Precast frames can be part of the seismic-force resisting system, designed to carry both gravitational and horizontal loads during an earthquake. To ensure a safe and controlled global response of the building, the designer must apply an appropriate hierarchy of resistances among the structural components of the frame. According to code-based capacity design principles, columns and connections are typically over-strengthened to remain in the elastic stage, while beams are detailed to undergo inelastic deformations in order to dissipate seismic energy. However, depending on the displacement demand of the building at ultimate limit state, inelastic deformations may also occur at the column base region. In such cases, overdesigned connections represent a generally preferred solution, where the connection is stronger than the connected column so that it remains elastic, while plastic hinging might develop in the column critical zone just above the base.
Strong connection design approach
Peikko bolted column connections enable fast and safe on-site installation, thereby easing the use of precast construction technology. Their excellent performance under static loading is well established and has been independently verified through the European Technical Assessment (ETA) procedure.
In addition to the safe transfer of static loads, Peikko bolted column connections can also be designed to resist seismic actions in buildings classified as Ductility Class Medium (DCM) in accordance with EN 1998-1. To achieve controlled behavior of the column base during an earthquake, a strong connection design approach can be applied to Peikko column connections, in accordance with relevant seismic design standards, to both provide a flexural resistance greater than that of the column multiplied by the overstrength factor and ensure sufficient resistance against brittle shear failure modes.
The updated Technical Manuals for HELKA® and BOLDA® Column Shoes present the design methods to ensure adequate flexural and shear resistance of the overdesigned connection, as well as reliable performance of individual column shoe-anchor bolt pairs.
Experimentally proven solution
Although precast technology is generally acknowledged, the amount of detailed, system-specific design guidance remains limited, especially regarding the seismic design. The acceptability of precast concrete systems and their connections can anyhow be assessed by adopting the requirements of relevant existing design codes, such as ACI 374.1-05. Precast concrete structures are generally accepted as seismic force-resisting systems on the basis of experimental evidence, when satisfying specified drift-based acceptance criteria. Seismic performance criteria can be defined to assess the cyclic behavior of precast concrete structures regarding strength, stiffness, and energy dissipation capacity.
As a leading global supplier of bolted column connections and a forerunner in this field, Peikko has taken the initiative and experimentally demonstrated the seismic performance of precast columns connected using anchor bolts and column shoes. When the strong connection design approach is applied, plastic hinging is forced to occur in the column, while the connection itself remains elastic. Tests proved the satisfactory performance of Peikko bolted connections even under demanding load conditions, well beyond the target displacement demands relevant for practical structures. A new white paper entitled “Strong connection design approach for precast concrete column connections resisting seismic loads” presents recent oligo-cyclic loading tests on Peikko column connections made with HELKA® and BOLDA® Column Shoes.
Peikko column connections have already been delivered to several large building projects located in seismic regions, many of them in Turkey, including areas of high seismicity. In these projects, customers have identified the numerous benefits of precast construction using bolted connections, while maintaining full confidence in the seismic performance of the connections, even under strong earthquakes that have already occurred and represented a real-life test of existing structures.
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Strong connection design approach for precast concrete column connections resisting seismic loads
 | Senior Manager, Sustainability & Research Peikko Group Corporation |
 | Customer engineer Peikko Italia S.r.l |
