Modeling Bridges to Optimize Intentional Damage for Bridge Health System Testing

Erica West Author

07/28/2020 Added

27 Plays

Description

Final poster presentation for Erica West, REU Summer 2020

Searchable Transcript

Search:

[00:00:08.560]Hi there, my name is Erica West
[00:00:10.484]and today I will be talking to you about
[00:00:12.410]modeling bridge damage for
[00:00:13.774]experimental purposes.
[00:00:16.910]This project is very tied into my team's
[00:00:19.249]larger work. We have developed a
[00:00:20.946]bridge monitoring system using an iPhone
[00:00:23.041]and an inexpensive attachable accelerometer.
[00:00:26.413]The system has shown promise
[00:00:27.783]when analyzing healthy structures
[00:00:29.414]against established methods,
[00:00:30.912]but the truest test for any health
[00:00:33.110]monitoring method is to detect when
[00:00:35.010]something has gone wrong.
[00:00:37.086]For some background, there are over
[00:00:38.811]11,000 county managed bridges in Nebraska.
[00:00:41.373]Around 16% are officially considered
[00:00:44.644]“structurally deficient” and
[00:00:46.449]36% are at least 50 years old.
[00:00:48.687]Many of these aging structures
[00:00:50.608]are in rural or isolated areas
[00:00:52.538]making effective health monitoring and
[00:00:54.715]evaluation very difficult,
[00:00:56.295]often relying on qualitative
[00:00:58.025]visual inspections instead of
[00:00:59.893]anything more quantitative.
[00:01:01.939]One method of quantitative monitoring
[00:01:04.239]is using accelerometers.
[00:01:05.978]Accelerometers can measure
[00:01:07.386]minute changes in acceleration
[00:01:09.046]and can detect natural frequencies
[00:01:10.796]in structures.
[00:01:11.760]High quality ones are sensitive enough
[00:01:14.125]to detect damage in structures
[00:01:16.045]using vibrations and
[00:01:17.445]fundamental frequencies.
[00:01:19.136]Unfortunately, that technology is
[00:01:21.026]very expensive and often out of budget
[00:01:23.071]for county transportation departments.
[00:01:25.372]That said, not all accelerometers
[00:01:27.138]are quiet so advanced.
[00:01:29.094]A great example is the accelerometer
[00:01:31.014]in your smartphone that lets you
[00:01:32.749]view 360 photos.
[00:01:34.486]While these accelerometers are
[00:01:35.966]inexpensive and widely available,
[00:01:37.770]they are not very sensitive.
[00:01:39.801]The most precise thing the average
[00:01:41.421]smartphone accelerometer will have to do
[00:01:43.447]in its lifetime is use the level app
[00:01:45.547]so why waste money and chassis space
[00:01:47.756]on anything horribly advanced?
[00:01:49.853]Despite this, there have been indications
[00:01:51.837]that smartphones could be used
[00:01:53.619]in bridge heath evaluations.
[00:01:56.109]In 2015, a research team found the
[00:01:58.259]1st fundamental frequency of a bridge
[00:02:00.095]using only a commercially available
[00:02:01.812]smartphone.
[00:02:02.743]Though the phone could not measure
[00:02:04.376]anything more sophisticated
[00:02:05.726]with any accuracy,
[00:02:06.656]it does show the possibility
[00:02:08.266]of incorporating phones into
[00:02:09.736]inexpensive testing.
[00:02:11.773]Once properly developed and tested,
[00:02:13.633]our system could provide more accurate
[00:02:15.732]and complete updates on remote bridges
[00:02:17.563]at a price that counties can afford.
[00:02:20.881]As I mentioned earlier,
[00:02:22.321]the system has been tested on a number
[00:02:24.222]of healthy bridges to compare
[00:02:25.612]with established monitoring methods,
[00:02:27.600]but now we need to see how it handles
[00:02:29.426]damage on a bridge,
[00:02:30.640]which means we need a damaged bridge.
[00:02:32.670]With the permission of local government,
[00:02:34.790]we plan to take measurements
[00:02:36.380]of an existing bridge before and after
[00:02:38.313]inflicting known damage on the structure.
[00:02:40.641]In order to optimize the data
[00:02:42.381]we receive from this,
[00:02:43.662]I have modeled various types of damage
[00:02:45.506]in the SAP 2000 software.
[00:02:47.028]I was looking for damage that
[00:02:48.838]both dramatically changed the
[00:02:50.298]stress dynamics of the bridge and posed
[00:02:52.537]very little threat to the general public.
[00:02:55.008]I assumed the structure was non-composite,
[00:02:57.488]meaning the concrete deck did not hold
[00:02:59.336]its own weight.
[00:03:00.678]Of the damage patterns I had time to test,
[00:03:03.338]Deletion A and Deletion B changed the
[00:03:05.648]stress dynamics the most while
[00:03:07.378]not breaking from shear force.
[00:03:08.880]All data and results will be
[00:03:10.336]focused on them.
[00:03:12.895]Here we can see an approximation
[00:03:14.901]of stress levels and the moment levels
[00:03:17.034]for both the original undamaged
[00:03:18.785]M-164 bridge and Deletion A.
[00:03:21.365]The stress is in reference to shear force
[00:03:23.994]which is how likely is for a beam to be
[00:03:26.213]cut clean off and the moment is how
[00:03:28.283]the forces are attempting to make the
[00:03:30.164]beam bend.
[00:03:31.262]Note that the figures show the
[00:03:33.122]absolute value of measurements to best
[00:03:35.130]illustrate overall dynamics.
[00:03:37.116]As we can see, the shear stress
[00:03:38.956]and moment are very low and symmetric
[00:03:41.651]about Member 8 for the original structure.
[00:03:44.290]Deletion A was created by deleting the
[00:03:46.660]highest stress section on the structure
[00:03:48.795]which happened to be the leftmost
[00:03:50.443]portion of Member 2.
[00:03:51.859]As you can see, the shear force has been
[00:03:53.778]majorly redistributed when compared to
[00:03:55.681]the original, but the moment has only
[00:03:57.717]shifted slightly.
[00:04:01.152]Deletion B was created by randomly making
[00:04:04.032]variations of Deletion A and is missing
[00:04:06.397]the leftmost section of both Member 2
[00:04:08.569]and Member 6.
[00:04:09.792]When we compare Deletion B with the
[00:04:12.152]undamaged structure, we once again see
[00:04:14.308]a major redistribution in stress dynamics
[00:04:16.635]but also much different moment readings.
[00:04:19.774]As we look at the highest readings from
[00:04:21.954]each model, we can see that both the
[00:04:23.984]original structure and Deletion A are
[00:04:25.814]very safe overall, but the same cannot be
[00:04:28.354]said for Deletion B.
[00:04:30.110]The safety factor is below 1 meaning that
[00:04:32.568]a structural failure is very likely.
[00:04:36.514]Based on our initial requirements,
[00:04:38.594]Deletion A is the better option.
[00:04:40.660]While both patterns provide measurable
[00:04:42.800]damage, Deletion B is simply too extreme
[00:04:44.820]and poses too much of a risk to the public
[00:04:46.840]at large.
[00:04:47.660]In conclusion, Deletion A is recommended
[00:04:50.063]for optimal testing.
[00:04:51.338]It should let us test severe damage
[00:04:53.035]on a bridge while keeping the structure
[00:04:54.995]as safe as possible.
[00:04:57.328]I would like to thank my entire team,
[00:04:59.468]especially my faculty advisor Dr. Linzell
[00:05:01.690]and my post-doctorate mentor Samira Ardani
[00:05:06.334]This research was funded in part
[00:05:08.164]by the National Science Foundation
[00:05:09.864]through the Research Experience for
[00:05:11.584]Undergraduates program.
[00:05:12.984]Thank you.

The screen size you are trying to search captions on is too small!

You can always jump over to MediaHub and check it out there.

Comments

0 Comments

Modeling Bridges to Optimize Intentional Damage for Bridge Health System Testing

Description

Searchable Transcript

Comments icon comment

Related Channels

Comments