Regulators realize that high quality precast concrete components, sourced from certified precast facilities, can be used to minimize disruption to the public during construction projects. Precast concrete infrastructure components ensure a durable construction, especially when precast concrete components are used. Factory cured precast concrete structural components are delivered to the site where most of the drying shrinkage has already taken place.
All CPCI member plants produce in accordance with CSA Standard A23.4 "Precast Concrete—Materials and Construction." Precast concrete components achieve this goal with plant fabrication continuing while site preparations are underway. Bridges using full or partial depth precast integral concrete decks achieve high spans at depth.
More information is available in the CPCI Architectural Precast Concrete Technical Guide at http://tinyurl.com/mumektt. An improved concrete material resistance factor is allowed for certified precast concrete structural members. Precast concrete wall panels can be designed as load-bearing, eliminating the need for internal framing.
Precast Prestressed Double Tees
No other building material can match the long-term durability, low maintenance and cost-saving qualities of precast concrete.
Hollow Core Slabs
Precast Framing Systems
Precast Concrete Wall Systems
Fast Construction
Parking structures often represent the first and last impression a visitor has when visiting an airport, hospital, public building or recreation center. Excellent parking structures are designed specifically for the type of visitors a structure will serve, based on the facilities they support and the daily or peak flows of traffic.
Loads and Forces
Bay Sizes
Drainage
Durability
Often these projects are built on tight budgets and schedules to accommodate major sporting events. The technique of post-tensioning precast segments together has allowed precast concrete elements to form a complex cantilever and ring beam structure to support the roofs of some of these structures. Post-tensioning can be used to reinforce pre-cast concrete cantilevered rafters which support the seat and provide an unobstructed view of the playing surface.
Mass-produced seating units are produced in a variety of configurations and spans to ensure quick installation and long-lasting service. Pedestrian ramps, concession, washroom and locker room areas can all be framed and constructed using precast prestressed concrete elements. Precast prestressed concrete has become the structural and architectural system of choice for a variety of transportation facilities.
Acting as social hubs for thousands of daily commuters, LRTs are often designed with unique architectural treatments. No single building material lends itself to a more dazzling array of architectural treatments than prestressed concrete. Rich aggregates, decorative shapes, reveals and attractive stone and masonry veneers can all be used to express a wealth of architectural detail.
In addition to these architectural requirements, transit facilities undergo a tremendous amount of cyclic loading conditions. Required maintenance is low—saving long-term costs as well as reducing delays over the lifetime of these facilities.
Sound Walls and Fences
Retaining Walls
The lateral tiebacks are usually geogrids buried in the backfill's stable area. In addition to supporting the wall, the geogrids also stabilize the ground behind the wall, allowing for higher and steeper walls to be built. These counterfort columns are T-shaped, can taper at the rear and are anchored to the foundation by reinforcement or post-tensioning.
Precast concrete panels are placed between the flanges of the buttress columns to retain the earth. Retaining walls resist the shear forces and bending moments placed on the wall by the soil. Precast concrete crib wall systems use high strength precast concrete standard basket type units that are stacked and filled with soil for stability.
These walls provide stability and meet the concerns of citizens by providing sound reduction while conforming to the natural landscape. Shear walls can be used as retaining walls or slope stabilizers for earth or rock embankments, or as a noise-proof barrier; especially suitable for highways, railways and parks, gardens, residential and commercial districts.
Landscaping
Light Poles and Utility Poles
Utility Products (Vaults, Culverts, Etc.)
Precast Concrete Catch Basins (CBs) are catchment units that collect stormwater offline and convey this flow to the storm system. Retention/infiltration Precast concrete products take a unique approach that connects individual precast concrete modules into a configuration that meets each project's requirements. The clean, smooth surfaces that can be achieved in a precast concrete plant make this material ideal for food processing, computer component manufacturing and wet processing operations where cleanliness is a concern.
Prefabricated insulated wall panels can easily be used as load-bearing exterior walls or cladding. Exterior walls can be formed using standard molds that are efficiently prestressed in long line production facilities. Precast concrete has been put to good use for a variety of detention and correctional facilities and the support buildings that serve an important role in institutional complexes.
Precast concrete wall panels, frames and floor/roof slabs are excellent building components that are durable and safe. Security door and window frames can be pre-installed in precast concrete elements at a CPCI member precast plant to save time and money. Precast concrete wall elements are usually prestressed vertically in the precast plant and post-tensioned horizontally (circularly) through channels cast into the panels.
Other parts of a tank structure, such as columns, beams and roof slabs, can also be precast concrete. Tunnel liners are specialized precast concrete products that are cast in segments and used to form a complete ring in large diameter tunnels. The use of precast concrete tunnel linings has increased due to the efficient and economical installation process compared to that of normal cast in-situ lining practices.
Precast concrete is an ideal solution for projects in remote areas where local materials and labor may not be available. The Hodder Avenue underpass incorporated the full range of precast concrete elements and extensive use of Ultra High Performance Concrete (UHPC).
Proven Economy
Prestressed Girder Bridges
Girder Type Typical range of depths* Typical span range*
Girders
Benefits of Precast Prestressed Concrete for Bridge Construction
Precast prestressed concrete bridges can be designed to elegantly blend harmoniously with their surroundings and provide an attractive view from above, to the side and from below. Strong, tough, durable yet graceful bridges can be constructed using the low depth/span ratios made possible by the use of high strength precast prestressed concrete and the simple clean shapes of locally available sections. Precast prestressed members are particularly durable due to the high quality of materials and construction used in their manufacture.
Some bridge engineers estimate the life cycle cost of repainting steel bridges at 10 to 20% of the initial cost. Through the technique of prestressing, the designer can use the minimum possible depth-span ratio. Depth-to-span ratios as low as 1:32 can be achieved with solid slabs, voided slabs, box beams, channel slabs, or spherical tee sections.
Although deeper I-beam and beam sections will require less prestressing steel, the overall economics of a project may dictate the lowest possible depth ratio.
Planning
It may be cheaper to extend the bridge a bit than to use an extremely skewed angle to fit the bridge site exactly. Use prefabricated prestressed piles to act as foundations and piers where soil conditions are favorable. If pile foundations are warranted, prestressed concrete piles can act as piers and abutments, thereby reducing the amount of forming and casting on site.
Detailing
Wong, A.Y.C. og Gamble, W.L., "Effects of Diaphragms in Continuous Slab and Girder Highway Bridges," Civil Engineering Studies, Structural Research Series No. Sengupta, S., og Breen, J.E., "The Effect of Dia - phragms in Prestressed Concrete Girder and Slab Bridges," Research Report 158-1F, Center for Highway Research, University of Texas i Austin, okt.
Spliced Girder Bridges
Types of Splices
Precast girders are placed on false or temporary end supports, usually located near dead load inflection points. The ends of prestressed segments are clamped together with short cables or threaded rods. This splice is used when the construction of a temporary support is not possible (e.g. over river crossings or traffic lanes).
The joint can be designed as a hinge or local post-tensioning can be applied to promote continuity. Steel plates are cast into the ends of the beam segments to overlap the matching ends of the precast units. The strips are aligned end to end, either in their final position or on the ground.
The gap is filled with epoxy gel or grout and the post-tension force is applied later.
Traffic Barriers
Bridge Decks
They allow the use of quality factory-produced components for spans much longer than those where beams can be transported as single spans. The prestressing strands in the panels are perpendicular to the longitudinal axis of the beams and provide all the positive reinforcement required for the deck space between the beams. The panels are bolted to the appropriate height and made composite with the cast-in-place layer to resist superimposed dead and live loads.
Full depth precast concrete bridge deck panels are used both to replace worn or corroded decks on bridges where traffic must be maintained during construction and for new bridge construction. Prestressing strands in the panels are perpendicular to the longitudinal axis of the beams and may be in two layers to provide all the positive reinforcement required for the deck span between the beams. Shear bolts on the beams are grouted in place through pockets in the cover plates.
Edge grouting (and occasional longitudinal post-tensioning) is used to join the deck panels together. Consult your local CPCI structural precast concrete manufacturer for their standard slab sizes and rebar placement.
Pedestrian Bridges
CPCI Guide Specifications
Detailed Design Information
CPCI Members Near You and Your Project
How Precast Certification is a Requirement of the National Building Code of Canada
CPCI Precast Concrete Certification Program for Structural, Architectural and Specialty Precast Concrete Products and Systems
Purpose
