8 Precast Construction Overview
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Questions and Answers

What is added to precast slabs for improved floor strength and stiffness?

  • Sitecast concrete toppings (correct)
  • Metal plates
  • Hollow core
  • Steel angles

    • Steel reinforcing bars are omitted when joining hollow core slabs to precast beams.

    False

    What protects metal bearing plates and anchor bolts from fire and corrosion after the columns are mechanically joined?

    Grout

    Hollow core slabs are set on bearing pads on precast ______.

    <p>beams</p> Signup and view all the answers

    Match the following precast concrete connections with their descriptions:

    <p>Column-to-Column Connection = Metal bearing plates and anchor bolts are used and grouted. Beam-to-Column Connection = Beams are set on bearing pads and grouted. Slab-to-Beam Connection = Hollow core slabs are set and reinforcing bars are used. Sitecast Concrete Toppings = Improve fire resistance and integrate electrical services.</p> Signup and view all the answers

    Which of the following is an advantage of using sitecast concrete toppings over precast slabs?

    <p>Smoother floor surface</p> Signup and view all the answers

    Transverse bulkheads are used to divide the casting beds before concrete is placed.

    <p>True</p> Signup and view all the answers

    What method is primarily used to ship precast concrete elements to the construction site?

    <p>Truck</p> Signup and view all the answers

    What is a characteristic of a closed precast system?

    <p>Production is based on specific project requirements</p> Signup and view all the answers

    Precast concrete erection is unaffected by weather conditions.

    <p>False</p> Signup and view all the answers

    Name one type of precast system.

    <p>Large-panel system</p> Signup and view all the answers

    The __________ система produces parts that are used only in one project.

    <p>closed</p> Signup and view all the answers

    Match the following types of precast systems with their characteristics:

    <p>Large-panel systems = Multistory structures with concrete panels Frame systems = Load-bearing frame made of precast materials Slab-column systems = Combines slabs and columns for support Mixed systems = Utilizes combinations of various precast types</p> Signup and view all the answers

    What advantage does plant casting have over site-cast concrete?

    <p>Higher efficiency and quality control</p> Signup and view all the answers

    Both vertical and horizontal panels in large-panel systems resist gravity loads.

    <p>True</p> Signup and view all the answers

    What type of structure consists of large wall and floor concrete panels?

    <p>Large-panel structure</p> Signup and view all the answers

    What is a key advantage of precast beam-column sub-assemblages?

    <p>Connections can be placed away from critical regions</p> Signup and view all the answers

    Linear elements are generally considered more difficult to handle than spatial elements.

    <p>False</p> Signup and view all the answers

    What are two types of systems that rely on shear walls for lateral load effects?

    <p>Lift-slab system and Prestressed slab-column system</p> Signup and view all the answers

    The ____-slab system allows precast concrete floor slabs to be lifted by cranes.

    <p>Lift</p> Signup and view all the answers

    Match the following components with their descriptions:

    <p>Precast concrete columns = Typically two stories high Temporary supports = Keep slabs in position during installation Hinged connections = Facilitate ease of construction Rigid connections = Ensure continuity of reinforcement</p> Signup and view all the answers

    What is the primary purpose of ribbing wall panels in precast concrete constructions?

    <p>Reduce weight while increasing vertical span capacity</p> Signup and view all the answers

    Precast concrete stairs are not considered a structural element.

    <p>False</p> Signup and view all the answers

    What is a main purpose of using shear walls in slab-column systems?

    <p>To sustain lateral load effects</p> Signup and view all the answers

    Plant-Cast Precast Concrete is cast and cured on-site.

    <p>False</p> Signup and view all the answers

    What elements typically support the roof and floor slabs in precast concrete buildings?

    <p>Precast columns and beams or a combination of all three (columns, beams, and wall panels).</p> Signup and view all the answers

    What is the main structural resistance of slab-column systems mainly focused on?

    <p>Gravity loads</p> Signup and view all the answers

    Precast concrete structures can incorporate ______ cores for added space efficiency.

    <p>hollow</p> Signup and view all the answers

    Match the following precast concrete elements with their descriptions:

    <p>Hollow Core Slabs = Lightweight and efficient flooring solution Double Tees = Commonly used in parking structures Sandwich Panels = Insulated wall panels for energy efficiency Prestressing Strands = Strands that enhance tensile strength</p> Signup and view all the answers

    What is a typical feature of an AASHTO girder?

    <p>Depressed prestressing strands for tensile resistance</p> Signup and view all the answers

    Precast concrete elements are not manufactured on casting beds.

    <p>False</p> Signup and view all the answers

    High-strength steel strands are ______ to enhance the strength of precast concrete elements.

    <p>tensioned</p> Signup and view all the answers

    What is one of the main advantages of plant casting in concrete production?

    <p>Greater control of surface finishes</p> Signup and view all the answers

    Precast concrete elements are affected significantly by adverse weather conditions.

    <p>False</p> Signup and view all the answers

    What type of cement is typically used in plant-cast precast concrete for high early strength?

    <p>Type III cement</p> Signup and view all the answers

    The __________ is a device used to lift and place precast concrete elements.

    <p>vacuum lifting device</p> Signup and view all the answers

    Match the precast concrete elements to their primary functions:

    <p>Precast Concrete Slabs = Used for floor and roof decks Precast Concrete Beams = Provide support for slabs Precast Concrete Columns = Support beam and slab elements Precast Concrete Wall Panels = Can be solid or insulating sandwiched panels</p> Signup and view all the answers

    Which structural element is commonly reinforced with prestressed steel strands?

    <p>Precast Concrete Slabs</p> Signup and view all the answers

    All precast concrete wall panels are solid and cannot be hollow or sandwiched.

    <p>False</p> Signup and view all the answers

    What is the primary load that precast concrete columns carry?

    <p>Axial loads</p> Signup and view all the answers

    Study Notes

    Precast Introduction

    • Precast construction involves producing building components in a factory, then transporting and assembling them on-site.
    • Closed systems produce non-standardized units, leading to waste and uneconomical processes. 1000 housing units can be produced economically in this system.
    • Open systems offer more flexibility, usable in diverse building projects irrespective of project specifics.
    • Modular coordination enables construction for various building types (e.g., residential and commercial).

    Precast Systems

    • Systems are categorized based on the load-bearing structure.
    • Large-panel systems: Multi-story structures utilizing large concrete wall and floor panels. The panels form a box-like structure, resisting gravity and vertical loads.
    • Frame systems use linear elements or spatial beam-column sub-assemblages. Linear elements are preferred due to ease of handling.
    • Slab-column systems rely on shear walls to resist lateral loads, but primarily focus on gravity loads.
    • A lift-slab system utilizes precast reinforced concrete columns and slabs. Columns are frequently 2 or more stories high.
    • Precast slabs are often used in conjunction with other vertical systems (e.g., reinforced masonry or steel).

    Plant-Cast Precast Concrete

    • Concrete elements are cast and cured in a factory, then transported to the construction site.
    • This method improves efficiency and quality control.
    • Durable, reusable steel forms reduce formwork costs.
    • High early strength cement and steam curing accelerate the process.
    • Controlled casting and high-quality forms refine the surface finish.
    • Structural elements are often reinforced with tightly stretched prestressed steel strands for increased structural efficiency. Conventional reinforcing is also added for resilience against thermal and secondary stresses.
    • Onsite assembly procedures are like working with structural steel

    Manufacturing of Precast Concrete Structural Elements

    • Components are manufactured in beds up to 800 ft long.
    • High-strength steel strands and tension ensure strength
    • Reinforcing elements (plates, blockouts, loops, etc) are added.
    • Concrete is poured into molds to create the structural elements.
    • Sections are cut to specific lengths
    • Concrete is cured to desired strength
    • Sections are lifted from casting beds and stock-piled for delivery
    • Erection is completed by cranes on the construction site

    Joining Precast Concrete Elements

    • Metal bearing plates and embedded anchor bolts are used in column-to-column connections, which are then grouted to provide bearing support.
    • Beams are set on bearing pads on corbels and joined using steel angles and metal plates.
    • Steel reinforcing bars are inserted into slab keyways to connect slabs to beams.
    • Groat is used for connections to ensure integrity.
    • Sitecast concrete topping over precast slabs improves strength, stiffness and fire resistance, as well as ease of integrating electrical services.

    Precast Concrete Design Considerations

    • In seismic areas, structures are designed to respond safely to dynamic forces.
    • Innovations in joint design are improving connections in precast concrete structures, leading to better suitability for seismic regions.
    • Seismic testing facilities evaluate the performance of precast concrete structures.

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    Lecture 8 Precast Introduction PDF

    Description

    This quiz explores the fundamentals of precast construction, including its systems and advantages. You'll learn about closed and open systems, modular coordination, and the various types of load-bearing structures such as large-panel and frame systems. Test your knowledge and understanding of how precast elements are utilized in modern construction.

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