It's the shock load that works on bridges - the jarring, bouncing ect which is a direct result of the suspension ( or lack of ). Same effect when the 150 lb teenager "plops" down on the step of the coach - the step is feeling more the effect of 300lbs.
Good post Marc.
More Technical: Bridge design involves dead loads, live loads, stress, tension, shear, impact forces, vibration, harmonics and environmental conditions such as temperature, humidity (primarily wooden bridges), wind speed and currents.
Slowing down reduces impact forces and vibration.
This helps illustrate dynamic force. Link to video at bottom.
Subject: FW: To my engineering and construction friends
Engineering Made Easy !
A short video of a Pakistani pile driving construction technique. Notice that the pile driving only becomes effective when the extra man jumps on. Very finely tuned! The chant is also catchy!
If you want to analyze the engineering here:
6 men x 180 lbs = 1080 lbs static force. Jumping up and downwill create a 3 times dynamic effect = 3240 lbs/jump = 1.6 ton thumps.
If the pile is tapered to 2 in x 2 in, cross section at the tip = 4 square inches. So, dynamic pressure/thump at pile tip = 3240/4 = 800 psi.
"Add a man" feature will increase to 950 psi, so buy the option !
Increase the chant and dynamic force goes up to 5 times to bring max.pressure/thump to 1600 psi for a 7 man team.
Quite good and will penetrate hard clay and sandy soil but not hard rock!
Pretty ingenious AND doesn't cost a whole lot!
Click on the link for video.
Perhaps if this technique was used, the veterans hospital construction project in Denver wouldn’t be a billion dollars over budget.
https://www.youtube-nocookie.com/embed/c...Kypg?rel=0
So Kool cc!!! I love it. No gym memberships needed either!! It would only take 2 or 3 if they were my size! I might struggle to get "in the rhythm" though.
I actually said something intelligent.. Don't tell my wife she will expect it more often..
I'm wondering what this weight limit sign means in practical terms... In other words, I'm wondering if this kind of bridge would be ok to cross in 65,000 lb tag newell if I'm the only vehicle on bridge? It's about 80' long. It has this sign both directions so I would assume that 3 axles could weigh up to 46 tons (assuming only one vehicle on bridge as opposed to two 23 ton vehicles). Any guru thoughts on this?
I'm planning on visiting my friends ranch and would have to cross this bridge.
Just south of Osawatamie, KS. I always seem to be on these little two lane roads!
Most bridges are made to support the weight of a fire truck laden with water which probably weighs about the same as our coaches (or more), don't take my word for it, this is merely speculation. If it is in an old town and is an old bridge I would avoid it if possible.