Analytical Study of Spacing of Lateral Steel and Column Confinement

The effect of longitudinal spacing of transverse reinforcement on the confining stress in concrete columns is studied analytically. A linear-elastic solution is obtained for circular columns laterally confined by hoops. From this solution, an effective confining stress at any point and an average confining factor for circular transverse cross sections are defined. The relationship between the average confining factor and the longitudinal spacing of hoops is established from the numerical results of the analytical solution. The same procedure is then applied through a series of finite-element analyses to square columns transversely reinforced with welded-wire fabric. The resulting formula relating the longitudinal spacing and the average confining factor is remarkably similar to that found from the circular column analysis.