DILATION CHARACTERISTICS OF CONFINED CONCRETE

Confinement of concrete enhances its strength and ductility by restrai ning lateral dilation. The accuracy of a confinement model depends on how well it captures the dilation tendency of concrete. In recent year s, external confinement of concrete by fibre composites has become inc reasingly popular for civil infrastructure applications. This includes fibre-wrapping of existing columns or encasement of concrete in a fib re reinforced plastics (FRP) shell. A total of 54-concrete-filled FRP tubes were tested in uniaxial compression under displacement control m ode. Full instrumentation of the specimens has allowed the variation o f tangent Poisson's ratio for concrete to be captured. The dilation tr end of confined concrete is shown to be a function of jacket stiffness . In steel-encased members, once steel yields, confining pressure beco mes constant and the jacket renders itself ineffective in containing t he dilation of concrete. On the other hand, for linear-elastic materia ls such as fibre composites, a strain reversal occurs that results in containment of dilation. A method for predicting the dilation is devel oped that can be easily adopted in any active confinement model. Moreo ver, a new confinement model for FRP-encased concrete is discussed. (C ) 1997 by John Wiley & Sons, Ltd.