Economic Design of EOT Crane(FINAL)

i

A

Seminar II Report On

“Economic Design of EOT Cranes”

Submitted In Partial Fulfillment of the Requirement

For The Award of Degree of Master of Engineering

In Mechanical –Design Engineering

Pune University

Submitted By

Ashutosh kumar

Under The Guidance of

Prof. P.B.Deshmane

Department of Mechanical Engineering

Alard College of Engineering, Marunje, Pune

Pune University, Pune

2012-13

ii

Certificate

This is to certify that Mr. Ashutosh kumar has successfully completed his

seminar-II on “Economic Design of EOT Cranes” for the partial fulfillment of

the Master’s Degree in the Mechanical- Design Engineering as prescribed by the

Pune University, Pune during academic year 2012-13

Prof. P.B.Deshmane Prof. V.M.Junnarkar

(Guide) (P.G.Co-Ordinator)

Prof. V.M.Junnarkar Dr.T.R.Sontakke (H.O.D Mechanical) (Principal ACEM)

iii

ACKNOWLEDGEMENT

I wish to express my gratitude to number of people ,without whose constant guidance and

encouragement this seminar would not have been possible. I express my sincere thanks to my

seminar guide Prof. P.D.Deshmane for his continuous guidance and for providing me help as and

when required.

I am also thankful for the wholehearted support and the encouragement given by Prof.

V.M.Junnarkar, (H.O.D, Department of Mechanical Engineering).

Finally, I wish to thank my friends and all those who gave me valuable inputs directly or

indirectly in making this seminar a success.

Thanking all of you once again….

Ashutosh Kumar

iv

INDEX

SR. Name of Topic Page Number Title Sheet

Certificate

Abstract

Index

List of Figures i

List of Tables ii

1. Introduction 1

1.1 Types of Electric overhead cranes 1

1.2 Basic crane components 2

2. Literature Review 5

3. Design Details 8

3.1 Conventional details of the Crane Girder and 8

modern design of crane girder

3.2 Girder’s Plate Details 10

4. Boundary condition for Girder Design 15

5. Analysis of cases 19

6. Conclusions 23

References 24

v

LIST OF FIGURE

Figure No Title of Figure

1.1 Top Running Girder Crane

2.1 Girder section

2.2 Girder Details

LIST OF TABLE

Table No Title of table

3.1 Girder’s Plate Details

3.2 Plate sectional Properties

3.3 Buckling Safety factor

3.4 Buckling Coefficient for the Partial Panel (Without stiffener)

3.5 Buckling Coefficient for the Partial Panel (With stiffener)

4.1 Compressive stress

4.2 Fatigue stress

5.1 Input Data Table

5.2 Girder Section

5.3 Result Table

Economic Design of EOT Cranes

AlardCollegeofEngineering,Marunje,Pune Page1

CHAPTER 1

INTRODUCTION

Cranes are industrial machines that are mainly used for materials movements in Construction

sites, production halls, assembly lines, storage areas, power stations and similar places. Their

design features vary widely according to their major operational specifications such as: type

of motion of the crane structure, weight and type of the load, location of the crane, geometric

features, operating regimes and environmental conditions

1.1 TYPES OF ELECTRIC OVERHEAD CRANES

There are various types of overhead cranes with many being highly specialized, but the great

majority of installations fall into one of three categories:

a) Top running single girder bridge cranes,

b) Top running double girder bridge cranes and

c) Under-running single girder bridge cranes.

Electric Overhead Traveling (EOT) Cranes come in various types:

1) Single girder cranes - The crane consists of a single bridge girder supported on two

end trucks. It has a trolley hoist mechanism that runs on the bottom flange of the

bridge girder.

2) Double Girder Bridge Cranes - The crane consists of two bridge girders supported on

two end trucks.

The trolley runs on rails on the top of the bridge girders.



3) Gantry Cranes - These cranes are essentially the same as the regular overhead cranes

except that the bridge for carrying the trolley or trolleys is rigidly supported on two or

more legs running on fixed rails or other runway. These “legs” eliminate the

supporting runway and column system and connect to end trucks which run on a rail

either embedded in, or laid on top of, the floor.

4) Monorail - For some applications such as production assembly line or service line,

only a trolley hoist is required. The hoisting mechanism is similar to a single girder

crane with a difference that the crane doesn’t have a movable bridge and the hoisting

trolley runs on a fixed girder. Monorail beams are usually I-beams (tapered beam

flanges).

1.2 BASIC CRANE COMPONENTS

To help the reader better understand names and expressions used throughout this course, find

below is a diagram of basic crane components

Fig 1.1 Top Running Girder Crane



1) Bridge - The main traveling structure of the crane which spans the width of the bay

and travels in a direction parallel to the runway. The bridge consists of two end trucks

and one or two bridge girders depending on the equipment type. The bridge also

supports the trolley and hoisting mechanism for up and down lifting of load.

2) End trucks - Located on either side of the bridge, the end trucks house the wheels on

which the entire crane travels. It is an assembly consisting of structural members,

wheels, bearings, axles, etc., which supports the bridge girder(s) or the trolley cross

member(s).

3) Bridge Girder(s) - The principal horizontal beam of the crane bridge which supports

the trolley and is supported by the end trucks.

4) Runway - The rails, beams, brackets and framework on which the crane operates.

5) Runway Rail - The rail supported by the runway beams on which the crane travels.

6) Hoist - The hoist mechanism is a unit consisting of a motor drive, coupling, brakes,

gearing, drum, ropes, and load block designed to raise, hold and lower the maximum

rated load. Hoist mechanism is mounted to the trolley.

7) Trolley - The unit carrying the hoisting mechanism which travels on the bridge rails

in a direction at right angles to the crane runway. Trolley frame is the basic structure

of the trolley on which are mounted the hoisting and traversing mechanisms.

8) Bumper (Buffer) - An energy absorbing device for reducing impact when a moving

crane or trolley reaches the end of its permitted travel, or when two moving cranes or



trolleys come into contact. This device may be attached to the bridge, trolley or

runway stop.

The escalating price of structural material and energy is a global problem consequently

optimal consumption of the both cannot be considered redundant. Overhead crane, which is a

synonym for material handling in the industrial environment, utilizes structural steel for its

girder and energy (mostly electrical) for its operation. Light girder for overhead cranes not

only save material cost but also trim down energy expenditure because of subsequent

employment of low powered drive units. The general procedure for design of EOT crane

girders is accomplished through guidance stipulated in the prevailing codes and standards.

Thus optimal design in such case is not the one which just exhibit stress criteria offered in

structural design methods but the one which follows the limits restrained by the

aforementioned codes and safety rules. Shape optimization of closed box type section was

studied by Gibczynska et al.. Regarding optimal design of simple symmetrical welded box

beam Farkas J & Jarmai K incorporated bending stress, shear stress and buckling constraints

while kept cost, mass and deflection as objective function. Megson, T H.G. Hallak ,

parametrically and numerically analyzed load bearing diaphragms girder at single support

point. Narayanan, in his two consecutive papers examined strength capacity of webs with

cut-outs and rectangular holes and emphasized on prediction of stress in such cases..

Recently little literature is found which chiefly reviews crane box beam optimization except

for Tadeusz Niezgodzin´skia, Tomasz Kubiakb who considered buckling problem of web

sheets in box girders of overhead cranes due to welding of the backing strips.



CHAPTER 2

LITERATURE REVIEW Fig-2.1 & 2.2 shows the basic components of Crane girder. It’s construction can be any of

the below mentioned:

(1) Beam profile Section

(2) Built-up profile Section

(3) Box Section

Fig - 2.1

Fig - 2.2



Our topic is related to box girder sections. Usually for span (Girder length) more than 12

meters and load more than 10t box profile is selected because of having better sectional

property with lower weight.

In case of Box girders it is very important to define the sectional parameters in terms of

dimension. Poor selection will not lead to optimum design. There are certain instructions

about the section parameters as per IS-807-2006 listed below:

a) l/h shall not exceed 25,

b) l/b shall not exceed 60,

c) b/c shall not exceed 60.

Where,

l=Span of the crane in mm;

h=Depth of the Girder;

b=Width of the Girder;

c=Thickness of the top cover plate.

Once the Girder proportion is considered then we get some boundary to work in as to design

and optimize any girder we need to follow certain norms as well. Henceforth we will be

considering IS: 807-2006 &IS: 800-1984 as the guiding source. These standards only define

some boundary in which we have to design the structure. Basically IS: 807 & IS: 800 are the

Indian standard which is used in our country by all crane manufacturers who design as per

these Norms.

As mentioned earlier the box girder is the welded structure with the help of four plates- top

plate, bottom plate and two web plates inside the top and bottom, thus forming a box

structure. These plates are welded to each other. There are some more parts which keeps the



structure balanced and stable. These are diaphragm plates, Angular stiffeners and backing

strips for web (not shown in figure). Rail on which crane trolley runs can be either welded on

the top of the web above top plate (as shown) or can be placed on the girder top at the center

of the top flange. These two positions are not only the locations where the rail can be placed

as it also depends on the design and dimensional requirement of the Crane.

Rails used in the crane girders can either be flat bar type or can be profile rails as used in

railway. This selection depends on the wheel selected for crane trolley and also sometimes as

per customer requirement.



CHAPTER 3

DESIGN DETAILS

3.1 CONVENTIONAL DETAILS OF THE CRANE GIRDER AND MODERN

DESIGN OF THE CRANE GIRDER

(a) Conventional Design of the Crane Girder (Rail on Center Construction)

In such crane, Wheel load which is coming from trolley is directly applied on top

flange, which results in buckling of top flange in addition to stresses coming on it. In

order to avoid buckling we have to provide full diaphragm & short diaphragm

throughout length of girder. This not only helps in eliminating the buckling of top

flange but also helps in reducing the bending stresses coming in the rail. In addition to

these angular stiffeners are also added to web plates to avoid its buckling. Thus the

girder structure weight consists of Rail, Top & Bottom flanges, web plates, backing

strips, Short diaphragm & Long diaphragm.

(b) Modern Design of the Crane Girder (Rail on web)

In such crane, Wheel load which is coming from trolley is directly applied on web,

which results in load transmission through it. The web plates are then subjected to

buckling also but due to addition of angular stiffener the buckling effects are

nullified. Rail being on web has another one important advantage that the rail is not

subjected to bending stress. So here in this type of girder design Short diaphragms are

not required as the rails bending is taken care by web and the top flange is also not

subjected to buckling loads. Thus the girder structure weight consists of Rail, Top &

Bottom flanges, web plates, backing strips& Long diaphragm.



(c) Findings of above study

Girder manufactured as per the conventional design style is heavy as compared to the Girder

manufactured as per the Modern design way.

Out of the whole crane structure weight Girder Keeps the maximum share for small span

cranes, but for long span cranes girder weights are the major decisive for cranes weight.

It is always preferable to have lower crane weight from both customer and vendor point of

view. Thus in order to reduce the crane weight the girder’s weight must be minimized.

As the weight of girder increases

The loading on End carriage increases which results in heavier end carriage.

Once the structural weight rises up the mechanical component sizing also goes up

which results in the increase in cost of the mechanical components for the same usage

and hence the crane pricing goes up.

It results in selection of heavier electrical components like motor, drive etc. Heavier

electrical requires higher electrical input which again increases the cost of the

electrical energy consumption on daily basis.

Higher crane weight needs the gantry girder much heavier so here the customer also

faces. His workshop columns and gantry needs to be heavier if the crane weight has

increased.

Ultimately daily manufacturing cost goes up.



3.2 GIRDER’S PLATE DETAILS

Depending on the dimensional availability of the plates in the market some standard sizing

has been used as the regular practice now days.

FLANGE WEB Thickness (t) mm

(F)mm (W)mm 6 8 10 12 16 20

200 410 F,W F,W F,W F,W F,W F

300 490 F,W F,W F,W F,W F,W F

410 610 F,W F,W F,W F,W F,W F

490 740 F,W F,W F,W F,W F,W F

610 860 F,W F,W F,W F,W F,W F

740 980 F,W F,W F,W F,W F,W F

860 1230 F,W F,W F,W F,W F,W F

980 1480 F,W F,W F,W F,W F,W F

1230 1780 F,W F,W F,W F,W F,W F

NA

1980 W W W W W

NA 2180 W W W W W

2380 W W W W W

TABLE-3.1

Table 3.1 shows the preferred dimensions of Flanges and Web plates with various thickness

combinations. Usually rectangular Box sections with flanges more than 1230mm width and

20mm thickness are not preferred as it reduces structural stability with same construction.

Same is applicable for web plates also. But in case of web plates the total depth can be up to

2380mm with 16mm thickness. These dimensions cannot be considered as the bounding

figures.



Span

(l)

m

Flange

(b)

mm

Web

(h)

mm

Flange

thk(c)

mm

web

thk

mm

Ixx(cm4) Iyy(cm4) Zxx

(cm3)

Zyy

(cm3)

wt/mtr

(kg/m)

10 200 410 6 6 17276.2 5148.8 818.8 514.9 57.5

15 200 610 6 6 45466.2 7270.2 1462 727.1 76.4

20 300 860 6 6 131102.8 24102.7 3007 1606.9 109.3

25 410 1230 8 8 499472.8 85576.1 8017.3 4174.5 206

30 490 1230 10 8 624835.8 127378.5 9997.4 5199.2 231.5

35 490 1480 10 8 976171.6 149283.1 13015.7 6093.2 262.9

40 610 1780 12 10 2115299 348965.8 23451.3 11441.5 394.4

45 740 1980 16 12 3911066 696908.6 38877.4 18835.4 559

50 740 2180 16 12 4926967 756388.3 44547.7 20443 596.6

55 860 2380 16 16 7544746 1475129 62560.1 34305.4 813.9

60 980 2480 18 16 9571243 2043057 76083.1 41695.1 900

TABLE-3.2

Table 3.2 shows the chart which shows the plate dimensions of a girder for different spans. In

order to optimize the Girder Section web plate plays important role. As per Table-3.2 it is

clear that for the same flange dimension but different web dimension the sectional properties

increases much faster as compared to the increase in the weight.

Web Plate selection and design:

Web plates are not only selected as per the dimensions mentioned above but also checked for

buckling stresses. In case of box girder there are two important internal elements also as

mentioned earlier-Diaphragm and Horizontal stiffeners.



Role of Diaphragm:- Diaphragm not only support the structure internally but also is a

relevant support for web plates. It divides the web plates in different part known as panels.

IS-800 clearly specifies it. This panel is detailed by two dimensions-a & b.

a – Length of the panel.

b – Depth of the panel.

Buckling of this panel is checked as per the formula mentioned below:

Where,

σe – Buckling Stress; t1- Thickness of the panel; b1- Depth of the panel;

ν – Poisson’s ratio; E- Modulus of Elasticity.

Absolute value of maximum compressive stress(σ1) & Shear stress (τ):

σ1ki – Local ideal buckling stress calculated as below:

σ1ki = σe . k (kg/cm2) or (N/mm2)

S - Service factor (From Table-3.3)

K – Local Buckling Coefficient (From Table-3.4 & 3.5)



Loading Condition Safety Factor for Buckling

of the whole plane.

Safety Factor for Buckling of the

partial plane surrounded by stiffeners.

I 1.71 + 0.180 (ϕ -1) 1.5 + 0.075 (ϕ -1)

II 1.50 + 0.125 (ϕ -1) 1.35 + 0.05 (ϕ -1)

III 1.35 + 0.075 (ϕ -1) 1.25 + 0.025 (ϕ -1)

TABLE-3.3

Buckling Coefficient for the Partial Panel (Without stiffener)

TABLE-3.4

Table-3.4 shows the panel which is nothing but the web plate section which is dimensioned

as a & b. From the above table we can select the Buckling coefficient K. This Chart is

applicable to only unstiffened web.



Table 3.5 is applicable to the webs which are subjected to both vertical as well as horizontal

stiffener. In this the panel formed due to vertical diaphragm is further subdivided into small

sub panels with the help of angular stiffener. Buckling Coefficient for the Partial Panel (With

stiffener)

TABLE-3.5



CHAPTER 4

BOUNDARY CONDITION FOR GIRDER DESIGN

Crane girder design is guided by various design norms like-IS: 807, FEM, CMAA, EN etc.

We have following conditions to be satisfied in order to get the girder on the safer side:

(a) Static stresses to be within limit.

(b) Fatigue Stresses to be within limit.

(c) Horizontal & vertical deflections to be within limit.

(d) Horizontal & Vertical vibrations to be within limit.

(a) Static Stress Check:

In this check we are checking the stress ratio of the structure due to static loading which

arises on account of self weight and lifted capacity. The allowable value is well defined in

design norms. Basically tensile stress ratio and compressive stress ratio is checked in this

case.

The allowable value of tensile stress and compressive stress for steel plates as per IS: 807 are

given as below:

Tensile stress value: σt

σt = 0.66*Syt*Duty factor (As per IS-807)

Where,

Syt-Yield Stress of selected material (N/mm2)

Duty Factor- 1 (For class-I), 0.95 (For Class-II), 0.9 (For class-III),0.85 (For Class-IV)

Compressive stress value: σc

Allowable compressive stress value is considered from following two conditions (As per

IS: 807)

(1)Allowable compressive stress is to be considered 1235 Kg/cm2 if the ratio b/c is equal to

or less than 38



(2)When the ratio exceeds 38 then the allowable compressive stress value is considered

from the table below:

b/c σc (kg/cm2)

40 1145

44 990

48 870

52 770

56 690

60 625

TABLE-4.1

(b) Fatigue stress check

In this we check the fatigue stress occurring in the structure and compare it directly

to the corresponding fatigue stress value as guided by design Norms.

The allowable value of fatigue stress for different load cycles are given below which

is purely as per IS:807.

fatigue stress depending on stress cycles (Kg/cm2)

stress category 10000-20000 100000-500000 500000-2000000 over 2000000

A 2760 2210 1660 1660

B 2280 1720 1170 1030

C 1930 1450 960 830

D 1660 1170 690 620

E 1170 830 480 410

F 1170 960 760 620

TABLE-4.2



Stress category –C is applicable to crane girders so the fatigue stresses can be cross

checked for different hoisting cycles for different stress values tabulated above.

(c ) Horizontal & Vertical deflection Check:

In this we check the girder’s deflection in both direction –Horizontal and vertical.

For vertical deflection there is general guidance as per IS:807 which speaks that the

vertical deflection must be limited by ratio of span/900. The vertical deflection should

involve the live load deflection only and no impact should be considered.

For horizontal deflection there are no such guidelines so we generally restrict it by the

same ratio as mentioned above.

(d) Horizontal and Vertical vibrations

This is one of the important check which must be done at least for long span crane.

Unfortunately there is no guideline in IS:807 for this but we follow ISO standard for

this checking.

Formulae used for checking the vertical as well as horizontal vibrations are given

below:-

Where,

fV= Vertical natural frequency

E= Modulus of Elasticity (N/mm2)

Iy= Vertical Moment of Inertia

S= Span of the crane

Mc=Crab Mass

Mg= Girder mass



Above mentioned formula is given in ISO-22896. We use this formulae to check

girders vibration.

For Horizontal Vibration the calculation procedure is shown below:

Where,

Fh= Horizontal natural frequency

E= Modulus of Elasticity (N/mm2)

Iz= Horizontal Moment of Inertia

Kmg= Typical value considered as 0.4857

Mc=Crab Mass

Mg= Girder mass

The allowable values of vertical frequency and Horizontal frequency are considered

as 2 and 1.7 respectively as per ISO standard



CHAPTER 5

ANALYSIS OF CASES

Case-1

When the rail is placed on the top of the girder and the rail center is matching to the web

center

Case-2

When the rail is placed on the top of the girder and the rail center is matching to the top

flange center

2.1 Basic Inputs:

PARAMETERS Case-1 Case-2

Total payload 500000 kg 500000 kg

Design Standard IS-807 IS-807

Crane Duty class II II

Bridge travelling speed 40 m/min 40 m/min

Span 37900 mm 37900 mm

Trolley Rail gauge 8500 mm 8500 mm

Trolley Wheelbase 5600 mm 5600 mm

Trolley approach at end 1 1000 mm 1000 mm

Trolley approach at end 2 1000 mm 1000 mm

Trolley Wheel diameter 900 mm 900 mm

Trolley Wheel width 170 mm 170 mm

Trolley Wheel flange height 20 mm 20 mm

Trolley Traversing speed 20 m/min 20 m/min

Trolley weight 160000 kg 160000 kg

TABLE-5.1 Input Data Table



Above chart shows the basic input which is required to decide the girder section.

5.2 Girder Section

Parameters Case-1 Case-2

H 3480 3480

T1 12 18

T3 12 10

BL 1750 1750

T2 40 40

B 1750 1750

T4 40 32

F1 75 200

F2 75 125

F3 75 125

F4 75 50

RAIL A-150 A-150



NOTE: Rail is intentionally not shown in the girder section. For case-1 the rail will be on the

web top and for Cae-2 the rail will be on the girder top at the centre of the top flange.

The material of the girder confirms IS-2062 with yield strength 250 N/mm2.

Based on the above data the following results are tabulated below:

Parameters Case-1 (Rail on centre) Case-2 (Rail on web)

Component Ratio Condition Ratio Condition

Stresses 0.82 <= 1 0.86 <= 1

Fatigue 0.94 <= 1 0.94 <= 1

Displacements 0.65 <= 1 0.97 <= 1

Plate buckling 0.99 <= 1 0.99 <= 1

Vibrations 0.95 <= 1 0.99 <= 1

Weight 114T 100T

Table 5.3

Observations:

If the rail is placed on the Web top then the girder will have following advantages &

Disadvantages:-

Advantages:

(i) Better utilization of box property.

(ii) Better dimensions achieved for the overall crane.

(iii) No short diaphragm required as the rail is placed on the web.

(iv) Diaphragm thickness is not governed completely by rail so lower thick

diaphragm plate can be used.

(v) The loading on End carriage decreases which results in ligter end carriage

(vi) Once the structural weight goes down the mechanical component sizing also

goes down which results in the decrease in cost of the mechanical components

for the same usage and hence the crane pricing goes down.



(vii) It results in selection of lighter electrical components like motor, drive etc.

Lighter electrical requires lighter electrical input which again decreases the

cost of the electrical energy consumption on daily basis

(viii) As shown in the section 4.3 the girder weight for the same capacity decreases

by 14% for Modern girder design and hence decreasing the structural,

mechanical and electrical components in equivalent terms.

(ix) Lighter crane weight needs the gantry girder much lighter.

(x) Girder manufacturing becomes easy and fast because of absence of short

diaphragm.

(xi) Fast Manufacturing results in cheaper overall fabrication.

(xii) Better condition of hook along with rope for its position at top and bottom.

(xiii) Trolley design also becomes bit easier as the girder section constraint is

removed.

(xiv) Welding as well as bolting both becomes favorable for rail.

(xv) Ultimately daily manufacturing cost goes down for the end user.

Disadvantages:

(i) Girder experience torsion moments in addition to other moments.

(ii) Care has to be taken in mounting the rail on the web top. It should be within

specified limit.

(iii) Web plate needs to be thicker below the rail and sometimes at the end where

the shear height is low we need to add extra thick plate.



CHAPTER 6

CONCLUSION

Modern Girder design gives lighter girder as compared to Conventional Girder design

methods. Of course the actual stresses and deflection values goes above but remains in the

prescribed limit, so we can utilize this to reduce the sectional dead weight.

Due to lower crane structure weight the power required to drive the complete mechanism

also decreases and hence the electrical equipment prices also go down. This result in low

electrical consumption on daily basis as well.

This results in Lighter crane by weight and hence lesser capital cost & daily running cost.



REFERENCES

(1) Design Optimization of EOT Crane Bridge.(International conference of Engineering

Optimization)

(2) Optimization of an oversized beam part of a crane bridge by applying the economic

criteria.(ACTA Technical convensis-Bulletin of Engineering)

(3) Optimization of box section of the main girder of the bridge crane with rail placed

above the web plate.( Springer Verlag2012)

(4) Optimization of Double Box Girder Overhead crane in Function of Cross section

Parameter of Main Girder.( 15th International Research/Expert Conference)

(5) N Rudenko-Material Handling Equipment

(6) M P Alexandrov-Material Handling Equipment

(7) Crane supporting steel structures- R A Mac Crimon

(8) Overhead and Metallurgical cranes-Dr G M Nikolaevsky

(9) IS-807-2006, IS-800-1984,FEM-9.541, ISO-4301.

Economic Design of EOT Crane(FINAL)

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