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??