 The purpose of this presentation is to show how to inspect a timber bridge. In addition to making two bridge inspections, we will demonstrate how the condition ratings are determined. Many of the typical timber defects will be examined and rated. Many of the older and smaller bridges in this country were constructed of timber. Now, timber is not as common as concrete or steel and much of the expertise with timber has been lost. The fact is, many people do not know what to look for when inspecting a timber bridge, nor do they know how to evaluate what they have found. We will show many of the more common problems associated with timber bridges and discuss how to evaluate and rate the findings. We will examine the common problem of rot and will show how to use a drill to determine the extent of rot. We will also show how to fill out the bridge inspection form. The bridge inspector provides the source input data for initial input to a large and involved process that stretches all the way to Washington D.C. and involves millions of dollars. The inspection sheet the inspector fills out is a basic document in the whole process. The part played in this program by the field inspector is extremely important. For this reason it is imperative that the inspector be accurate and unbiased in his report. You must remember that if you are the inspector you are reporting the condition of a bridge and signing your name to it. If the bridge falls down the next day I hope your inspection report said it was bad because the inspection report will be one of the first things that they will look at. Then bridge inspector will be helped in his work. He will be trained before he ever goes out on the job and he will usually have the advice of a supervisor. In addition there are two good manuals to serve as reference works even after training. One is the bridge inspector's training manual and the other is the AASHTO bridge maintenance inspection manual. Both these manuals should be kept at hand for reference. In addition to the basic manuals the inspector should also have the state and federal coding guides to assist in filling out the inspection form. For each inspection it would be helpful to have the last inspection report if there was one as well as a set of plans. The bridge inspection form is straightforward it will have an area at the top to record the physical data of the bridge. The body of the form is divided into each major area of the bridge with a list of sub items that must be rated. The major items include the substructure, the superstructure, the deck, channel and channel protection, culverts and retaining walls, approach alignment and signing. Each of these major items will be radiant. The rating will be a composite of the sub items under each heading. The condition rating compares the present state of an element in a bridge to its condition when the bridge was new. The numbers run from zero, a closed bridge, to nine, which is a new bridge. These numbers are grouped into four general categories. Zero, one and two are critical, three, four and five are poor, six and seven are fair and eight and nine are good. With these general terms in mind it should be easier to assign a condition number. We expect that you won't always agree with a specific number but you should be within the same category. In other words we should be able to agree on whether an element is good or fair. Coming up in this program Bart Bonney, our bridge inspector, will show what equipment an inspector should have with him to properly inspect a bridge. He will also inspect two bridges and give a brief explanation of timber drilling. This is most of the equipment that I use when I inspect a bridge. Over here on my left is my concrete testing equipment. We won't go into that right now. Next to it I have my miscellaneous equipment, which consists up here of a ladder. I use it quite frequently. My clearance rods, used for measuring my vertical clearances, shovel, I carry a four foot level to, as a straight edge, works real well. My cones, I carry a machete, flashlights, hip boots, coveralls, hard hat, my geology pick, also carry a torque wrench and the assorted sockets to go with it. I carry two or three different types of tapes and links. It really helps for measuring up the materials that you're going to need to reorder or just measuring your deficiencies in areas. To record the deficiencies, I use a camera. I'm a very poor draftsman and a picture is worth a thousand words. It's really a big help and I use a 35 millimeter camera to take my pictures. In the dark areas, I've got a strobe that enables me to get a good picture of underneath the structure. If I run into a deficiency that should be pointed out to my supervisor, as soon as I get back to the office, I take a picture with a Polaroid. This is really, the quality isn't quite there, but you still get a picture and it's a big help. Over here to the right, I've got my climbing gear, ropes and other paraphernalia. Here we have our timber boring equipment. This is a two and a half KV generator. It's big enough to run two drills off of if you desire. I carry a 100 foot extension cord and a 25 foot extension cord. I carry two drills, the first one being a 3 eighth inch chuck. It's a heavy duty industrial quality drill. I also carry a half inch drill. It's also a heavy duty industrial quality. Both these drills have a forward and a reverse. This enables you to withdraw the drill bit from a deep, if you've got it drilled in, 16 inches into a deep memory. It's a real handy function to have with your drill. I use a 3 eighth inch ship auger with a screw tip on it. You should have two different sizes, I'm speaking a length. One 18 inches in length, another 12 inches in length. This will enable you to get into tight areas, up between the stringers and so on. Some of our members we require plugging after we extract the drill bit and we do this with some older plugs that have been creosote treated. All this equipment that you see here is essential in making a proper and complete bridge inspection. When we start an inspection the first thing we want to do is stop off the bridge and take a look at the entire layout of the road, the bridge and any other factors that might affect the structure. The first item that we want to look at is the approach alignment item 65. In this particular case the alignment is straight both horizontally and vertically right at the bridge, although there is a hill at either end and we would call the alignment of the roadway an 8, which is good. There is no approach slab, there are no relief joints, there is no approach guardrail. The pavement however at the bridge is very rough and would cause high impact loads of vehicles using the road and cause some damage to the bridge. Because of this we have downgraded the pavement to only fair or a 6. The embankment appears to be quite satisfactory and is not settled and we have called it good or an 8. For item 65 the inspector's condition rating would be fair or a 6. This would reflect the seriousness of the pavement at the end and on the bridge. The next thing to look at is the signing on the bridge. The bridge is posted with a 3 ton load limit sign at each end. In addition there are warning signs at each end of this section of road. The signing is legible and we have rated it as an 8 or good. It is very visible which is also an 8. The inspection condition rating for this item is therefore an 8. We are now ready to start inspecting the bridge proper. We have the inspection vehicle parked well off to the side of the road. We have warning signs on either end of the bridge and our inspector is clothed in orange clothing to be more visible. He comes out and starts looking at the deck and the wearing surface. The wearing surface as we can see is in fairly good condition on the bridge except for a couple patches. The wearing surface at the end of the bridge however is rutted and has settled approximately. How much would you say Bart? There is an inch and a half there. An inch and a half. This causes a high impact load on the structure and we would call this a poor condition and we would rate it as a 4. The next unit under item 58 the deck that we will look at will be the fellow guard and rail. The inspector looks at all of the rail and posts and fellow guard in detail and takes pictures of any bad areas that he might find. Most of the rail on this bridge is in pretty good condition. The rail on the left side is new. This area here is about as bad as any part on the bridge. This post has some rot which is just beginning. The fellow guard has some rot around the bolt holes. Because this condition is limited to this area only and the rest of the rail is pretty good we would say that the rail would be in poor condition and be rated as about a 4. We will now start looking at the deck. We can see in the gutter where the asphalt has come off the tops of the deck planks. By sounding with the geologist hammer which is a very useful tool we can hear the punky dull sound. This indicates rot the very dull sound like that it shows that it is hollow. Good sound wood would have a ringing noise. One area is not sufficient we will want to look at as much of the top of the deck as we can find. In the corners is another good area to get to. Again it is dull sounding, very punky wood but we can't inspect all of the deck from the top. We must also inspect the sides and the bottom. We have now moved around to the side of the bridge to examine the ends of the deck plank. Some of them are in good condition some have been replaced as we can see here others don't look so good. Ends of these deck plank are badly rotted. This one we can see looks sound but upon probing with the G pick it comes apart quite easily. The wood is wet which is a needed criteria for rot. In digging out this wood we find we have a termite or carpenter end in the wood. These bugs will eat up the wood and cause very rapid deterioration of the member. We have now moved underneath the bridge to take one last look at the bridge deck. We can sound the deck plank, oh there is some soft wood there, this plank is really rotted. We can see some green stain on the wood which is usually an indication there might be rot. We can also see some white fungus in other areas. This also is an indication that there might be rot present. In view of this rotten nature of the deck that we found both on the top and the sides and the bottom we are now ready to give the deck a rating that would be poor. We have chosen the number three in this case that is very poor. We have now completed the inspection of item number 58 the deck. The wearing surface we have rated as a four. The deck itself we have rated as a three. The fellow guards and railing we have rated as a four and the overall condition rating for item 58 is a three based on the condition of the deck itself which we call the three. We are now ready to start inspecting item number 59 the superstructure. In a timber bridge the superstructure is pretty well limited to the timber stringers. Our inspector has been boring the ends of the timbers on this bridge. He does this in conjunction with sounding with a geologist pick. Sound from the pick is obviously very sharp and shows good wood. Did you find any rot? This one stringer I found four inches of rot but there is a little bit of rot throughout the structure. What would you rate the stringers based on what you found? I'd give them a six. All right a six. The other items under superstructure that would be applicable would be timber decay we would call a six. The deflections under load are also pretty fair we'd call them a six. The alignment of members is also fair we'd call that a seven. Vibrations are pretty fair we'd call that a seven. The rating for item number 59 superstructure overall would be a six. We are now ready to start inspecting the substructure item number 60. We've started by inspecting the pile caps. Our inspector has drilled these caps and has not found any rot at all and we've rated them as a seven which is pretty fair condition. We've also drilled some of the piling and they too are in fair condition and we've called them a seven also. We'll now try some of the piling in the stream area and move on after that to the abutment. The drilling that we have done we will cover in detail in another segment of this presentation. We have now moved into an interior bend near the creek where we'll look at the piling. We will sound these piling and we already have drilled the piling and haven't found any evidence of rot. We'll look at the outside of the piling. The critical area of piling is where they enter the water or the ground. In this case we can hear that the piling are quite sound. There is some weathering of the piling right on the surface but this is only a superficial defect. When we drill these we drill right out the water line or mud line and in this case they were sound so we would rate these piling as a seven. The last item under the substructure is the abutment. We're checking the cap and it sounds quite well. We won't drill this one the other ones have all been sound. The piling again are quite sound looking. They sound fairly good. We'd rate the cap a seven, the piling a seven. This obviously is a new back wall, it's treated timber, quite sound. We'd rate it a seven or an eight even. This pretty well concludes the substructure item number sixty. We have rated everything a seven therefore the condition rating for item sixty would also be a seven. The last item that we have on our inspection form as applicable is the channel and channel protection item number sixty one. Here we can see a small meadow type stream meandering down to the bridge. There is a minimum amount of vegetation along the creek. We would rate this as a seven, it's fair condition. We do have a problem with this tree growing out over the stream right adjacent to the bridge which probably should be pruned back to give the stream more flow capacity. The adequacy of the opening is more than adequate, we'd call that an eight. The overall condition rating for the channel and channel protection item sixty one we would call an eight. We have finished inspecting this bridge. Now we want to show what the completed inspection form looks like. This is the form that the state of Oregon uses. At the top is the physical data on the bridge. The body of the form contains the inspection results and there is room at the bottom for remarks. This is not shown on this slide. Every low rating should be explained. First we look at the superstructure item number sixty. The abutment back wall is a seven, the piling were a seven, the bent caps were a seven, and the timber decay we called a seven, and the overall rating is a seven. For the superstructure item number fifty nine we called the stringers a six, and timber decay here was a little worse and we called it a six, deflection under load was a six, and alignment and vibrations were seven. The overall rating was a six because of the sixes up above. The deck item fifty eight, the wearing surface was a four, the deck itself was a three, the fellow garden railings were rated as four, and the overall rating was a three because of the seriousness of the deck. The channel and channel protection item number sixty, the vegetation was rated as a seven, the adequacy of the opening was an eight, and we called the overall rating an eight. Culverts and retaining walls do not apply on this inspection and are marked out. The approach alignment item sixty five, the alignment was an eight, the pavement was a six, the embankment was a six, excuse me an eight, and the overall rating was a six. The signing was all eights and we called it an eight overall. This is what the completed form looks like. Now we'll move on to timber boring. Your G pick is the easiest and quickest way to determine if decay is present in a timber member, but it won't tell you the extent of decay. So at this point I'll give you some guidelines for test boring the timbers on your structures. First, you must make up a boring diagram consisting of sketches showing configuration of decking, stringers, and the vents, whether they may be frame vents or pile vents. Also dimensions, denoting structure length, span lengths, and all structural members. General locations for decay in a bridge are areas that tend to retain moisture, such as bolt holes, splices, connections, bearing points, checks and splits. Next let's touch on recording our results. X represents good sound wood. X348 denotes three inches of good wood, four inches of decayed material, and eight inches of good wood. R represents rotted or decayed wood. R282 would then denote two inches of decay, eight inches of good material, and two inches of decay. Keep in mind there are basically three reasons why your drill bit won't feed into the wood. One is decay, two is drilling with the grain of wood, and the third is if you drill into a checker or a split. Next we'll cover how and where to drill. It's not necessary to bore the two bitoos in the deck. Failure is visible in the wearing surface. Note I've placed spikes in the various structural members to show the location and position you should bore it. Bore the deck planks in the bottom next to the stringers, angling over the stringer. This is done at the exterior three stringers over each bend. Bore the stringers in the sides up near the deck planks. Bore also in the bottom at the cap, angling slightly to get up over the cap. Bore three to six inches if no decay is found. If decay is found, record its vertical distance in the stringer. Bore all stringers at the end bends and at least the outside three stringers at each interior bend. It's not necessary to plug these holes. Cover the pile trestle now, and in the caps you bore within three inches of the edges. And under the exterior stringers and over the exterior piling. I recommend plugging these holes. Bore the top of the exterior piling, and at the ground or water line of all the other piling. Also at the average high water mark. Plug these holes also. The frame bent bore within three inches of the edges of all structural members. Bore under the exterior stringers and over the exterior post. I recommend plugging these holes. In the posts you bore the top of the outside post, and the bottom of all the other posts. Plug these holes. Nacils bore under the outside posts, and over each concrete pedestal. Plug these holes also. As far as the fellow guard and railing are concerned, decay can be determined visually or with a hammer. Bore the bulkhead in the center of the boards, and at an upward angle. It's not necessary to plug these holes. To go one step further, you should bore any questionable areas, such as stained and discolored areas, fungus growth, vermin activity, timbers covered with soil, and any member in contact with a decayed member. We have now moved to another bridge on a small feeder road between two main highways, and again we will start out our inspection by looking at the overall view of the bridge and its setting. We see that the alignment is straight. The road does have a small hill coming into the bridge, but the speeds on this road are quite low, and this does not detract from the visibility of the bridge as you approach it. We have rated the alignment as good or an eight. There is no approach guardrail, and the road is unpaved. The embankment is in good shape, and we have rated it good also or an eight. The inspection condition rating for this item, number 65, is therefore an eight. The next thing to look at is the signing on the bridge. The bridge is posted with a three-ton load limit sign at each end. And in addition, there are warning signs at each end of this section of road. The signing is legible, and we have rated it as an eight or good. We are now ready to start inspecting the bridge itself. One of the first things we want to look for upon arriving at the bridge is the rail. We want to look along the rail to look for sags or dips that might indicate damage on down below in the substructure. On this rail, we don't see any obvious defects. We are now going to start our detailed inspection with item number 58, the deck. This includes the wearing surface and rail fellow guards. We'll start out by walking the full length of both rails, checking them for rot, checking the posts, taking pictures of very bad areas. We can see the posts on this bridge is quite rotted, as is the fellow guard and the rail. We have now moved into a single post and fellow guard area to make a more thorough examination. This is typical of quite a few areas on the bridge. The fellow guard is rotted in the center. Does it look wet, Bart? No, it's not wet, but there's only a shell left. It looks pretty far along in the rotted stage. The post sounds hollow. Is there any good wood at all there? No, it's also a shell. The nails that hold the rail together are just loose. That doesn't look too safe. The post appears to only be about 90% or 90% gone. Well, I would say this being typical of the entire rail on the bridge that we would call it critical, and I wouldn't rate it any higher than a 2 under any circumstances. We now want to look at the wearing surface on the deck. We see that it has broken off the timber planking in several areas. Other places, it appears to be solid. We notice in quite a few areas on the deck that there are many transverse cracks. What causes these cracks, Bart? Two-but-two decking is non-existent. And that means that the crack is over each one of the transverse deck planks. I think the wearing surface is to be considered poor on this, and we would rate it a 4. We are now going to inspect the deck itself. We'll want to look at the top of the deck, the sides and the bottom, anything that's out where we can see it. In this case, the deck is exposed along the edge of the wearing surface. We can sound it with a hammer, step on it, do anything to get an idea of what it looks like. Oh, there's a good spot. We have now moved around to the side of the bridge to inspect the ends of the deck planks. Our inspector is using a ladder that he has brought along with him. We can most easily check by tapping the ends of the plank. There's one that's pretty well rotted, another. That's a nice-looking piece of nothing. This would indicate the deck plank is rotted well beyond the first stringer, and there's little support for the rail or the edge of the deck. We're now down at the abutment end of the bridge, looking at the bottom of the deck. It looks even worse than the areas out in the middle of the span. How far is that settled, Bart? Right at my tape, it's settled approximately three quarters of an inch. That's crushed in the deck, isn't it? Yes, uh-huh. The stringer seems to be sound. It's not crushing the stringer, it's crushing the deck plank. No, the deck plank's rotted and has settled, crushed past the top of the stringer. Based on what we've seen, what would you rate the total deck? About a three? I think a three would be good. Yeah, that would be in the poor condition. I'd say that item 58, in view of a three on the deck, a four on the wearing surface, twos on the rail and fellow guards, we'd rate as a poor condition a three overall. While we're down in this corner of the bridge, we'll start our inspection of the superstructure, item number 59, which in a timber bridge is pretty much limited to timber stringers. We see in this corner that the outside stringer is quite rotted and there is crush over the cap. How much crush is there in the stringer, Bart? Oh, there's two inches of crush. Two inches of crush on the outside one, the next one has about a half inch and then they seem to be better on through. We've now moved to an area out in the center of the bridge where we're checking the interior stringers. They have a sharp ringing sound, which indicates their sound. We check as much of the stringers as we can reach. We want to be careful to check the bearing areas too. These sound good. It wouldn't be necessary at this time to do any drilling because the wood does sound like it's solid. We've now moved to an outside stringer. By bounding with a hammer, we can hear that it's got rod in it. It's not too sound. Over the bearing area, which is a place you always want to check, the stringer is in very bad shape. Now, we've noticed that both exterior stringers are bad. At the abutment, there was quite a bit of crush. There is some crush over this cap. The outside stringers are not in too good a shape. But we also found that the inside stringers were still sound and very good. Because of this, we will rate the item number 59 superstructure as a 6. This is because the outside stringers are bad, but they don't carry any load. The good stringers are on the inside. We are now ready to start inspecting item number 60, the substructure. This includes the abutments, piling, caps, the piers, or bents, and the caps, and piling. We see on this bent that there is a mud cell. The pile has been cut off. The first thing that we want to ask ourselves when we're inspecting a bridge that has been repaired is whether the repairs are temporary or permanent. What would you consider this part? I'd consider this a temporary repair. The piling has been cut off here, and the mud cells have been added. So it's definitely a temporary repair. And we can see that the mud cells have started to rot. We also can see on this bent that there are three piling that are supported on mud cells. We've now moved to another bent near the creek, and we see that there is a temporary piling that has been added. The original pile we see as we get down to the bottom of it has been cut off. The temporary pile is sitting on a mud cell, and again we would call this a temporary repair work, and we would have to call this a critical situation. Several of the piling in many of the bents in this bridge are like this, and we would have to call this a critical situation where we have temporary piling. We disregard the temporary piling and rate the original structure, and in this case we'd have to rate the piles in the bents as a two, zero and one being reserved for closed bridges. You might point out that the bracing is rotted off here too, Bob. Right. The bracing throughout the structure is rotted. It's also nailed. It isn't bolted to the piling, which is not normally the correct way of putting bracing on a structure. I would say the bracing is in poor condition. What kind of a number would you like, Bart? Four? Four would be good. Right. The next item in the substructure that we want to inspect are the caps. This cap appears to be quite sound. We won't drill it because it does sound good. We are now ready to inspect another cap that is out over the water, and we can't reach it with a ladder. In this case the inspector has a safety harness. He can reach the end of the cap directly over the rail. This cap, as we can see, is well rotted. The rod extends back into the area of the first pile. It's so bad that it's falling apart and can be picked part easily with a hammer. In view of this bad pile, bad pile cap, we would rate the pile caps as a four. We have now moved into the abutment area. We see that the pile cap appears to be new and is quite sound. We'd rate the pile cap as an eight. The next thing we'll look at will be the piling. Here we see again a new temporary helper pile. The old pile, is it broken off there, Bart? No, it's rotted off, Bob. Oh, it's rotted off. This is a mud seal supporting the temporary pile. All right. So we're back to a similar condition that we had before. The piling would be critical and we would rate them as a two. How about the back wall? The back wall is an agglomerate of some scrap lumber, and it's in various stages of decay. So we'd be in the same critical rating or a two for the back wall also. All right, that pretty well wraps up the substructure item number 60. We have rated the abutment back wall as a two and the piles as a two. The pile bents and the rest of the bridge, we've rated the caps as a four and the piling as a two and the bracing as a four. The overall rating for item number 60 would be a two, a critical condition. The last item that we want to inspect on the bridge is the channel and channel protection item number 61. Here we see that there is not much drift or embankment erosion, but there is quite a bit of vegetation. This is a poor condition. We notice the biggest problem is the bents of the bridge are across the stream on about a 45 degree angle and would cause drift to hang up or impede the flow of the water. The adequacy of the opening is therefore a poor condition or a four. We have rated the item number 61 as a four overall. Here is the completed inspection form for this bridge. This bridge was much worse than the first one in the form reflects this. As you can see, we have rated the abutment back wall as a two and the piling as a two. The abutment caps as an eight. The bent caps we rated as a four and the piles as a two. The bracing we rated as a four. The overall rating for item 60 substructure was therefore a two. The superstructure, item 59, stringers we rated as a six. Timber decay was again a six. Deflection under load was a seven. Alignment of members was an eight and vibrations a seven. The overall rating for item 59 was a six. The deck, item 58, wearing surface we called a four. The deck itself we called a three. The curbs a two. And the railing a two. The drains were a seven. And the overall rating for item 58 was a three. The channel and channel protection, item 61, the vegetation was a four. And the adequacy of the opening a four. And the overall rating was a four. Culverts and retaining walls, item 62, do not apply in this inspection and we have marked them out. The approach alignment, item 65, the alignment was an eight. The embankment was an eight. And the overall rating was therefore an eight. The signing was very good. And we called the posted loading an eight, legibility, invisibility is an eight. And the overall rating was therefore an eight. Remember the inspection is only as good as the inspection report. It should be complete and accurate. You should take time also to make it readable. This inspection form is all your supervisors will have to tell them about the bridge. This concludes our presentation on the inspection of timber bridges. We hope that we have been a help to the inspector who may not be too familiar with timber bridges. The two bridges we have shown are not necessarily typical of all timber bridges. They were picked to show as many defects as possible. The first bridge was probably more typical. Oftentimes the timber deck will go first as it is exposed to weather and wear. The second bridge is definitely in need of replacement. It has not been replaced only because it is on a minor farm road and replacement funds are not available. We have shown what it is like to make a timber bridge inspection and have emphasized thoroughness and accuracy. If you keep your eyes open and think you'll do all right. Good luck.