2013 Competition Guide

Lateral Load Test
Rule 12.4

Competitor Preparation:

• Make sure that you bridge is sufficiently stiff to pass this test.
• Team members participating in this test must be wearing all the safety gear stated in the rules.
• A minimum of four team members are normally required to perform this test, depending on how the test is setup.

-----------------<0>-----------------

Host Equipment/Preparation:

• Have the construction site completely ready prior to the start of the competition
• Assign a Marshal to the bridge. The Marshal should have the judging forms for the bridge.
• A set of the rules and current clarifications at each load station.
• A piece of decking.
• A coin or other means of randomly selecting the side to be tested.
• Tape or other marking device to indicate the 'A' and 'B' sides of the bridge.
• 75 lbs of load to go on the decking.
• A plumb bob and a sway target on the ground or some other means for measuring lateral deflection.
• A means for restraining lateral movement at the far abutments. Team members can be used for this purpose.
• A means for applying a 50 lb lateral pull on the bridge at the deck level.
• A clipboard with pencil per load station.

-----------------<0>-----------------

Lateral Load Test Video: LateralLoad.wmv, 2:53 minutes, 7.5 MB

-----------------<0>-----------------

The lateral load test is often conducted at the same location as the vertical load test, but not always.

While transporting the bridge from the erection site to the loading areas, 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.

Also, 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 Nationals, 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 makes sure that all team members have the required safety gear then will use a random means (normally a coin flip) to determine the 'A' and 'B' sides of the bridge. Once this is established, grating and a small load are added to the bridge as specified by the rules, a means for measuring the lateral movement and a means for restraining the bridge are put in place, and the specified lateral load is applied.

Lateral load application methods vary.  At Nationals we use a weight over a pulley as shown in the video. We've also seen large spring scales use where the competitors pull laterally until the scale indicates that the proper force has been applied.

A major concern has always been slip at the foundation during the lateral load test.  While slip has rarely been a realized problem, it has lead to lots of headaches for host chapters who've tried to provide a number of ingenious devices--none of which have been universally accepted.  The major change to the rules regarding the lateral load test in 2012 (an retained this year) is that it is up the competitors to provide their own lateral restraint devices (Rule 12.4.1) to resist sliding.  Note that any device must only resist sliding and not uplift or rotation.  The devices must not do damage to the floor either! 

Check out more sway device options by clicking on the thumbnail below:

-----------------<0>-----------------