5 IntroductionTower 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.
7 Dimensions The tower crane is approximately 120m tall 10m wide The counter weighted arm is 60m longAnd the main jib can be as long as 90m
8 Modelled Tower Crane Looked at 2 scenarios The aim was to determine the differences in both 2D and 3D cases in relation to displacement and stress analysis
9 ObjectivesTo use Strand 7 on a complicated structure such as a tower craneModel the tower crane to the dimensions given from relevant dataDetermine stresses and displacements associated from various locations of loads on the structureTry and improve the structure
10 ObjectivesTo see if there was a better way of modelling the tower crane on Strand 7Through using different materialsModifying the shape
11 MethodDetermined the dimensions of the tower crane using data from the internet and other relevant crane construction guidesDetermined various components involved in the tower craneIdentified the materials for each of the various components and then selected these from the strand 7 library
12 MethodDrew a 2D representation of the tower then the arm and then used strand 7 commands to convert into a 3D structureEntered various loading scenariosRan analysisModified the elements accordingly to meet acceptable limits in the results.
13 MaterialsThe materials used were predominantly structural steel of various sizesThe cable also is made from steel with a free length ranging from 50 to 80mAll sections are circular hollow sections
14 Load Cases Taken a variety of load cases Loads were placed at individual nodes along the arm of the tower craneIn the final report the natural frequency is also going to be considered but hasn’t been included now due to time constraints
15 Simplifications The main simplifications were: Simplifying the concrete counterweights into a few point loadsNot having a pivoting base. I.e. the nodes at the bottom of the tower are fixed in all directions and rotationsThe 3d case didn’t incorporate the service crane and the extra cables
20 Displacement Analysis 1ST Case load at the end of the jibMaximum displacement 1.5mLoads : counterweight = 3x 30kNJib =150kN
21 Displacement Analysis 3D Load case 2 : Maximum Displacement 0.41mLoads : counterweight = 4x 20kNJib =150kN
22 Displacement Analysis 3D Third Load Case : Maximum Displacement 0.6mLoads : counterweight = 4x 20kNJib =150kN
23 Displacement Analysis The 2 and 3D cases give quite similar displacementsUp to 1.5m depending on the loads appliedThe worst case is when the load is applied at the end of the jib, which is what is to be expected.
24 Stress AnalysisThe stresses observed are not realistic ie. In the thousands of MPaThis result is evident in all of the load cases
27 Stress AnalysisIn 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.
28 ErrorsThe 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.
29 Modifications Main modification factors are : Modifying the cross-sections of some members to decrease the high stresses observedWind load scenarioNatural frequency analysisSeeing the effect of other materials and how they affect the results.