2013 Competition Guide
Vertical Load Tests
Vertical Load Tests Video: VLoading.wmv, 4:39 min, 12.1 MB
Again, while transporting the bridge between the various sites, it is possible that the fasteners may fall off or other damage occur. If this happens, the Marshal should notify the Head Judge at once. There is a penalty for falling fasteners.
Again, care should be taken during transport and staging to ensure that the bridge is not 'preloaded' either by bouncing or other means that would remove as-built slack from the bridge. Marshals should make sure that no one leans or sits on a bridge. At the national competition, if such situations arise, the Head Judge will make the team disassemble their bridge and start over again, from the end of the rotation. There are safeguards put in place to ensure that the rebuild cannot improve on the original performance (but you can do worse!). So, don't mess with the bridge!
At the load station, the Judge make sure that all team members have the required safety gear then will have the team position the bridge in the loading area, making sure that the 'A' and 'B' sides are correctly placed and the safety supports placed under the locations for the grating.
On the subject of safety supports, it is vitally important that the supports be designed and constructed in such a way that they prevent grating from falling more than a few inches while still permitting the maximum allowed deflection. They should be placed so as to minimize the possibility of dumping the load off the side of the bridge if a unsymmetrical collapse occurs. At the National competition, stacked plastic buckets have been found to be effective. Some enterprising individuals have additionally built brackets that sit on top of the buckets and have a socket that will accept a piece of 6x6. They have small chunks of 6x6 in varying lengths on hand which they use to get support right up to the decking. There are other methods that work quite well also. Whatever you do, just be safe.
Once the safety supports are in place, the Load Judge will carefully locate the decking on the bridge and have the team apply the preload. The sway targets and vertical deflection measuring devices are then installed and initial readings taken and recorded on the judging form for the load station. The Team Captain should be invited to verify the setup and initial readings.
Once loading starts, it should be accomplished in a safe, smooth, and continuous manner as shown in the video. If loading manually, teams should not be allowed to stop the loading to look at gages or develop strategy. All teams should load in the same manner. Judges may stop loading for safety reasons or if the bridge exceeds sway or deflection limits.
Concerning loading. At Nationals and most ASCE student conferences, loading is done manually by the team members. A few conference hosts over the years have devised ingenious 'automated' systems that can make the load test go very quickly and efficiently without requiring anyone to get close to the bridge. These systems take lots of time to devise, design, build, and test but feel free to take on the challenge if you wish. (Click here to see one such device) If you can come up with a relatively simple system that is easy to transport, please let the Rules Committee know. We'd like to consider such a device for the national competition.
At the end of each load stage, the Judge will record the deflection readings and allow the Team Captain to verify them.
After the last deflection reading, the team should unload the bridge safely and quickly. Note that the bridge does not pass the load test until it is fully unloaded. If it collapses at any time it will be penalized according to the rules.
Note to Judges: There is no need for you to compute the deflection. This will be done at the scoring table by the spreadsheet. Just make sure that you include signs when you record the numbers.
Another note to Judges: Don't ever let anyone stick their head or any other body part under the bridge to read gages or for any other reason. It's just not safe! Competitors must be encouraged to keep their feet from under the bridge as well. Sometimes these bridges come down very quickly and without warning.
WARNING: At Nationals, if the measurement devices are compromised in anyway by anyone during load testing, then the bridge is disassembled and starts the entire competition sequence again. The reason for this is that the initial loading will take out any slack in the joints and reloading the bridge has the potential to result in smaller deflections than would have been seen in an uninterrupted first loading. So... DON'T TOUCH THE DEFLECTION DEVICES!!!
When all is done and recorded, the Judge reviews the data form with the Team Captain. The Team Captain signs the form when all questions have been resolved and the forms given to the Marshal who accompanies the bridge to the next station.