Want quick responses to our most asked precast questions? Our blog series, “FAQ Fridays,” is designed to answer your most popular questions, organized by topic and product category. In Part 3 of this series, we discuss key installation and erection considerations.
Precast products can be made large and installed in accelerated fashion. These considerations can sometimes constrain and drive product design size, weight limits, and costs. How big, how heavy, how many? Is a transportation permit more than the cost to erect per piece? How does it affect production costs? Are there unique or repeating sizes and shape?
There are many variables that can tip the scales one way or another. Understanding the parameters to determine the right and most economic configurations can be complicated, but our most important installation considerations are logistics, equipment, coordination, and connections.
The A/E drawings should include basic or generic types and quantities; the final engineered design of connections is delegated to the producer. A/E design should understand and delineate the basic types of connections needed.
Common connections include gravity, lateral, and seismic connections, including bridging components like miscellaneous steel from structural steel or CIP to precast products. Connections are fundamental to all buildings and construction no matter what material is used. The purpose of a connection is to transfer loads, restrain movement, and provide stability to a component or an entire structure. Connection design is one of the most important aspects in the design and engineering of precast/prestressed concrete structures.
Many different connection details will result from the combination of sizes and shapes of precast concrete components and the variety of possible support conditions. Individual precast producers have developed connection details over the years that suit particular production and erection preferences, and they should be considered for a specific project early in the design stage. All connections should comply with applicable building codes, and the final structural design should be done by an engineer licensed in the location of the project. It’s common for the architect and engineer of record to show connection loads and locations on the contract documents and allow the successful precast producer's engineering department to provide the final design and details of the connections. Learn more about connection design considerations, connection materials, and sample connection types from PCI Mid-Atlantic, and browse additional publications on the topic:
Erection tolerances control the position of the individual precast concrete members as they’re located and placed in the assembled structure. Here are some rules of thumb regarding erection tolerances:
Erection tolerances can vary by account for unique project conditions. In these instances, they should be carefully reviewed by the designer and contractors and adjusted, if necessary, to meet the project requirements. The effects of adjusted tolerances on specific details at joints, on connections, and in other locations in the structure should be evaluated by the designer. Different details may have varying amounts of sensitivity to tolerances. For information on specific erection tolerances, download PCI’s Designer’s Notebooks: Envelope Tolerances for Architectural Precast which is free of charge and available in PDF format, and locate a PCI-Certified Erector in your state or region by entering your search criteria into the PCI-Certified Erector Directory.
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