 |
  |
MISSOURI DIVISION |
|
 |
 |
PROCEEDINGS OF THE SEPTEMBER 2000 POST EARTHQUAKE HIGHWAY RESPONSE AND RECOVERY SEMINAR HELD IN ST. LOUIS MISSOURI
POST EARTHQUAKE SAFETY EVALUATION OF ROADS & BRIDGES BY ROBERT FROSCH
MR. NEMMERS: Robert Frosch is an associate professor of civil engineering from Purdue University. He earned his doctorate in civil engineering from the University of Texas before moving to Purdue. He also has some international experience. This summer he was part of a National Science Foundation funded team that went to Turkey to evaluate post earthquake damage focusing particularly on building damage. Mr. Cooper talked this morning about the post earthquake structure highway damage and made some references that there was quite a difference in relationship between the building damage and the highway damage. Purdue University is looking at the post earthquake safety evaluation of roads and bridges in cooperation with the Indiana Department of Transportation. Purdue is developing a training package for inspectors to effectively evaluate post earthquake damage in highway structures.
MR. FROSCH: I´m going to talk about a workshop put on by Purdue University and the Joint Transportation Research Board for INDOT to look closer at earthquake safety for roads and bridges. The purpose was to develop an effective system to train INDOT personnel of various backgrounds for inspecting roads and bridges after a major earthquake. So we wanted to have a very effective system and teach people with a variety of backgrounds.
There are two different levels of inspection that we divided the training into and two levels of inspection that will occur following an earthquake. The first level is called level one, which is the immediate visual safety inspection. The purpose of the level one inspection is to determine if traffic needed to be restricted from unsafe bridges. The target of this level is to find the obvious unsafe bridges.
Following that up is a level-two inspection. Level-two inspections will be conducted by people with higher technical backgrounds such as maintenance engineers or design inspection engineers. At this level, we will follow up with the bridges that were strictly yellow tagged. We have a three-tiered tagging system of red, yellow, and green. The yellow tag means undecided and we need to provide a more detailed assessment than the one done in level one.
One of the first parts of the training is an introduction to earthquakes in Indiana because we wanted to be sure the participants understood the earthquake potential in Indiana and the Midwest. People have the misconception that we never have earthquakes here. So there is a public awareness problem.
We developed a training manual to go along with the workshop. The participants are able to take away this resource guide that contains more in-depth information.
From earthquake awareness, we cover a little bit about bridge behavior during an earthquake. This is for various personnel and not just engineers. We talked about the typical bridges in Indiana. We look at some of the key bridge components, the type and classification damage, and whether it's red, green, or yellow. We give examples so the participants know what to expect when they go out to do damage assessments. Finally, we show actual bridge and road damage from other parts of the country or other parts of the world.
We first talk about how the motion moves through the ground and gets into the bridge site. Through the ground acceleration, there is ground displacement that is measured at the bridge site. This concept exposes them to the idea that an earthquake in the New Madrid fault zone will affect Indiana and not just that an earthquake will happen in Indiana.
Then we talk about bridge behavior once the seismic waves hit the site. We show some very simple sketches of a bridge and how the loading of the structure occurs through the mass. The superstructure is going to act as a simple beam and the abutment resists most of the force. So one of the key areas to look for damage is at abutment area.
Our handbook illustrates all of the different structures that may be seen across the state. So our inspectors will have some familiarity with those structures before they even get out to the sites.
It's amazing, how little those who work in the department know about bridges. But after this training, people have a new respect looking at bridges and really seeing the details and differences between the various bridges for the first time.
It is important for people to know that bridges carry other lifelines such a utilities across them. There may be a natural gas pipeline attached to the bridge. So we stress safety at the site. They shouldn´t be climbing underneath the bridge on an initial inspection. They need to notice what else is out their for their own safety.
We try to have two person teams, especially on a level two inspection. The buddy system provides that added level of safety of each team member. If one gets in trouble, the other can help or call for assistance.
Again, for level one training, we show some of the typical bridges, try to identify names to all the different components, and we show what is considered a superstructure verses a substructure. So everyone learns the basic terminology.
Next is the damage classification section. We adopted a three-tag system: green, yellow, and red. Green means that the structure is safe for traffic and the bridge remains open. Yellow means the bridge can remain open but needs a level two evaluation. If there is any question, we yellow tag a bridge for a follow-up level two inspection just to be safe.
Red tag is the final level and means unsafe. The bridge must be closed. We go over the official bridge closing procedures required by the state of Indiana.
As part of level one, we developed a very specific procedure. It includes 5 steps. For step one, the inspector checks the bridge for collapse, partial collapse, or roadway damage. For step two, the superstructure is checked. At this point all the terminology training is starting to come into play. Step three is a check for substructure damage. Step four is a check for bearing damage. And finally, step five is a check for soil problems.
The handbook includes illustrations and we also have a field guide that goes out with the inspectors. This walks them through the steps right to filling out a form evaluating the damage.
In the finishing or concluding part of the level one training, we go through a series of slides showing different damages that have occurred in past earthquakes. In addition to showing the slides, we provide some discussion on our opinion of the damage. So we might give an example of a red-tagged bridge and give specific reasons why. From this point, they get a pretty good feel on how to classify or tag a bridge.
A site in Turkey had some settlement or lost part of the approach. A quick repair allowed for emergency access but did not allow the public to cross so we would have red tagged this site. This would be a fairly large bump to hit driving 50 or 60 miles an hour. People try to get out of an earthquake area quickly so a big bump wouldn´t be safe.
So as we finish the training, we then go into some examples. We hand out the actual forms and everybody looks at a series of photos of damage and goes through an evaluation. So people go through the damage and give their opinion. After they fill out the form, we start talking about it and get opinions. So we have an interactive discussion at this point.
On a level one form, an inspector fills out the information and if there are any yeses across any of the categories, it's automatically a red tag. So if you actually meet any of the problems, we red tag the structure. We also have criteria for a yellow tag or a green tag. In doing this, we go through a few examples. We show different pictures of a damaged bridge and everyone fills out the form. Then we show after what the opinion was of each of the categories. So we go through step-by-step and given an opinion for each category. So that´s level one and it´s very quick. It should be no more than 15 to 20 minutes per bridge. We pick up the obvious.
Level two involves more engineers that can do the in-depth evaluations. Again, this is a follow-up of level one. In this part of the training, we go into more of the bridge damage type that would be seen following the first level one. We show photos of questionable red or yellow situations. Typically the inspectors are going to be trained at the yellow tag level. But also, level two inspectors are expected to go after the red tags, too. Something that´s red tagged needs some follow-up work so we train our inspectors on red tag damage.
Finally, we discuss repair and monitoring of these structures. Monitoring in trying to see if there is still some question of yellow tagging of a level two inspection.
In going through the training, we show some of the more questionable areas. We get into some very detailed and technical discussions like deciding what to do about a bolt that is sheared through.
Level two form is more complex than a level one form. There are many more areas. We still have a six-step approach that follows the level one procedures but more detail under each step.
Then we finish the training with reviews and exercises. So we have hands-on training where we actually show some examples of damage. For instance, we might show a photo of some spalling at the top of a column, some settlement down at one of the footings, and some damage to the abutment. We would then go through the inspection report and everyone in the class fills it out independent of others. Then we go through it step by step together. We review the photos and discuss what we see just to reinforce what we taught them so the ideas stick.
Just to give you a brief view of some of the tools. As in the level one inspection, we train our people in using the tools. We have detailed tool list and go over how to use them. First of course is in the handbook that has the level one inspection form. Level two is following level one, so they're going to get the sheet from the level one inspector. They will the bridge inventory book, bridge or county route maps to find the structures, detour information, water, food, tents, shelters and supplies for three days per person. We tell them not to expect to get back home the first night. So those are their tools we recommend they have.
Finally, the training wraps up in discussing, especially the red tags that we want to fix and opened as quickly as possible for the emergency access and open the lifelines for the recovery efforts that's coming. So we talk about very temporary repairs or emergency repair. Permanent repairs or replacements can follow.
We also have a brief discussion about some long-term monitoring under a level two inspection. Now, if a bridge is yellow tagged, it´s still going to remain open. The inspector may have some question that there is still potential problem with the structure. We're looking for any indication of changes in the behavior the structure that would push it over to red tag condition. If there is no change, we're keeping it open. When we do see a change in behavior that indicates a potential closure, we need to take an action. As part of this training, we show very simple methods to monitor. It doesn´t involve elaborate strain gauge technology but very simple techniques that can detect evidence a problem has happened. For example, putting some plaster over a crack and seeing if cracking occurs over the plaster. If so, the cracking might be growing or moving on you.
The primary objective of this workshop is to insure the safety of the traveling public. In doing this, we're trying to maintain an open lifeline. We don't want to shut down the roadway system of Indiana and we want to keep as much open as possible. That's why we're going after the obvious unsafe bridges.
We conducted this training back in March. We had a very large group of trainees. Our plan is to continue this training throughout the years.
But one of the next steps is looking for priority routes. Where are the high priorities are, we will try to keep lifelines open. I think trying to interconnect to the other states is also imperative. We´re not isolated in Indiana.
So with that, I would like to turn it back to the moderator.
MR. NEMMERS: Thank you very much, Robert. Are there cameras in your toolbox?
MR. FROSCH: Yes, we do.
FROM THE AUDIENCE: Are you certifying these inspectors as you train them or are you having like a cadre of inspectors, or is that more of an emergency management?
MR. FROSCH: I think I need to defer that question probably either to Wayne Detrich or Bill Reinhart, who are in the audience.
FROM THE AUDIENCE: The term certification might be a little bit grand. We at least are training our maintenance workers and construction inspectors to be able to do it.
FROM THE AUDIENCE: Were you intending on providing this training to city and county road and bridge people?
FROM THE AUDIENCE: We expect to share what we're doing. For now we´re not training other groups. One of our big questions is how big we take it? Do we train people up in northern Indiana so they can come down and help out southern Indiana? We´re just beginning to deploy this training.
FROM THE AUDIENCE: The reason I ask is we have spent a lot of time in Missouri doing CUSEC training. We have what we call SAFE volunteers. Volunteers who do post earthquake damage inspection per structure using ASE, SESMO, AIA and as one of those programs from California. We´re trying to transplant it in Mississippi, Indiana, Illinois and other CUSEC states. And it´s a very successful program and I can see that this is an excellent program that needs to have a lot of attention before the earthquake happens.
FROM THE AUDIENCE: In your visit to Turkey, did they have any systems for inspections or were they looking like we would if we don´t train ourselves?
MR. FROSCH: I visited Turkey in June and was quite a bit away from the actual earthquake. People are still living in tents there. This is not something that they have already cured. For many houses that we inspected, most people asked me if their house was safe. I would tell them it was safe but they would reply they weren´t going back because of the aftershocks. They were just scared to death. Tent cities were everywhere.
FROM THE AUDIENCE: Somebody remarked in the earlier session that from Federal Highways was over in Turkey two different times. Maybe he can answer the question.
MR. JIM COOPER: In answer to your question, yes. The national forces, the bridge engineers, from different districts outside the affected area moved in. This was similar to what you are proposing for Indiana, that is, using northern forces to help in the southern sections. In Turkey, most of the repairs were done in a very short period of time...within a week in most cases. Typically, the inspection forces were brought in from outside of the disaster area. Fortunately they had a few very strong individuals who stood up, made some decisions, and it really paid off for them.
MR. NEMMERS: Ed would like to add one more thing.
MR. ED GRAY: Yeah, I just wanted to point out something here that, you know, can't be stressed enough. I think Al Masuda from FHWA and Dave Musser from MoDOT would agree with me. The earthquake response and recovery problem is a partnership. There are a lot of active people here. Dave Hoffman from the Geological Survey. I see my friends from CUSEC, the association of CUSEC state geologists, and CERI. We´ve just started a new partnership with the University of Missouri at Rolla. I´m very proud to say we´re working on this earthquake problem in Missouri. But I´m also saying to you other people in Illinois and Indiana that we need your help, too. It has to be a partnership, folks. We´ve got a lot of work to do because that earthquake is going to come before we´re ready for it.
 |
Send mail to scott.holder@fhwa.dot.gov with questions or comments about this web site. |
