Calculate Design Beam Jib Crane
Post on 03-Oct-2015
169 Views
Preview:
DESCRIPTION
Transcript
2CRANES I
INTRODUCTION
The dynamic structural calculation allows to determine the
stress of the elevator during its operation.
Phases:
1. Find the external forces and their combination, that act on the
structure.
2. Displacement, stress and reaction calculation of each of the
components applying the adequate calculation process.
3. Verification of the obtained values of elasticity, resistance and
stability.
Nowadays: Finite element programs are used
CRANES I
Loads to be considered:
Principal loads acting on the structure for the motionless elevator. The worst
loads are:
Normal operation load: service load + accessories
Self weight: crane components weight (set aside operation load)
Loads due to vertical movements:
Accelerations or decelerations
Vertical impacts due to the rollers
Loads due to horizontal movements:
Accelerations or decelerations
Centrifugal force
Lateral effects due to rolling
Impact effects
Loads due to changes in climate:
Wind, snow and temperature effects
Various loads:
Dimensioning of rails and aisles
INTRODUCTION
3CRANES I
STRUCTURAL CALCULATION: CASE I
CASE I: Without wind: The next loads are considered: static due to self weight SG, forces
due to service load SL multiplied by the dynamic coefficient and the two most unfavourable horizontal effects SH, set aside
impact effects, multiplied by an increase factor c:
( )c G L H S +S +S Increasing factor c [UNE 58132-2] : Depends on the elevator
classification group
1,201,171,141,111,081,051,021,00c
A8A7A6A5A4A3A2A1Elevator
group
CRANES I
STRUCTURAL CALCULATION: CASE I
Dynamic coefficient : takes into account The service load lifting.
The accelerations and decelerations in the lifting process.
The vertical impacts due to the rolling in the track.
( )c G L H S + S +S
L=1+V
VL is the lift speed in m/s
is an experimental coefficient obtained by carrying out several tests in different elevators
4CRANES I
STRUCTURAL CALCULATION: CASE I
Bridge and gantry crane
Jib crane
CRANES I
STRUCTURAL CALCULATION: TOWER CRANE
It is important to know the
maximum load depending on the
position: its values are usually
specified in points A and B
Pi=Q+Pc
(load+trolley)
G: crane weight
Gc: counterweight weight
Jib
Mast
Jib pendants Jib pendants
Counterweight jib
Cat head
5CRANES I
STRUCTURAL CALCULATION: TOWER CRANE
Above structure
( )
( )
B1
c2
PT =
sen
GT =
sen
2 2
T = +3
Traction forces in the jib ties
( )
( )
B1
c2
PT =
sen
GT =
sen
The jib pendants are subject to
traction, while the cat head is
subjected to compression, flexure
and shear
11
1
22
2
T =
A
T =
A
Forces in the cat head are:
( ) ( )( ) ( )
1 2
1 2
V=T sen +T sen
H=T cos -T cos
M=H h
c
p
f
pf
z
V =
A
M =
W
H m=
b I
Von Misses
2 2
T f c = ( ) +3+
m: first moment of the
principal area
CRANES I
STRUCTURAL CALCULATION: TOWER CRANE
Above structure
pl,f A 3
pl,c A
M = P L
V = P
The jib is subjected to flexure and
shear forces:
pl,f A 3
pl,c A
M =P L
V =P
A 3f
pf
A
z
P L =
W
P m=
b I
2 2
T f = +3
Von Misses
6CRANES I
STRUCTURAL CALCULATION: TOWER CRANE
Mast
f B 1 c 2
c B c
M =P L G L G e
V =P G G
+
+ +
The mast is subjected to flexure and
compression forces
B 1 c 2f
mf
B cc
m
P L G L G e =
W
P G G =
A
+
+ +
f B 1 c 2
c B c
M = P L G L G e
V = P G G
+
+ +
T f C = +
MfVce LL2
L1=L+e
Jib tie Jib tie
Jib
Cat head
Counterweight jib
Tower
CRANES I
STRUCTURAL CALCULATION: CASE I
Loads due to horizontal movements: Accelerations and decelerations due to translations
movements of the crane
Acceleration or decelerations due to movements of the
load
Centrifugal force
Lateral effects due to rolling (loads due to obliquity)
( )c L HG S + +SS
7CRANES I
STRUCTURAL CALCULATION: CASE I
Accelerations or decelerations of movements : Accelerations/decelerations due to translation movements
of the crane
The acceleration/deceleration value depends on: The desired speed
Time to accelerate/decelerate
Usage of the elevator
( )c L HG S + +SS
aH = V
g
CRANES I
STRUCTURAL CALCULATION: CASE I
0,0642,500,16
0,0783,200,25
0,162,500,0984,100,40
0,193,200,125,200,63
0,333,000,254,000,156,601,00
0,433,700,325,000,198,301,60
0,474,200,355,600,229,102,00
0,524,800,396,302,50
0,585,400,447,103,15
0,676,000,508,004,00
Acceleration
[m/s2]
Time to
accelerate
[s]
Acceleration
[m/s2]
Time to
accelerate
[s]
Acceleration
[m/s2]
Time to
accelerate
[s]
(c)
High speed with great
accelerations
(b)
Medium and high speeds (usual
applications)
(a)
Low and medium speed with
large travellingDesired
speed [m/s]
8CRANES I
STRUCTURAL CALCULATION: CASE I
Accelerations or decelerations of the load movement: Inertia force of the load (with weight W):
Rotational movement:
( )c L HG S + +SS
T=J
WaF= =ma
g
T: Inertia moment
J: Inertia polar moment =
: Angular acceleration
2
i im d
CRANES I
STRUCTURAL CALCULATION: CASE I
2
i ie 2
m dm =
D
eF=m a
a= D
Inertia forces due to rotation:
Equivalent mass Tangencial acceleration
2
i im dF=D
9CRANES I
STRUCTURAL CALCULATION: CASE I
Loads due to obliquity: Tangential forces between the wheels and the rail track.
Guide forces.
A simple translation mechanical model is needed: n pairs of wheels in line.
p coupled pairs.
( )c L HG S + +SS
Fixed/Fixed(F/F)
Fixed/Mobile(F/M)
Coupled (C) Individual (I)
CRANES I
STRUCTURAL CALCULATION: CASE I
Loads due to centrifugal forces: Effects of the cable inclination
( )c L HG S + +SS
2
c
WR nF =
g 30
W: Load
R: Radius
n: Rotating speed
g: gravity acceleration
10
CRANES I
STRUCTURAL CALCULATION: CASE II
CASE II: Normal operation with service limitwind To the loads considered in CASE I it is added the
effect of service limit wind Sw and, if needed, theload due to variation in temperature:
Overloading due to snow is not considered.
( )c G L H w S +S +S S+
CRANES I
STRUCTURAL CALCULATION: CASE II
Wind effect
( )c G L H w S +S +S S+
A is the net surface, in m2, of the considered element, that is, the solid surface
projection over a perpendicular plane in the wind direction.
Cf is a shape factor, in the wind direction, for the considered element.
p is the wind pressure, in kN/m2, and it is calculated by means of the following
equation:
where vs is the calculated wind speed in m/s
fF=A p C
-3 2
sp 0,613 10 v [kPa]=
11
CRANES I
STRUCTURAL CALCULATION: CASE II
1,1Square structures filled (air cannot flow
beneath the structure)
Machine
room, etc
1,2
0,8
Circular metal sections
in which Dvs < 6 m2/s
in which Dvs 6 m2/s
1,7Flat side metal section
Simple
lattice work
2,2
1,9
1,4
1,0
2,1
1,85
1,35
1,0
1,95
1,75
1,3
0,9
1,75
1,55
1,2
0,9
1,55
1,40
1,0
0,8
b/d
21
0,5
0,25
Square metal sections of more than
350 mm side and rectangular of more
than 250 mm x 450 mm
1,1
0,8
1,0
0,75
0,95
0,70
0,90
0,70
0,80
0,65
0,75
0,60
Circular metal sections
in which Dvs < 6 m2/s
in which Dvs 6 m2/s
1,91,71,651,61,351,3Metal section in L, in U and flat plates
Simple
elements
50403020105
Aerodynamic drag coefficientl/b or l/DDescriptionType
Cf: Shape factor [UNE 58-113-85]
CRANES I
STRUCTURAL CALCULATION: CASE II
Wind
Element length 1 1Aerodynamic coefficient= or
Section height facing wind b D=
Section height facing wind bSection proportion=
Section width parallel to wind d=
12
CRANES I
STRUCTURAL CALCULATION: CASE II
0,5028,5Dock cranes that should continue
operation in case of strong wind
0,2520Every normal crane installed in exteriors
0,12514
Cranes which can be protected against
wind and designed exclusively for light
wind (for example, low height cranes
with an easily folding jib to the ground)
Wind pressurekPa/m2
Wind speedm/s
Type of crane
Speeds and pressures of service wind [UNE 58-113-85]
-3 2
sp 0,613 10 v [kPa]=
CRANES I
STRUCTURAL CALCULATION: CASE II
Snow overloading: It is not considered
Temperature effect: Only when the elements cannot freely expand
Temperature limit -20 C + 45 C
( )c G L H w S +S +S S+
13
CRANES I
STRUCTURAL CALCULATION: CASE III
CASE III: Elevator subjected to exceptional loads
a) Elevator out of service subjected to maximum wind.
b) Elevator in service subject to impact.
c) Elevator subjected to static and dynamic tests.
CRANES I
STABILITY
m m b bW d W d W d> +
14
CRANES I
STABILITY
( )m m f o f b b rW d W d d W d Wd+ > +
Wm
Rotation axis
CRANES I
f
QM =- L
2
c c
QG d=G e+(P ) L
2 +
f
QM = L
2
COUNTERWEIGHT CALCULATION
f c i cM =(P Q ) L+G e-G d+
It is usually calculated so that it counteracts the half
of the material moment and the jib moment
P=Qi+Pc(Load+hoist)
Moment:
Without load: Qi=0
With load: Qi=Q
With this type of counterweight the mast, with and without
load, has a uniform solicitation in a favourable way
Most unfavourable
situations:
f c i c i
Q QM =(P Q ) L+G e- G e+(P ) L Q L
2 2
+ + =
15
CRANES I
It is used by manufacturers and clients so that a specific elevator operates within
certain required service conditions.
CLASSIFICATION
Crane and elevators classification allows to establish the design of the structure and of the mechanisms
Elevator classification Mechanism classification
It gives the manufacturer
information of how to design and
verify the elevator so that it has
the desired service life for the
operation service conditions
Used by the client and the
manufacturer to achieve a
fixed elevators service
conditions
CRANES I
CLASSIFICATION OF THE EQUIPMENT
The total number of manoeuvre cycles is the sum of all of the cycles carried out during the elevator life.
The user expects that the elevators manoeuvre number of cycles is achieved during its life.
The total number of manoeuvre cycles has a relationship with the usage factor:
The manoeuvre spectrum has been conveniently divided in 10 usage classes.
CLASSIFICATION OF THE EQUIPMENT (standard 58-112-91/1)
Number of cycles of a manoeuvre Load spectrum coefficient
A manoeuvre cycle begins when the load is prepared to be lifted and finishes when the elevator is prepared to lift the next load
16
CRANES I
CLASSIFICATION OF THE EQUIPMENT: TOTAL NUMBER OF CYCLES
CRANES I
CLASSIFICATION OF THE EQUIPMENT
Depending on the available information of the number and weight of the loads to be lifted during the elevator life:
Lack of indications: manufacturer and client have to achieve an agreement.
If the information is available: the load spectrum coefficient of the elevator can be calculated.
CLASSIFICACIN OF THE EQUIPMENT (standard 58-112-91/1)
Number of cycles of a manoeuvre Load spectrum coefficient
The load condition is the number of times a load is lifted, which is suitable to the elevator capacity
17
CRANES I
CLASSIFICATION OF THE EQUIPMENT : LOAD LEVEL
3
i ip
T max
C PK =
C P
Ci is the mean number of cycles of manoeuvre for each different load level.CT is the total of the individual cycles for every load level.Pi are the values of the individual loads characteristic of the equipment service operation.Pmax is the maximum load that the equipment is authorized to lift (safe working load).
CRANES I
CLASSIFICATION OF THE EQUIPMENT : LOAD LEVEL
18
CRANES I
CLASSIFICATION OF THE COMPLETE EQUIPMENT
CRANES I
CLASSIFICATION OF THE COMPLETE EQUIPMENT
19
CRANES I
CLASSIFICATION OF THE MECHANISM
Maximum service duration can be computed by means of the mean daily service, in hours, of the number of working days per year and the number of the planned years of service.
A mechanism is considered to be on service when it is on movement.
CLASSIFICACIN OF THE MECHANISMS (standard 58-112-91/1)
Usage of work equipment Mechanism load level
It is calculated for the planned service duration in hours
CRANES I
CLASSIFICATION OF THE MECHANISM: USAGE
20
CRANES I
CLASSIFICATION OF THE MECHANISM
CLASSIFICACIN OF THE MECHANISMS (standard 58-112-91/1)
Use of work equipment Loads applied to the mechanism
The load level is a feature that shows how much a mechanism is subjected toa maximum load, or only to low loads.
3
i im
t max
t Pk =
T P
ti is the mean service duration of the mechanism when subjected to individual loads.Tt iis the sum of the individual durations in all load levelPi is the individual load level of the mechanismPmax is the maximum load applied to the mechanism
CRANES I
CLASSIFICATION OF THE MECHANISM: APPLIED LOAD
21
CRANES I
CLASSIFICATION OF THE MECHANISM
CRANES I
CLASSIFICATION OF THE MECHANISM
22
CRANES I
CLASSIFICATION
Crane with hook:
CRANES I
CLASSIFICATION
Crane with hook: Usage class U5
Lift cylce
Load liftMovement of the loadRotationLoweringUnhook the loadUnloaded liftRotationMovement of the loadUnloaded liftTo hook a new load
tmc=150 s
23
CRANES I
CLASSIFICATION
mcN tT [h]3600
=
Total length usage of the machine:
tmc= cycle mean length [s]N = Number of cycles
55 10 150T 20835 horas
3600
=
CRANES I
CLASSIFICATION
mechanismi
mc
t
t =
For each of the mechanisms it is defined:
tmechanism= usage time of the mechanism during onecycle [s]tmc= mean duration of one cycle [s]
Load liftMovement of the loadRotationLoweringUnhook the loadUnloaded liftRotationMovement of the loadUnloaded loweringHook a new load
Lift mechanism
Slewing mechanism
Movement mechanism
24
CRANES I
CLASSIFICATION
Lift mechanism
Slew mechanism Travelling mechanism
63%
10%25%
Load liftMovement of the loadRotationLoweringUnhook the loadUnloaded liftRotationMovement of the loadUnloaded loweringHook a new load
Load liftMovement of the loadRotationLoweringUnhook the loadUnloaded liftRotationMovement of the loadUnloaded loweringHook a new load
Load liftMovement of the loadRotationLoweringUnhook the loadUnloaded liftRotationMovement of the loadUnloaded loweringHook a new load
CRANES I
CLASSIFICATION
Lift mechanism i====0.63
Total duration of the mechanism in hours:
i====13126 h 7777
Slew mechanism i====0.25
i====5209 h 5555
Travelling mechanism i====0.10
i====2084 h 4444
25
CRANES I
ENGINES
Power calculation:
2e
G VP = [CV]
4500
Lift movements
Travelling movementsPower
G1: self weight (trolley,span, etc.) [daN]
G2: load + accessories [daN]
V: speed [m/min]
: mechanical efficiencyW: friction coefficient
7 for rolling bearing
20 for friction bearing
1 2t
(G +G ) W VP = [CV]
4500000
CRANES I
ENGINES
Torque needed to accelerate:
MA = Mw + Mb [daNm]
Starting torque = resistance torque + acceleration torque
22 21 21
(G +G ) dGD [daNm ]
=
2
1 1
b
a
GD nM [daNm]
375 t
=
tw
1
716 PM [daNm]
n
=
Masses moved linearly
Rotating mass2
2 2 221 2 2
1
nGD GD [daNm ]
n=
n1: engine speed in rpm
GD12: inertia torque sum referred to engine axista: acceleration time:
Lift, cierre cuchara = 2 s
Trolley travelling or bridge crane, rotation = 4 s
Gantry travelling = 6 s
V: Mass lineal speed1
Vd [m]
n=
The resistance torque only has to be taken into account for travelling engines
26
CRANES I
ENGINES
CRANES I
ENGINES
Power needed to overcome wind resistance:
v v
S VP F [CV]
4500
=
Fv: wind pressure [daN/m2]
S: surface exposed to wind
To select travelling engine:
t v
w b
Engine power P +P [CV]
Max. motor toruque M +M [daNm]
To select lift engine:
e vEngine power P +P [CV]
top related