 Well, welcome back to all you ocean people who learned how to swim yesterday. That's what I was told you were doing. Are you ready? You know it was so quiet with them gone. I don't know, man. Next time I'm going to say I only want non-ocean people. They don't have to go learn how to swim. All right, we had already discussed the edge distance requirements on these things and how strong these things were in bearing. We found out that you had to determine how strong a little plug being pushed in front of the bolt was when you pull the plate to the right and crashed it into the bolt. That shearing stress was called a bearing limitation. You also had to make sure that the bolt, when it crunched into the plate, didn't crunch into it any more than a quarter inch. They were two separate distinct limits, the way it's written, even in the specs. It says, tell me the shear plug number and make sure it doesn't exceed the crush a quarter of an inch number, but they're just two separate things. You got to calculate them both anyway, write them down and take the smaller of the two. Some edge distance requirements are listed as L, Sabee, and a table depending on the size of the bolt. That does actually also pertain to this L, Sabee, this L, Sabee, so they call that L, Sabee also, but it's not got anything to do with the strength. They're just trying to keep that bolt away from the load and keep it away from the edge. Then, of course, they also have to keep it away from this edge, and this is the one that's used in the calculation of the shear plug strength. Quick summary was that the nominal strength without a factor, a resistance factor on it yet was 1.2 times the clear length. In this case, this was the clear length. That would be the L, Sabee, minus half of a hole with only 1.16 added to the drill size, and this would be the clear length, which would be the spacing of the bolts minus a complete hole size. That would be diameter of the bolt plus 1.16 instead of 2.16, because we don't care that that steel was messed up, it's underneath the head of a bolt, and we're getting ready to crunch the heck out of it anyway, so it won't get any worse than it was. We still count it in this case. Spacings were, had to be greater than two and two-thirds of the diameter of the bolt, preferably 3D, here were the specs and where we have it in our notes. The L, Sabee had to be bigger than the thing came out of a table. Not sure we saw that table, but I guess we already did, because I don't see it in front of us, so it must have been behind us. It was based on the size of the bolt, and it told you the limits on how close these things can get together, the minimum spacing. Though for an example, I think, I don't know if we got started on this one, it doesn't matter. Got to check bolt spacing edge distances and bearing strengths for, by, either in the wrong class, or he says, I can't take another one of these, don't know which. Check the bolt spacing edge distances and, oh, okay, he's coming in. I thought he was leaving. Connection drawn in so-and-so, so here's the connection. Nice little plate. Got four bolts in it. That's the plate, that's the gusset plate. This is probably connected to a column or something like this. This may be a bracing member, it may be 20, 30 feet long. It'll have to be checked for stretchiness, gross section yield, it'll have to be checked for net section fracture, it'll have to be checked for all kinds of stuff. It's like before. Added stuff will be bearing strengths and shear strength of the bolt, which we haven't done yet. So according to the table, it's on page 385A, how can I miss that? It's not on 385A, yeah, it is on page 385A, but I must have stole it, put it back earlier in the text or in the notes. Anyway, you go to this table and he tells you you want two and two-thirds of D for the minimum spacing. And he has got two and a half, let me go back up to the picture here. He's got two and a half for the spacing, and so those spacings are okay. Where I've got that, let me see if I can find it right quick. Table, table, table, table, table, table, table, table, table, table, table, table. Somebody stole my table, pull that out of your book right quick. It is table, well let me just tell you what page it's on, because I usually at least always tell you that. 16.1-123, and I believe it, I just want to hear you say it. For our bolts, we are using three-quarter inch diameter bolts. Is that table a function of the bolt size? I can't, come on man, no, no, no, don't bring it up here. I can't see it up here to the edge of the connection. So what does it have for a three-quarter inch bolt? One inch, okay, you see, and that's what he says, actual age, distance, we are using one and a quarter greater than one. So right from the horse's mouth, that's right out of this table on this page. So we are okay on spacing, now we are going to find out how strong these things are. For computational bearing strength, we are only going to add one-sixteenth to the hole size, so we will be able to get our little plug links in here by taking off half of a hole diameter. So we have 13-sixteenths inch hole, not a D plus an eighth inch hole. Check the bearing on both the tension member and the gusset plate. So just for what we are doing, this is all for the tension member. We'll do the gusset plate on the next page. What we are doing, we are doing bearing strengths. What we are doing first, it is a version of bearing strength, it is a shear strength of the plugs, and here it is for the end holes, and here is the shear strength on the tension member for interior holes, so all divided up into what in the world we are doing here. Check the bearing strength on both the tension member and the gusset plate, gusset plate comes later. The tension member, the holes nearest the end edge of the member, because this dimension could be won and be legal, and if you think that we are calculating the bearing stress strength on this one-inch dimension and use that to get it wrong, the thing I need that is to just meet the specs. This is the one where we pull the plug out, so this is the one, even though it is the same in this case, but I'm calculating. The clear length would equal to L sub e, that's the distance from the hole to the end, one and a quarter, minus the new hole size over two, 13.6 is over two, the little plug this shearing out of here will be this long. The normal, the nominal strength of the resistance is 1.2 times that number times the thickness of the plate times the ultimate stress. Check it out if you don't remember what that is, and it must not exceed the crush strength of the plate, and that crush strength was measured at a deflection of about a quarter inch worth of crush in the plate. Continuing with what we're doing here, here's our 1.2L clear, 0.84 inches times the thickness of the plate in tension times the F sub u of the A36 steel plate, 29 kips worth of strength, that prevents shearing out a metal plug. Then to check, I don't like that, upper limit, it is an upper limit, but to check crushing to prevent excessive deformation of a quarter inch, you have the second limit state, 2.4 downward bolt, thickness of the plate, F sub u, 2.4 downward of the bolt, thickness of the plate, F sub u, 52. So of the two types of bearing limits, pulling the little plug out is the limit, and he says that here, since the plug pull is less than a plate crush, use the 29 for this hole. Now for the interior holes, we'll do the same thing, the L clear changes because we're not using L to the end, we're using the distance between the drilled bolts, which was two and a half inches minus a half a hole, minus a half a hole, if I didn't see that or understand, raise hand, tie, and that's the clear length, that's the shear plug length, the nominal resistance is 1.2 times that clear length times thickness F sub u, and yeah, it has to be less than that, but just getting back to this number here, so you don't confuse it with some other thought in the meantime, here's your 1.2, here's your 1.688, here's the thickness of the plate, there's your F sub u, gives you 58 kips of strength for the plug shear strength. Now once you've calculated 2.4 diameter of the bolt thickness of the plate F sub u, it's the same for all the bolt holes, you won't ever need to calculate that again, because you'll notice the length of anything isn't in there, length to the end is not in there, spacing is not in there, it's just a function of the bolt size, thickness of the plate F sub u and the constant necessary to get the right answer that agrees with theory and mostly test. So once you had this 52.2, that's it, for all the other bolts, oh here it says right here, same for all bolts, and I scratch this out, the result means that the L sub clear or L sub end, either one, small enough so that it will control, must be accounted for, well everything has to be accounted for, but it controlled. So the crushing upper limit, which was as before 52.2 is compared against the new plug, the shear of the plug out, and in this case, the crushing number controlled. So what's that saying is on one of them the plug shear controlled and the other one the crushing limit controlled. So that's what he did. And over and I said the bearing strength of the tension member, we have two bolts where shear plugs control plus two times where the crushing of the plate controls gives us a potential bearing strength of 163. Little early to be calculating that really because we don't know about the bolts yet. We don't know the bolt shear strength. That's the only thing they have to do with anything from now on, then it's possible none of these numbers control. We'll see. Now we calculate the gusset plate. And you do it, and you do it, and you do it, and you do it, and you do it, and you do it, and that's your thing. Numbers sure do look about the same. And then you look back at these numbers here, you say, dang, every number in there is identical. Only difference is the plate is not the same thickness. It's no longer half inch thick. It's three eighths think thick, but it has the same F sub u has the same bolt bearing against it has the same constant necessary to make it real world. And so there's no reason for this might as well just go get the number you had in the first place, which was 161. Multiply times the thickness of the new plate divided by the thickness of the old plate. I think when Coudic was around, he knew this guy real well, he says, kind of curious. He says, well, if you make a practice with it twice, they understand it better, and they're so mad, you made them do it twice. They never forget it point. So the strength could be up to 122 kips nominal. All these are sub in still need a fee of 0.75 a resistance factor that is to be applied to this failure type of behavior over here. He does it. No, no, no. This is the this is here's the design strength. There's his fee times the 122 and evidently back there. He told us the dead in the live loads. So 1.2 dead 1.6 live was 90 less than the 91.7 needed. And so the whole system as far as bearing is control is considered. It's okay. But Dilly tells me what kind of bolt he's going to stick in there. If they're crummy bolts, this whole thing may be no good at all. But now we get into how strong the bolts are in shear. I can tell you now the bolts are tremendously strong in bearing. And so they have no, no, no bearing, no pun intended. I don't have any bearing on the bearing stress calculations. Almost ever the plates are always much weaker in bearing than all the bolts. Basically, the allowed load would be equal to whatever shearing stress you're going to permit me to put in there times the area of the bolt in shear. Whatever the area of the bolt happens to be or whatever you consider the area of the bolt to be. For example, if you have a bolt and you cut the shank, you cut all of the area that's in there. If on the other hand, you consider that you have cut threads in it and you think that's the area over which the load is distributed, then you would use what we call the root area. If because it's impossible to cut through a bolt without at least picking up one thread, then you might have the calculation of this area plus how much area is in a thread when it gets cut also be a little higher. That'd be called the tensile stress area. But our basic equations would be, here's R nominal is equal to whatever nominal stress you're going to let me put in there in shear times the area of the bolt, whatever you choose to use. And then of course you're going to have to make sure that R sub u is less than phi times that number, which is equal to, this is less than phi f sub n shear nominal shear area of the bolt. My guess is when we go for this number here, you're going to see something called f sub u in there and you're going to multiply it times what number? 0.6. That's correct. Now, admittedly, the bolt people are the people who do this, so they may not pick a 0.6. You and I for all of our plate steels have always taken the shear numbers as 0.6, so the tension numbers, whether they were ultimate or whether they were yield. But we still got to get the bolt people's opinion because they're the experts. Now we have rivets. I think we mentioned those before, little slugs of metal that they heat up, throw it up to the floor necessary. The lady puts it in one side of the thing to be connected and the person on the other end bangs ahead on the end of the rivet and then lets it cool and it gets pretty tight and it does a job. It doesn't have a calculable, I mean a consistent tension in it, so you really can't count on any friction between the two pieces. They just aren't that strong and it's not that consistent. Then we have common unfinished bolts, typical one would be called an A307. They're just what they call common bolts, the common unfinished and they have some good strength that we use for years. The rivet people were screaming they're no good, they're gonna fatigue, they're gonna break, the audio buildings will fall in a few years, you know, but we started using them they're able to be installed by somebody less skilled. Somebody who does this work here got at least be accurate in throwing things at people or you'll have these things down all people's back of their shirts. This can be put together by somebody you give them a wrench you say you know what to do he says no and you show him once and that's it good to go. High strength bolts then, these are not high strength bolts, high strength bolts come in two groups, high strength and really high strength. We use to use A325 as a typical bolt or an A490 as a typical bolt. I don't know what the strength of these things is. I got a table of these which I'll show you in a minute. Here's information on how they're made, what they're made to have higher tensile strength when they came into general use. You ought to read this so you're just not ignorant about it. Some of these numbers like the 2280 bolts they're pretty much the same as these bolts but they are made so they have a little twist-off tail on them and I'll show you how they're used so that you can tighten them to a very close accuracy. These two bolts you can tighten them up so tight that you clamp the two surfaces together reliably and you get a lot of the load carried in friction between the two plates. Old notes, really old notes, used for the sketches only. Here's a pair of plates to be joined once thick, once thin. Here's the bolt put in there, you'll notice the threads only come up here in a short distance. Therefore the bolt is sheared through the shank. Don't see one where this happened but basically it was threaded to the head and therefore this one was sheared through the root area or if you think you deserve it the root area plus one thread is what they call a tensile stress area. It is incidentally the same stress area if you pull the bolt in tension because you have to break it around the root but then when it gets around to the bottom of that it has to kick up back to this top of the bolt and you do get a little more area inside of the thread itself. Here's the little twist-off thing on the bolt here the threads you put a special tool on there it holds on to this piece and it turns the nut on the bottom when this little piece breaks off you've got the right tension in the bolt. They all start off bolts looking like that. Here's a bolt in double shear that's probably excessively drawn because it's only supposed to be about a quarter inch of gouge in the plate and it probably wouldn't do that to the bolt. Here's a washer that they put between the head the nut and the plate they have little square things pushed out on them it's it's not pushed out here not pushed out here and they push the little thing down and then break it loose here such as these little pieces stick up and since this sticks up it would take a lot of pressure to push it down back in the hole and what they do is here's the head of the nut or head of the it's the nut I think they use that in here's the nut right now feeler gauge goes in there no problem when you crank this nut down just the right amount to push this little thing back in the hole from whence it came you can just barely get a gauge of a certain size in there and that means you have pulled that head of that nut down cause the right pressure between the head of the nut and the connected surfaces have no idea what that's for load comes like this comes down comes through the plate comes around the backside bears against the bolt the bear bolt pushes this way bears against something wrong there goes like that one of the thing wrong with having these things not threaded at the head is you got to make sure they install them from the right side because you had one like this and bolt was not threaded to the head and you're counting on it cutting through the threads if you install it the wrong way the threads will be you know in the plane of shear when you didn't want it to be weren't counting on it on being typical table off the internet there's your grade A bolt I'm sorry that's a common unfinished that you're a 307 that's lower medium carbon steel here's your tensile strength right here you're going to get some percent of that probably point six here are your a 325 group a high strength wow that tensile stress 120 it's in the fair up to about an inch and a half bigger than that they go down obviously they have more defects that you haven't gotten out by making them smaller and then here you're a 490 those are one of the ones in group B 150,000 psi of which case the bolt people are going to let you have some percentage of that in shear the heads look like a 307s don't have any markings a 325 say a 325 a 490 say a 490 so it should be pretty easy to know which ones are there when you go inspect the place. Chief distinction between the 307 and the type A and the type B group A group B the high strength bolts can be tightened to produce a predictable tension in the bolt and that will produce a calculable clamping force and a calculable friction between the sliding surfaces. A 307 rarely used today nominal strength based on the ultimate tensile stress of the bolt with several modifications first the ultimate shear stress is son of a gun it's not point six why not talk to the bolt people don't remember if I had a slide on that if I don't I probably do in a minute where you can download the whole thing for free we get a point six two five for bolts as opposed to the point six for the plates and it's according to these people and the references are listed in Segui says note there's a link factor of point nine for the connection links no longer than 38 inches was okay how short it is there's a point nine on it once it gets over 38 inches long they were gonna make you cut it down to point where where where point seven five at point seven five is not your feet at point seven five is because you have such a long connection it's kind of hard to get the stretchiness in the plate to distribute the load in the bolts if the threads are in the plane of shear the reduction of the bolt angle is accounted for by using 80% of the nominal bolt area and leaving the loud stress alone now what that what that really means is is they're going to give you I think I said that wrong the threads are in the plane of the shear the reduction of the bolt area is actually she's accounted for it's actually about 80% of the nominal bolt area the shank bolt area and what they're going to do is rather than make you remember I told you gonna have to go in the table and find the area of the bolt the shank area you know you don't have to go on the table for that is pi d squared or before but to get the tensile area or the root area you're gonna have to know how that thing was made and have to know this dimension here dimension here and you're gonna have to know the area of a thread you have to figure all that out they say we don't want that I say well you got to do something because if you cut the shank you get your nice pi d squared over four he says we're gonna let him use that for everything kidding you can't do that there's a cut through the threads in this much area by a lot he says well what we're gonna do is if they have it cut through the shank we're gonna give him one allowed stress and if they cut through the threads we're gonna let him use the same area but we just gonna dock them with a little less allowed stress well aren't I want to see how you did that not a problem so if the threads are in the plane of shear well the reduction of the boat area he says about 80% so I guess they're gonna let me only have 80% of the stress that of applying this reduction directly to the ported boat area a factor of 0.8 is applied to the stress this way you don't have to go get the area out of a table you just take 80% of the stress okay so let me see you to calculate this he says okay well say the threads are excluded from the shear plane in other words it really cuts to the shank how much stress do they get well they get 120 for a group a bolt check that a group a bolt a yeah that's a good group a bolt uh-huh there you go 120,000 times 0.625 I thought would have thought of 0.6 but they say look we know more than you do times 0.9 because we're assuming that your length of your connection will be not over 38 inches if it is come see me we've got another number for you right there so you get 67.5 ksi permitted okay now let's talk about this threaded if it cuts through the threads well this is if the threads are in the shear plane in other words they are included you'd like not excluded fine with me then you get 8 tenths of that stress which means 54 there well okay I guess my only question is that number you said was 0.8 right here where'd you get that 0.8 from so we'll go look at any bolt chart alright this one comes out of you the AISC specs screw threads they're called okay bolt diameter okay say a one inch bolt has a pi d squared over four using one as the D a 0.785 that's right because pi over four is 0.785 one squared is one and he says I know the root area and I know the root area plus a thread okay and he says we'll divide the root the threaded area the tensile area where you cut through the threads plus a plus a thread divided by the shank what do you get I say well 0.606 or 0.785 so I don't get 0.8 don't get me that how close is it three out of what 77 says do you ever get numbers that close he says go away it's a way to one check one more it's an inch and three eights one point one six divided by one point four nine point seven nine point eight is in the specs that's where it comes from rather than making you come find the real area and which is really just point eight times the shank area he puts it on the allowed stress but you should know that you really should you should know that the permitted stress in a piece of steel doesn't change just because you put threads on it the area may change because you put threads on it regardless of how they try and make it simple to use there was the one I was thinking about here's a person who wanted to cut through the shank and so they made sure the bolt was only threaded up to a certain point and they got to keep track of them of course and then they got to make sure the plate thicknesses are right because you can't use this on a three-quarter by three-quarter plate because not enough will stick out and in this case if they put it in upside down it won't matter because it was still cut through the shank but you got to be careful that you don't have like a two inch plate connected to a one inch plate and you put the things in the wrong way then you'll cut through the threads that you hadn't planned on this is X colluded this is in included here is the table from the AISC specs a 307 it's good for 27 KSI shear you don't get to say the threads are included or not and that kind of a bolt the threads always used to be included and they there just is whether they are or not you can't count on a group a if they are excluded then you get to what we said 120 times point six time five times fee wait a minute is that fee I thought fee was supposed to be point seven five see something hearty hearty here today hearty what's that point nine for don't feel bad I don't know we there find who I wouldn't have asked you gamble where's gamble there's gamble what's that point nine for yeah this one here no this one over here yeah that one there anybody the area is nine tenths that right I thought that area thing was point eight that point nine for less than 38 inches you say dang man you told us 83 things you expect us to remember one of them no but I have fun watching you squirm it's because the connection is soon to be 38 inches or shorter what's it gonna be does anybody remember what it was if it gets longer than that very good point seven five that is correct so you get a 68 and down on the notes here he's gonna tell you that if you have a thing longer than 38 inches you're gonna definitely tell you right here what you get instead of this number now then going to where the threads are not excluded the threads are in included in the shear plane you get the 68 and the only other factor is the point eight due to the reduction in area so you use this stress based on pi d squared over four which is wrong which is wrong now whoever said two wrongs don't make a right we're not engineers I just want the point eight in there someplace here it is for the higher strength start with 150 with the same numbers and you get 84 and the 84 for threaded drops to 68 and some other items oh this is interesting now right here they're talking about the nominal shear strength and here it was a shank area here it was cutting through a smaller area so understand that drop here the tensile strengths here it is excluded and here it's included they're the same numbers why does it not change as you go from threads excluded to threads included tension and tension and tension because it's the same isn't it when you put tension on a bolt the bolt gets loaded right on down through the shank it goes where down to the threads you can't stop it from going through the threads so the area is the same for both of these types of connection in tension so the nominal strength of your bolt is the 120 times point seven five we'll get into that later for 90 ksi good worth of tension so here's a simple connection got two bolts what's usually check it for a 307 group a threads in the plane and group a threads not in the plane bearing stresses the bearing strengths I don't really have any new comments to tell you go through the calculations for bearing check the shear out of the plug for the end bolt check the crushing of the plate at the end bolt and then realize it's good for the end bolt or any other bolt plate crushing here's what you'll find you'll find the strength to shear out a little end plug was 28 you'll find the shear to pull out a little plug down in the middle where the spacing is much larger was 57 you find the crushing was 28 and the crushing is 28 everywhere then you go to bolt shear let me see but that's for a different case one of the things you really need is you need kind of like a summary sheet of what you're finding on these because you'll find plate pull or yeah plug pullout of 28 here and plug pullout of 57 for this one because it's so much longer then you'll find plug crushing of 39 you'll find plug crushing of all of them 39 then you'll find that that was it that's all we've done so far then you would say the total load on that plate would be the sum of what two numbers the lower of the two is the generic response and your individual response was getting ready to be 28 plus 39 those are both correct now then when we went and got the shear strength of the bolt we haven't done that yet that one was 30 and of course the shear strength of all of them were 30 and you took the lower of this set so this was a 28 it took the lower of this set and this was a 30 and so you got that much strength for one bolt that much strength for the other bolt then your feed gave you the strength but you have to do these people one at a time you can't just go get the strength in bearing and say okay that's one thing and then you get the strength in shear for all the bolts and that's one thing and you take the lower of the two that doesn't work every little bolt against every little hole has to you have to find out how strong it is and if it's not the same strength up here because different people control you have to keep tabs of that so now here's our first bolt shear the bearing and shear strength can't be considered independently that's what he's saying here you got to get the individual strength at each bolt location take the minimum of the bearing either one out of the shear strength use that that bolt location says it's explained in this spec at these pages in the user notes here they are right here look around for users notes you can't find them you realize okay yeah I can because they're gray as the effective length of an individual fastener is the less lesser shear strength effective strength of the bearing strength at the bolt hole or the shear strength at the bolt hole what he's telling you what he just told you so now then the bolts in this connection are subject to single shear so he's going to go ahead and get the area he is not bolt dependent yet because the cross section area that's the only one you'll ever need with or without cutting the threads now we start for a 307 bolts nominal shear strength let me check that right quick normal shear strength 27 27 for a 307 bolts 27 times cross section area gives me a nominal bolt strength of 11.93 this is smaller than everything in sight all the bearing strengths therefore we get 11.93 plus 11.93 because there's two bolts then we apply the resistance factor to take care of all that variation in these bolts 17 kips is the permitted load that includes bearing crushing the plate in shear that includes bearing excuse me bearing pull out the plug in shear bearing crushing the plate in shear and bolt shear next we do group A bolts with the threads in the plane of shear these these this shear plane is the threads are included in this plane of shear nominal strength is 54 54 a 325 bolts a 325 typical 68 no no no that's excluded 54 that's in included are included 54 that's the right allowed stress nominal stress we get that number times point 44 18 that is already taken into account that the connection is no longer than 38 inches this one right here this is already taken into account the fact that the thing is being cut through the threads it's also including the fact that what else was in that mess one other number in that mess oh the point six to five instead of my point six that I keep telling them point six to five gets that much load nominal strength for the shear in the bolt nominal strength of shear in the bolt is still smaller than any of the bearing numbers we had and therefore you get that much nominal and you get that much permitted then for the strong bolts a 325 was stronger because the threads aren't cut x we got group A when they're not cut gotcha understand when it is not cut you go to 68 hello hello 68 68 excluded a 325 68 and 68 times the area is 30.04 says that the hole nearest the edge the bearing strength back there was only 28 so I never controlled before he says well look back there you're gonna find that this number was only 28 so now then the shear strength of the bolt is stronger than the bearing strength at the hole nearest the edge so you're gonna have to tell Mr. Bolt sorry you're so strong but we don't get to use your number we use the bearing strength at the at the hole in the end of the plate do you remember I don't remember whether this was a crush or a plug pull but I don't care we got both the numbers we have to go back and look and see which one it was it's less than the bolt shear strength where bolt ought to be added to your notes reason is there's a lot of shear strengths going on in here there's a shear strength of a plug at the other hole the bolt shearing strength is still 30.04 but at the bolt shearing hole we had a bearing strength the worst one was 39 so now then the bolt controls so we get one where the plug or the crushing control I bet you that was plug because it was so close plus 30 for the bolt 59 bearing of the plug there we go no that's just bearing that doesn't tell you what kind of bearing plus bolt shear therefore you get 0.75 of that once you use that type of bolts all edge spacing requirements and so on so so this is where I think you do well if you're not sure what to take as you get them just write them down plug pullout was 28 for him plug pullout for him was 57 plug crush was 39 on the end that tells us which is where that came from and plug crushing is 39 everywhere and bolt shear is 30 and it's not everywhere and so you add up who you can have you can only have that number and you can only have that number and that's why they took that number plus that number and multiply times 0.75 and got the load on the bolt on the plate a little later on they're going to say that we are going to design these things as if all the bolts take the same load that's not quite true you notice right now all the bolts are not taken the same load so that's not a limitation but it is only true if the bolts control everything and I'll tell you now we usually try and make these things so the bolts do control everything if you start going in there and start finding that this thing here is controlling your best bet probably move it back a little so it doesn't control you want to know it doesn't control before you start designing your bolts so you can say when you design my bolts the bolts will control and therefore I know how many bolts I need all right see you next time when his quiz a coming up Wednesday it's coming Wednesday it's coming Friday no no no anybody who controls is breaking that's that's it that's right we'll see what no no it's actual oh it's a failure well then the books no no no no no when I tell you that the bolts are gonna fail at 54 ksi they don't fail they'll come apart not at all guaranteed nothing comes apart anywhere now if you run that if you run that number on up to I don't know how many maybe maybe 20% more on those bolts then things bad may start coming apart but when I say the plate failed in bearing and bolt failed in shear the word failed is only to keep you and me on the right side of a magic number well that keeps it away from that but they don't they don't fail at that for instance when somebody tells you it's 0.75 that's one of the reasons they're keeping you away from that yes yes that's correct it just it just popped right out into this hole in other words and of course again it doesn't really literally come out but I mean it is it's just pretty much lost all its strength at that time that's correct and does it really come apart and everybody dies no there's still a long room before that's gonna happen okay