C V R Murty

The paper reviews seismic behaviour and performance of reinforced concrete (RC) deep vertical members, particularly bridge piers and structural walls. The provisions of the relevant Indian codes of practice, concerning shear strength and shear demand in these members, are reviewed in light of the provisions of international codes of practice. The deficiencies are identified in the seismic shear design philosophy, prescribed by Indian codes.

Capacity design precludes brittle actions thereby maximising energy dissipation capacity of moment resisting frame buildings through flexural yielding in beams before possible yielding in columns during strong earthquake shaking. The flexural strength of columns is required to be more than that of beams framing into it. Seismic design codes stipulate guidelines for design and detailing of members to achieve desired ductile behaviour of buildings. This paper examines seismic behaviour of RC moment frame buildings in seismic Zone V and IV designed as per the column-to-beam strength ratio (CBSR) requirements of the draft IS 13920, and its adequacy along with the detailing requirements. The CBSR of 1.4 specified in the draft code is not sufficient for buildings in seismic Zone V.

Based on the review of seismic shear design provisions of Indian codes for reinforced concrete (RC) deep vertical members (i.e., bridge piers and structural walls) in a companion paper, basic provisions are identified for shear resistance of RC sections. Draft provisions are presented for the consideration of the relevant Indian design code committees on bridge and building. The best seismic design practices seem to suggest that these provisions will be beneficial for the seismic performance of deep RC vertical members.