Experimental Study on Seismic Performance of Ungrouted Confined Concrete Masonry Walls with Unbonded Tendons

摘要

A novel concrete masonry wall for enhancing seismic behavior is adopted and justified in this paper, namely, ungrouted posttensioned confined concrete masonry (PTCCM) wall with unbonded tendons. The wall is posttensioned as well as confined by the ring beam placed on the top and constructional columns placed at the both ends of the wall. To validate the effectiveness of this technique, 14 walls were tested under lateral cyclic loads. The main parameters studied in this research are prestressing level, opening and horizontal reinforced concrete strip as well as axial load. The damage pattern and failure mode, force deformation response, ultimate strength, ductility and damping coefficient of each wall were carefully studied as well as stiffness degradation. The effects of posttensioning, opening and horizontal reinforced concrete strip on the seismic behavior of the PTCCM walls were analyzed in detail. The test results indicate that the posttensioning is significantly effective in improving the cracking resistance and seismic behavior, slowing down the stiffness degradation, as well as enhancing the shear and energy dissipation capacity of the PTCCM walls. The confinement effect provided by the ring beam and constructional columns can effectively improve the seismic behavior of the concrete masonry walls. By utilizing unbonded posttensioning, the ungrouted PTCCM walls had little residual deformation after cyclic loading. It can also be concluded that horizontal reinforced concrete strip can increase the cracking resistance, ductility and energy dissipation capacity of the walls. Based on the test results, a simple analysis method for predicting the shear strength of the PTCCM walls is proposed.