Week 9

This week we will be testing our model based on the process described in Week 8's post.  We will then make our calculations for the force.  We will take the inverse sine of the height at the tipping point divided by the length of our board (hypotenuse).  This will give us the angle.  We will use that angle to calculate the horizontal force applied at the tipping point.  This can be calculated by taking the mass of the model multiplies by the acceleration of gravity multiplied by the sine of our angle found.  We will then compare the force we find from each position, and combination of weight to formulate the final results of our experiment and project.  After we examine our results we will put the finishing touches on our final report paper and presentation for Week 10.

Figure 1: Example of FBD for a similar situation.  We will use Physics methods to make our calculations.

We were pleases with the results of our tests.  The results are shown below.  They seem to show that the modification did have an effect because when the weights were placed on the appropriate side, the tower was able to sustain a higher force.  This should translate to the swaying of the tower we believe in the real structure.  Test results for side "A" and "B" respectively:

Source: http://www.cheops-pyramide.ch/khufu-pyramid/force-friction.html

Week 8

This week our group did preliminary testing for our final tests and were pleased by what we observed.  The first suggestion for our tests was to use a hair-dryer to act as wind to simulate wind on the tower.  The hair-dryer was able to move our structure but it was hard to get any data on the differences our simulation of the tuned mass dampening system mad.  The air blown would only shift our tower and there was very little difference with and without the modification.  It also did not test at all the swaying of the towers which is what we are trying to limit, since the entire tower was shifted we could not calculate the shift in center of gravity.  

Figure 1:  Hair dryer test

Our following tests proved to be more useful.  The concept of the test is to show that the shift in weight in the building will help the building stay more rigid and sway less while horizontal loads are applied (wind).  The idea is that the tower will be unrooted and raised up while it is on a platform resting on a thin ledge.  We will measure the height of the platform at the moment the tower flips (we will take three measurements of each scenario and average the distances for most accurate results).  Since the tower is not rooted by its foundation in our test we are only testing the structure's willingness to shift its center of gravity as a result of horizontal wind loads.  Based on our research our hypothesis is that when more weight is situated on the side of the acing force, the structure's center of gravity will be harder to shift (and thus tip) and therefore will sway less when it is truly grounded.  We will do these measurements with the model alone and then the model with 8,6,4,2, and 1 washers attached to the tower.  We will repeat this with the washers on the other side of the acting force.  We will repeat this entire process with the washers on the second tower, since the structure is not symmetrical.  Through our preliminary tests this week this process has shown good results that should support our thesis.  In Lab on week 9 we will conduct the experiment in its entirety so we can make accurate measurements and formulate useful data.  

Figure 2:  Tower with washers simulating tuned mass dampening system

Figure 3:  Testing horizontal force it can withstand at first angle

Figure 4:  Testing horizontal force it can withstand at another angle

Week 7

This week we turned in our Draft Final Report. We also received the final version of our 3D model after it was printed. After seeing our model, we decided on how we are going to do tests and gather results. We decided to use a hairdryer/fan to pose as wind and determine how well it stands with and without our design difference. Alternatively, we will test its stability by raising the model to an incline until it reaches its tipping point with different weights at positions on the towers.  This will give us the ability to calculate the horizontal force it can withstand through a calculation of the horizontal gravitational force that we can calculate. The design change of a tuned mass damping system will be represented by a number of washers that we will attach with wire to the different towers of the structure.  This will give us the ability to change the weight shifting of structure.  This is our prototype before our design change:

Figure 1: Front View

Figure 2: Right View

Figure 3: Top View

Week 6

We had a minor set back this week as we were told that the file we submitted to be 3-D printed was too large and would cost nearly $1,000 dollars to print and take 48 hours to do so.  Obviously, this is not within the budget for our freshman design lab so we will have to scale down our model significantly to make sure it is able to be printed.  Below are the CAD images of our design.

Figure 1: Back view of CAD design

Figure 2:  Front view of CAD design

We also explored new wind prevention techniques and came upon the Tuned Mass Damper device found in some large buildings.  It is a system that measures the harmonic waves of the wind through a computer system and shifts a huge concrete block or steel body in the opposite direction of the wind force by means of springs, a pendulum, or fluids.  This provides for less swaying in the structure and makes the structure more comfortable for the residents (1).

Figure 3: Example of a tuned damper in tower in Taiwan 

The CCTV tower already has a built in diagrid system and horizontal trusses that transfer loads from the overhang to the vertical so it is structurally very strong from twisting and torsion.  The problem is that the building as a whole can sway a lot from side to side when high winds occur.  This makes the building feel unsafe to residents and can cause some internal damage.  The tuned mass damper system would counteract a lot of these problems.


Source:
1. http://www.popularmechanics.com/technology/infrastructure/a14564/the-121-story-tower-that-never-sways/

Week 5

This week we completed our Creo Parametric design of the CCTV tower with scaled dimensions.  We sent the .stl file to the Drexel 3-D printing facilities.  The design is more or less a replica of the original structure but scaled down.  Our plan is to add an enhanced foundation and possibly a middle shaft through the middle of the structure with cross sections that connect it to each tower.  This will provide for a more rigid structure particularly in the occurrence of high winds and seismic waves.  We will add these features to the 3-D printed prototype through normal construction.  We were not able to add the new design features to the original print job because we have not finalized exactly what we would like to do since we are having difficulties finding weaknesses in the structure, although the ideas expressed earlier are what we will likely add.  We will continue to explore design techniques to counter wind and earthquake loads as we continue.