By John Liedig

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Tower Crane

• By John Liedig Jouline Nour

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(No Transcript)
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Counter Weight
Cables
Main Tower
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Jib
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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.

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Arm and Tower Sections
Tower Section
Jib section
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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

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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

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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

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Objectives

• To see if there was a better way of modelling the
  tower crane on Strand 7
• Through using different materials
• Modifying the shape

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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

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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.

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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

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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 hasnt been included
  now due to time constraints

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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 didnt incorporate the service crane
  and the extra cables

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2D Tower Crane
Service Crane
Cables
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3D Tower Crane
Cables
Loads
Fixed Nodes
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2D Displacement Analysis Case1
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2D Displacement Analysis Case 2
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Displacement Analysis
1ST Case load at the end of the jib Maximum
displacement 1.5m
Loads counterweight 3x 30kN Jib 150kN
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Displacement Analysis 3D
Load case 2 Maximum Displacement 0.41m
Loads counterweight 4x 20kN Jib 150kN
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Displacement Analysis 3D
Third Load Case Maximum Displacement 0.6m
Loads counterweight 4x 20kN Jib 150kN
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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.

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Stress Analysis
The stresses observed are not realistic ie. In
the thousands of MPa This result is evident in
all of the load cases
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2D Stress Analysis Case 1
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2D Stress Analysis Case 2
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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.

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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.

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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.

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Thank you for listeningAny Questions??