The Bagnell Dam, which impounds the Osage River to form the Lake of the Ozarks in central Missouri, was completed in 1931. The 148-ft-tall, 2,543-ft-long dam has 12 floodgates. Eight water-wheel turbines in the Osage Energy Center, on the north end of the dam, have been on the job for 85 years and today provide reliable, clean electricity to more than 40,000 homes.
The concrete for the dam originally was placed in 40-foot-wide blocks designed to slide individually in case of a breach. The dam received a structural update in the 1980s when crews tied the dam into the underlying bedrock by installing 277 post-tensioned anchors.
A new $52 million stabilization project began in 2017 adding 27 new high capacity post-tensioned anchors in the dam’s west retaining section, 33 anchors in the spillway, and eight anchors in the east retaining section. In addition, 17,000 cubic yards of concrete—more than 66 million pounds—is being added to the dam’s mass on its downstream face. The new concrete is being doweled into the existing concrete as an overlay to replace deteriorated concrete on the east and west retaining sections.
MC Industrial, the contractor, is using approximately 280 lineal feet of PERI’s SCS single-sided climbing system in combination with VARIO GT24 Girder Wall Formwork to place the new concrete, which is one-sided mass concrete with wall thicknesses up to 14 ft.
SCS provides a load-bearing structure for supporting single-sided, non-tied, or two-sided, anchored wall formwork. The system transfers loads from the fresh concrete—without formwork ties—through brackets into the climbing anchors of the previously placed section. This cost-effective, modular system uses multi-piece brackets to easily adapt to project-specific requirements and geometries.
Because the SCS system eliminates the need for form ties, it solved a complicated layout and access problem on the Bagnell Dam’s mass infill pours, which are 55 feet above grade. Simple form design and functionality also helped limit the amount of manpower required.
PERI customer service and field support have been exceptional. They were readily available for quick fixes and the custom form design helped us work through issues that arose.