Bi-Axial Loading

Examples

Test Specimen

Reinforced concrete columns in need of strengthening and repair and that are subjected to combined axial compression and bending moments are very common. Columns and pier caps in bridges and beam-to-column connections in rigid frames are examples of such structural elements. The use of Fiber Reinforced Polymer (FRP) wrapping as a rehabilitation and retrofitting technique present real advantages with regards to durability, maintenance costs, serviceability, and ultimate strength.

SDR performed the first comprehensive investigation dealing with optimum design of wrapped columns subjected to simultaneous axial and bending loads. The full size 12 feet long reinforced concrete columns were wrapped with the MAS2000 Fiber Wrap System and subjected to varying degrees of combined axial compression and bending moment. The research investigation provided valuable data and a method of designing this type of column.

The MAS2000 Fiber Wrap System enhanced both the compression capacity of the column through confinement action and the flexural capacity through the longitudinal reinforcement. The maximum increase in capacities was slightly below 30% in pure compression and over 54% in pure flexure. Under combined axial force/bending moment conditions, the gain in moment capacity was approximately 70%. The increase in compressive strain due to the confinement effect varied from 49% to 166%. Interaction diagrams have been developed for retrofitting columns subjected to combined loading using the MAS2000 Fiber Wrap System.