Structural Reliability of Off-System Steel Girder Bridges Under Emergency Vehicle Loads

Giovanni Ortiz Author

07/29/2021 Added

26 Plays

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This study will focus on steel girders only and will use a field-tested case study bridge as the starting point. A Monte Carlo simulation will be used to conduct a reliability analysis for the composite and non-composite bridges, and to investigate how composite effectiveness is related to reliability.

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[00:00:01.500]Hello everyone.
[00:00:02.340]My name is Giovanni Ortiz and I am a civil engineering student working with Dr.
[00:00:06.870]Stillman.
[00:00:07.740]And today I'll be presenting my research project that focuses on the surgical
[00:00:12.330]reliability of assistance.
[00:00:14.130]They'll get over just on their emergency vehicle lows. All right,
[00:00:19.050]to get started.
[00:00:19.800]We need to look at the big picture and across the U S there are 600,000 bridges.
[00:00:24.870]Uh,
[00:00:25.590]67,045 of those bridges are categorized as role bridges occurred into the
[00:00:30.420]national breach inventory data 2020, uh, as you can also see in the picture,
[00:00:35.010]uh,
[00:00:35.550]every blue dot represents their location and there's high.
[00:00:40.500]There's a high density of blue dots, uh, near the central area of the country,
[00:00:44.940]and a feel. Another density is, you know,
[00:00:47.610]concentrating in the east part of the country,
[00:00:52.650]shrinking down to a state level. Nebraska has 15,348 bridges in total.
[00:00:57.750]Uh, 26% of his bridges are load restricted,
[00:01:00.780]meaning that there are certain vehicles of a certain way that are not allowed to
[00:01:05.100]go across them. And 89% of this post,
[00:01:08.280]the bridges were the sign to known unknown loading.
[00:01:12.060]That basically means that their capacity, they took capacity.
[00:01:15.870]It's not known by engineerings and, uh, people that do service.
[00:01:20.640]Then, um, you can also see the picture, uh,
[00:01:23.160]down below where most of this real bridges are located. Yeah,
[00:01:30.420]December, 2015, the 16 American surface transportation act for,
[00:01:35.060]for sure fast act was implemented.
[00:01:37.580]And basically this act pretty much define a
[00:01:41.900]new, uh,
[00:01:43.220]set of heavy vehicles that they call emergency vehicles or UV for shirts.
[00:01:47.780]And the definition they provide is a vehicle design sign on their emergency
[00:01:51.470]conditions to transport personnel and equipment.
[00:01:54.410]And there are two comments EVs via ladder and atypical, uh,
[00:01:59.420]fire truck. So you can get an idea of how these vehicles, uh,
[00:02:04.370]physically look like and how heavy, uh, they can be.
[00:02:09.110]We have set three objectives for this, uh, research project. Uh,
[00:02:13.190]number one is determine how composite effectiveness relates to the reliability
[00:02:17.540]of rail bridges, subject to emergency vehicle loads. Number two,
[00:02:21.140]evaluate is string one in service to limit states based on reliability analysis
[00:02:25.820]and number three,
[00:02:26.510]estimate the reliability and assist for string one and service to limit state
[00:02:31.130]functions for the mental energy part. We have chosen at cases,
[00:02:36.080]study of reach called a union breach, located and owned by the Sounders county.
[00:02:41.360]And as you can already appreciate in the big church, the, this is a rural,
[00:02:45.270]a bridge located in a rural area, and it has been in service for over 60 years.
[00:02:49.700]And this is the bridge for our theoretically youth into run reliability analysis
[00:02:54.560]of a strange one and service to this,
[00:02:58.990]this flow chart represents how are we doing our reliable analysis?
[00:03:02.290]And this can be breaking down into three major steps, basically.
[00:03:05.500]So step number one would be to the terminal year,
[00:03:08.170]requires shear near phase B prime. Uh, we create a distribution for this,
[00:03:13.210]and then we'd go to a step number two,
[00:03:14.860]which is to compare the distribution of value.
[00:03:18.370]Be simulated is greater or equal than the deep prime. Uh,
[00:03:22.150]we can have a yes or no. So for purposes of design Graham,
[00:03:25.600]we're going to say that's a yes. So if it's a, yes,
[00:03:28.930]we have a moment of resistance that we create a gnome,
[00:03:31.930]a log normal distribution, and our final steps.
[00:03:34.570]And since we have now a log normal distribution of assistance,
[00:03:37.960]and we compute our, uh, live love and that load distributions,
[00:03:41.650]we run a reliability analysis. And then we come out with this safety index, uh,
[00:03:46.300]coal beta.
[00:03:49.090]We're also accounting for B equals in an adjacent lane to an emergency vehicle.
[00:03:53.620]So we have taken the national rating low and our L low vehicle and
[00:03:58.720]low vehicle, uh, in a simulated in the adjacent lane to see load effects
[00:04:06.130]in terms of results.
[00:04:07.300]We're going to start looking at some resistances and we're going to do this by
[00:04:10.630]section. So we're going to start with brutal behavior. And as we can see,
[00:04:14.260]there is a distribution of assistances for an alpha of 1.25.
[00:04:18.760]And what's the alpha, I'll try as the interface,
[00:04:20.740]your simulator over the interface, shear to reach full composer behavior.
[00:04:25.540]And as we can see, there is a minimum there's a low, uh,
[00:04:29.590]minimal load distribution and a maximum load with solutions.
[00:04:32.890]So that means that we have,
[00:04:34.810]we have a load persistence that might indicate sufficient load capacity,
[00:04:38.830]and that also confirms the precedent of no composer members now in comparison,
[00:04:43.240]uh, if we have ductile behavior, uh,
[00:04:46.090]it's only one nice smooth curve that that indicates there is sheer
[00:04:50.620]strength transfer, uh, happening successfully. So as we compare this to, uh,
[00:04:55.960]curves and distributions, uh, there are more, uh,
[00:04:59.020]values located on the right-hand side,
[00:05:01.540]so that can give us a good sign. The, the ductile behavior, uh,
[00:05:06.190]yields more, uh, reliable resistances.
[00:05:12.070]Now we're going to look at some, uh, limits states,
[00:05:14.860]and we're going to start by string one and basically, uh,
[00:05:18.280]our target beta or reliability and target it's 2.5 or greater.
[00:05:22.690]And as we can already see here, there are some red numbers,
[00:05:25.420]one point 69, 2 0.31 and two point 71, 2 76.
[00:05:28.810]So this are numbers that theoretically means failure on
[00:05:33.790]our breach. So for ductile behavior, uh, as we already talked about it,
[00:05:38.170]that yields higher assistances.
[00:05:40.240]So it makes sense that this yields higher reliability in the system.
[00:05:43.660]And that's pretty much the low end of this graph. Uh,
[00:05:46.510]as you can see on the X axis that yields higher assistances over 2.5,
[00:05:51.280]however forbid will behavior. That is a slightly 2.5, uh,
[00:05:56.020]at the greatest, uh, that suggests that it needs further load analysis.
[00:06:02.570]Now, in comparison, we're going to look at service to, uh,
[00:06:05.630]and then the target reliability index here is anything greater than a 1.8.
[00:06:09.800]And as we can already see again, Fred numbers.
[00:06:12.920]So these are for brutal behavior,
[00:06:16.760]0.11 and 1.15.
[00:06:19.940]Meaning if there's a failure case again for Phillip for real behavior, uh,
[00:06:24.170]for dovetail, uh, it seems to be increasing again. So, uh,
[00:06:28.520]as we said in the past,
[00:06:30.530]creating higher assistances will give us higher reliability analysis,
[00:06:37.210]summary and conclusions. If the mechanism is ducktail,
[00:06:40.030]there's a large benefit available from any level of compulsory transfer
[00:06:43.870]strength. If the mechanism is brittle,
[00:06:46.360]then the trend remains very low, no matter what these transfers Trent is.
[00:06:51.520]And also ductile behavior provides there is smooth distribution of resistances,
[00:06:56.230]which also yields higher level reliability innocence
[00:07:01.630]for future work.
[00:07:02.950]We could conduct non-destructive tests to establish a sec like
[00:07:07.750]thicknesses, uh, what could conduct, uh,
[00:07:10.660]destructive tests to examine low capacity and behavior. And we could also,
[00:07:15.190]uh, find out what the probability is of emergency vehicles, you know,
[00:07:19.930]multiple pressing, uh, are in bridges in reality. So, uh,
[00:07:24.130]would that set finally, I like to, uh,
[00:07:27.160]say thank you to my UNL mentor, Dr. Jessica Steelman to my, uh,
[00:07:31.990]graduate student, uh, mentor bloomin' young and, uh,
[00:07:35.410]on your login and the national science foundation for this project.
[00:07:39.220]And thank you so much for watching this.

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Structural Reliability of Off-System Steel Girder Bridges Under Emergency Vehicle Loads

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