Problem: Cracks were observed on the beam during its construction phase only and on in-depth investigation it has been revealed that it requires additional tension reinforcement.
Structure Details: It was a 16,000 seat capacity new basketball arena and the raker beams that required strengthening were at the second level.
Our Approach: An optimum solution consisting of an external post-tensioning system and externally bonded FRP reinforcement was recommended. The external post-tensioning system was composed of high strength T-headed steel bars and special steel cross heads for anchorage. The post-tensioning system provided vertical and horizontal "clamping" forces that actively engage this reinforcing system and reduce beam cracking and deflection.
Installation: Core holes were drilled through existing transverse beams to install the vertical T-headed bars. To avoid damage to existing steel bars, small areas were chipped open on the topside of the beams prior to coring. Locations of the core holes were then adjusted to minimize damage to existing steel reinforcement. At less deficient locations, externally bonded FRP system was used to provide the additional tensile reinforcement. To address issues related to FRP development length and anchorage requirements, bonded concrete block was cast-in-place on the underside of each raker beam. At locations where pre-cast concrete tubs were already installed on the raker beams, a special jacking system was used to lift the tubs during strengthening installation. To achieve this, several hydraulic jacks were operated simultaneously to avoid overstressing the precast concrete elements.
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