Tower Crane

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Tower Crane Powered By Docstoc
					By John Liedig & Jouline Nour
Counter Weight           Cables




                 Main Tower
Jib
            Introduction
Tower cranes are a common fixture at any
major construction site.
They often rise hundreds of feet into the
air, and can reach out just as far.
Tower cranes are used to lift steel,
concrete, large tools like acetylene torches
and generators, and a wide variety of
other building materials.
Arm and Tower Sections




Jib section       Tower Section
           Dimensions
The tower crane is approximately 120m
tall
10m wide
The counter weighted arm is 60m long
And the main jib can be as long as 90m
         Modelled Tower Crane
Looked at 2 scenarios
   2d
   3d


The aim was to determine the differences
in both 2D and 3D cases in relation to
displacement and stress analysis
             Objectives
To use Strand 7 on a complicated
structure such as a tower crane
Model the tower crane to the dimensions
given from relevant data
Determine stresses and displacements
associated from various locations of loads
on the structure
Try and improve the structure
                Objectives
To see if there was a better way of
modelling the tower crane on Strand 7
   Through using different materials
   Modifying the shape
              Method
Determined the dimensions of the tower
crane using data from the internet and
other relevant crane construction guides
Determined various components involved
in the tower crane
Identified the materials for each of the
various components and then selected
these from the strand 7 library
              Method
Drew a 2D representation of the tower
then the arm and then used strand 7
commands to convert into a 3D structure
Entered various loading scenarios
Ran analysis
Modified the elements accordingly to meet
acceptable limits in the results.
              Materials
The materials used were predominantly
structural steel of various sizes
The cable also is made from steel with a
free length ranging from 50 to 80m
All sections are circular hollow sections
            Load Cases
Taken a variety of load cases
Loads were placed at individual nodes
along the arm of the tower crane
In the final report the natural frequency is
also going to be considered but hasn’t
been included now due to time constraints
             Simplifications
The main simplifications were:
   Simplifying the concrete counterweights into a
    few point loads
   Not having a pivoting base. I.e. the nodes at
    the bottom of the tower are fixed in all
    directions and rotations
   The 3d case didn’t incorporate the service
    crane and the extra cables
            2D Tower Crane
Service Crane                Cables
          3D Tower Crane
 Cables




                           Loads

Fixed Nodes
2D Displacement Analysis Case1
2D Displacement Analysis Case 2
      Displacement Analysis
     1ST Case load at the end of the jib
     Maximum displacement 1.5m




Loads : counterweight = 3x 30kN
        Jib =150kN
 Displacement Analysis 3D
 Load case 2 : Maximum Displacement 0.41m




Loads : counterweight = 4x 20kN
        Jib =150kN
 Displacement Analysis 3D
Third Load Case : Maximum Displacement 0.6m




 Loads : counterweight = 4x 20kN
         Jib =150kN
     Displacement Analysis
The 2 and 3D cases give quite similar
displacements
Up to 1.5m depending on the loads
applied
The worst case is when the load is applied
at the end of the jib, which is what is to be
expected.
              Stress Analysis




The stresses observed are not realistic ie. In the thousands of MPa
This result is evident in all of the load cases
2D Stress Analysis Case 1
2D Stress Analysis Case 2
          Stress Analysis
In all cases the stress is beyond the yield
strength of the steel used.
Therefore there are errors that need to be
corrected.
This will be done by making the critical
tension members solid and looking at the
weights of each member.
                  Errors
The main errors involved so far have been in
relation to the units associated with the loads
applied to the structure.
The high stress involved may be due to the
weight of the structure as a whole.
Initially we were faced with problems relating to
the stiffness matrix “K”.
This involved, free or unconnected elements and
also defining an element more than once in the
same position.
              Modifications
Main modification factors are :
   Modifying the cross-sections of some
    members to decrease the high stresses
    observed
   Wind load scenario
   Natural frequency analysis
   Seeing the effect of other materials and how
    they affect the results.
Thank you for listening

  Any Questions??

				
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posted:11/30/2011
language:English
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