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By John Liedig & Jouline NourBy John Liedig & Jouline Nour
Main Tower
CablesCounter Weight
Jib
IntroductionIntroduction
Tower cranes are a common fixture at any Tower cranes are a common fixture at any major construction site. major construction site.
They often rise hundreds of feet into the They often rise hundreds of feet into the air, and can reach out just as far.air, and can reach out just as far.
Tower cranes are used to lift steel, Tower cranes are used to lift steel, concrete, large tools like acetylene torches concrete, large tools like acetylene torches and generators, and a wide variety of and generators, and a wide variety of other building materials. other building materials.
Arm and Tower SectionsArm and Tower Sections
Jib section Tower Section
DimensionsDimensions
The tower crane is approximately 120m The tower crane is approximately 120m talltall
10m wide10m wide
The counter weighted arm is 60m longThe counter weighted arm is 60m long
And the main jib can be as long as 90mAnd the main jib can be as long as 90m
Modelled Tower CraneModelled Tower Crane
Looked at 2 scenariosLooked at 2 scenarios 2d 2d 3d3d
The aim was to determine the differences The aim was to determine the differences in both 2D and 3D cases in relation to in both 2D and 3D cases in relation to displacement and stress analysisdisplacement and stress analysis
ObjectivesObjectives
To use Strand 7 on a complicated To use Strand 7 on a complicated structure such as a tower cranestructure such as a tower crane
Model the tower crane to the dimensions Model the tower crane to the dimensions given from relevant datagiven from relevant data
Determine stresses and displacements Determine stresses and displacements associated from various locations of loads associated from various locations of loads on the structureon the structure
Try and improve the structureTry and improve the structure
ObjectivesObjectives
To see if there was a better way of To see if there was a better way of modelling the tower crane on Strand 7modelling the tower crane on Strand 7 Through using different materialsThrough using different materials Modifying the shapeModifying the shape
MethodMethod
Determined the dimensions of the tower Determined the dimensions of the tower crane using data from the internet and crane using data from the internet and other relevant crane construction guidesother relevant crane construction guides
Determined various components involved Determined various components involved in the tower cranein the tower crane
Identified the materials for each of the Identified the materials for each of the various components and then selected various components and then selected these from the strand 7 librarythese from the strand 7 library
MethodMethod
Drew a 2D representation of the tower Drew a 2D representation of the tower then the arm and then used strand 7 then the arm and then used strand 7 commands to convert into a 3D structurecommands to convert into a 3D structure
Entered various loading scenariosEntered various loading scenarios
Ran analysisRan analysis
Modified the elements accordingly to meet Modified the elements accordingly to meet acceptable limits in the results.acceptable limits in the results.
MaterialsMaterials
The materials used were predominantly The materials used were predominantly structural steel of various sizesstructural steel of various sizes
The cable also is made from steel with a The cable also is made from steel with a free length ranging from 50 to 80mfree length ranging from 50 to 80m
All sections are circular hollow sectionsAll sections are circular hollow sections
Load CasesLoad Cases
Taken a variety of load casesTaken a variety of load cases
Loads were placed at individual nodes Loads were placed at individual nodes along the arm of the tower cranealong the arm of the tower crane
In the final report the natural frequency is In the final report the natural frequency is also going to be considered but hasn’t also going to be considered but hasn’t been included now due to time constraintsbeen included now due to time constraints
SimplificationsSimplifications
The main simplifications were:The main simplifications were: Simplifying the concrete counterweights into a Simplifying the concrete counterweights into a
few point loadsfew point loads Not having a pivoting base. I.e. the nodes at Not having a pivoting base. I.e. the nodes at
the bottom of the tower are fixed in all the bottom of the tower are fixed in all directions and rotationsdirections and rotations
The 3d case didn’t incorporate the service The 3d case didn’t incorporate the service crane and the extra cablescrane and the extra cables
2D Tower Crane2D Tower Crane
Service Crane Cables
3D Tower Crane3D Tower Crane
Loads
Cables
Fixed Nodes
2D Displacement Analysis Case12D Displacement Analysis Case1
2D Displacement Analysis Case 22D Displacement Analysis Case 2
Displacement AnalysisDisplacement Analysis
1ST Case load at the end of the jibMaximum displacement 1.5m
Loads : counterweight = 3x 30kNJib =150kN
Displacement Analysis 3DDisplacement Analysis 3D
Load case 2 : Maximum Displacement 0.41m
Loads : counterweight = 4x 20kNJib =150kN
Displacement Analysis 3DDisplacement Analysis 3D
Third Load Case : Maximum Displacement 0.6m
Loads : counterweight = 4x 20kNJib =150kN
Displacement AnalysisDisplacement Analysis
The 2 and 3D cases give quite similar The 2 and 3D cases give quite similar displacementsdisplacements
Up to 1.5m depending on the loads Up to 1.5m depending on the loads applied applied
The worst case is when the load is applied The worst case is when the load is applied at the end of the jib, which is what is to be at the end of the jib, which is what is to be expected.expected.
Stress AnalysisStress Analysis
The stresses observed are not realistic ie. In the thousands of MPaThis result is evident in all of the load cases
2D Stress Analysis Case 12D Stress Analysis Case 1
2D Stress Analysis Case 22D Stress Analysis Case 2
Stress AnalysisStress Analysis
In all cases the stress is beyond the yield In all cases the stress is beyond the yield strength of the steel used.strength of the steel used.
Therefore there are errors that need to be Therefore there are errors that need to be corrected.corrected.
This will be done by making the critical This will be done by making the critical tension members solid and looking at the tension members solid and looking at the weights of each member.weights of each member.
ErrorsErrors
The main errors involved so far have been in The main errors involved so far have been in relation to the units associated with the loads relation to the units associated with the loads applied to the structure.applied to the structure.The high stress involved may be due to the The high stress involved may be due to the weight of the structure as a whole.weight of the structure as a whole.Initially we were faced with problems relating to Initially we were faced with problems relating to the stiffness matrix “K”.the stiffness matrix “K”.This involved, free or unconnected elements and This involved, free or unconnected elements and also defining an element more than once in the also defining an element more than once in the same position.same position.
ModificationsModifications
Main modification factors are :Main modification factors are : Modifying the cross-sections of some Modifying the cross-sections of some
members to decrease the high stresses members to decrease the high stresses observedobserved
Wind load scenarioWind load scenario Natural frequency analysisNatural frequency analysis Seeing the effect of other materials and how Seeing the effect of other materials and how
they affect the results.they affect the results.
Thank you for listeningThank you for listening
Any Questions??Any Questions??
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