Good afternoon, welcome to PCI's webinar series. Today's presentation is Precast Floor and Roof Systems. I'm Nicole Clow, Marketing Coordinator at PCI, and I'll be your moderator for this session. Before I turn the controls over to your presenter for today, I have a few introductory items to note. Earlier today, we sent an email to all registered attendees with handouts of today's presentation. The email contained a webinar attendance sign-in sheet, a guide to downloading your Certificate of Continuing Education, and a PDF of today's presentation. The handouts are also available now and can be found in the handout section located near the bottom of your webinar toolbox. If there are multiple listeners at your location, please circulate the attendance sheet and send the completed sign-in sheet back to PCI per the instructions on the form. The attendance sheet is only for use at locations with multiple listeners on the line. 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We need your email address to get you your certificate for this course. Our presenter for today is Chad Van Kampen, manager of pre-construction at Fabcon. He has spent 25 years in the precast concrete industry where he started out as a QC technician. Chad is currently the chair of the PCI FRP Committee and PCI Total Precast Systems Committee, and vice chair of the PCI Hollow Core Committee. He graduated from Calvin University in Grand Rapids, Michigan. One of the precast concrete projects Chad worked on is located in the Marshall Islands and was for the US Army Corps of Engineers. I'll now hand the controls over so we can begin the presentation. All right, well, welcome to the show today. I'm going to be talking about precast floor and roof systems. This is an introductory course designed to equate the design professional and design teams with basics of precast floor and roof systems. I'm going to start by going through how each one of these products is made in the plant. Some design examples will be shown on each of the projects. In fact, it's going to be shown throughout the presentation, and you should be able to see how these are used inside a project and how to incorporate them into your building systems. So the learning objectives for today are understanding the process of design and manufacture of precast floor and roof systems, understanding the features and benefits of precast floor and roof systems, understand the advantage of manufactured precast and prestressed concrete products, and understand other design advantages and considerations specific to integrating precast floor and roof systems into the construction process. So before we get into the manufacturing of the products, I'd like to go a little bit over the PCI certification. Each plant that's PCI certified has to undergo some qualifications and some visits from inspectors to maintain PCI certification. PCI certification has three different categories, two different spec sections. PCI MNL 117 is for architectural precast units. MNL 116 is for structural products. This is broken into two categories, B for bridges and C for commercial. Most of what we talk about today is going to be in the C category for commercial, straight strands, structural products. We won't talk much about architectural or bridges. Higher erectors also go through certification. There's three levels of certification for an erector. There's S1 for simple structural systems. So this would be hollow core plank bearing on walls, double teeth bearing on walls, really simple erection projects. Category two is complex structural systems, which includes everything contained in S1, as well as potentially multi-story projects, beams, columns, and even architectural precast load bearing members that would be on a total precast project. And then category A is for architectural systems. So this is a purely architectural system and would include like GFRC cladding, architectural precast cladding, something you typically see on like a tower in like Chicago, New York, or one of the big cities, which is cladding against a different structural system. Most of what we talked about today is going to fit in either the S1 or the S2 category. So the PCI training program and personal certification began back in 1985, when the goal was to provide the plants with personnel inside the plant that can monitor the quality of the precast being fabricated. PCI trains the field auditors and the field technicians. I'm going to show you a little bit about those programs here in a minute. And each one of these programs is audited by a third-party auditor. So we have two different categories, 116 and 117, as explained earlier. Those are two different spec sections and they have differences in tolerances and quality control procedures. We have two unannounced auditors, audits each year that come into our plant. The auditors are accredited by the IAS. They're not hired by our precaster. They're actually a third party that comes in here and they cover all phases of the production up to and including engineering tickets that enter the plant and the product that leaves the plant. There's three levels. The first level is level one. You have to be in the precast industry at the plant for six months. You have to maintain your ACI, concrete field testing technician, grade one. And then you have to go to a PCI training course and pass level one exam. Level two, maintain all the requirements of level one in the precast industry for one year. And then there's some additional training that goes on during those six months, including understanding concrete mixes, starting to get into well basics, strand elongation, curing methods, and elongation corrections. Again, there's a class that PCI has, it's a level two class, and you have to take that class and pass the exam. Level three is the highest level. This is two years of experience in the precast concrete industry. You have to complete all the level two requirements. And then this class is a four day PCI school. And then there's an exam at the end of that class. And after the end of that class and the exam, if you pass it, you can become a level three inspector. So everything that comes into our plant comes into our plant because it's a quality control environment, as opposed to being on the job site where you're highly susceptible to weather and different conditions. All the plants that are PCI certified have a very controlled environment that they cast their products in. This allows us to control temperature, humidity. We have better craftsmanship because we're in an environment that's not impacted by outside forces. And in most plants, we make our own concrete mix right at the plant with our own aggregates and old sand. So it's very easy to control the mix design. And all of our formwork, this plant is built by our own carpenters, and we're allowed to provide very sharp details in some of our precast products as a result of this. So the advantages of PCI certification come with a high quality product. With PCI's inspection process, there's a high level of oversight on everything we do. We have to document everything we do, and at the request of an engineer, architect, or even the owner, we can provide all those documents to back up what we've been actually making in the plant. We also have a better quality and reinforcement cover than you would on, say, a site cast project because all of our reinforcement is inspected in the bed prior to pour, and that's for every piece that is in the plant. So before we get into fabrication, one of the thing is precast versus prestressed concrete. So there's two types of products we make in the plant. One is precast, which is just mild steel. It does not have any pre-compression forces and no strand or post-tensioning. So it's just rebar and concrete. And then we have a prestressed product, which is rebar, concrete, and prestressing strand. So the photo on the left is a picture of a beam form with six-tenths strand. Each one of those strands is pulled to about 44,000 pounds. In addition to what you see in that photo, we also put a mildly reinforced steel cage in there. So your stirrups and your top bars and your door handle bars will all go in that form as well, and then we pour concrete around it. When you prestress the concrete member, the stressing is typically towards the bottom of the piece, and when you're eccentric of the center of gravity and you put a compression force into the bottom of the piece, you get camber. All of our strength is high strength, 5,000 to 10,000 PSI mix. Every piece that comes into our plant is specifically engineered for a specific location on your project. We don't stock any product in our yard for shipping at a later date. Most of the elements that we make here, such as hollow core beams and spandrels and double-T's are actually prestressed. So we don't do a whole lot of precast members in that. So remember the diagram on the left. I'm going to talk about it throughout the presentation and I'll get a little bit deeper into it later on in the presentation. All right. So this is the hollow core manufacturing facility. You're just looking at four, four foot wide by 500 foot long steel beds with a gantry precast concrete delivery system. This is for hollow core manufacturing. It's pretty common in the hollow core plant. There's two types of hollow core manufacturing. There's extruded and there's slip form concrete. All of these are cast on long line beds. The beds are four to 500 feet long and they're cut to the specific length of the piece that's detailed. So all the hollow core pieces you see on this bed here are manufactured for a very specific location. They're not stocked and then cut later. Typically we see eight, 10 and 12 inch and 16 inch hollow core in the market. There is six and 24 inch hollow core that's available in select regions. I would recommend you talk to your local PCI producer and call around to see who has those sections if you want to use them. This is a picture of a hollow core machine getting ready to pull some strands. So every piece that comes into the plant is again, specific to the project. We do not mix strand. So if a piece has five strand in it, we do not want to pour it with seven strand in it. One of the reasons is because it causes a camber issue. We try to keep all like pieces on a bed with like strand pattern. Casting beds are typically four to 600 feet long. They're steel. There are eight foot wide steel beds. There's also concrete beds that hollow core gets cast on. We use seven wire, 270 KSI pre-stressing strand. These strands are laid out on the bed full length and then they're tensioned. They're put 70% of the U of course is typically put into it, into the strand. So for a half inch strand, that's 33,000 pounds, I think at 75% and 30,000 pounds at 70%. This particular system that you see here is a gang tensioning system. So all seven strands on the bed would be pulled at the same time. There is also single strand tensioning systems where you use a ram to pull a strand versus pulling them all. Our quality control department then has to inspect the elongation of the strand to ensure that the strand performed as designed. So the elongation of the strand is measured and it's confirmed with the calculated value based on the materials of the strand that came out of the school. And those have to be within a certain percentage of each other or the engineering team has to be notified that it is out of tolerance. And that's all part of the PCI inspection process for the hollow core plank. This is the extrusion machine. This is a machine that has one hopper. The concrete gets dumped into the top. There is augers inside this machine that force the concrete out through the back with the back die, liken it to a Play-Doh. You ever played with Play-Doh when you're a kid and you stick the Play-Doh in the barber's chair to push it down and the hair squeezes out of the guy. This is very similar to that. It just pushes the concrete out of the back and squeezes out of shape. The concrete coming out of the machine pushes on the concrete that's on the bed and the machine gets pushed down the bed by the concrete itself. We use a fibro-compacted dry concrete mix. It's also called earth dry or zero slump concrete. And it creates a very dense, very strong concrete mix as soon as it comes out of the machine. So in most cases, you can walk across that concrete as soon as it comes out of the back of the extruder. The left is a picture of the augers inside the machine. You can see where they would grab the concrete and push it through the die. And then in the front of the machine, we have a strand guide. The strand guide is designed to keep the strand at the proper elevation as it enters the plank. So we can ensure that the plank and the strand is at the proper location as it's being cast. This is the slip form machine. It's a little different than an extruder, but it uses the same concrete materials, same concept. The difference is it's a two-part process. So there's a bottom process where the bottom hopper where you pour the concrete into, and the top hopper where you pour the concrete into. And this concrete is separated over a sliding tube, slides back and forth. And as the concrete's being fibro-compacted, these two levels firm up and form in a hollow core slab section. Different method of making the hollow core slab, but you still get the same high quality, very dense concrete product that you get with an extruder. We can put notches and openings in our plank. Large openings, we typically green cut, and we expose all the concrete, take out all the concrete, expose the strand. This opening that you see here in the top center would be then covered and cured and would actually be removed the next day after the bed has been cut down. The embed plate that's in the lower center, we dig down out of the core, put the embed plate right on the steel bed, and then we come back and fill it with a six to eight inch slump concrete mix. This is an erection connection. It's not designed for very heavy loads. It's more designed for stability during the installation of the plank. We also put notches in the top of the plank for connections to, say, concrete and CMU walls. This notch, we open up a core. This would be where you have a piece of rebar that gets drilled in an oxygen to the top of the wall, and then it has a tail bar that is bent into the core. And then that core is filled with grout, and it can be used for a hidden connection or a diaphragm connection in the hollow core plank. So about eight hours later, after the plank is cured, we release the tension of the strands. We do this by cutting the strands, and then we have to measure the slippage into the plank. So quality control is then called to ensure that the initial release of the strand does not create a strand slip. Strand slip is where there is no bonding of the concrete to the strand, and the strand actually slides into the piece. After that check is made, we break the cylinder. Once the strength is confirmed, we go ahead and cut the plank with a wet saw. You see here is a 48-inch-wide saw. We do have saws for 96-inch-wide product as well. These saws are cut at predetermined locations on the bed. We also cut plank to width. So all the product we cast are four-foot wide, and the next day we'll come out and we'll cut to width. There is some rules about cutting to width. One of them is we do not want to cut on top of, between, or within one inch of the stressing strand. And this is to prevent the strand from unfurling from the piece while it's sitting in the yard or being driven down the road to the job site. We also don't cut a core that's wider than one-half the diameter of the core. This is to ensure that the top and bottom of the precast piece, as you see in that diagram, do not crack off during transportation or installation of the piece. It's very hard to repair those and it's very unsightly as well. This is a double T bed, very similar to Holocore, it is longline cast. The only difference is we do not cut these to length. These are actually poured to a very specific length on the bed. These are not gang tensioned either, at least not in our plant. We single tension each one of the strands in this particular bed. They're typically used for longer, open, clear spans and vary in width from 8 to 16 feet. I think there's 8, 10, 12, 15, and 16 at a count of widths, and depths vary from 24 to 48. There are different widths and depths out there, so again, I would recommend if you have a specific section you're looking for, you call a local producer. One thing that's nice about the double Ts is we can upset the bearing into the double T. This is called using a DAP. What you're seeing here is a DAP in a beam and a DAP on a button haunch. What this does is allow for the structural system to maintain minimal thickness as required by design, and especially for the button haunch when you're bearing on, say, an architectural precast exterior spandrel, say in an office building or a parking deck, the outside pedestrian or person in the building across the street is not going to see the floor system from the outside. There's two types of double Ts we manufacture. There's a pre-topped and a field topped. A pre-topped is a double T with a four-inch deck thickness and a finished surface. So what you're seeing here is a pre-topped deck with a groomed finish in a parking garage. The ends are typically left un-topped, and this is so that at the bearing conditions you can pour a wash or a diaphragm or slash cord steel into the project. One thing with these pre-topped double Ts is you will have camber in your final structure that will be visible. In between each T is a stainless steel connection that will be put on center to help with the connections between the double Ts and with your diaphragm forces as well. Typically these joints are caulked. We also have field topped double Ts. So we'll see this in like rooftops, safe rooms, especially hardened structures or locations where the final structure cannot tolerate camber. So the picture you're seeing on the left is a medical office building in a subterranean parking deck and it was next to one of the PDIC's office and the hospital wanted to make sure that anyone traveling from the car to the office did not have to contend with uneven surfaces. So we do this by roughening the surface of the precast and at a later time another trade can come in and lay reinforcement as required and pour the topping. You'll actually get a thicker topping at the bearing ends than you will at the center and you can work with your precaster to work out all those details. Double Ts can have openings as well. We have pre-manufactured inserts that go into the top of the T right between the stem and the deck and what happens is you can put your fire protection electrical or data right to the tight of it tight to the underside of the deck of the double T allowing it to be hidden from view. Larger mechanical openings typically are cast into the double T in the plant so they're coordinated with mechanical drawings prior to fabrication. We can also field cut openings into the double T if that's the method that's preferred. Solid slabs are manufactured much like double Ts. They can be long line but they are cast in individual pieces. They're typically used for locations that require very special shapes, heavy loading or in specific areas that require something unique. So the picture you see on the lower right is a slab that has roof scuppers cast into it versus applied in the site. Our slabs that we cast can be pre-stressed or conventionally reinforced. We cast our slabs with key ways that they're going to be integrated into a hollow core slab deck. So you'll typically see this on a podium structure where we have extremely high loads from say four stories of wood that is bearing on this. One thing that's nice about the slabs due to their custom shape is it makes it really easy to change directions. So this particular project the plant changed direction slightly along an expansion joint and in order to avoid some very awkward details along the expansion joint like custom slab was formed to shape in this location and omitted a lot of very complex connections. The other nice thing about the slabs is we can put air pins in them. This is great when you have heavy point loads and you have to transfer some pretty heavy loads into the topping and by doing air pins you can up the horizontal shear forces between the plank and the topping without relying on just the raked surface. Solid slabs are also good for custom locations such as these. So the picture on the left is a dryer tower. You can see how forming that void that circle would be very hard with hollow core double Ts. So this is actually two custom solid slabs that form the circle. And then on the right we have an area that was hollow core and due to the loads coming down from the monorail the plates were very big and cumbersome and it was decided to go to a solid slab which would provide a smaller more compact inbed plate that was less visible in the final structure and could sustain the high loads. So precast is very sustainable. It's corrosion resistant. It doesn't rot, doesn't mold. This particular project had insulated walls which helps with the heat on effect and thermal mass. This is a storm shelter at a campground. It is a total precast structure with insulated walls, hollow core floor, and hollow core roof. The pip roof you see there is actually sacrificial and made out of wood and it was designed to protect the occupants from flood, fire, and storm and still maintain full use before, during, and after the event. There's a PCI journal article about this. I'm not sure what year but there was a storm shelter issue that this was featured in. Precast offers accelerated construction schedule as well. That lowers the construction financing cost, reduces the contractor overhead time on site, general conditions, and there's less labor on site. And we're able to mitigate the weather during our manufacturing process as well as on site with accelerated precast direction. The tower you see on the right is a 14-story, two elevator shaft and two stair shafts with stairs that was erected in 18 working days. So we stand on other structural systems as well. I'm going to kind of go through a few of these for you and show you the benefits of each one of these systems along with some details and how they all work. We're going to do structural steel, block, cast in place walls, total precast systems, and then I'll show you some hybrid framing options as well. So structural steel is a very fast, very common way to use hollow core slabs and pieces in this area. A simple welded connection to the steel beam. You can see here we've got some cantilever balcony slabs that are also custom to the project that are welded to the steel beams. It's a very clean construction method and one of the benefits is that trades following our precast direction have a flat surface to work on as opposed to a metal deck system which can be very rough and hard to walk on. We also can sit on caps in place. This is an alternate method to say flat slab or PT slabs especially over expansive soils. This particular project was a PT slab over void form and they were able to switch it to hollow core plank and allow the space below the deck to be somewhat open so they can access their plumbing should they have a problem later in the day, later in the life of the building. We can use similar connections. We can have a well plate that's connected to a angle in the wall or we can use the previously shown dowel bar that gets drilled and epoxied into the top of the concrete wall and then filled with concrete into a hollow core void. Precast wall support is also another very common construction method. On the picture on the left is a pool with long span double Ts and an insulated precast concrete wall. This offers a very fast way to an enclosed drive-in structure which allows for some of the other interior trades that are weather sensitive to continue at a rapid pace. There's also mid to high rise construction using total precast systems with wall bearings and hollow core plank. This is a hotel located in the Detroit metro area with solid demising walls and hollow core plank. This is a coordinated systems approach where the precaster designed and fabricated and installed this entire system and it allows access to other trades with a much more rapid schedule than you would with say a cast in place PT system. There's also precast framing support which would be precast beams and precast columns. This is typically used for large open spaces where you want very wide expansive areas rather than a column filled area. These systems are very popular with architectural load bearing or cladding as well as other methods such as glazing stone and masonry facades as well. Hybrid framing is something that's sort of unique and beginning to take root in the United States. It's pretty popular in Europe and pretty popular in Canada. These are third-party proprietary systems. They support hollow core flooring and their goal is to compete with cast in place post-tension systems by providing a thin flooring system. This uses cast in place concrete, steel, and precast and it maximizes the benefits of each one of those building materials to form a very efficient thin floor system. I'm going to go through some projects now that have been completed with some of these products. You can kind of see where they were used and how they were used and the stories behind them. This is the West Michigan Academy of Environmental Science. This was a pre-engineered metal building. It was built in the early 1900s. It was built in the pre-engineered metal building. It was designed originally with metal deck and joist. One of the owner's requests was to have a school building that could be used for whatever purpose necessary, including moving walls down the road, expanding classrooms, splitting classrooms, without having to worry about impacts to the structural design. With the joist and deck system, there was some bracing requirements that had to be taken into account if they wanted to move walls. And with the hollow core system on this building, it was a simple connection detail to the bottom of the hollow core plank that could be placed basically anywhere. You can see here it's clear span from the outside bearing beam wall all the way to the inside corridor wall, creating an open space for them to do with what they want. We also have an office building slash training center. This was recently completed in Carmel, Indiana. The left side of the building is a 50-foot tall, 50 by 50 bay. Inside this is aircraft pilot training units. They had a very large radius of freedom that they had to move these things around in. This is a 16-inch plank that you see on the roof. This is a 16-inch plank that you see on the roof. On top of this roof is a pilot lounge area, including an outdoor theater, green roof, and bar and restaurant. So they had a very heavily loaded roof area. The office building on the opposite side was a two-story office building, again, with very heavy loads. There was a lot of training equipment for aircraft maintenance personnel and safety equipment that required this loading. And also on the top of this roof was the remaining part of the green roof. So this was converted from other building materials. It was surrounded with insulated architectural wall. And we were able to keep the spans wide enough that they could get all their training equipment in and out and not be obstructed by what they previously had, which was columns, I think, that were at half the spacing we were able to get in that. Oliquor can also be used in industrial. All three of these pictures are pictures from projects where we were told that mechanical coordination was going to be extremely difficult. The one on the left is a dryer with a double T, solid slabs in the middle of the food processing plant, and then a sausage patty plant on the right here. Each one of those pieces of wood you see on top of the plank is actually a penetration through the plank that was coordinated with the process vendors prior to fabrication of the blank. The key to each one of these projects was that they were all done in BIM. And all the mechanical openings were fully coordinated prior to the precaster entering into production. So it ensured that the product would actually arrive on site with the openings as they needed them and where they needed them. Oliquor and residential. This is one of those hybrid systems that I spoke about earlier. This was a conversion from a cast-in-place PT slab to this system. One of the issues that the owner had that he wanted to make sure that Oliquor could meet was that he wanted to make sure that the floors could be exposed and he could get lighting into his floors. They had recessed lighting in the cast-in-place PT slab. We were able to accommodate them. We did not cast those lights in the plank. They were actually put in after the plank was installed. They were coordinated with the core locations of the plank and all the electrical that fed those lights is actually fed through the course. Oliquor can also be used in a hotel. This is a 2022 PCI Design Award winner for Best Hotel. This structure was originally steel with masonry and stone on the outside and the hotel brand that wanted to come into this particular structure had a minimum required for square inches per room and they could not meet it with the steel structure because the steel structure had columns inside the room that took away from that required space. We were approached by the developer and we were able to use 8-inch plank Oliquor plank that span from the exterior bearing wall to the interior core creating a column free space and allowing the hotel to get the minimum room space that they required and the project was able to proceed forward. Another neat thing on this project is that there's actually a pool hanging off the Oliquor on the second floor. So most pre-casters either do or coordinate with you installation with the PCI certified director. Typically when we erect the precast we require a precast erection zone that is clear of all of the trades but those the erectors for the precast. When we're doing big giant tees like you see on the left we like to clear the whole site. It's a very complex highly coordinated event. It's very slow moving and we want to minimize distractions and any possible room for error when we're setting big tees like that. All PCI certified directors have certain standards and procedures they are supposed to follow. I'm going to go through some of those with you now. One of the things before we get into that is some very difficult erection. This is a what we call an in and under installation. This is the plant getting erected inside an existing building and under an existing structure. Pre-cast concrete products have to be picked from the end unless they're specifically reinforced not to be picked from the ends. If you pick them from the center you will typically fold them up like a taco. So in order to pick up product like this we have to put a strong back on top of the plank and then actually tie that strong back to the plank at the ends and then pick from the center of the strong back. This reduces the headroom from the crane hook to the boom and allows us to get into tight spaces. We can do this it's just a slower more complex installation process. If you do have a building that requires this I encourage you to get with the local PCI director in your area and talk it through with them to make sure you have your bases covered before you proceed too much further. So all erection all erectors on pre-cast project sites should be coordinating their installation with the site contractor. We like to coordinate the crane access path, the crane pads, how the truck is going to enter, how the truck is going to leave. We also like to provide you with the ground bearing pressure of the crane so the crane pad can be designed for the proper loads. You'll want to make sure that the trucks are lined up with the crane so that when we pick the loads don't want to rotate. And then as you see in this picture we also need to coordinate especially in urban environments with road access, lane blockage, and parking blockage as well. So some design considerations. All right remember this diagram from a while back. This is camber. Camber is caused when we pre-stress a member eccentric to the center of gravity especially to the bottom. It will cause the plank to camber up. It's an inherent property pre-stress members but as most you probably know concrete is great in compression and not so great in tension. And when you put a load on the top of the beam you put the top into compression and the bottom into tension. To overcome that tension we put compression into the bottom by using pre-stressing strands. This allows us to put more load on top of the beam before we reach that tensile limit. Typically, the higher the loading on the member, the longer the spans, the deeper the member, it increases the eccentricity and therefore you have a larger camber. Theoretically, the camber should come out when the member is loaded with live load, but in theory, in practicality, when the structure is completed, you're going to see very little movement in the camber throughout the life of the program. So this is an ideal project for camber. Same plank, same span, no change in direction, very little holes. This should give you very little difficulty with camber. You should have very uniform camber across this and it should be a pretty nice project with minimal problems. A project like this may be a little different. You have a lot of plank in different directions with different spans against plank that are also changing direction. On top of this, if you have a precast beam and column system that's supporting the plank, you have the camber and the beams to deal with. One of the reasons I show this is because even though this is a very complex project, by working with your precast design engineer and design team, you can actually work to minimize the impacts of the camber by pre-planning and by use of elevating or changing your bearing conditions in some locations. The goal would be that anything such as topping would cover the camber. If you have a topping slab or you have a system where the camber differential is not going to cause you any issues in the final structure. Long span roof members are a little bit more sensitive to camber than the hollow core plank. This is a double T roof on a warehouse that's sloped to the center. So not only does the water have to slope just because of the flow, but it also has to be sloped over the camber, the double Ts, which had to be coordinated in the design of this building. It's very important when you've got a building like this that you keep the widths of the Ts the same, depth of the Ts the same, the strand pattern the same, so the camber can be the same for the roofing to actually be put on the building without any issues. In parking decks like you see on the right where you have some double Ts overloading docks, in this particular location we had double Ts that were pre-topped against double Ts that were not topped against some narrow Ts. Anytime you're changing the T configuration, especially on a long span like this, you get some impacts to camber that are going to have to be addressed. So in general, a hollow core plank can span roughly 20 to 55 feet depending on the plank thickness. Your typical double T roof would be about 45 feet. We do have a T form here at my plant that can go upwards of 120 feet. I would ask you guys to reach out to your precast producer and verify what sections they have and what their load tables are for each one of their products as you're designing a building. Pre-trussing strand is another common issue we come up with on a job site, especially when products in place. So we need to do some cutting of some openings and some penetrations. So cutting a hollow core plank is critical and the engineer needs to know about how we can coordinate with you prior to your project to ensure that the cutting of a strand is acceptable. We do not cut strands in the stem members such as a double T and we do not cut strands in members such as a beam. You can see in this picture there's highly congested areas of strands and even a small penetration would probably hit multiple strands. What we like to do is if you do need a penetration and beam like this you're in a double T that we coordinated prior to fabrication and we put a sleeve in the member that's in a position for the mechanical trays to use. This again can be done very easily by use of BIM in the design of the building. What we typically see when we cut a strand is a design issue and it typically creates a situation where this member is no longer capable of supporting the loads it was designed for and you need additional engineering or some creative method to get around the hole that was cut. So precast uses very high strength concrete. It's very dense. It's very good for modular construction. It's vibration resistant. It doesn't squeak and groan like you would in say a wood structure. A lot of the ceilings can be left exposed. They can be painted. You can use a textured paint as shown in this photo or you can actually use a drop seal. With the dense concrete mix and the sections that we have, we have a very high sound transmission class which provides an acoustical superiority to the structure. So it's great for precast floors, roofs, dorms, theaters, housing units, and office buildings. Precast is also inherently fire rated, fire resistant. A lot of precast structures made of concrete are made with non-combustible materials. A lot of the fires in buildings that are constructed out of wood tend to be exasperated when they travel from floor to floor. Using a precast floor system will prevent this and you use demising walls that will also prevent the lateral spread of the fire. Usually a precast building that has a fire in it, the fuel will burn out before the fire will be put out before there's any damage to the precast concrete. You can clean up the concrete and reoccupy that space fairly rapidly. Concrete is very durable. We use natural materials, typically local aggregates, local sand. We make everything in our plant and therefore it's UV resistant. It's not going to grow mold, it's not going to deteriorate in any way. Precasters are famous for wanting to minimize the amount of pieces we send to the job site, maximize the size of the pieces we send to the job site. What that means for you is less joints, less hawking, and therefore less potential for moisture penetration into your building. This is a case study. This is 28 West Grand River. This is in downtown Detroit. This is a 14-story total precast structure and has roughly 1,000 square feet of hollow core and solid plank. It has 14,000 square feet of 12-inch insulated load-bearing architectural precast bearing walls. The lateral system for the building was a solid precast concrete shearwall system and a stair and elevator course. The artwork you see there is artwork that was painted on the building. It was not cast into the precast. The local artist in Detroit painted that just before the building was occupied. So this was a total systems approach. We were brought into the design by the design team as a member of the AE team where we worked with them to create a modular approach to the building. One thing we wanted to do in this building was make sure that we could cast pieces repeatedly, use the same forms without many changes. This creates a very efficient casting process in the plant, minimizes errors, and allows the plant to produce it at a fairly rapid rate. We worked with other trades on site as well to coordinate all mechanical plumbing, doors, openings, windows in this building. We erected about a floor every week, week and a half. The nice thing about this building for the contractor was that when we got to the fourth floor, the mechanical trades were able to enter the building at the lower level, start their work, and they were not dealing with shoring and reshoring that you typically would see with a cast-in-place structure, which made them proceed at a rapid rate and able to complete their work more efficiently than working around a bunch of shoring and reshoring. The exterior walls on this were furred out with additional insulation and drywall. Most of the walls and ceilings that you see were left exposed. These are furnished micro-apartments, so the only thing that the tenant has to bring in are the dishes and their clothes. Everything else was included. All the amenities for the tenants were on the lower level. You can see a picture of the finished stair core there. That's a total precast stair core, shear core as well. Very clean look for a precast system. The brick details around the upside were also coordinated with the City and the AE team. Again, these repeat up the building to maintain efficiency. The amenities level you see there has been installed once the crane is torn down. This is part of the erection coordination that I spoke of earlier. The big crane was actually sitting in that amenities level as the building went up. When the crane was torn down, we used the assist crane, which is a smaller crane, and that smaller crane was used to set the amenities level once the big crane was gone. Therefore, it minimized the impact of the overall street closures. When that crane was gone, the structure on our end was done. So, I appreciate your time today and I think we have some time for some questions. Thank you, Chad, for a great presentation. We will now start the Q&A portion of our presentation. The first question is, in regards to the precast framing support slide, do you consider the CL slash BM connection to have any moment capacity or just considered pinned? We have the ability to make the connection a fixed connection and transfer moment. Most of the connection details you saw on the screen were pinned connections. Wonderful, thank you. Our next question is, did you ever fabricate round precast concrete column? We do, yes. One of the challenges with a round precast column is we cannot, we, at least not at this plant, can cast them flat and get the full round surface. So, if we cast them, we typically cast them vertical, limiting them to one story. There are some producers that probably have some ability to cast longer columns of that that are also round. Perfect. Our next question is, what design software do you use to design precast elements and total structures? Well, I can't really tell you who I use. I don't think we're allowed to divulge names, but there is a variety of precast softwares out there. Can I tell them names? Is that allowed or no? I would say if you know multiple companies, that would be fine, but I probably wouldn't mention the one that you currently use. Okay, so there's Soundman's PC, there's Leckwall, there's Ericsson, and there's probably a bunch of others out there that I'm missing. There's a lot of software out there that's used and also integrated with 3D software for design that precasters and consultants use. Great, thank you. Our next question is, how difficult would it be to cast a steel tube perpendicular to the round column to work as a cantilever for a support of steel framing? We would not cast the steel in the round column, but we would design an embed plate that you could weld your tube to the column. Sounds good. Next question is, how accurate can you predict camber on hollow core planks and double T's? I should have seen this one coming. We try our best because the product is natural product and it's stored in the yard under various environmental conditions. It's very hard to pinpoint exactly what your camber is going to be, but the PCI specification and tolerances are basically based on camber differential between planks of the same design. So, we should be able to provide you a plank of same span, same design loads with the same camber on the job site without any issues. When we start getting into various lengths and various loads and various storage conditions, it's very hard to predict with any level of accuracy what that's going to be. Perfect. Thank you. Next question is, how do you currently consider and account for vibration considerations for longer span precast elements? Well, we have to run calculations on the vibration based on what's being used for, and that may require thicker topping to make the section heavier, or thicker, deeper section to meet the vibration requirements. Wonderful. Our next question is in regards to 28 West Grand River. Is the hollow core slab skim coated or do they have a structural concrete topping? I believe it was a structural concrete topping. Okay. Perfect. Our next question is, is it possible to have a portion of a double T with a cantilever extension over support of 10 feet or less? Yes. Wonderful. Next question, what is the longest precast pre-stressed slab that can be shipped? That depends on how deep and how heavy you want to go. So, the deeper the section, the more eccentricity of the strand you can get, so you can get longer spans. For a 16-inch hollow core slab, we can get in the neighborhood of 50 to 58 feet. Wonderful. Thank you. Our next question is, if we are comparing hollow core floor systems to alternatives, what would you say is the best approach? It's kind of a difficult question to answer if I don't know what other floor systems you're comparing it to, but hollow core is probably one of the most efficient products for span-to-depth ratio as opposed to other structural systems. So, I think you're going to get a longer span with a shallower system than you will with other structural systems. Great, thank you. Another question, are there any issues with bearing a hollow core plank on one material at one end and a different material at the other bearing end? Nope, there's not. We do that quite often. Perfect. How do you typically lift double Ts in hollow core slabs? Do you use lifting hardware or slings or some other method? So, hollow core plank, we use slings at the ends of the hollow core. And then for double Ts, we have lifting loops that are cast into the ends of the double Ts. Wonderful. Our next question, does hollow core camber grow over time due to creep in the concrete below the neutral axis? Yes, it does. And that's one of the reasons I had a hard time answering that camber problem, that camber question, is because depending on where the plank is, how long it's in a yard, sitting in the sun or not, and creep, I'll impact the overall camber when I actually make it to the job site. Perfect. Our next question, can a hollow core panel reinforcement layout be customized to include top and bottom reinforcement? Yes, it can. But the strand locations in the top are going to be similar to the strand locations in the bottom because the strand is going to have to be located in the web, but we can put top strand in our plank. Perfect. Is it possible to fabricate a sheer wall and precast elements for a tall building? Yes. That 28 Grand River was, I think, 14 stories tall, and that had a precast sheer core in it. Perfect. We have time for a couple more questions. How wide of a, I cannot pronounce this word and I should know it, tributary area will the support along the side edge of a precast wall be? Will the support along the side edge of a precast slab need to consider in the design? So I think you're asking if you have a wall on the edge of a plank at the end of the wall, what your tributary area width is, and I believe it is 0.25 L. So a quarter of your span would be the overall width of tributary area you could distribute that load over. Perfect. I'll ask one more question. Can you use embed plates in hollow core? Yes. I would check with your local producers. Producers all do those embed plates and how they put them in, in different manners. So I would call your local producer and speak to them about if you have a specific load you're trying to put on an embed in a hollow core plank. Wonderful. Perfect. There'll be all the questions for today. So on behalf of PCI, I would like to thank Chad for a great presentation. As a reminder, certificates of continuing education will appear in your account at www.rcep.net within 10 days. If you have any further questions about today's webinar, please email marketing at pci.org. Thank you again and have a great day.

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