Precast Concrete Framing Systems

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Chapter 15 Precast Concrete Framing Systems
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Precast Concrete

• Definition

Structural
Architectural
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What Can Be Precast?

• Slab Elements
• Beams ( Girders)
• Columns
• Wall Panels
• Other

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Precast Concrete

• Advantages
• Production _at_ Ground Level
• Controlled Environment (Plant vs. Jobsite)
• High Quality Formwork (Often steel, reuse)
• High Quality Materials (5000 psi conc., HSS)
• Controlled Curing (High Early, steam cure, 24hr
  cycle)
• Erection Time Conditions (quicker, no formwork
  required, no temperature restraints concrete
  already cured)

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Precast Concrete

• Disadvantages
• Elements large heavy
• Transportation
• Site Mobility
• Hoisting / Erection
• Less field modification flexibility
• Often Require a Topping Slab

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Precast Slab Components

• Solid Flat Slab
• more dead weight

Double Tee

• Single Tee
• Stability during erection
• Depth vs DT

Hollow Core Slab
most commonly used
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Hollow Core Slab

• Manufacturing Process
• Extruded - Most common, or
• Cast in layers (proprietary systems)

Widths 2, 4, 8 Thickness typ. 6- 12
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Uses - Intermediate Spans / Average Loading
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Hollow Cores - some of non-working concrete
eliminated
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Edge Sloped
Reinforcing Units typically not prestressed
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Joints

• Typically Supported by
• CMU, Concrete
• Steel

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Erected with a Crane
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Grouted Subsequent to Erection
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Double Tee
Depth 12 to 36

• Uses
• Heavier Loads
• Greater Spans

Double Tees (Stacked in the Yard)
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Casting Bed - Metal
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Top Slab / Flange Reinforcing
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Haunch Armor/ Reinforcing
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Flange Anchorage
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Coils of Cable (Tendons) for Prestressing
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Hydraulic Stressing Machine
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Stressed Cable
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Finishes
Broom - Exposed

• Broom - Rough
• Held down for Topping

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Lifting Eyes
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Precast Slab Manufacturing

• Controlled Environment
• Casting Beds
• Reinforcing Embeds
• Pour, Finish, Cure
• Validate Strength
• Removal from Bed (Transfer stress to Member)
• Plant Storage or Transport to the Jobsite

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Camber
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Precast Slab Erection

• Transportation to the Job Site
• Erection
• Anchorage
• Bearing Pads
• Topping Slabs

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Bearing PadsTypically between Double Tee
Support Member
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Bearing Pad for I Beam
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Beams Girders
Reinforcing - Conventional, Prestress, or Combo
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L-Shaped Beam Inverted Tee Beam Prestressed
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AASHTO I Beams used for a Bridge
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Columns
Columns
Support notches For exterior beam
Typical Base Details
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Precast Wall
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Arena / Coliseum Precast Seating
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Arena/Coliseum
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Arena/Coliseum Bearing Pad
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Parking Deck
Precast columns., beams, double tees
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Parking Deck
Precast spandrel beams
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Parking Deck
Precast columns spandrel beams
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Parking Deck
Support haunch
Precast walls double tees
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Haunch Support for Double Tee Member
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Parking Deck Erection
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Parking Deck Erection
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Precast Connections Column Splicing
Reinforcing Dowels Grouted
Bolted Connection
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Precast Connections Non-Moment Beam to Column
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Precast Topping
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Precast Highrise

• San Francisco
• 495 Apartments
• 39 Stories
• 420 ft high
• Seismic Zone 4
• Near the San
• Andreas Fault
• Tallest Building
• to Date (inc CIP)
• 6/14/99 ENR

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Precast Used with other Structural Materials

• Precast Cast-in-Place Concrete
• Precast Masonry
• Precast Structural Steel

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Fully Precast Structure

• Range
• Parking Decks Common to
• Highrise Buildings - Rare
• Minimal Industry Experience ()
• Lateral Loading - Moment Connections

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Parking Beck with Architectural Precast Exterior
Panels
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Architectural Precast Exterior Panels
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Precast Structural Steel
Staggered Truss System Structural Steel Frame
with Hollow Core Floor Slabs
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Precast Cast-in-Place Concrete

• PC Slabs CIP Beams Columns (common)
• PC Columns Beams with CIP Slab (unusual)
• Often less to form beam w/ slab forming

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Precast Masonry
Masonry Precast Hollow Core (common)
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Architectural Precast
Architectural Precast Panels
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Architectural Precast Panels
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Architectural Precast Panels
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Architectural Precast Panels
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Architectural Precast Panels
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Architectural Precast Panels
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Architectural Precast Panels
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Architectural Precast Panels
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Architectural Precast Panels
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Architectural Precast Panels
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Precast Panel Anchorage

• Often Supports no Building Loading except
• Its Own Weight
• Weight of Cladding (ex. stone)
• Single elevation of Glass Glazing
• Transmits lateral forces to the structure
• Anchorage to the Structure
• Embeds in PC Panel
• Embeds in Structure
• Welded or Bolted
• Lateral Support/Bracing (or 2nd connection)