Karl`s PC Help Forums Last active: Never
Not logged in [Login ]
Go To Bottom

In memory of Karl Davis, founder of this board, who made his final journey 12th June 2007

Post Reply
Who Can Post? All users can post new topics and all users can reply.
Username   Need to register?
Password:   Forgot password?
Subject: (optional)
Icon: [*]
Formatting Mode:
Normal
Advanced
Help

Insert Bold text Insert Italicised text Insert Underlined text Insert Centered text Insert a Hyperlink Insert E-mail Hyperlink Insert an Image Insert Code Formatted text Insert Quoted text Insert List
Message:
HTML is Off
Smilies are On
BB Code is On
[img] Code is On
:) :( :D ;)
:cool: :o shocked_yellow :P
confused2 smokin: waveysmiley waggyfinger
brshteeth nananana lips_sealed kewl_glasses
Show All Smilies

Disable Smilies?
Use signature?
Turn BBCode off?
Receive email on reply?
The file size of the attachment must be under 200K.
Do not preview if you have attached an image.
Attachment:
    

Topic Review
JackInCT

[*] posted on 6-1-2018 at 13:30
Elementary Physics, Albeit Likely Oversimplified:

In physics, resonance is a phenomenon in which a vibrating system or external force drives another system to oscillate with greater amplitude at specific frequencies.

Frequencies at which the response amplitude is a relative maximum are known as the system's resonant frequencies or resonance frequencies. At resonant frequencies, small periodic driving forces have the ability to produce large amplitude oscillations, due to the storage of vibrational energy.

What I remember is that an internal combustion engine/a jet engine/whatever has a (inherent) resonance frequency that if the rpms are at occurring at that frequency (speed), the engine will, literally, vibrate to the point of a form of shaking self destruction. All objects have such a resonance frequency, but it's a very very narrow frequency, I. e., as an imaginary example, 100 rpms and not one rpm above or below that. I recall the prof in introductory physics saying that even a mountain has a resonance frequency that would cause it to disintegrate but the energy that would be needed to do that is impossible to achieve. I know that jet engines (at least used to) have a resonance frequency, and there is a warning in the flight manual to never set the throttle at that rpm.

In the bridge, my guess is that if the cadence of the walkers (and there was a sufficient number of them) happened to be, cumulatively, in sync, and that sync was the resonant frequency, the bridge would began to wobble and theoretically would collapse. I suppose the wind blowing could add to the wobble.

Lesson learned: don't ever find yourself standing on a bridge when a marching band goes over it; you never know what might happen!!
John_Little

[*] posted on 6-1-2018 at 11:18
I've no idea if that was before of after. But the day it opened it was frightening as people poured across and started the bridge wobbling.

And Leigh is so right about the builders!
LSemmens

[*] posted on 6-1-2018 at 10:02
The biggest problem with these sorts of bridges isn't the fears of the pedestrians who attempt to cross them. Have a thought for the blokes that had to build it!
JackInCT

[*] posted on 5-1-2018 at 23:02
Quote:
Originally posted by John_Little
It looks very similar to our wobbly bridge. They cured the wobble in the end. Can't remember what they did.


Did you post a 'before' OR 'after' pix?
John_Little

[*] posted on 5-1-2018 at 17:32
It looks very similar to our wobbly bridge. They cured the wobble in the end. Can't remember what they did.
JackInCT

[*] posted on 5-1-2018 at 17:12
The passion continues:

Today (01/05/18) from CNN:

"World's longest glass bridge opens in Hebei, China--Spanning two mountains in the Hongyagu Scenic Area, the new bridge also has an added fear feature -- it sways."

Well I see they also upped the ante with the swaying--that should help cull out the soft core of bridge walkers for whom the swaying is more than they can bear (after having successfully navigated the other bridge in the original topic).

There are 9 pixs in the CNN article; I picked this one only because the words on her pants are in English--it's been a long while since I read about this, but I seem to recall that a good many Chinese are bilingual [at an early age].

1-2 of the 9 pixs show the guard rails on BOTH sides of the bridge bowed (undulating) like they were a series of sine waves-really pronounced bowing. Holy Mackerel!!!! And there were crowds of people on the bridge when this was occurring (no signs of a panic that I could see in the pix; I wonder if there were 'auditory cues' created by the bowing/flexing--I'm betting there were.

Many positive things can be said about not only the engineers, etc., who designed this bridge, & those who built it, but the character of the individuals who in their own way overcame what must be significant fear to traverse it.
LSemmens

[*] posted on 22-8-2016 at 22:51
A lot of fears are learnt, SWMBO has a fear of heights, and has also, to a great extent, conquered it. Her mother was extremely afraid of heights and she attributes her fear to that. She also made a decision early on, not to transfer those fears, and other behaviour attributed to her childhood, on to our Children. None of whom do display those traits.

FYI: She grew up in an abusive home and carried a lot of baggage as a result. I was blessed in that I was able to support her and help her combat those demons from her youth. I did not know her when she was young.
John_Little

[*] posted on 22-8-2016 at 20:18
Quote:
Originally posted by sceptre
I was bad enough walking across the glass part on the CN tower so
I reckon this would be a bridge too far .


Excellent!
marymary100

[*] posted on 22-8-2016 at 19:11
For me it was more of the speed of the great glass elevator rushing up the side of the building I think. It was akin to a very high roller coaster ride which shot upwards, and conversely downwards when riding to/from the restaurant. On the other hand being on top of a revolving restaurant in a city was lovely because it was a leisurely circuit.
JackInCT

[*] posted on 22-8-2016 at 18:18
Quote:
Originally posted by sceptre
I reckon this would be a bridge too far .


Your comment got me to thinking of whether there are some vision technical "work-around" that could be used to, at least, minimize someone's anxiety (especially the 'rubber legs'/shaking in one's boots' reaction).

The pix of the children would seem to indicate that they are not the least bit perturbed, and I, for no logical reason, presumed that children would be the age group most susceptible to having an anxiety reaction.

As an example, I'm wondering if a blindfold with just a small peep size hole (for each eye) would create a kind of tunnel vision effect, so that one's brain would NOT be overloaded with the ENTIRE visual sensory stimuli of the panorama view of the scene.

Please consider this a 'mind over matter' reply (my own time tested remedy for dealing with irrational and unfounded anxiety)---perhaps someone will create a topic about how individuals on this board deal with extreme anxiety (my personal one is skidding in the snow, becoming frozen (unreactive) with fear, and doing nothing to counteract that which can get you killed, i. e, better to get killed while trying to regain control than doing absolutely nothing; airbags & a seatbelt, IMO, are no panacea).
marymary100

[*] posted on 22-8-2016 at 18:00
Quote:
Originally posted by sceptre
I was bad enough walking across the glass part on the CN tower so
I reckon this would be a bridge too far .


I see what you did there...;)
sceptre

[*] posted on 22-8-2016 at 17:12
I was bad enough walking across the glass part on the CN tower so
I reckon this would be a bridge too far .
JackInCT

[*] posted on 22-8-2016 at 13:32
Re the wedding pix: in any relationship there are ties that bind, AND then there are ties that REALLY bind!!!

Another pix from a glass bridge with children (I presume that the glass's reflection is not seen in this pix because of the position of the sun which creates a pretty nice 'illusion' of being suspended in mid-air).
LSemmens

[*] posted on 22-8-2016 at 01:04
And the little one said......roll over......
marymary100

[*] posted on 21-8-2016 at 13:17
May married life continue to give them thrills and excitement...
JackInCT

[*] posted on 21-8-2016 at 13:05
So the Chinese have a "Chinese Valentine's Day"-who knew ???

It's not everyone's idea of a special day, but one couple in China chose to celebrate their wedding by dangling in mid-air from a glass bridge.

The bride and groom married on the Shiniuzhai bridge in Pingjiang, Hunan province on Chinese Valentine's Day on 9 August, China News Service reports.

Despite dangling 180m (590ft) above the ground, they were still able to smile for the camera in their wedding photos.

Glass bridges have become increasingly popular in China recently.

Me Here: There are multiple sites with these glass bridges. AND a good number of YouTube videos at the various sites, to include several of folks experiencing severe anxiety attacks (no one ever accused SOME YouTube uploaders of having good taste, or sensitive to the trails and tribulations of life).

IMO this is NOT a PhotoShopped image, but who knows for sure.

IMO the attached pix simply cries out for puns!!! Such as, 'our love is without restraints'.
John_Little

[*] posted on 21-8-2016 at 08:07
Wouldn't catch me on it. Not after they've been smashing it with sledge hammers
LSemmens

[*] posted on 21-8-2016 at 04:53
No probs here.
marymary100

[*] posted on 20-8-2016 at 17:31
I read that earlier. I had a bad experience in a glass elevator on the outside of a hotel in Benidorm so personally a glass bridge wouldn't be appealing.
JackInCT

[*] posted on 20-8-2016 at 16:01
China Opens World'S Highest And Longest Glass (Bottomed) Bridge

The much-heralded "world's highest and longest" glass-bottomed bridge has opened to visitors in central China.

It connects two mountain cliffs in what are known as the Avatar mountains in Zhangjiajie, Hunan province.

Completed in December, the 430m-long bridge cost $3.4m (£2.6m) to build and stands 300m above ground, state news agency Xinhua reported.

It has been paved with 99 panes of three-layered transparent glass.

And according to officials, the 6m-wide bridge - designed by Israeli architect Haim Dotan - has already set world records for its architecture and construction.

But officials have staged high-profile events to try and reassure the public of the bridge's safety.

Officials sent in sledgehammers and even drove a car, filled with passengers, across the bridge earlier this year.

The BBC's Dan Simmons was invited to take a bash at the bridge (pix attached).

Me here: if you've always wondered just how 'susceptible' you are to acrophobia, it would seem to me this is just the place to see if you are.

There were several very interesting photos embedded in this article (BBC) for anyone who would like a more detailed look- see (and probably YouTube videos as well).