00:00Why does a newly built bridge get covered with rows of giant bags right after completion?
00:04Not decoration, not construction materials, this is a load test before the bridge opens to traffic.
00:09Completing construction only means building is done.
00:11Whether it can safely carry traffic still needs verification.
00:14Design drawings specify how many tons it can bear, but that's just a calculated result.
00:18The real question is whether problems appear once actual weight is applied.
00:22Loading begins, the bridge deck slowly deflects downward slightly,
00:25as long as it stays within design tolerance and springs back, it's safe.
00:29Too much deflection and problems emerge.
00:31Stress concentrates at weak points, the tension side can't hold, rebar resists,
00:35concrete cracks, cracks widen, structure starts becoming unstable.
00:39These risks must be identified in advance.
00:41Why not use trucks?
00:43Because trucks are dynamic, weight, acceleration, breaking all create impact,
00:47data fluctuates and trucks are difficult to remove quickly.
00:49Testing requires controllable static weight.
00:52So water bags are used, each several to over 10 tons, positioned precisely, added gradually.
00:57Load part first, observe data, no issues then continue adding, approaching design load capacity step by step.
01:03Instruments record bridge deck deflection and stress changes throughout.
01:06Data within range, test passed.
01:09Data abnormal, water immediately released, weight reduced, bridge deck recovers, test stops.
01:14This isn't a construction site anymore.
01:16It's the bridge confirming it's ready before facing real traffic.
01:19After opening, the weight becomes real.
01:21If you don't resolve people ulcer as a merchant, yes, you've got a puppy.
01:21You're still off
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