The webinar will begin in 30 seconds. Hello, I am Jim Schneider, Executive Director of PCI Mountain States. I'll be your moderator for today's webinar, Precast Holocore Floors and Walls. This course will instruct participants about holocore products, how they are made, handled, and how to design and build utilizing holocore floors and walls. Participants will also learn about the inherent fire resistance of holocore, a major life safety consideration, as well as the inherent low sound transmission of holocore floors, which increases occupant comfort. After attending this program, participants will be able to identify the different precast, prestressed holocore concrete systems, explain the benefits of using precast, prestressed holocore concrete within building systems, and identify innovative ways to use holocore holistically within the HVAC system. This webinar is sponsored by PCI Gulf, South, and Clark Pacific in conjunction with a broader effort by PCI regions all around the United States to deliver online learning to design and construction professionals. Be sure to reach out to your local PCI region to learn more about online learn at lunch opportunities for your firms. Contact information for your local chapter is available at pci.org slash regions. This webinar is registered for one hour of HSW continuing education credit with AIA and RCEP. To receive credit, you must attend the full webinar and provide complete registration information. If an AIA number was provided at the time of registration, your attendance will be reported to AIA. Within two weeks of completion of the presentation, you will receive an email from RCEP to download your certificate. If there are any groups in attendance, we do have a group attendance form you can download in the handout section. That can then be emailed to Ruth Lehman, whose email address is on the form. Also in the handout section, you'll find a PCI regions contacts, region contacts, and a PDF of the slides. During the webinar, you may ask questions through the questions function on your screen. With time allowing, we'll have a question and answer session at the end and try to get to as many questions as we can. Today's presenter is Aaron Pratt, S.E., Structural Engineering Manager with Clark Pacific in the Southern California region. Aaron has been designing Holocore for over 25 years and has been very active in industry committees dedicated to the material. Thank you very much for joining us today, Aaron, and over to you. Thank you very much. This is Aaron Pratt. As was mentioned, I'm the Structural Engineering Manager for the Southern California region, and I'm with Clark Pacific. We have been producing a Holocore plank here in Southern California, I believe, since about 1967, 68. So we have a little experience in the Southern California market on this. So let's first talk a little bit about how Holocore product is made. So every producing plant has a slightly different process. Extruding, slip forming, producing Holocore generally follows the steps you see listed here on the screen. We'll delve into these steps a little deeper on the following slides. And also I just want to mention that we're covering like a broad spectrum of Holocore today, but my experience is in the Southern California market, which is also a very high seismic market. So I may be making little comments here and there about how we might do things a little differently out here on the West Coast, as opposed to the other regions. First step in Holocore process is to clean and prepare the casting bed for layout and production. Although different producers have different processes for this phase, essentially all of them require some form of scrubber and water to hose off latent debris from the casting bed. Once the bed has been cleaned and dried, a release agent is applied to the casting bed and allowed to dry. Panel layout is the next step. This includes marking where each panel end is and any bottom plate locations, as well as transverse bars in the case of eight foot wide product. And as I mentioned here that some producers pre-layout the bed. If there's a lot of steel plate embeds required for structural stability of the product, those would be pre-laid out on the bed, whereas other producers like we generally run the whole line. As a first step, we run the whole line, and then we will come back and mark out where all the cut points are for the product. Because on the West Coast, we generally don't use a lot of embed plates or hardly ever use embed plates, as opposed to the rest of the country. And I'll explain why when we get down a little bit, but first some basics. Concrete is strong in compression, but weak in tension and requires a little help in order to span any type of distance. This is the idea behind the placing of pre-stressed strands within the concrete product. The strands, which are made up of seven slightly twisted wires, as shown in the upper middle there, come in various sizes. The most common sizes are three-eighths inch and half inch. The strands are stretched over the casting bed and pulled to a predetermined force. I like to use the analogy of tuning a guitar. A guitar string is pulled to a predetermined force until the desired tone is achieved. Here we are not worried about the sound, but how much force the strand is pulled to. And by the way, compared to mild reinforced steel, which is generally about 60 KSI in yield strength, these strands are 270 KSI. And there is our tuned guitar. So first, reels of strand are readied for the pre-stressing operation. This usually involves placing the strand pack into a rack so that the wire can then be pulled from the rack. The strand is then pulled along the length of the bed or form and locked into place at the fixed abutment ends or the dead end. And depending on producers, that length will vary depending on producers. But in our case, it's over 600 feet from abutment to abutment. Most times, multiple strands are pulled at once by a machine traveling the length of the bed. The individual strands are then elongated or stressed at what is commonly called the live end by a hydraulic jack to reach the required tension and then locked into place by strand chucks. For a plank, the strand will only be on the bottom of the plank and will sit about one and a half inches above the casting bed. One and a half to two inches, depending on fire cover requirements as needed. Most producers use what is called a dry cast or zero slump concrete. As the name implies, there is not much water content in the mix and typically the aggregate size is slightly reduced to accommodate the slip forming process. Here can see the characteristics of a low or zero slump concrete. Not to be excluded, there are a few manufacturers that use standard concrete mixes. Now the water cement ratio in a zero slump concrete is really low. It's like 0.3 to 0.32 maybe. And the reason why we use that zero slump is the way that the machine extrudes the concrete, it has to hold the shape of the hollow cells immediately past the machine without any form work whatsoever. So this concrete is kind of like building a sand castle with wet sand. Sometimes transverse bars are placed at the bottom of the plank to assist with handling and lifting. This is particularly helpful with the eight foot wide plank. At the same time, bottom plates, if needed, are attached to the strand, which are later used to attach the plank to a steel beam during an erection. Now, this is a really common detail where the planks are welded to some steel support. But again, out here on the West Coast, as I will explain further later, almost all of our structures in the California market have a cast in place topping slab that performs as the diaphragm for seismic lateral loading. And so with a topping slab with that diaphragm in place, you really have no need for welding any plank to any of its supports. So just a little difference that we do here. As with most but not all hollow core products, a machine is then used to produce the hollow core. The concrete literally goes in one end and comes out the other. Some operations use tubes that extrude the concrete and push the machine down the bed as it is forming the cores. Others use pre-formed insulation and cast concrete over the top of the form insulation, which creates the hollow cores. The large machine you see here is called a slip former. And that's very similar to what we do. And the concrete that you see the men working over right there, that concrete is minutes old and is already holding its shape. After the plank is cast, crews proceed behind to open the cores in order to place top end beds and any additional reinforcement as needed. The cores are then grouted closed using standard concrete or a pea gravel grout mix. Some hollow core producers manufacture both floor plank and hollow core wall panels. The structural element of the wall panel and the hollow core plank are essentially the same except a wall panel has strand at both top and bottom locations. Once the structural part of the panel is made, a crew proceeds behind and attaches the insulation to the structural element using various techniques. After the insulation is secured, the top wife is then cast. This section is typically three inches thick. And I understand this is a pretty common product, again, everywhere east of us. But out here in high seismic regions, you won't see very much of this construction just due to drift and ductility concerns. As with other concrete products, the hollow core production is covered with a moisture capturing tarps and cured for a determined time period. After the concrete reaches 75% of 28 day design strength, the hollow core product is ready to be detensioned and cut. Detensioning is achieved by cutting the strand at both ends simultaneously and in sequence using either a torch or a cut off saw. After the detensioning is complete, the product is then cut to length using a large movable circular saw. So yeah, the way we do it, again, is we will run 650 feet of spancrete or product, hollow core, in one run. And then we will come back, mark out exactly where all the cuts are, and perform all the cuts in a secondary operation. It makes the product very, very efficient in terms of materials and labor, the way that it's performed. After the hollow core is cut, it is moved to a storage yard. Most manufacturing plants have clamp-like equipment to remove the plank from the casting bed. A green dot is placed on the plank or panel to signify that the product is quality approved and ready for the next stage. Typically, hollow core is stored in stacks no more than four or five units high. There's a little video demonstration of casting of hollow core plank. Not sure if the sound is coming across, but you can visually see the operation. So this fellow here is putting in or put in lower embed plates to allow this particular product to be welded to something in the field. And then after the plate has been placed, they come back and put a grouting operation. Generally, you got to plug the cells on either side. You don't want to fill the whole plank full of grout. Okay, I believe that's it for that. There are a few standard ways of handling hollow core plank and wall panels. The most basic way to handle plank is by using cables and slings on the product. Slings are typically no more than 12 inches from the ends and should not angle more than 30 degrees. And as an important note here, as you see the lower left image where we have some slings wrapped around a hollow core plank, getting ready to set it in the stacks there, it's very important that whoever is handling the hollow core understands that you always, always have to pick it up from the end. And sometimes if folks want to use a forklift to lift up the hollow core, you got to make sure that the fork spread far enough to the ends that the plank doesn't feel like it's cantilevering from a center point and that could damage the product. A typical hollow core plank utilizes a key to help with distribution of shear loads. Contractors use the shear keys to handle the plank. Special equipment is required for this type of handling. Some but not all producers use embedded anchors. Talk to your local producer to find out if this is how they handle their plank. Embedded lifters are placed during the casting process and typically are tied to lower reinforcement. An erection crew can use embedded anchors to set the plank into position. I find that this does vary region to region, producer by producer. We ourselves will produce a four foot plank or an eight foot plank. The eight foot plank requires lifters, the four foot plank we can use slings. Vacuum lifts literally create a vacuum on the top side of the plank and use suction, they lift the plank into place. This process uses very specific equipment and is not always available. Handling hollow core wall panels differs from handling plank. Most producers will handle from the top and sides. Some use top plates for their top of panel connection and place pins with lifting plates for the side. A two part crane is used in these instances and the panel is tripped in the air, taking it from a horizontal position to a vertical position as you see in the lower left image. Once the panel is vertical, the side cables are let loose and the panel set into place and braced. Sometimes if the panel is short enough, the panel can be tilted on the trailer and will not have to be tripped in the air. Grouting operations. These are a few ways that plank are grouted. A concrete pump with a special metal tube at the end of the hose is sometimes used. This tube is made to fit into the grout key. The advantage of this type of delivery system is that it can be employed on any floor and virtually anywhere. It also reduces mess and cleanup. In the lower right hand corner, a picture shows a special grout buggy being used to deliver grout directly into the grout key. Some crews will use a grout pump and bucket as seen in the upper right picture. In this scenario, a crane is used to lift a grout bucket and pump up to the floor elevation and using a small chute delivers the grout to appropriate locations. Now you might be thinking as you're looking at that image on the left of the fellow pumping grout, doesn't all that grout just kind of go right through the plank and onto the floor below? But no, the way that the hollow core is formed with the key, at the very bottom, just above the chamfer, those points of concrete come into contact and do a pretty good job of sealing that joint. Some of the grout might weep through, but it predominantly stays there. And then the way that they did it with the pump there, you come back with a broom and just sweep the top. Now again, to our local market, or actually it's not just our local market, it's any market that has high seismic factors, but in high seismic regions, typically a cast in place diaphragm will need to be added for seismic lateral forces. So the image that you see with the fellow grouting, if this was one of our jobs in California, everything is exactly the same, but then after that operation, the contractor would come back, tie up a grid of diaphragm steel, and typically you can't really use mesh anymore. It's got to be rebar, number threes, number fours. They'll tie up a grid and they'll pour a three to four inch thick concrete slab on top of all the hollow core that you see here. And that slab acts as the seismic diaphragm for the stability of the structure. Let's take a look at how hollow core is used in two of its most popular applications, floors and ceilings. Depending on size and location, openings and floors and ceilings can easily be cut on site. These details are coordinated by the pre-caster in pre-planning stages. This is a key reason why bringing the pre-caster into the design stage as early as possible is imperative. Some pre-casters create the openings before the plank is covered at the end of production. This obviously requires more coordination than being cut in the field and increases the chance that the opening will be in the wrong location. Standard concrete cutting equipment can be used to cut openings in the field. Our general rule of thumb, just our local ideas of how we do it, is basically any opening that is more than 12 inches by 12 inches will be cut at the plant. Any opening that is less than 12 inches, like the two round openings you see on the upper right, are typically cored in the field. And then whatever penetrations, whether they're cast in the yard or cut in the yard or cored or cut in the field, just need to be coordinated with the pre-caster's engineering department to be sure that the plank is still adequate with those openings. Larger openings can be framed using metal hangers called headers, and the metal hanger will bear on the adjacent planks, thus distributing the load to either side. So if it's really too big, I mean, clearly you can see that one plank in the middle would have no support if the opening was that large. So we structurally frame across it using steel headers. Concentrated loads, such as line loads or point loads, are resisted by more than one slab or one hollow core plank. The grouted keyway joint allows the loads to be shared between the pre-cast planks, and if you have a topping slab, that works even better. If you have heavy concentrated loads, it is recommended you consult with the local pre-caster to confirm the plank strength is adequate. Let's briefly talk about some of the types of systems that are associated with PCI and included in your design manual for the hollow core. Here's a table included in PCI's hollow core design manual, manual 126. As you can see, there are several systems associated with PCI. These systems vary from slip formers to extruders to fixed forms. So what's on the screen here, the manufacturer, those are brand names, and then we have different types and some attributes of those types. Pictured here are generic load tables. Load tables in these manuals, for instance, ensure that designers specify the correct size of slab and proper strand pattern based on dead and live load requirements. They also provide details showing proper bearing and connection methods to load bearing walls or assemblies. Keep in mind that all pre-cast manufacturers hollow core plank is unique, and so are their load tables. The only sure way to determine your specific needs is to contact the hollow core producer and discuss the project needs with them. So yeah, and one other note about load tables, on a pretty regular basis, I will get contacted about existing jobs, jobs that have been in constructed years ago, and somebody wants to modify the building in some way. I've had it from as little as we need to put some more electrical lines through here to we would like to put an elevator through here to, I had one fellow call me and said, I need to put an MRI machine up on the deck and that's 26,000 pounds. Would that be okay? But what I caution about the load tables is that generally speaking, these load tables or a specific pre-caster who has generated their own load tables are really only reporting maximum stranding for the benefit of the user. So if you look up a 10 inch plank, what you're looking at is maximum stranding. And the caution is that if you're looking at an existing structure, you may or may not be looking at maximum stranding in that particular structure. So I would use these as a guideline, use these to get you in the ballpark for kind of estimating the new project, but always contact this specific precast manufacturer if you need detailed information. These details illustrate hollow core plank bearing on different types of material. The left drawing depicts bearing on top of a steel I-beam. The second one is a hollow core plank tucked into the web of an I-beam and the two on the right show hollow core bearing on CMU. Each manufacturer may have particular connection detail that they use. It is well worth the time to inquire about this during the design phase. And again, one West Coast note about the two right-hand figures, in high seismic regions, generally speaking, you would not connect the plank to the wall directly. The wall would have steel reinforcement that would go up and bend into the topping slab. Topping goes to the diaphragm and the diaphragm would dump the load directly into the wall in seismic regions. Illustrated are some connection details for wall panels, both at the footer and the bar choice at the roof. This slide shows the clean lines and open areas that are achievable with the use of hollow core plank. This also allows for future repurposing of the structure if that ever needs to be. Let's discuss some ways hollow core walls and panels can be used in various types of projects. Precast wall panels can be used as a supporting element. The use of precast speeds the construction and enables warehouse manufacturing facilities, such as food packaging facilities, to go up quickly. Hollow core provides a clean, indoor environment that meets stringent USDA requirements and can withstand wash-down processes better than other building materials. Using precast concrete, hotels can be built fire-safe, private, and secure, all within a limited footprint. The new Marriott Courtyard in Troy, New York was constructed on a tight site utilizing 72,000 square feet of 8-inch hollow core plank on load-bearing metal stud and incorporated 127 precast concrete bathroom modules. As part of the mixed-use waterfront district, the hotel reflects the energy of the city's redevelopment while meeting the needs of visitors. Somebody has looked up while staying in a hotel room and observed the familiar 4-foot or 8-foot lines on the ceiling. These lines are the transverse joints of the precast plank. Typically, hotels condition these ceilings with standard paint or popcorn paint. It is also not unusual in some chain hotels to see an unfinished gray ceiling. And we've done quite a few of these out here on the West Coast, and it is always super cool to stay at a hotel and then look up at the ceiling and go, oh, wow, this is one of ours. And we like to think, I'm pretty sure it's true, but we really like to think that the hotels that utilize the hollow core plank, you really can't hear people stomping around, and you can't hear conversations like you can in wood-framed hotels. In single-family homes, hollow core components provide long, clear spans and solid construction. This is ideal for an under-garage workshop or office in that it alleviates the need for supporting beams. Precast concrete homes also withstand high winds, fire, and floods far better than standard frame construction. In the image that's on the screen here, if you look right through the garage door, right above the footer there, you can see the hollow core that is spanning across an opening or a basement in this garage. For multifamily apartments, condos, senior living, occupant comfort from floor to floor, and again, one of the big benefits is sound dampening and also the fire-resistive construction that comes with hollow core. Hollow core is a superb choice for multifamily mixed-use structures due to low sound transmission. Precast concrete provides solid construction and compartmentalizes the units, making them safer than other types of construction and maximizing occupant comfort. What you see here is the CAP, located in Minneapolis, Minnesota. CAP is a building that includes a five-story, 148-unit residential building along with 3,000 square feet of retail space, a 46,127-square-foot cub food grocery store, heated underground parking, and a large public plaza. Precast for this project includes 2,457 lineal feet, 81 pieces of precast columns, 3,743 lineal feet or 158 pieces of prestressed beams, 99,685 square feet of 8-, 12-, and 16-inch hollow core and solid slabs, and 55,200 square feet of insulated and non-insulated architectural precast wall panels. Student housing constructed from precast concrete results in improved sound quality, better life safety standards, and superior durability for walls and floors. In this project, student housing was built using precast and, I'm just not going to be able to do this one, Ataca, New York, that's a Southern California boy trying to pronounce that one, at Cornell University. The lower section of the project was constructed using precast columns, beams, and hollow core plank. The design is referred to as a podium style construction. It has the garage on the lower levels and the building framing on the upper floors. And this is something that we do out here as well, the podium construction, where many times they need a concrete separation between parking and living units, but they also need something that is robust and strong to bolt down shear walls, again, for seismic loads to the upper stories. And all the seismic loads need to go through a concrete system and get resolved into the basement walls below. And we've done quite a bit of testing and gotten some phenomenal values out of Holocore, holding down and holding up and holding down shear walls. The 65,000 square foot Loomis Professional Building in Greenfield, Wisconsin incorporates precast and pre-stressed concrete throughout. The structural frame on the interior of the building is composed of precast columns supporting precast, pre-stressed inverted T-beams. In this case, the floors are constructed at 12-inch thick Holocore slabs running 38 feet with four inches of structural concrete topping. The roof consists of eight-inch thick Holocore slabs, but without a topping slab. The California ISO headquarters, pictured here in Folsom, California, utilizes precast columns and beams with Holocore planks that were left exposed to provide a loft-like quality to the space. The system also allowed large exterior openings for extensive day lighting. The building is equipped with raised access floors and an underfloor HVAC system. Insulated wall panels cut energy use, and the mass of the floor system serves as a heat sink. Pictured here is the Red Bull Stadium in Harrison, New Jersey. The floors of the stadium are 10-inch Holocore plank. 90% of the plank had to be skew cut in order to fit the radiused ends. The designer of this project wanted the solid construction of concrete with the speed of precast. Holocore fit perfectly with their expectations. We also do housing. Housing that requires more stringent requirements, such as prison facilities, benefit from the use of Holocore due to its economical construction, high durability, security, fire resistance, and quick construction. In the image that's before you, it's kind of hard to see. You can see the precast columns and the pre-stressed beams, but the Holocore is up above all of the ductwork and piping. With the extremely sensitive nature of medical equipment, concrete and Holocore concrete planks play a vital role in the overall structural system and stability of a hospital. Additionally, the security aspect and safety requirements for vulnerable populations is a major consideration for medical facilities of all types. Holocore is just what the doctor ordered for these living, saving structures. As part of this grocery store chain, Wegmans, out of Rochester, New York, uses textured Holocore insulated wall panels for their dock door location at the rear of the stores. They previously used CMU, but made the switch to Holocore wall panels due to the relative maintenance-free qualities and structural stability. The smaller picture at the lower left is a texture on the wall, which was made by a roller following behind the Holocore machine. With a heightened sense of safety and security needed in public spaces, governmental structures benefit from the use of Holocore as well. Pictured here is the Freedom Center in Chicago, Illinois. 687 Holocore plank units were used on this project. Combined with precast wall panels, this structure stayed on schedule even in the face of weather-related challenges and has provided the occupants with many years of functional safety. Holocore, when used in conjunction with other precast elements, provides a structure that is both conducive to learning and safe for students. Here you can see the construction phase of the Willow Creek Elementary School in Fleetwood, Pennsylvania. This two-story, 108,000-square-foot project utilized precast wall panels and Holocore floor plank to provide a safe, energy-efficient structure on a compressed construction schedule. A total precast-pre-stress structure offers speed and construction, occupant comfort, durability, sustainability, low life-cycle costs, along with a host of other benefits. In this particular image here, you can see that they spanned over quite a bit of distance with the precast-pre-stress truss system. The truss system is a single-story, truss system. The trusses are there with the diagonals on them. And what is really neat about these trusses is that the truss will support the Holocore plank from the bottom and from the top. So every other floor is column-free in that whole space there, a popular solution when you need column-free spaces. Most structures built under today's code are designed to save life and limb in an earthquake, but not the structure itself. With advances in structural seismic design, total precast structures not only save lives in an earthquake, but can also save the structure itself. Self-riding precast structures, such as a precast hybrid moment frame, enable swift recovery for affected businesses and the wider community. One example of this is the Caltrans District number headquarters, I think that was number seven, headquarters in Marysville, California, which was the first California state office building to feature the precast hybrid moment frame. And looking at the image, the image kind of in the lower middle is an outside view of the hybrid moment frame itself. This is during construction, so those buildings are in the middle of the building. This is during construction, so those steel corbel supports you see are removed after the grouting and post-tensioning operation. This building was a 208,000 square foot, five story class A building, providing office space for 800 employees and a 200 seat auditorium. The use of the precast hybrid moment frame for seismic resistance with hollow core flooring system was key to this feature. The long span moment frames allow for large expanses of glass, fewer interior columns means that more natural lighting, reaching more workers in the structure. And this particular structure, 2,750 planks were utilized for the flooring of the building. Typical size was a 40 inch wide by six inch thick plank up to 42 feet in length. I believe that's a typo, I'm thinking 22 feet in length. Some hollow core units were eight inches thick and localized or localized high loading areas, file rooms, et cetera. And the image that you see on the left, actually both of them, the left and the right, but this is an interior view of that same building that was the Caltrans facility. And a lot of the hollow core was left exposed. A lot of the precast in general was left exposed and that was part of the architectural feature of the building. The HVAC design took full advantage of the thermal mass of the concrete, exposing it to interior as well as the exterior to maximize its benefits. Utilizing precast in this way enhances the thermal lag, reducing peak heating and cooling energy loads and maximizing user comfort. The design team's mechanical engineer estimated that the energy savings from using the thermal mass of concrete was approximately 15% for this structure. The result of this design is a building with an open energy efficient building that achieved a USGBC silver rating. In addition, the total precast elements of the building were erected in only 12 weeks. Let's talk about the benefits of using hollow core and the value it provides to the designer and the owner. Hollow core products reduce cement consumption versus cast in place. This reduction results in a lighter structure which may reduce the size of the foundation needed. And of course, in seismic country, lighter is always better when everything starts to move. Also worth noting is the decreased maintenance costs over the life of the structure. Concrete has proven its worth and is one of the oldest and most widely used building materials in the world because of its numerous benefits. Hollow core is cast at a factory away from the site under controlled conditions. It remains unaffected by the critical path of other construction work. Production begins even before foundation preparation commences, ensuring components are ready for delivery and erection as soon as the site is ready. Once erection begins, site disturbance is minimized. Subcontractors are also able to access lower floor sooner than with other sites, than with other systems, which results in a decreased schedule. And I might add, we do quite a bit of work in very congested urban locations, Los Angeles particularly. And so the choice of using precast and using hollow core comes down to the time it takes to demolish whatever is existing on the site, clean up the site, pour the foundations and then build a new building. Whatever can be done to minimize the time from when what is there is making money to what is going to be there in the future, again, making money. You want to minimize that time and using the precast is the perfect solution for that. While any type of precast concrete exterior offers a wide variety of distinctive looks that can mimic many of the more costly materials, hollow core offers benefits that go beneath the surface. Perhaps one of the most critical benefits to building occupants is privacy. Because the cavities within the hollow core walls and floors act to dampen sound vibrations, it results in less noise transmission between spaces than other types of construction, including conventional wood framing. In turn, this means less intrusive sound from overhead or next door sounds in hotels, apartments or offices. Hollow core floors dampen noise and keep private things private. In essence, hollow core products make for good neighbors. Best of all, the use of hollow core floors and walls together creates a segmented design that better contains fire at its point of origin. This not only helps save lives, it also reduces fire insurance premiums and helps prevent significant property and life losses for both occupants and first responders. Each different manufacturer may have a different product, but the hollow core product that we produce can be rated from one or two or even three hour separation as required. Constructed of inorganic elements, concrete offers a non-combustible environment that helps curtail fire danger and confines the damage into smaller compartments. It offers up to a four hour fire rating and passes a hose stream pressure test, which minimizes damage from firefighting and water. Smoke damage is also reduced because the walls and floors cannot ignite. It is also becoming increasingly popular for insurance premiums to be reduced with a total concrete structure. Love this photo. Another great advantage of hollow core plank systems is the ability to achieve longer spans without intermediate support. This is conducive to massive open spaces and is important with future reuse and repurposing is a topic of concern. Here you'll see a plank being tested for its ultimate load carrying capacity. Producers perform these types of tests periodically to ensure theory of design, meets actual design. So yeah, there's some great advantages here. As you can see, that's a pretty long span, but even more so look at the span to depth ratio. That's a very long span with what looks to me like maybe an eight or 10 inch hollow core plank. Clearly those blocks are very heavy, but what is also being illustrated here is a tremendous amount of ductility in the design. This amount of ductility in these, look how far that thing is deflected. I mean, I'm just kind of eyeballing that's over a foot of deflection and it hasn't failed. It's deflected, it's cracked, but it's still carrying the load. I think that speaks volumes to the ductility and resilience of the product. Not only can hollow core provide resistance in case of fire, it also provides structural protection in the event of a blast and helps with egress routes in case a blast does occur. As seen in this picture, the hollow core plank is still intact and functioning after a blast blew the brick and mortar away. This is a picture from a hotel in the Chicago area that suffered an explosion. While the building was not specifically designed for blast loads, you can see it performed very well. Note a large portion of the bearing wall is gone, demonstrating the effectiveness of the gravity keyways, which is really amazing. If you look at that first elevated floor there, you can see the ends of the hollow core and there's no support. So it's basically just bridging across that in transverse bending, which we don't design for, by the way, but it's nice that it's there. Typically, finishes on hollow core floors are either smooth or broom brushed. Hollow core wall panels, on the other hand, can have various types of finishes. Since most hollow core walls have a relatively thin exterior white, colors can be added for an inexpensive finish. It is also not uncommon for these panels to have an abrasive blast finish, as well as reveals and textures. Various aggregates are used to create varying appearances. Since finishes differ widely between producers, it's always best to ask for a sample prior to specifying a finish. And again, this is a product that looks fantastic, but this is not something that is typically provided in high seismic regions. There's other solutions that we have for wall panels in high seismic. The cost effectiveness of hollow core components is most readily apparent when the building's full lifetime is considered. While hollow core construction may have slightly higher out-of-ground costs than wood frame or other construction methods, savvy builders and developers realize that they must look at the entire life cycle of the building when they're considering which construction materials to specify. This is one of the areas where long-term benefits of hollow core really shines. Hollow core planks are also very compatible. With other types of structural systems, including structural steel frame, cast-in-place concrete, masonry, and light gauge steel framing. A little example of each of these images here. Precast components are erected throughout the harshest weather. Something that I really can't speak of from experience here in Los Angeles, but in the image there, that looks kind of nasty. Limiting delays that slow other construction methods. This advantage results in faster installation and faster completion, as well as less added cushion in the planned timetable to allow for unknown delays. The process leads to less downtime and more control in scheduling other trays resulting in quicker occupancy, less interest on loans and other readily measurable savings. And a lot of hollow core manufacturers that I have visited across the country, a lot of them are indoor facilities. And so they will just keep producing day in and day out right through one of the ones that I visited was Maple Grove, Minnesota. And it gets pretty cold there, I understand. And they just keep producing day in and day out. Our facility in California is in the open, but because of our weather. Hollow core also offers a sustainable solution for construction. The raw materials are typically locally sourced and usually have a high recycled content. Because of the dry cast method and the low water content, as well as an ideal curing environment, cement replacements can be made with fly ash or slag. The pre-stressing steel that is used typically has a recycled content of over 90%. The concrete also provides thermal mass that assists in the reduction of heating and cooling demands. While cement does have a lot of embodied energy and releases CO2 during its manufacture, this amortizes out when considering the long-term service life of the structures and subsequently becomes insignificant when compared to the energy savings a quality structure provides. Studies are also currently being conducted to show that aging concrete actually absorbs CO2. On any project that includes or may include pre-cast products in the design, early involvement of the pre-caster is critical. Not only will the pre-caster provide technical help, they also provide engineering guidance on various issues such as connections and surface finishes. It has been well-documented that early involvement and planning with various segments of the project team has positive cost-saving implications. Pre-cast is no exception. So let's go over a few industry trends. Podium-style construction is use of pre-cast concrete under structure and the placement of the building on top is becoming a widely used construction style, as I mentioned earlier, is popular in California as well. The advantage of this approach is that the lower portion is usually a parking garage area and the concrete provides a fire separation between the cars and the dwellings, which needs to be three-hour. The City Row Apartments in Madison, Wisconsin used pre-cast to provide the underground parking and the podium level for the apartment buildings. From the street view, beautiful townhouse apartments with a large courtyard area are visible, but the underground interior parking and all the vehicles remained hidden from sight. Project included 33,532 square feet of hollow core plank, 51 pre-cast columns, 81 pre-cast beams. We need to think of hollow core as not just the floor system, but also as part of the overall building system. Loads can be added to the plank and cantilever to accommodate some out-of-the-box designs. Pictured here is a design by Stephen Hall Architects at Columbia University for an athletic building. The plank was cantilevered eight feet outside walkway and left untouched on the bottom so that the natural concrete was visible. This illustration shows a system using ducts within the plank to transfer air heated or cooled into the building. Using hollow cores within the plank is not a new concept. Designers have been incorporating them for electrical chase for a while, but the use, of course, as part of the HVAC or energy system within the building is a relatively new idea. This is an example of using the plank holistically in the building. Using the natural heating and cooling thermal mass of the concrete in conjunction with the hollow cores, energy can be stored or used at peak times to reduce overall energy consumption and increase occupant comfort. Pictured is St. James Intermediate School in Horry County, South Carolina. The architectural team at SFL Plus A, Stantec, and Mozingo F Plus Wallace used the hollow core plank floor system as the duct work for the building. This design allowed for a storage of thermal energy in the concrete and a reduction in height of the building by six to eight feet, thus reducing the first construction costs, electrical costs, and maintenance costs. Architect used a geothermal HVAC system with a prefabricated HVAC penthouse, which allowed for the use of only three air handlers for the entire building. The question is often asked by designers, why PCI is so special? The answer, besides being the only institute that oversees prestressing products, is PCI Certification Program. PCI Certification Program is second to none and provides designers with the security of knowing that they will get what they specify. Every PCI certified plant goes through a meticulous quality control process and to ensure a consistent high quality product is produced from each plant. As part of the manufacturing process, each plant keeps and maintains detailed records of all materials that are used in the plant, as well as records of the actual process itself. Each plant has two unannounced audits each year by a third-party inspection firm, skilled and precast technologies. These audits review not only the precaster's records designed in QC systems, they review current projects being produced and look for any errors and omissions by the plant. There are four primary categories for PCI certification. G is category for glass fiber, C is for commercial classification, category B covers bridge components, and category A is being updated and includes a re-categorizing the four sub-classifications. I believe A is for architecture. The guiding manual for Holocore design is PCI's Manual 126, third edition. This manual is available as a free electronic download on PCI's website and the bookstore under publications. For more information regarding Holocore design and case studies, visit pci.org. You will find various design manuals and resources such as connections and PCI periodicals, such as the PCI Journal and Ascent Magazine. And I would like to thank you for attending this presentation about Holocore planks, floors, and walls. And I will now take any questions. Thank you very much, Aaron. That was extremely informative. And we really thank you for taking the time to share that with us today. We do have a few questions that have come in. So we've got a couple of minutes here so you can field some of these. One here says, what are the typical topping slab thicknesses you see in California? Okay, great question. Well, first of all, ACI 318 is the controlling code manual that we must follow for all reinforced concrete design. According to ACI, the minimum is two and a half. And we do see two and a half from time to time, but only for the smallest of buildings or diaphragms. Typically we will see three on Holocore, but three and a half and four are almost as equally seen as well. So I would say the range is generally between three and four inches. Okay, another question that says, when a wall panel has rigid insulation and a concrete topping installed in the plant, how is the topping attached to the wall panel? I would say, and I am sure there's going to be exceptions to this. And I apologize to any manufacturers out here who have a different way of doing this. But I would say in general, that if you have Holocore insulated wall panels, you are in a part of the country that does not have high seismic. And therefore you probably are not looking at a topping slab. So there's a whole host of standardized details for connecting wall panels to Holocore floors. Quite frankly, I'm just not very familiar with those, because that's just not a detail construction that we do here in California. Okay, we have another one here. It says, please discuss formed crown and impacts on toppings. Formed to crown, is that what you said? Formed to crown is what it says in quotes, yeah. So like formed a crown, like a, I don't know if that has any resonance with you. Okay, well, I will take a stab at it. And I apologize if I missed it completely, but I'll take a stab at it. I'm thinking what you're talking about is that all pre-stressed concrete members have a camber to them. When you release the energy of that strand into the pre-stress, and usually the pre-stress is located off center, it's towards the bottom to balance the loading that you're gonna see in service. And so when you release the energy of that pre-stressing, it causes the pre-stress member, hollow core in this case, to camber up. So when that plank shows up at the job site, it's gonna have a positive deflection, so to speak. It's gonna be about half an inch to an inch or so higher at the middle than it is at the ends. And generally speaking, the way that we account for this is when they pour a topping slab, they will use screed pins to follow, say the topping slab wants to be a three-inch topping slab, they'll use three-inch screed pins and the topping will follow the crown or the camber of the hollow core. And over the years and under service loads, that will tend to drop out somewhat, but we don't design them to allow for bellies. They will always be flat or positive. Now, if it's one of those applications, we get these kind of commonly. If it's an application where a flat floor is desired for whatever reason, a retail space or whatever, if the building requires for a flat floor, then we will design the hollow core to have the minimum topping thickness at the center, at the camber where the hollow core is at its highest. And then we will design it to go from say three to three and a half to four inches, so it actually thickens towards the end. And that way the finished floor is flat while the hollow core itself has its built-in camber. Great, well, thank you, Aaron. And I think we're pretty much at time. So I think we're going to call it from here and thank everybody for attending today. And thank you again, Aaron, for taking the time to share your expertise with us. Just a reminder to attendees that you'll be receiving an email from RCEP to download your certificate. Be sure to complete the one minute survey at the conclusion of this webinar. This also provides an opportunity for you to ask additional questions or request follow-up. And finally, please mark your calendars. We've got another free webinar coming up at 1 p.m. Eastern time on Thursday, October 22nd. This one is Accelerated Bridge Construction. The presenter will be Rita Saradarian, Executive Director of Precast Pre-Stressed Concrete Institute Northeast. Please keep an eye out for an email with more details and a link to register. Hope to see you then. So thanks everybody, be safe and be well. Take care.

precast holocore floors

precast holocore walls

Jim Schneider

construction benefits

fire resistance

low sound transmission

holocore in HVAC systems

Aaron Pratt

sustainability

PCI certification