BUCKLING OF FERROCEMENT PLATES

Abstract

Ferrocement structural members are generally cast in thin sections, which are slender as well. So buckling in ferrocement compressive and flexural members, is a most important mode of failure. in order to investigate the buckling behaviour of ferrocement, a study was conducted on ferrocement plates of various slenderness ratios and volume fractions. In the present investigation varying plate thicknesses of 15,20,25,40 and 60mm were cast. Two types of meshes 2x2 No.22 (0.72mm diameter) aAclAx2 No.20 (0.88mm diameter) were used. In each thickness both types of meshes were used in two and four numbers. Total number of ferrocement specimen casted were 20. Five plain mortar specimens were also cast. Specimens with thicknesses of 15,20 and 25mm were tested with hinged end conditions and that with 40 and 60mm thicknesses, were tested with partially fixed end conditions. Therefore the slenderness.ratio varied from 47 to 220. Surface strains and central lateral deflections were measured for selected specimens. The penultimate crushing and buckling load were measured for each specimen. The theoretical analysis, in crushing failure zone, was done by assuming that skeletal steel and wire mesh do not contribute towards the ultimate strength. The crushing strength is obtained by multiplying with the nominal strength of ferrocement in compression,wiiimstrength reduction factor to take in to account the slenderness effect ,In the buckling failure zone, the strength of the specimen is predicted by (x) Euler-Engesser's buckling strength formula., considering the inelastic behaviour of ferrocement. The composite modulus of elasticity is calculated by method of Law of Mixtures and empirical equations obtained by. some experimental investigationS. For both, crushing and buckling zones, a straight line is fitted. Test results show that in the buckling zone, prediction of the strength is satisfactory. The ratio of the experimental and theoretical buckling strength is about 1.t5. In the crushing zone, test results are lower than theoretically predicted values. Ratio of experimental and theoretical crushing strength is about 0.70. Lower values may be attributed to buckling effect of skeletal steel.