2020 FAQ

Question: Since bridges are allowed to extend below the support surface all the way up to their vertical sides, can bridges be intentionally designed to apply outward force to the supports under testing?  In other words, can a bridge use the supports as abutments?

Answer: Yes, this assumes that the support surface can provide horizontal support.  In Chicago, the test stand is designed to do this.  I do not know if this is the case for all other test stands. When this is allowed, arch bridges do very well.  Allowing this is not done every year.

Question: Can you clarify section 2c of the speifications? Does this mean that the loading plate and rod/eye-bolt must be lowered together to the loading plane?  Or can the students take apart the plate and rod, place the plate on the loading plane between 0-20mm and then connect the rod/eye-bolt?

Answer: A student can put the loading apparatus into position by using either method.  The rule is really to inform the student that they must account for the plate and eye-bolt during the design and construction of their bridge.

Question: If the loading platform that holds the bolt is 40mm wide, what does it sit on if my bridge is 75 mm wide.  Do I have to build something for it to sit on, or do the judges put it on some kind of ledge on the bridge to hold it?

Answer: You need to install cross member, called floor beams, on your bridge,  The 40 mm square loading plate will sit on these floor beams. You are correct that the floor beams can not interfere with the eye-bolt portion of the loading apparatus.  As the rules specify the loading locations and the diameter of the eye-bolt, you can calculate where the floor beams need to be positioned. Please note that there are other rules that also control the location of the floor beams.  These also need to be followed.

Question: The rules say that the block must be lowered from above with 2 sides parallel to the side of the bridge. Does this mean that for a side break the block can be lowered on its side through the center and rotated 90 degrees into place? The reason why I ask is I would like to put an “X” or two on top of the bridge to keep it from twisting. The question is, is that allowed?

Answer: Your idea to place x-bracing on the top of the bridge is good.  This type of bracing is allowed. The students have been allowed to place the loading apparatus on their bridge by any means they choose.  Many students disassemble the loading apparatus, place the loading plate into the required position, and finally reattach the i-bolt from the bottom. It is good to position the x-bracing so it does not coincide with the loading locations. This is particularly important if your bridge is not very tall.  The i-bolt will project vertically above the loading plate and poorly placed x-bracing could interfere with it.

Question: I am setting up a middle school bridge building contest this year and just want to make sure I’m doing it right. I see that the initial weight that is added to a bridge is 2 kg. Does this mean that two kilograms is the increment so that we are adding 2kg plates until a bridge breaks?

Answer: The two kilograms represents the loading apparatus that we use for the contest at Illinois Tech.  After that, the load can be increased by what ever weights you have on hand.  At the regional and international contests we use 1, 2, and 5 kilogram weights.  I have been to a school contest where they poured sand into a bucket, which was suspended from the bridge.  They used a slight variation on the rules, by recording the weight under which the bridge broke. It all depends on what you have available.

Last update: October 4, 2019
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For further information, contact: Prof. Carlo Segre -, Illinois Institute of Technology
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