Study On Seismic Behavior Of Specially Shaped Columns With Super-high Strength Steel Bar

The bearing capacity of columns with special-shaped section is poor under the action of strong earthquakes.It limits the application of special-shaped column structure in the earthquake area.However,the popularization and application of high strength steel has become an important way to solve this problem,and 600MPa-grade steel is a new type of high strength steel with good ductility.Tests and theoretical analysis are conducted to discuss the seismic performance of special-shaped concrete columns with 600MPa-grade reinforcing bar.14 special-shaped concrete columns with 600MPa-grade reinforcing bar are conducted under cyclic loading.And applicability of 600MPa-grade reinforcing bar in special-shaped columns is studied.It is shown that bending failure is occurred for special-shaped columns under the combined action of compression,bending and shear.The bearing capacity and ductility performance of T-shaped columns are asymmetric.Special-shaped columns with 600MPa-grade reinforcing bar show better bearing capacity compared with special-shaped column with HRB500 reinforcing bar and exhibit good seismic performance.And the bearing capacity of +-shaped column is increased by 7%,while the bearing capacity of T-shaped column is increased by 12%.The influences of stirrup spacing and axial compression ratio on seismic performance are analyzed.The results indicate that encrypting stirrup can effectively enhance its inhibition of concrete,and special-shaped columns with smaller stirrup spacing exhibit better displacement ductility and better energy dissipation capacity.When the stirrup spacing reduce from 120 mm to 60 mm,the ductility is increased by 8%-11% and the energy dissipation capacity of special-shaped columns is increased by 17%-40%.Axial compression ratio has a great effect on ductility performance.As the increase of axial compression ratio,the ultimate displacement is decreased by 12%-14%,while the displacement ductility is decreased by 20%-25%.In order to study seismic behaviors of special-shaped concrete column with 600MPa-grade reinforcing bar,finite element analysis models are proposed.It is shown that computational results are acceptable,indicating that the model proposed could be applied to the seismic analysis of special-shaped column.Special-shaped columns with different parameters are simulated by using the validated model.It is shown that the longitudinal reinforcement ratio obviously effect the bearing capacity of special-shaped columns with high strength reinforcement.As the increase of reinforcement ratio,the bearing capacity of T-shaped columns and +-shaped columns is increased by 21% and 26% respectively.