Good afternoon. Welcome to PCI's webinar series. Today's presentation is Precast Pre-Stressed Concrete Piles. I'm Nicole Clow, Marketing Manager at PCI, and I'll be your moderator for this session. Before I turn the controls over to your presenters for today, I have a few introductory items to note. Earlier today, we sent a reminder email to all registered attendees. 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 GoToWebinar 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. If you're the only person at your location, there is no need to complete an attendance sheet, as we already have your information from registration. If you cannot download any of the handouts, please email PCI Marketing at marketing at pci.org as shown on your screen. Please note that all attending lines are muted. The GoToWebinar toolbox has an area for you to raise your hand. If you raise your hand, you will receive a private chat message from me. If you have a question, please type it into the questions pane where I'll be keeping track of them and will read to the presenters during the Q&A period. Also, a pop-up survey will appear after the webinar ends. Today's presentation will be recorded and uploaded to the PCI eLearning Center. PCI is a registered provider of AIA CES and has met the requirements of the AIA Continuing Education System and can offer one LU for this presentation. Any questions about the content of this webinar should be directed to PCI. Credit earned on completion of this program will be reported to CES Records for AIA members. Questions related to specific products or publications will be addressed at the end of the presentation. PCI has met the standards and requirements of the Registered Continuing Education Program RCEP. We can offer one PDH for this presentation. Credit earned on completion of this program will be reported to RCEP.net. A Certificate of Completion will be issued to each participant. As such, it does not include content that may be deemed or construed to be an approval or endorsement by RCEP. With hundreds of attendees for our webinars, it is impractical to prepare individual certificates. As PCI has met the standards and requirements of the Registered Continuing Education Program, we will upload attendance data to www.rcep.net within 10 days and you can print your Certificates of Continuing Education. Your login name at www.rcep.net is your email address, so please do not leave that blank if you are completing the sign-in sheet. We need your email address to get you your certificate for this course. I will now turn the controls over to Katrina Walter, Project Manager with WSP USA. Good afternoon. My name is Katrina Walter and I am a Project Manager in the WSP Maritime Group and a long-serving Associate Member of PCI. I am also currently Chair of the PCI Pre-Stress Concrete Piling Committee. My fellow speakers and I are so excited to be presenting today on the use of Precast Pre-Stressed Concrete Piles for Deep Foundations. Precast Pre-Stressed Concrete Piles, or PCPs for short, are the preferred choice for durable and resilient deep foundations in building, bridge, and marine applications. The introductory materials presented in this webinar will allow attendees to recognize Pre-Stressed Concrete Pile applications for their future projects, understand the fabrication process of Pre-Stressed Concrete Piles, identify key raw materials and concrete mix attributes, and understand Pre-Stressed Concrete Pile handling, transportation, and installation considerations. At the end of this webinar, attendees will be able to easily define the advantages of Pre-Stressed Concrete Piles and understand the basic structural design considerations through their life cycles, as well as learn how to access the Precast Pre-Stressed Concrete Institute resources for additional information. But first, let's begin with a brief background of the Precast Pre-Stressed Concrete Institute. PCI was legally chartered as the Precast Pre-Stressed Concrete Institute in June of 1954 in Tampa, Florida, before eventually moving its headquarters to Chicago in 1959, where it is currently based today. PCI is made up of committees and councils which direct PCI's activities and continually add to and update the Institute's body of knowledge. Since its founding, PCI has been responsible for many industry innovations, including the development of long-line casting beds, which made Precast an affordable product because of repetitive manufacturing. Various advances in admixtures have also been made which allow producers to turn their beds over quickly, and accelerated and controlled curing systems have been developed to ensure concrete strength is achieved in a timely manner. PCI is looked at as the authority for Precast Pre-Stressed Concrete products, so much so that 45 state DOTs recognize PCI certifications. As a result of early innovations and the growing interest in Pre-Stressed products, PCI developed a certification program revolving around standard quality control procedures. The industry recognized the need for quality above all else, and it is this quality system that provides assurances to owners, contractors, and specifiers that a manufacturing plant has been audited for its ability to produce quality products consistently. PCI certification requires, among other things, that the facility be audited once every six months and has a two-day inspection of the facility. These audits are unannounced and are performed by a third-party inspection agency. A typical audit will review a plant's records of design and production, as well as materials that were used in the product. PCI has also instituted a Certified Erectors Program, which ensures the Precast Pre-Stressed products that are made by a certified plant are installed as designed and within PCI tolerances. PCI certification is the industry's most comprehensive certification program for both a plant and its personnel. PCI is also IAS-accredited. Along with the certification process for the actual fabrication and installation of Precast, PCI also supports industry-leading research efforts. As a technical institute, PCI develops, maintains, and disseminates various publications for the design, fabrication, and erection of Precast concrete structures and systems. They accomplish this by conducting research and development projects in concert with universities and research laboratories nationwide. They also publish a broad array of technical resources, including design manuals, state-of-the-art reports, periodicals, and more. This is a map of affiliate chapters and partners of PCI. Each area of the country has an executive director who can assist with additional information relative to their specific region. Please contact them with further questions. As we move through our presentation today, let's be mindful of our learning objectives. Our speakers will review the definitions of unreinforced versus reinforced versus pre-stressed concrete elements and what pre-stressing is, as well as review more specific structural design considerations for pre-stressed piles, including pile types, production methods, pile handling, and transportation and pile installation. They will summarize the advantages and benefits of using pre-stressed piles in your projects and provide a brief look at some of the structural design considerations for those projects. They will highlight a case study where pre-stressed concrete piles have been successfully incorporated and will conclude with a review of additional resources from PCI and where you can acquire that information. At this time, I would like to introduce today's presenters. Jim Parkins is Vice President and Director of Marketing for Concrete Technology Corporation in Tacoma, Washington. He has been involved in piling applications for 18 years, developing, estimating, and contracting for their use in marine structures and building foundations. Roy Erickson is President of Erickson Technology Roy Erickson is President of Erickson Technologies Incorporated, a full-service structural engineering firm specializing in precast pre-stressed concrete design. He has been responsible for the structural analysis, design, and detailing of many projects that incorporate precast pre-stressed concrete piles. Thirdly, Justin Yard is Vice President of Sales for Gulf Coast Pre-Stressed Partners Limited. Supporting his company's facilities in Mississippi and Texas, Justin is responsible for their estimating, sales, and contractual negotiations. At this time, I would like to pass the presentation over to Roy. Before we get too much further along, let's take a moment to define what pre-stressed concrete is. Later in this presentation, we'll go into some detail on the engineering aspects of pre-stressed concrete piles, but for right now, let's just try to get a basic understanding about pre-stressed concrete. Concrete can be classified as either non-structural concrete or structural concrete, which is the focus of our discussion here. Structural concrete is concrete that is capable of carrying or transferring significant structural loads. For purposes of discussion, we can organize structural concrete into three basic types on reinforced concrete, reinforced concrete, and pre-stressed concrete. Now, what do we mean by each of these? Unreinforced concrete is simply concrete without any reinforcement in it. While it behaves well in compression, it behaves very poorly in tension. Very low levels of tension lead to cracks, resulting in a member with no load carrying capacity at all. It also lacks ductility, so there is no early warning prior to failure. Similar to a piece of chalk breaking in two, unreinforced concrete is not typically used for structural members. The downside of reinforced concrete is that, while it can carry heavy loads, the member still cracks. Concrete cracking can cause a significant reduction in member stiffness, which leads to serviceability concerns, including diminished aesthetics, increased deflections, and exposure of the reinforcement to corrosion. To reduce or eliminate cracking and maintain member stiffness, which is important under sustained loading, members can be pre-stressed with pre-stressing strand. To maintain member stiffness, particularly during sustained loading, members can be pre-stressed with high-strength pre-stressing strands. In the case of a simple beam with transverse loading, as shown above, tension will develop in the bottom portion of the beam under load. This tension in the concrete can be offset with pre-compression in the concrete, such that the net result is low or no tension in the concrete. Pre-tensioned concrete elements can be designed to limit or prevent cracking under surface loads. In the case of a concentrically applied pre-stressed force, as shown above, a permanently applied compressive axial force is applied, but with no accompanying moment. Pre-stressed concrete piles are an example of a concentrically pre-stressed member. This photo shows an ordinary rebar and a 7-wire high-strength pre-stressing strand. Both types of reinforcement are made of steel and both are about the same stiffness. However, rebar, also known as mild steel, yields at a stress of about 60 KSI, while pre-stressing steel has an ultimate strength of about 270 KSI. Per unit area, pre-stressing steel can carry several times the force of rebar. Note in the graph above that while rebar has more strain capacity than strand, strain is typically not a governing factor in pre-stressed design. And pre-stressing steel has other important properties too as compared to rebar, which will be discussed later in the presentation. And now to Jim. Thanks, Roy. Let's discuss where concrete piles are used, specifically in deep foundation applications. Deep foundations are required where shallow soils are inadequate for bearing capacity or where there might be property line issues. Loads are transferred from at or above grade down to the soil layer that's capable of resisting the required loads. This can be accomplished by axial bearing, pile-side friction, or a combination of both. Piles are commonly used to support pier or wharf structures built over the water. There are multiple examples of common deep foundation types. Drilled shafts, which are sometimes known as caissons or drilled piers. They are cast-in-place concrete formed by pre-drilling a hole and may or may not have a steel casing. They are typically used in large diameter applications. Another form of cast-in-place concrete pile is auger cast used in smaller pile sizes. Reinforcement is typically only used in the top portion of the pile. Both of these CIP methods require the extraction and disposal of soil. Stone columns are columns of crushed stone and are used to improve the soil resistance of the site and enable heavier loads to be transferred deeper into the soil. Driven piles can be wood, steel, or prestressed concrete. They are driven with an impact or vibration hammer and densify the surrounding soils by displacement. A common pile is the square shape as seen on the left. Octagonal piles, as seen on the right, are used on the west coast. Cylindrical, solid, and hollow piles are sometimes used in marine applications or bridges. Typically, strand patterns are symmetrical about the axes, but asymmetric patterns are possible if needed in a specific application. Any shape is achievable with the flexibility concrete casting offers. It is recommended to consult with your local producer for available pile types and options as well as the cost for custom applications. We will now walk through the life cycle of a pile from fabrication to handling to installation. Prestressed concrete piles are fabricated in dedicated permanent plants. Common attributes of a certified manufacturing plant include anchored bulkheads and casting beds built to resist millions of pounds of pretensioning force, long line casting beds for producing multiple products in one bed concurrently, purpose-built yard with handling equipment and loadout cranes, self-contained operations with minimal outsourcing, which is critical for daily production, train certified personnel, and proximity to multi-modal transport to deliver products by road, train, and water. Precast plants provide quality control during the manufacturing process. Owners or contractors typically provide quality assurance. Plants should be PCI certified. The PCI certification program is a rigorous process for both the plant and personnel. Certified plants provide verification that they follow a robust quality system covering all aspects of manufacturing. This information is contained in the plant's quality systems manual and that they employ a staff of PCI and ACI certified inspectors and technicians whose tasks include pre-pour inspection, intentioning verification, fresh concrete testing, hardened concrete testing, as-cast inspection. The plant quality system ensures that the concrete mixing, placement inspections, stressing verification, and equipment are per specification. For the past 70 years, millions of pre-stressed piling have been installed with well-documented longevity and the harshest exposure conditions. The fundamentals of long service life are utilization of high-strength, high-performance concrete with low water binder ratio. High-performance concrete assures low porosity which limits chloride ion penetration and also sufficient cover over reinforcing. These simple economical principles will exceed durability requirements for most projects. For unique projects requiring extreme service life, there are premium concrete enhancements and coated reinforcement options. Consult with your local producer for options and pricing. Engineers are encouraged to contact local producers early in the process to attain concrete mix information as local material supplies are regionally distinct. Pre-cast concrete piles typically use a high-performance concrete mix resulting in a strength of 6 to 10 ksi at 28 days. These mixes often have high total cementitious content, low water cement ratio, and high range water reducing admixtures to enhance workability in the mixes with low water content. Type 3 cement, we call it high early, is recommended in pre-cast applications. This cement helps to obtain the high overnight strength required to transfer the pre-stressing force overnight. Type 3 is critical to maintain production efficiency and minimize costs. Pre-cast mixes tend to focus on release strengths more than 28 day strength because the pile needs adequate strength for the imposed pre-stress force at the time of transfer. 3.5 to 5 ksi is a typical range for piles and keep in mind that 28 day strengths are often exceeded since the mix design is focused on attaining high strength in a short period. Pozzolans such as fly ash and slag are often used in addition to standard cement. These cementitious materials improve workability and durability. Silica fume is occasionally specified for enhanced service life. However, this significantly increases costs and may compromise workability and finishes. Corrosion-inhabiting admixtures may be available for enhanced service life. These admixtures provide a chemical barrier that delays onset and acceleration of corrosion. Many plants are using self-insolidating concrete or SEC. SEC flows under its own weight, eliminating the need for vibration and provides better finishes. The net result is a reduction in labor both for placement as well as sacking of the piles after curing. SEC can be attained with minor variation to conventional mix design or through the use of viscosity modifying admixtures. The differences between conventional and SEC concrete are illustrated in these two photos where we measure the slump of conventional concrete above versus the spread of SEC concrete below. An interesting concrete material gaining traction is UHPC, ultra-high performance concrete. PCI has several initiatives researching different sizes and shapes of UHPC piles. Whereas typical mixes are composed of cement, fine and coarse aggregate, UHPC uses cement, pozzolan, fine aggregate, and steel fibers. The result is a denser, less permeable mix, achieving strengths of 18 to 24 KSI. Consult with your local producer for availability of UHPC. The key reinforcement in piling is prestressing strand, which is a game changer for reinforced concrete design. Early types of reinforcement could not be prestressed. These materials resulted in a loss of prestressing force as the reinforcement would relax over time. Advancements in material science led to the development of 270 KSI strand about 30 years ago. Strand sizes could range in diameters from 3 eighths to 0.7 inches, with a common size of a half inch in piles. One half inch strand is pre-tensioned to 31 kips. Confinement reinforcement is used throughout the pile length. Uncoated, smooth, or deformed wire per ASTM 1064 is typically used in lieu of conventional rebar. This material has a yield strength exceeding 70 KSI. The spiral diameter and spacing are a function of in-service design. Most piles utilize uncoated reinforcement. There are premium reinforcement options for extreme service life, which can be 2 to 10 times higher in cost than uncoated material. Piles are cast with multiple pieces on a long line casting bed, which greatly increases efficiency and lowers product costs. Typically, pile sizes are standardized and steel forms are used to ensure the cross-section dimensions are precise. Utilizing the available steel form sections of your local producer is recommended since standard forming cost is amortized over numerous projects. However, for large projects, consult your producer as the purchase price of a new form may make sense if it optimizes the design of a large quantity of piles. Pre-tensioning techniques vary by plant and or product. The primary method is to pre-tension strands against permanent embedded bulkhead in the casting bed. The pile form sits on the bed and is independent of the strands. Self-stressing forms are sometimes used. In this system, the pre-tension force is resisted using the steel pile form cross-section. Pre-tensioning is applied either one strand at a time, or in more complex systems, multiple strands at a time. Proper pre-stress force in the strand is verified by measuring the theoretical strand elongation to actual elongation, as well as correlating the gauge pressure of the hydraulic stressing ram to the total force in the strands. After strand tensioning is complete, spiral reinforcement and other embeds are placed around the strand and secured in the form. Positional tolerances are checked. Embeds are secured with tie wire and other means to ensure they do not displace under the concrete fluid pressure during pouring. Concrete mixes are placed with overhead buckets or specialized delivery vehicles like the one shown above. Conventional mixes require internal and or external vibration for consolidation. As mentioned previously, self-consolidating concrete flows under its own weight, eliminating the need for vibration. Piles are generally cured by applying external heat, accelerated curing. Since cement hydration is an exothermic reaction, this accelerates strength gain. Hydrations include steam, electric, or radiant heat. So accelerated curing eliminates additional curing once the product is removed from the form because hydration is complete. Accelerated curing is critical to attain release strengths needed to detension the strands. Once the concrete has been placed, cured, and reaches the required release strength, the strands are detensioned. Pre-stress transfer methods can include detensioning multiple strands at one time with an engineered release system or cutting individual strands in a sequential pattern to ensure equal incorporation of pre-stress force into the pile. As mentioned on prior slides, release strength is a calculated value, not an arbitrary value such as a percentage of the 28-day strength. Unnecessarily high release strengths can significantly increase costs by disrupting the daily production cycle. Once the strands are detensioned, the product is removed from the form and moved to the storage yard. Embedded steel strands are typically used for plant handling and loading. Piles are not only designed for final service loads, but are also checked for stresses induced during handling, storage, and transportation. Piles need to be designed for plant handling, transportation, and lifting and rotation at the site. At the plant, either an overhead crane is shown above on the right, or a travel lift straddles a casting bed to remove the piles from the casting bed. Piles are typically handled in the yard by specialized straddle cranes such as a MIJAC or travel lift. It's common to use between two to four pick points based on the structural properties and lengths of the pile. Piling is typically stored in a stacked condition to save space, but is limited by overhead crane height. Drainage supports are placed at multiple locations along the pile length to ensure creep deformation does not occur. Drainage is also analyzed to ensure it can support multiple piles and to ensure it does not settle into the supporting surface. Just-in-time delivery is optimal to ensure yard space utilization is not excessive. Transportation is a coordinated effort based on the capabilities of the pile producer and the equipment available in the region. Transportation by truck is possible for piles up to 200 feet in length with the proper equipment as long as the configuration does not overstress the pile. The example in the lower right utilizes rocker bunks to evenly support the pile at four locations. Barge transportation is also common on marine projects and can provide significant savings versus truck transport. Long cylinder piles are subjected to highly localized stresses during the various stages of handling and transportation. Movement of the pile results in highly dynamic loads, so impact factors must be considered. Stresses must be checked against allowable limits in the code. These limits are set to prevent cracking during handling and transportation of the pile. Designers may need to add additional support points or lifting points if circumstance require. Resources for calculating the correct handling procedures will be discussed at the end of this presentation. Now we'll discuss some of the basics of pile installation. The installation of pre-stressed concrete piles requires a specialty operator who is experienced in selecting the pile hammer and the crane size to match site logistics. There are a lot of factors involved such as the size, type, and length of the pile, the required driving capacity of the pile, whether they're vertical or battered piles, and the type of substrate. The number of piles and the layout of the group is also a major consideration. Site limitations must also be considered, including impact on existing structures and noise and vibration impacts to both human and animal populations. A more in-depth review of pile installation can be found in PCI Manual 133. The most common method of installing pre-stressed concrete piles is by driving with an impact hammer. Commonly used hammer types are air powered, diesel powered, and hydraulic powered. The hammer selection is driven by pile type and site conditions. Cushion selection and design is also key in preventing damage to the pile during driving. Experienced geotechnical engineers may complete wave analysis to determine hammer selection, predict installed pile capacity, and expected driving resistance and driving stresses. Pile test programs are also sometimes required to verify design and installation. This slide illustrates less common installation aids for tougher driving conditions. The image on the left demonstrates water jetting to break through granular soil layers. Another option is use of short steel stingers to break through hard layers and protect the tip of the pile. Pile driving, whether wood, steel, or precast concrete piles, creates noise and vibrations that can affect the local population and wildlife during construction. Project-specific pile driving vibration monitoring may be required for impacts to existing structures. Some projects also include windows for installation dictated by wildlife migration patterns. Designers should factor procurement into these project windows. The industry has deployed many techniques over the years to reduce these effects. Consult with your local producer and pile installation contractor for potential options. On this slide I have a short video demonstrating impact hammer installation of a marine pile. Sometimes a pile needs to be longer than what can be transported or handled by the driving rig. There are several options for splicing piles. The examples on this slide include mechanical splices or epoxy-dell connections. Splicing designs can be for axial loads only, for axial and full moment capacity, or for any imposed loading conditions. Field adjustments are often necessary to achieve the desired elevation of the top of the pile. Pile cutoff is common, using either manual methods or hydraulic shears. For pile-to-pile cap connections using grouted mild reinforcement, grout ducts may need to be longer than required by design to account for cutoff. Pile buildup is used for piles that are driven lower than the desired elevation. CIP concrete is formed in the field with rebar extending from the precast pile. Lowering the pile cap is another option for dealing with overdriven piles. There are multiple ways to integrate the pile into the deck structure. Connection details between the head of the pile and the pile cap depend on whether the pile will be subjected to axial compression loads only, to axial tension loads, or to a combination of axial loads and bending moments at the pile cap interface. The image on the right shows potential details for moment transfer. I'm now going to hand this presentation back to Roy to talk about the advantages of concrete piles. Thanks, Jim. With more than seven decades of successful implementation across the country, there are many advantages to using precast prestressed concrete piles. Advantages of prestressed concrete piles include standardized sections, minimal concrete waste, and high-performance materials, which result in high structural efficiency and lower initial cost. No periodic coating or maintenance required, which means lower life-cycle cost. From small-diameter pin piles on land to 200-foot-long single-piece marine piles in saltwater, PCPs are highly adaptable to project requirements. PCPs support a high level of sustainability by featuring local materials and labor, long service life, reusable formwork, and reduction in concrete and material waste. PCPs are manufactured under very high-quality control, using nationally recognized QA-QC procedures. Finished piles are visible prior to installation. PCPs exhibit high structural efficiency. High-strength concrete and prestress allow for smaller cross sections. Greater capacity means fewer piles with smaller footprints. Confinement reinforcement runs the full length of the pile rather than just in the upper portion. High lateral stiffness is inherent in the product. PCPs have a long design life. High-performance concrete means low permeability. Permanent axial compressive stress provides excellent crack control. This combination results in resistance to moisture intrusion and corrosion. There is accelerated construction with precast concrete elements. While the site is being prepared, the pieces are manufactured, inspected, and staged for delivery. When the products are delivered to the job site, the time required is less, and the construction schedule is accelerated. There are other benefits, too. Workers are exposed to fewer unsafe conditions at a plant than on a job site. Also, the process at a plant is greener through the use of local materials, local labor, and less waste. The accelerated construction benefits provided by PCPs include prefabricated elements, parallel construction activities, minimal job site time and equipment, increased on-site installation rate, and handling and installing precast piles is easier than coordinating concrete truck logistics and traffic, and displacement installation eliminates the need to dispose of spoils. An important attribute of driven piles is that every driven pile is essentially a tested pile. Most of the time, the worst loading is during driving, at least with regard to tensile stresses. If the pile makes it through installation, you've essentially proofed that pile. The photo on the right shows an impact hammer driving a rectangular pile. With each strike of the hammer, the pile develops skin friction and a resistance to the applied loading. Once the pile reaches the required loading or resistance to the applied force, the driving process stops. Each pile has therefore been tested to verify that the specified load has been attained. A successful driving process also proves that there were no hidden obstructions or that the pile had broken during installation. There are several disadvantages associated with using other pile types on your projects. These photos are examples of poor consolidation of concrete or grout mixes during installation of cast-in-place or auger cast piles. Inherent to any cast-in-place pile or drilled shaft is the possibility that when complete, the pile or shaft is not cylindrical and has flaws. Visual inspection of the pile in place is not always possible. With auger cast or drilled shafts, the contractor runs the risk of the piles experiencing necking, cracks, breaks, or bulging during installation. Poor installation methods may lead to honeycombing and exposed reinforcement. None of these happen with prestressed concrete piles. Construction for these types of piles also requires a lot more on-site construction congestion with the addition of constant concrete haul trucks and soil removal equipment. The on-site construction schedule also tends to be longer for other pile types as cast-in-place concrete and grout materials must cure before casings or other formwork can be removed or before adjacent piles can be installed. For these other pile types, there is no pre-compression, so they have much lower tensile capacity than prestressed piles. The higher strength mixes associated with precast prestressed piles also results in higher shear capacity than these other piles. Drilled-in installation also requires removal of soil, which is problematic, and is extremely expensive as the soil is contaminated. Drilled-in installation is not advisable if groundwater is present at the site. With steel piles, extended service life requires expensive supplemental coating, the installed price is higher, excessive noise is caused for marine life during installation, and cost and availability are highly unpredictable. With timber piles, extended service life requires undesirable coatings to prevent organism degradation, and they have limited capacity with respect to other types. This presentation is not meant as a deep delve into the structural design requirements of prestressed concrete piles, but as an overview of important considerations in the design process. A prestressed concrete pile goes through several stages during production. Pile design must consider each of them and not simply the final in-service condition. Each stage subjects the pile to a unique set of loads. For instance, during manufacturing, piles are cast horizontally, strands are cut, and the pile is moved to a temporary storage area when the concrete is at its lowest strength. During the handling and storage stage, the pile is stored in a horizontal position and subjected to bending moments caused by self-weight. During transportation, the pile is subjected to impact or dynamic effects. When the pile arrives at the job site, it is rotated vertically and driven. This is typically when the pile is subjected to the highest tensile stresses of its life due to axial forces down the length of the pile caused by the driving hammer. Once the piles are installed, they begin to carry their in-service axial loads as well as lateral design loads that may be quite high, especially in high seismicity regions. The pile engineer must review several pile capacities during the design process. Pile axial loads, both tension and compression, flexural or bending moments from lateral loads as well as eccentric axial loads, and various combinations of axial and bending moments. The pile engineer must design for factored demands as well as unfactored serviceability requirements. While the axial compression capacity of a concrete pile is reduced by the effect of prestressing, the flexural resistance of a pile at both the service and strength limit states is significantly improved by prestressing, and deflections of the structural system are reduced. The location of maximum moment in a pile is dependent on several factors, including the properties of the supporting soil, the properties of the pile, and the degree of fixity between the pile head and the cap or footing. The graphics shown are representative of how a geotechnical engineer may present a pile's axial and bending moment requirements. Soil layer parameters play an important role in these calculations, and therefore an important part in the size, reinforcement, and tip elevation of the pile. The pile engineer performs several calculations in concert with the geotechnical engineer to complete the final design of the piles. Three major components of pile design include service stresses, ultimate strength, and serviceability limitations. This slide depicts the stress-strain distribution across a square prestressed concrete pile, subjected to a moment at the top of the pile. The pile engineer verifies that the pile capacity exceeds the pile demands and that the pile's supported structure does not see excessive deformations or visible cracking. Transverse reinforcement typically consists of spiral reinforcement to provide confinement for axial loads and to provide ductility for lateral loading. It is also required along the length of the pile to control longitudinal cracks, which may form during driving, handling, or under design load conditions. As a side note, UHPC piles may not require transverse reinforcement in areas of low to moderate seismicity. The size and pitch of spiral reinforcement may vary along the length of the pile. For exceptionally long piles, continuous spirals may need to be spliced together to keep the confinement continuous down the entire length. Adequate concrete cover is critical for durability, but consider that increasing cover reduces moment capacity by narrowing the strand pattern. Prestressing strand patterns are generally concentric for most piling applications, with the exception of fender or guide piles, which may have horizontal loads only and act more like a beam than a column. Piles are generally stripped from their casting forms using embedded lifting eyes consisting of unstressed 7-wire strands bent to shape in the plant. Mild reinforcement is seldom used within the length of the pile other than at connections such as the head of the pile or at a splice. There are numerous ways to connect the pile to the pile cap depending on the demand and fixity requirements. Examples include a fully embedded pile head, exposing pile reinforcement for pourback in the cap, and reinforcement bars grouted into ducts in the pile after driving. The design of precast concrete piles, or any pile, relies heavily on the information provided by the geotechnical professional. Design for pile-soil interaction is dependent on many variables, including soil properties as determined by a site, subsoil investigation, and or laboratory tests, installation methods, and the pile arrangement. It is important that the geotechnical professional and structural engineer work together in conjunction with the local precaster, owner, and contractor to consider options and economics. Look at it as a partnership to determine the best solutions. The geotechnical engineer should be familiar with the geology of the region and the project requirements. Piles are not just designed to meet nominal load carrying requirements, but must also meet serviceability requirements for bearing, foundation settlement, and lateral displacements. The ability of a single precast concrete pile or group of piles to resist lateral loads in their bending moments is well understood in the engineering community. In addition, the structural design must consider the environmental conditions to ensure the mix and materials meet durability and service life requirements. And now to Justin. Thank you, Roy, and thank you all for joining us today. The next few slides provide a couple case studies that highlight prestressed concrete piles' usefulness and efficiencies, and why project owners continue to utilize PCPs in their projects. The Lake Pontchartrain Causeway, also known as the Causeway, which connects New Orleans to the North Shore in St. Tammany Parish, holds the Guinness World Record for the longest continuous span over water in the world. The original causeway was built in 1956 and has 2,246 spans, while the second parallel bridge opened in 1969 and has 1,506 spans. The original bridges consist of over 9,054 inch spun-cast post-tensioned cylinder piles and also features an all-precast method of construction utilizing precast caps and spans that are monolithically cast with precast, prestressed concrete girders, decks, and rails. During Hurricane Katrina in 2005, a total of 17 spans were lost, however, the piles remained and were structurally acceptable, but with over 40,000 vehicles traveling across the bridge every day, there is approximately 10 breakdowns per day and 180 crashes per year. Therefore, the GNOEC decided on a major safety upgrade by adding 12 1,008-foot safety bays at multiple locations along the bridge. The project owner and team elected to go with the 54-inch spun-cast cylinder pile, which has the same overall circumference as the original 9,000 piles. However, the new pile have a 6-inch wall, while the original have a 5-inch wall. This added coverage ensures the new safety bays will perform as long or longer than the original structure. Spun-cast piles are spun in 8 and 16-foot sections and once cured, the sections are post-tensioned together and grouted. Once the grout achieves the necessary strength, strands are cut and released into the pile and at that point, the pile is considered a full-length prestressed concrete pile. The safety bay construction included adding one 54-inch cylinder pile at each bend. The caps were cast with a 5-foot cage extending out of the bottom, which was inserted into the pile void, and then connecting the pile and cap with self-consolidating concrete through a void left in the cap, which ultimately plugged into the pile 5 feet 2 inches. The contractor utilized an off-site, long-line 1,008-foot fabrication bed to assemble the prestressed girders and cast 8-inch decks on the span units. The assembly process allowed the contractor to ensure vertical adjustments and alignments were correct with as-built conditions, therefore bringing efficiency to the project schedule, limit disruptions to the existing traffic, and also provide enhanced safety during construction. Loaded barges were steered into position by tugs and secured so that each span in the bay could be unloaded and placed into position using self-propelled modular transporters, or SPMTs. All final horizontal and vertical geometric adjustments were made by the hydraulic jacks on SPMTs so that each span would fit exactly to the desired position in the existing structure. The only cast-in-place portion of the project was the capped pile and capped-to-existing cap connections. Many liquefied natural gas and petrochemical facilities along the southern states consider driven prestressed concrete piles to be the answer to their defoundation needs. Owners, EPC contractors, and pile drivers have seen their projects succeed through the high volume, quality, and safety requirements and design capacities concrete pile offer. Based on project needs and site conditions, concrete pile can offer advantages over other methods. The following list are some of the advantages prestressed concrete pile offer. Material cost is generally 30% up to 50% less than that of steel, while maintaining similar equipment and labor installation costs. Significantly reduced truck traffic entering the project versus cast-in-place piles where concrete needs are considerably more. Concrete pile can be driven adjacent to the previously driven pile immediately, whereas cast-in-place piles typically require a minimum of 24 hours of cure time before installing adjacent piles. Concrete pile installation equipment moves around on timber matting, while cast-in-place pile often require geogrid and up to 24 inch of base material to support their equipment, which has major cost and time implications. Concrete pile do not produce drill spoils, while auger cast piles require these spoils to be properly tested, loaded, and hauled off, which can be very expensive. Concrete pile installation rates generally exceed that of cast-in-place piles, resulting in a more favorable schedule. Concrete pile generally possess a higher resistance to design bending forces due to the structural properties with the use of prestressing strands as opposed to grade 60 rebar cages typical for cast-in-place piles. Pile sizes, lengths, and designs can be modified per project needs by utilizing different concrete strength, strand, size, quantity, spiral, and pitch. For example, most of DOTs and private projects use half-inch low-relaxation strands, however half-inch special or 0.6 can be used to offer higher moment requirements. Concrete pile offer a variety of different pile head connections that have been proven effective for aggressive uplift and lateral requirements. Port Arthur LNG Phase 1, located in Port Arthur, Texas, is a natural gas liquefaction and export terminal under construction that will produce up to 13 million tons per annum of natural gas. The owner, SEMPRA, and EPC contractor, Bechtel, elected to use 18-inch square prestressed concrete piles for the deep foundations on the natural gas liquefaction trains and LNG storage tanks. With over 2.6 million linear feet of 18-inch pile, the Port Arthur LNG project's production and delivery schedule required multiple producers, and each producer were tasked with satisfying rigorous project specifications. Each of the materials within the pile design not only had to meet quality standards, but also had to meet the intense schedule demands. With prestressed piles, the pile drivers are able to stage piles on-site, which allows them to have inventory for their crews to never run out, which also allows them to have excess piles, giving pile-driving crews the opportunity to drive more than their expected quota. This is a massive benefit, and a testament to all the successful driven pile projects that have been completed on time or early, and within budget with minimal cost overages. The supply chain of a prestressed concrete pile producer is an outlier that provides the highest possible quality and efficiency to a project owner, contractor, and pile driver. Vetting the material suppliers through testing, financial capabilities, and service allows for concrete pile producers to enter into contracts with project owners with confidence that the assembly line production process can be performed within an agreed-upon price. To meet the schedule for Port Arthur LNG, all pile producers daily combined materials, including cementitious and steel materials, added up to approximately 64 total flatbed and tanker loads. Time for a little comparison. With skin friction surface area of an 18-inch precast pile and a 24-inch auger cast or displacement pile being within 4.5%, also considering potential factored moment capacity similarities, a general comparison can be made for a pile-to-pile replacement between the two types of piles. Please note that the final design comparison should include all loading demands acting on the piles to include lateral loads, moments, compression, tension, along with type of pilehead fixity and allowable pilehead deflection criteria should also be determined. Another note, majority of DOTs require no more than 6.0 KSI, however, many private projects have requested higher concrete strengths to aid with drivability. As we compare the concrete cubic yardage needs on a Port Arthur LNG type project between a prestressed pile and an auger cast or displacement pile, especially considering we are only adding a 10% concrete overrun of theoretical volume to the cast-in-place pile because these overruns can go 50, 60, 100% or more depending on soil conditions, the concrete needs is almost 40% more in a cast-in-place pile than that of a prestressed concrete pile. If cast-in-place piles were utilized, this comparison shows a minimum of 106 loads for displacement piles and over 130 loads for auger cast, including spoils, would be needed on-site for Port Arthur LNG's aggressive schedule. Prestressed concrete pile provide unmatched supply chain quality and efficiency, coupled with reducing concrete which also reduces carbon dioxide emissions, is proof and recognized by all successful high-profile, high-volume projects prestressed concrete pile have been a part of. To conclude today's presentation, we want to ensure everyone knows where to find the various resources available to provide guidance for the design, detailing, and specifications of precast concrete piles. PCI provides a variety of resources to support the precast prestressed concrete industry. Visit our website at www.pci.org for a full list of publications. Registered PCI members receive full access to online resources and discounts on the purchase of designed handbooks and manuals, as well as subscriptions to various PCI periodicals and journals. Standardized details for piling were first published in the 1960s by members of the bridge community, and many of these details are still in use today in areas of low to moderate seismicity. The first PCI recommended practice was published in 1977, and PCI continues to publish updated design recommendations, including documents that provide current, state-of-the-art confinement and spiral details for pile designers. And on a personal note, over the last six years, my PCI Piling Committee, an amazing voluntary group of educators, researchers, manufacturers, suppliers, and engineers, have been working towards one goal, to write and publish the first PCI specification on the design and construction of precast prestressed piles. So I am pleased to announce that the ANSI PCI Standard 142 was recently published in July of this year, and you can find it on the PCI website. And of course, there are other organizations, including ASCE, AASHTO, and ACI, that continue to publish other, more specific pile-related design specifications and codes for your use. As a designer, you must consider all local or state specifications governing the use and availability of certain products or materials used to construct your prestressed concrete piles. The PCI resources, specific to prestressed pile design and installation, have been gathered in a central location on the PCI website. Please visit us at www.pci.org forward slash how precast builds forward slash component forward slash piles. Beyond the recommended practice and new pile design specification, there is also a list of other pile design, fabrication, and installation-related articles that have appeared in various PCI journals and Ascent magazine publications. Beyond the PCI publications, our regional producers are also great resources for information as they can provide valuable feedback on designs, fee estimates, and proposals. PCI has also developed a very useful and powerful spreadsheet tool for the design of piles. It's a very straightforward design tool with user-friendly input features, as well as informative output figures and graphs. Axial moment interaction diagrams can be developed for both unique pile sizes and shapes, as well as varying prestressed strand patterns and slenderness ratios. The program also computes safe lifting points and dunnage points for lifting and handling. This is a valuable tool and it's available online for free at PCI's bookstore. PCI is currently in the process of publishing a four-part webinar series on prestressed concrete piles. Each of the webinars will be free for PCI members and will provide a one-PDH credit. These webinars provide a more in-depth review of the current recommended practice and the use of precast prestressed concrete piles for buildings when they are not considered as part of the lateral force-resisting system. The webinars will also cover the differences in prescriptive requirements for building versus bridge and pier piles when they are a part of the lateral force-resisting system, as well as the conclusions of a recent study completed at the Citadel in South Carolina on axial load limits for prestressed concrete piles. As mentioned at the beginning of the presentation, PCI is made up of several committees and councils, and most, if not all, of the PCI-produced content on precast prestressed piles is being developed by two specific committees that are devoted just to piles, the Piling Committee and the Pile Producer Committee. As PCI is always focused on the future, we are also currently tracking several ongoing efforts and upcoming publications related to pile design and fabrication, including a recently formed PCI Subcommittee on the Use of UHPC. Their mission is to review requirements for the design and construction of precast H-piles made with UHPC. PCI is also continuing to review applications of new materials in the market, including the implementation of stainless steel and carbon fiber strands and their use in pile design. Precast prestressed concrete piles have been in use for over 70 years within the United States. These piles have been proven to perform very well across a wide range of site conditions and loading requirements, including under extreme conditions such as salt water and high seismic zones. With the introduction of workable concrete mixes that feature both low permeability and high durability, as well as the use of UHPC mixes, precast prestressed concrete piles are becoming even more marketable to the mainstream industry. With the continued publication of PCI's design guidelines and the other code requirements and specifications available to the public, and the added benefits of strict quality control procedures inside of a certified PCI precast plant, precast prestressed concrete piles have become a standardized product for owners, engineers, and contractors alike. I would like to conclude today's presentation with a bit of a personal note. Being an active member of a professional organization like PCI has brought a lot of fulfillment to my professional life, and there is just something so rewarding and tangible about playing a part in bringing the PCI population to life. If there is anyone in this audience who is interested in learning more about PCI committee opportunities, please reach out to any of today's speakers, and we would be happy to point you in the right direction. On behalf of Roy, Jim, Justin, and myself, we would like to thank you for your attendance at this webinar, and we look forward to hearing from you. On behalf of Roy, Jim, Justin, and myself, we would like to thank you for your attendance at this webinar. We hope you have learned about the important aspects of precast prestressed concrete piles. At this time, we would welcome any questions. Thank you. Wonderful. Thank you to our presenters for a great and informative presentation. We do have a few questions that we're going to get through to include in our Q&A for today. The first question being, for rebar coatings and premium concretes, it was mentioned that these contributed to life expectancy at a higher cost. The additional cost for different rebar coatings was mentioned two to three times for epoxy and six to ten times for stainless steel, but the additional cost for the premium concrete wasn't mentioned. What is the cost increase for using premium concrete, and what is a typical life expectancy increase? I can take that one, Nicole. Basically, yeah, if we're saying we're doubling the cost of reinforcement in the epoxy, that probably increases the total pile cost more like 30 to 50 percent, whereas if you're working on your concrete mix design, maybe you're increasing the cost by 30 percent, which only has an effect of maybe 10 to 15 percent on the pile itself. So, I think I would probably work on the mix design before I do anything else, and whether that's adding more cementitious material for lower porosity or adding corrosion-inhibiting admixture, I think I would start in that direction for the most cost-effective approach. Perfect. Thank you, Jim. Our next question is, how long is an extreme service life, and what are some examples of structures that would meet this? This is Roy, Nicole. I'll take that question. Normal service life of a structure is in the range of 50 to 75 years. Extreme service life is normally a service life greater than 100 years. As far as examples, highway bridge foundations in the marine environments and foundations in industrial structures, heavy storage tanks, those would be good examples. Wonderful. Thank you, Roy. And then our final question for today is, are strand lift loops cut off and or covered after installation? I'll take that one. Thank you. Yeah, so typically your DOTs will want those lift loops cut and patched, so we'll install some pockets that you can easily remove those lift loops and then patch them back with an epoxy grout. And typically on private piles, we do not see those lift loops cut and patched because normally those are completely embedded underneath the ground. So it just depends on the owner, but yeah, those are the two areas that may see them cut or may see them left off. Perfect. Thank you, Justin. So that concludes our Q&A portion for today. On behalf of PCI, I'd like to thank our presenters again 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.

Precast Pre-Stressed Concrete Piles

deep foundations

building applications

bridge applications

marine applications

structural efficiency

sustainability

installation methods

case studies

PCI certification