An experimental investigation of spirally prestressed concrete columns.

Abstract

This thesis is concerned with an experimental investigation of the effects of initial prestress and slenderness ratios on the ultimate load carrying capacity of spirally prestressed concrete columns. The experimental investigation was carried out on 6 inch diameter concrete columns. The program was divided into series A, B, C and D with slenderness ratios 16.6, 25.4, 37.05 and 49.4 respectively. Series A and B were made of plain concrete, while series C and D had longitudinal reinforcing of 4 - #3 vertical and #2 ties @ 6 inches c/c. Lateral prestress, which varied from 20% to 60% of the compressive stress of the concrete was applied by means of a high-strength piano wire of 0.031 inch diameter. Details of fabrication, materials and testing are discussed in Chapter 3. It was found that an increase in initial spiral prestress increases the load carrying capacity of columns, but the column capacity decreases with an increase in slenderness ratio of the column. Increase in initial spiral prestress showed considerable effect on the elastic behaviour and durability of the column. Spirally prestressed concrete columns behave in a manner similar to plain concrete columns, and can be analyzed in the same-way using the ultimate triaxial concrete strength in place of the cylinder strength.