Stress-averaged strain model for confined high-strength concrete

When a concrete structure fails, the damage is usually concentrated in a narrow region. The fracture zone and localization behavior have to be captured to accurately assess the structural behavior. In this research, large-scale high-strength reinforced concrete columns were tested under concentric loading. The experimental results show that in columns with sections ranging from 200 to 500 mm (7.88 to 19.7 in.), the length of the compressive fracture zone increases with the cross section dimension; however, the post-peak compressive fracture energies are independent of cross section dimension and column height, provided that the columns have the same concrete compressive strength and lateral confining pressure. A formalized stress-averaged strain model for confined concrete has been developed by using the compressive fracture energy. Regardless of gauge length, cross section dimension, and concrete strength, the proposed model provides good agreement with the test results.