Friday, October 12, 2012

CALCULATION OF TOWER CRANE ANCHORAGE REACTION :

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1. Calculation of supporting reaction

1.1 Load and key dimension

Load: M = 3518KN.M T = 369.1KN.M W0 = 0.95KN/㎡

Where : M — maximum overturning moment
T — maximum torque
W0 — wind velocity pressure ( According to TCVN 2737:1995)

Key dimension:






h1 = 38.48m h2 = 62.88m h3 = 87.28m h3 = 108.63m

1.2 Calculation of wind load
Wk=W0×μz×μs×βz = 0.950×2.64×0.8 =2.0kN/m2
Where :
us — type coefficient of wind load
uz — factor of height variation
βz — gustiness factor, it is 1.0.

q = Wk×B×Ks = 2.0×2.000×0.200 = 0.8 kN/m;
where:
B — section width of tower crane
k — reduction coefficient of windward

1.3 Calculation of supporting reaction
As per specification of tower crane, the top anchorage shall bear the maximum supporting reaction. Therefore, we just take the top anchorage to calculate considering the safety. The mast of tower crane can be seen as rigid supporting continuous beam with cantilever end.


q = 0.8 KN/m M = 3830 KN.M


In accordance with the continuous beam theory to calculate:
Nw=282.2KN


The anchorage system of tower crane is statically structure. The detailed calculation can be seen as follows:








 
Because the section material of all the anchorages are the same, the following result can be adopted based on above-mentioned equation:
.



The tensile & compression forces are as follows:

The maximum tensile force of anchorage member No.01 : 280.0kN
The maximum tensile force of anchorage member No.02: 463.0kN
The maximum tensile force of anchorage member No.03: 463.0kN
The maximum tensile force of anchorage member No.04: 280kN

The maximum compression force of anchorage member No.01:280.0kN
The maximum compression force of anchorage member No.02:463.0kN
The maximum compression force of anchorage member No.03:463.0kN
The maximum compression force of anchorage member No.04: 280.0kN

2. Checking calculation of anchorage member
As per specification of manufacture of tower crane, the lattice structure with Channel steel No.20 and pattern panel of steel plate shall be applied. The section drawing can be seen as follows:



Considering the safety, we take the combination of maximum compression and longest anchorage member to calculate:

Tmax = 465.0 kN Lmax = 8.825m

2.1 Checking calculation for U steel
2.1.1 Checking calculation of strength in Y axis
iy=0.44h=0.44×20=8.8cm
λ = Lmax/iy=882.5/8.8=100.3<[λ]=150
According to the specification, φy= 0.549
Where:
iy— turning radius of lattice structure
h — height of web plate of U steel
λ — slenderness ratio
[λ]— allowable maximum slenderness ratio. Supply turning radius big enough to satisfy the rigid requirement.
φy — stability factor of lattice structure which is decided by the value of slenderness ratio as per specification .
σ=Nmax/(φy A)=465/0.549/57.6=147.1MPa<[σ]=215MPa
OK !

2.1.1 Checking calculation of stability in X axis
When the axis compression lattice member lose the stability around virtual axis, the additional deformation shall arise from this failure, which is called “ lattice shearing deformation” . This affect shall be considered by the application of conversion slenderness ratioλox.
λox===121.4
Where:

λ1—slenderness ratio of single U steel
λ1=l/i1=75/2.11=35.5< 40 , OK !
L — spacing of steel pattern panel between the U steel
λ1—slenderness ratio of single U steel
λx —slenderness ratio of steel lattice structure
=l/ix==l/(0.38b)=882.5/(0.38×20)=116.1< [λ]=150, OK !
According to the specification of steel structure, φox = 0.453
σ=Nmax/(φox A)=465/0.453/(57.66+25.6)=123.3MPa<[σ]=215MPa
OK !

Stability of separate Channel steel
= 35.55 < 40 but > 0.5λmax= 116.1/2 =58.1
So, the integral lattice member shall lose stability earlier than single U steel. The checking calculation of stability for single Channel steel is unnecessary.
2.2 Design of pattern panel of lattice structure



According to specification of lattice steel structure, the dimension of pattern panel should follow:
ü b> = =133.3 180mm shall be applied. OK
ü t> = =5mm 8mm shall be applied. OK
ü “ The lapping length of pattern plate and Channel steel can not be less than 30mm.”
Llap= =55mm>30mm, OK
Therefore, the dimension of pattern panel is 180×160×8mm.

2.3 Checking calculation of fillet weld




2.3.1 Calculation of internal force of fillet weld
According to specification of lattice steel structure, the internal force of fillet weld can be adopted by following equation:



Where:

vmax — maximum shearing force of lattice steel member
v1 — shearing force of one pattern panel
T — shearing force of one fillet weld
M — bending moment of one fillet weld

2.3.2 Checking of fillet weld
= 10mm
Ln=b-2hf=180mm-2×10mm=160mm



Analysis of internal force of fillet weld

Where :


2.4 Checking calculation of stability in plane

According to the specification of lattice steel structure, the yield of section fringe fibre of lattice member shall be applied as the design criteria.


OK

3. Checking calculation of embedded bolts
Considering the safety of anchorages, we take the embedded plate with the minimum nos. of anchor bars to carry the checking calculation, the detail of which can be seen as follow:




OK

Where:

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Beita Terkait : 

www.hotsblack.com - CATEGORIES AND FEATURES OF TOWER CRANE(1)

www.hotsblack.com CATEGORIES AND FEATURES OF TOWER CRANE(2)

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