 2

Results:-

Fig1: Design of Loads case 2


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Fig2: deflection of dam in STAAD pro for case-2

Fig 3: Shear force (SX) for case-2


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Fig 4 SY local for case-2

Fig 5 maximum absolute shear force for case-2


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Fig 6 design of loads for case-3

Fig 7 deflection of dam in STAAD pro for case-3


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Fig 8 max absolute shear force for case-3

Fig 9 major principle stress for case-3

CONCLUSION:


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The behavior of Gravity dam for

stability and response towards seismic forces are

studied in this paper. With problem

consideration, the stability analysis of gravity

dam is done in absence of seismic forces initially.

Thus analysis highlighted that in presence of

various loads like dead load, water/ hydrostatic

pressure, uplift pressure, total cumulative values

of positive moment and negative moment,

summation of horizontal and vertical forces are

overall responsible for dam stability. Further with

analysis it is clear that moment resulting due to

self-weight act as resistive moment against

moment produced due to water, uplift pressure

etc. This means that stability against overturning

is achieved when positive moment is greater than

negative moments. Whereas stability against

sliding depends upon coefficient of friction, sum

of all vertical forces and all horizontal forces.

Thus sliding is governed by uplift pressure.

However, if horizontal force increases stability

against sliding decreases if vertical forces remain

approximately same. Third stability of dam is on

basis of shear friction factor, this depends upon

coefficient of friction, summation of all vertical

forces, summation of all horizontal forces,

geometry of dam and materials shear strength.

For same problem material shear strength,

geometry friction remains unchanged, thus

stability should depend upon sum of all vertical

forces and all horizontal forces. For problem

considered in study, dam achieves stability

against all factors i.e. overturning, sliding &

shearing.

The factor of safety of overturning for load case

of fully fill of reservoir is 2.17 for the manual

calculations it is safe for the dam. The sliding

stability of the concrete gravity dam for fully fill

load case 1.76, which is greater than 1.5, which is

safe for sliding stability. The factor of safety of

overturning for load case of half fill of reservoir

is 4.23 for the manual calculations it is safe for

the dam. The sliding stability of the concrete

gravity dam for half fill 3.58, which is greater

than 1.5, which is safe for sliding stability.

Reference:

1 “Seismic and Stability Analysis of Gravity

Dams Using Staad PRO” by T Subramani,

D.Ponnuvel. in June 2012

2 “Stability Analysis of Concrete Gravity

Dam for Seismic Loading in Afghanistan”

by Mohammad Ejaz Shahir, Priyanka

Dhurvey in June 2017.

3 .”Stability Analysis of Gravity Dam by

Using STAAD Pro in Time History Method”

by S.Sree Sai Swetha in March 2017

4 “Seismic & Stability Analysis of Gravity

Dam” by Miss. Meghna S. Bhalodkar in

2014

5 “Analysis of Concrete Gravity Dam by 3D

Solid Element Modeling using STAAD Pro”

by Jay p. Patel, R. Chhaya in May 2015

6 “Design And Analysis Of Gravity Dam –A

Case Study Analysis Using Staad-Pro” by

mettu Rajesh Reddy, M.Nageswara rao in

2017


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7 “Finite Element Analysis of Concrete

Gravity Dam by Using STAAD-PRO” by

Rampure Aarti Baburao, Mangulkar

Madhuri in 2016

8 Structural Stability And 2D Finite Element

Analysis of Concrete Gravity Dam by

Khalid Dawlatzai, Dr. Manju Dominic

9 Stability analysis of concrete gravity dam on

complicated foundation with multiple slide

planes by Ren Xuhua, Shu Jiaqing, Ben

Nenghui, Ren Hongyun in 2008.

10 Seismic cracking analysis of concrete

gravity dams with initial cracks using the

extended finite element method by Sherong

Zhang, Gaohui Wang, Xiangrong Yu in

2013

11 “Comparison of Design and Analysis of

Concrete Gravity Dam”by Md. Hazrat Ali,

Md. Rabiul Alam in 2011

12 Shake table sliding response of a gravity

dam model including water uplift pressure

by Mathieu Rochon-Cyr, Pierre Léger in

2009

13 Shake table sliding response of a gravity

dam model including water uplift pressure

by Mathieu Rochon Cyr, Pierre Léger in

2013

14 Seismic fracture analysis of concrete gravity

dams including dam–reservoir interaction by

Yusuf Calayir, Muhammet Karaton in 2005

15 Seismic structural stability of concrete

gravity dams considering transient uplift

pressures in cracks by Farrokh Javanmardi,

Pierre Léger, René Tinawi in 2004


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STABILITY ANALYSIS OF CONCRETE GRAVITY DAM USING … · STAAD Foundation to provide engineers...

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