our next speaker will be Kyle Standish who Asian with with dan Moser both out of Klein and Hoffman Kyle was one of the major contributors to the 364 document Kyle's a senior associate to it at Kyle Klein in Hoffman in Chicago and Kyle's gonna speak to us today on assessment and repair of precast parking deck with construction defects Kyle thank you Paul I just really wanna before I get started I really acknowledge my co-author Dan Moser actually did this work I was with a company the previous to where I am now at Walker consultants and so I want and I want to acknowledge they're allowed me to present this work for them and I also want to acknowledge the work not only that Dan did but my other people want in the my team who worked on it and I probably have to say that particularly because two of them are sitting in the back of the audience bill and Diego so I can't ignore them they're here to catch me out so I'm gonna change direction a little bit between before what Ben and a shook did they were talking about I shook was talking about the document as a whole and Ben was talking about a specific chapter what I'm going to be doing is taking a project that I did that and that I really used the techniques and the concepts and the plan that this document has developed kind of how it applies and how it works to it in to a specific project so really what the way this started there's this precast parking structure not a huge structure to supported levels three Bay's wide so it's about 200 or so 150 to 200 cars so not a big structure constructed at fill top double tees central Bay is the ramp it's about seven-year-old seven-year-old there's really nothing remarkable you see thousands of these you know across the country is in Illinois so not so you subjected to fairly significant um environmental conditions but was only seven years old so they weren't expecting any deterioration from you know chlorides or corrosion or that kind of thing at this point but what happened yeah and that's just an over picture so that's kind of a plan of what it looks like there's a picture looking up one of the ramps again nothing remarkable about it you see thousands of these being built everywhere but one day what happened was walking along and they saw this crack and they didn't have the shoring at this time as just the crack that kind of developed in the middle of one of the TT stems and it was a fairly severe crack the it was you know varied in dimension from over over its height but the base of the crack was about 1/4 3/8 of an inch wide so that's not one you'd normally expect it's particularly in the prestressed TT so owner kind of like what's going on we need to figure this out and that's when they kind of started calling us in calling us in to have a look at it and really work through the assessment and this is the procedure I think I shook through this through this chart around and this is the procedure that's outlined in these three sixty four point one document for doing an assessment it's got a lot of things in there and a lot of iterations and things going back but what I really like about this document and what I think one of the strengths of it is it does outline a number of steps that you need to go through and that you need to think about when you put together your assessment plan when you're starting talking to your client and figuring out what are you going to do so there's a lot of iterations here a lot of small different so it's different texts so in my mind I almost want to more break it down into these five different parts and they're not no they're shouldn't I'm going to talk about them literally they're shown literally as if you do one and then the other but in reality this kind of it does become an iterative process kind of do things you figure something out and you all I need to check this all based upon this information I need to go back to the plans and look into that kind of information so I want to talk about it as if everything was magic and I did this and I did this and I did this for that realize that's an oversimplification of how things are happening but if you think about these five things and you kind of went them through in your mind data helps you to do kind of a complete assessment so the first one we did or the first one we want to talk about his document review so for this as I said it was appreciate it's a precast parking garage only about seven years old the part the owner had a fairly good documentation of what was going on so that you know that's not something that's always the case that you can always get design drawings you can always get shop drawings but we were able to get all of these information so we had were able to have a good look at the architectural drawings the structural drawings the precast shot drawings and details that were provided as well as the design calculation so we had a fairly good set of information to start with to try to figure out what the heck I'll be so we and one of the key things that we did in this that was very useful in this review was compared the calculations to the shop Giants so we looked at the loads yes the loads are correctly to design them for the right loads we were able to compare the drawing and client requirements that were on the structural drawings to what we're done in the calculations by the precaster and yes that looked okay we looked at the span the depth the width requirements they all kind of met so the calculations seemed to be pretty flying fine for what we were we're doing they kind of made sense to what the structural Giants were requiring we were able to I said I had a really great advantage we were able to get piece drawings for each member and we could compare those drawings to the calculations and overall dimensions yep they agreed with what we're showing on the structural drying concrete shrink that required that were called out in the calculations yep that's what they were being Orser on the structural drawings oh yeah and the calculations that were used by the structural engineer for the precast yeah that's what was being called out on the precast shop drawings number of tendons that the calculations were showing yeah that agreed to it but then kind of hit this thing and that was kind of interesting and obviously it's kind of like our unique Eureka moment when we came across this you know the calculations were using point 6 diameter tendons while the shop drawings were using point 5 diameter tendons that's kind of a little bit different can't use no smaller tendon for a bigger tendon expect it to the off the same way you know what's point 1 of an inch well if you do the math and the relative size and ins are 83% of the size of the point 6 diameter tendons so you're really oversimplification but you're at 83% of what the strength is what it's supposed to be so kind of right in the shop drawing fail or in the initial document review phase we kind of found something that said yeah hey this is something we need to look into further which is nice you don't always see that usually it takes a little bit it's a lot more complicated than that but no that wasn't the end of an issue we have the shop drawings that we were provided and you know we have these calculations well do we need to know how does that relate to behavior of the structure so we needed to come back in and we still did the field investigation and testing all this thing so talking about the field investigation a little bit one of the bit most important things we're dealing with cracks we need to document what was the nature of the cracks so we not only documented the primary crack I'm going to call it the one that kind of started all this thing that you know what's kind of a big flaming issue we figured out where we document where it was on the double tee we talked about its width and how it changed with hi-8 you know we looked at how height it was and if it was different from one side of the other trying to skip this crack it's kind of something that's causing everything to happen we need to know as much as we can so just doing that type of information in depth the one of this one crack was very important but we didn't stop there in terms of the assessment of the structure we have something is something else going on elsewhere what it elsewhere that no we should be seen because did they you know if we go back to our cause if we have 0.5 versus point 6 diameter tendons why is it only happening it's only happening in this one t or is it something that I'd spread if the shop drawings are showing one thing then we need you know we think it to be widespread so we did do a visual exam of basically the rest of the structure and we kind of documented what we saw and it was and we were able to find other cracks so but they were you know and this is I don't know how well you can see those on the on the on the screen that's always a challenge when you're you're showing pictures of cracks in the presentation but they did have hairline cracking of the other tea stems and when we documented it the nature was different from this primary crack and instead of having one big crack there was a lot of smaller cracks that were kind of spread along the length of the stem but um they were still present and which kind of was good information to know that this may not be something that's going on on just this one tea stem but it's something that's a little bit more widely spread and then I don't know whether this fits but as part of the investigation because we knew that the size of the tendons were may were potentially part of the problem we did do an opening and we did expose one of the tendons and we and were able to visually confirm that yes they use half-inch-diameter tendons this wasn't something that was found that was caught somewhere along the line so we're going down this rabbit hole and they actually you know they may said point five in their pre cast shop drawings they but the use point six no no we were able to get in there and expose a tendon and confirm what we found in the shop drawings at 0.5 inch diameter tendons were being used so that's kind of one of the things that you really should be doing is kind of take all this information kind of related one and together so our shop drawing review our document review informed what we did in the field investigation so we were able so once we found that out we included in our infield investigation looking at what the size of the tendons were we did a bunch of other field work - not as relevant so I'm not going to really get into it you know we did visual review of the rest of the structure made sure nothing else was going on we did some chain dragging make sure no wasn't no we weren't having widespread delamination interior asian we confirmed some dimensions of the structure that of the members that that they all seemed to work out and we did examine the TGT connections we did a bunch of other stuff as well remember this is only a half hour presentation you're getting the highlights but we really you know so we didn't just do we we but why I wanted to bring this up was because you don't want to get blinders on find something and go down that rabbit hole and assume we know the answer we want to make sure we have enough information to kind of confirm that hey it's not anything else there's not you know other things going on which well this case it was fair getting a head it was else it was fairly straightforward more often than not you really have a lot of different things going on and that's what's causing your issues after we did our field investigation well time was kind of simultaneously but we also did do some testing we did we didn't do all the tests that Ben talked about we really were focused on really on those these three that these are more related to what the structural condition was we weren't worried about deterioration at that point we didn't see anything we didn't find any significant delamination we didn't see a lot of corrosion and so forth so we were really focused on these three tests compressive stress testing wasn't super exciting kind of found that guess it was what it's supposed to be so it's not really a concrete strength issue so not super exciting but good to know bond pull off tests we so it was a field top system so we have that concrete overlay over the top of all the double tees we did found that yes it was generally well adhered so that wasn't really an issue with something like that but we did but GPR was the one that was most important for what we found and that helped us to confirm that they didn't do something like okay we only used half inch diameter tendons but we use more of them to make it up they did match no what we found the dimensions and the locations of the steel and the tendons and how it was laid out matched what were the shop drawings GPR doesn't tell you the size of the tendons which we why we had to do the opening but it was able to confirm that yes except for this potential issue with tendon size it did match what was going what was going on and what was expected so that was very useful in its way so this is just just the really out from the GPR so after now we go to the evaluation which is kind of pulling everything together we take all the information that we found and we did primarily first primarily looking at as a structural evaluation so we went back and we didn't just rely on the what the structural engineer was calling out as the required local world requirements we checked them to make sure that yes they they agreed with what the code requirements were very simple fairly basic but important first step and then we took that and we calculated you know what were the applied loads what should they be resisting what should they designed for kind of separate from what they were called out and what they what was done by the precast design engineer based on the requirements and then we calculated the capacities and what we did based upon our knowledge that there was two tendon sizes potentially being used or potentially being considered we we did it we ran the numbers both with 0.6 diameter tendons and 0.5 diameter tendons and what we found was we agreed with the precast engineer who did the calculations that point six inch strands were fine they they met the met the clawed requirement factors of safety the point five inch diameter tendons did not did not meet those kind of things so not surprising you smaller tendons they're not strong enough you wouldn't have used 0.6 if you didn't need them so that kind of was great that kind of all fit out and then we were able to take our results and did reporting great so yeah and I'm not going to talk about a report a report is just a bunch of pieces of papers but we have you know so but that was an important step in communicating it to the owner just to conclude that we had in a exterior post-tension tt FRP strengthening so we what we ended up doing we took that one with the TT and then that when we did experience and then we did FRP strengthening of the rest of the remaining double teams that had all that cracks and just because I'm an engineer and I like these I'm even though it's nothing to do with the assessment I do have some pictures of the repairs so I have a couple minutes left that I can quickly run through them I hope all yeah yeah so this is a kind of a couple of pictures of the repairs the other the exterior post-tensioning I'm kind of put in see it takes it takes a little bit you've got the kind of bars to make it continuous can or you can't see them to see my mode so you can see yeah you haven't you have a number of bars kind of make it composite I there are I don't know how well you can see those you seem a little better in the next picture but there are tendons there you know Drake tendons that runs one from the other I'm kind of another picture maybe a little better picture showing where the tendons are located trying to really restore and the idea was the way we work this was we weren't no longer because of the width of the crack and deflections that we saw we weren't going to rely on the original tendons we actually after so as to not overload this after we showed the TT we cut the original tendons to make sure that they weren't doing anything because we don't want to get too much uplift when we add the our exterior post tensioning but we went in and so but we went in and redesigned everything so that the post tensioning there will take care of the load of basically replacing the tendons because of the sear post tension set of the straight ones we did draped ones and a few things like that but that's kind of where we ended up you couldn't you kind of see the tendons you see the formwork here's kind of a picture on the right is for the concrete place the left is out there placed we left a little bit at the end to allow us to stress them and then poured the concrete stress them and this is a kind of pictures at the end kind of what it looks like you kind of see don't know how well you can see that you can see the second pour to encapsulate the tendons and really what we ended up with was a wider 10 a wider TT stem at the end so that's what we did for the main one and then running real quick here's for all the other ones first step was injecting the cracks kind of repairing the cracks making sure they're not going to be an ongoing issue and then adding FRP as you can see it was basically every piece stem that we needed to add the FRP so there's a fair amount of it on the right we did do conformation quality control testing taking some samples from the end of the FRP doing bond pull-up testing make sure that the prep was fine and the application was flying confirmed that it worked but you know we wanted them to be located at the end so it's not really affecting the main strength of the FRP and to make everything kind of hidden we coated the coated everything so you don't walk in there you don't see all those big block ugly FRP systems I know some people love it you know if you're an FRP manufacturer it's music to your ears but most people you want to kind of hide what the FRP looks like that's kind of quick over you I think no talking about an assessment these are my big five things that we need to think of that's we're certainly reflected in the document you know I think if you go through these as a mine through your checklist as you set up your assessment kind of definitely covered what can be done you may not need to do all of them for a specific project but it certainly helps you getting on in that direction and following that assessment process improves your quality and completeness of the assessment kind of understanding what's going on thank you very much any question my question is given the load and resistance factors that are used in design what was your conclusion as to the the cause of the cracks was a simple overstraining in the in the tendons yes when we ran through our calculations that whereas it wasn't fully over the crack even including the prestress force that was there so was in that kind of intermediate range and that's definitely a concern particularly for parking structures that you know you start once you start cracking it these are designed specifically to be non 3 crack free to avoid durability issues down the line so we wanted to address that but also it just didn't meet the code required factors of safety but when we did it without you know looking at as an assessment viewpoint it was in that range below the ultimate but above the cracking load of the structure thank you I wonder why didn't you make a load test let's say instead of this analytical method and if it passes that's it could it be possible to do the loading tests in this case the loading test is always possible for something you want to want to do instead of doing the whole rehabilitation by just relying on energy a limited part of the issue was we've already seen the stress that we didn't like that we didn't want to keep going it was all you know we had that one that had I've not failed in the sense that it collapsed it definitely is beyond what your what you would expect and its performance so we definitely needed to address that one no matter what the results of the low test were because we did have an exposed exposed tendon and the other locations it was you know we had something was already cracking it was already something that was not beat not performing correctly and once you get into the cost of the repairs versus in this situation given the amount it's a lot more comparable than I think you're maybe thinking FRP is fairly inexpensive to get to get it done and you know the owner wanted something to address these issues that were that we're developing so it was then something like even if we load tested it we weren't but and it's fine we weren't going to be walking away from it anyway we needed to address some of the crime tree from a durability viewpoint if not from a structural viewpoint Thanks [Applause]