1 00:00:00,684 --> 00:00:02,723 (graphic whooshes) 2 00:00:02,723 --> 00:00:05,390 (pensive music) 3 00:00:09,330 --> 00:00:10,770 - [Narrator] Many Texas bridges use 4 00:00:10,770 --> 00:00:13,050 simple span girder decks. 5 00:00:13,050 --> 00:00:16,080 But because of expansion joints in these type of bridges, 6 00:00:16,080 --> 00:00:18,813 issues with durability and maintenance can arise. 7 00:00:20,160 --> 00:00:22,590 An approach to intentionally form cracks 8 00:00:22,590 --> 00:00:26,550 called a Texas Poor Boy method has been used for decades. 9 00:00:26,550 --> 00:00:29,820 But there is no comprehensive assessment of this technique. 10 00:00:29,820 --> 00:00:33,000 Researchers with the Texas A&M Transportation Institute 11 00:00:33,000 --> 00:00:35,340 and the Texas Department of Transportation 12 00:00:35,340 --> 00:00:38,670 surveyed the performance of the current bridge methods 13 00:00:38,670 --> 00:00:40,680 to make recommendations on new construction 14 00:00:40,680 --> 00:00:42,870 and rehab designs. 15 00:00:42,870 --> 00:00:45,510 - When you're building a bridge, you've got multiple spans, 16 00:00:45,510 --> 00:00:47,670 and between those spans, there's a gap 17 00:00:47,670 --> 00:00:49,290 between the ends of the girders. 18 00:00:49,290 --> 00:00:52,920 This is intentional and it allows for thermal expansion. 19 00:00:52,920 --> 00:00:55,080 - With the weather in Texas being hot and cold, 20 00:00:55,080 --> 00:00:58,080 hot and cold, the bridge is actually gonna move quite a bit 21 00:00:58,080 --> 00:00:59,640 and want to expand and contract. 22 00:00:59,640 --> 00:01:01,590 So that's what the joint is there for. 23 00:01:01,590 --> 00:01:03,480 - [Anna] These often involve lots of maintenance 24 00:01:03,480 --> 00:01:04,740 and can allow water through 25 00:01:04,740 --> 00:01:07,200 that can eventually damage the substructure 26 00:01:07,200 --> 00:01:08,880 beneath the bridge deck. 27 00:01:08,880 --> 00:01:10,320 - [Daryn] Ultimately, what we would like to do is, 28 00:01:10,320 --> 00:01:13,080 we like to be able to remove that joint from a bridge system 29 00:01:13,080 --> 00:01:16,080 and just make those spans continuous all the way through, 30 00:01:16,080 --> 00:01:18,480 which would be no joint from start 31 00:01:18,480 --> 00:01:19,680 of the bridge to the end of the bridge. 32 00:01:19,680 --> 00:01:22,830 - [Anna] Have the deck be continuous over the gap 33 00:01:22,830 --> 00:01:25,980 and hence the name continuous deck detail. 34 00:01:25,980 --> 00:01:28,500 Because the girder deformation introduces stresses 35 00:01:28,500 --> 00:01:29,880 into the continuous deck, 36 00:01:29,880 --> 00:01:31,680 there are unique design considerations 37 00:01:31,680 --> 00:01:33,330 for this portion of the bridge deck 38 00:01:33,330 --> 00:01:35,370 relative to the rest of the deck. 39 00:01:35,370 --> 00:01:38,850 - [Daryn] We were able to build a computer model 40 00:01:38,850 --> 00:01:41,730 that showed the initiation of the cracks. 41 00:01:41,730 --> 00:01:44,490 Then we were able to take that into the laboratory 42 00:01:44,490 --> 00:01:48,810 and replicate that exact data into the full scale models. 43 00:01:48,810 --> 00:01:50,910 - We had students build four bridges 44 00:01:50,910 --> 00:01:53,460 with six unique designs on them. 45 00:01:53,460 --> 00:01:56,700 Two designs replicated existing details, 46 00:01:56,700 --> 00:01:58,890 two designs implemented retrofits, 47 00:01:58,890 --> 00:02:02,160 and two designs were proposed new designs. 48 00:02:02,160 --> 00:02:04,380 The new designs were selected for testing 49 00:02:04,380 --> 00:02:06,030 based on the results of dozens 50 00:02:06,030 --> 00:02:08,910 of options investigated in the computer models. 51 00:02:08,910 --> 00:02:11,340 The benefits of full scale tests is replicating 52 00:02:11,340 --> 00:02:13,413 the exact details in Texas Bridges. 53 00:02:14,250 --> 00:02:17,010 Such details have been absent from prior research 54 00:02:17,010 --> 00:02:19,350 on links labs, yet these details are critical 55 00:02:19,350 --> 00:02:21,873 to where cracks develop and how severe they are. 56 00:02:22,920 --> 00:02:25,650 But the test successfully replicated damage 57 00:02:25,650 --> 00:02:27,810 in existing bridges with the new designs shown 58 00:02:27,810 --> 00:02:29,643 to improve the performance greatly. 59 00:02:30,810 --> 00:02:32,970 One aspect of the new designs is to allow 60 00:02:32,970 --> 00:02:34,770 for more flexibility of the deck. 61 00:02:34,770 --> 00:02:36,540 Another aspect of the new designs 62 00:02:36,540 --> 00:02:38,160 is eliminating some details 63 00:02:38,160 --> 00:02:40,710 that allowed cracks to initiate. 64 00:02:40,710 --> 00:02:42,390 - So the benefits for the department would be, 65 00:02:42,390 --> 00:02:44,430 we get to eliminate that expansion joint 66 00:02:44,430 --> 00:02:46,590 or the need for that expansion joint, 67 00:02:46,590 --> 00:02:49,470 which would then further reduce our maintenance cost 68 00:02:49,470 --> 00:02:52,110 and a few headaches in the future. 69 00:02:52,110 --> 00:02:54,090 For the traveling public, this would also mean 70 00:02:54,090 --> 00:02:56,640 that we could probably have a smoother riding bridge. 71 00:02:56,640 --> 00:02:59,760 When you obviously have to put in that expansion, 72 00:02:59,760 --> 00:03:02,040 you have to start your concrete placement 73 00:03:02,040 --> 00:03:03,330 and then finish at the joint 74 00:03:03,330 --> 00:03:05,400 and then start back up at the other side of the joint. 75 00:03:05,400 --> 00:03:07,950 So that kind of gives it that, the bump 76 00:03:07,950 --> 00:03:09,630 in the middle of the bridge usually. 77 00:03:09,630 --> 00:03:12,330 So we would be able to get away from that 78 00:03:12,330 --> 00:03:14,790 and actually have a continuously graded slab 79 00:03:14,790 --> 00:03:16,860 so it would be a little bit smoother. 80 00:03:16,860 --> 00:03:18,060 - [Narrator] For more information 81 00:03:18,060 --> 00:03:20,490 and to find the publication for this project, 82 00:03:20,490 --> 00:03:22,800 please visit the TxDOT research library 83 00:03:22,800 --> 00:03:24,003 at the link shown below.